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This chapter describes systems operations. The chapter includes the following sections:
This section presents system engineering recommendations and describes key features that influence the configuration and management of your network.
Decide on the number of homes passed per upstream port and the number of CMs supported per Cisco CMTS. Answer the questions below to help determine the number of CMs per downstream:
The Cisco CMTS software supports up to 256 QoS policies. Each SID is assigned to a QoS profile. Each CM has one or more SIDs:
Each QoS profile can be dynamically updated in real time; for example, peak time access is slower than off-peak access for a particular pricing plan.
The service class is the QoS profile identifier. The first three are reserved by the Cisco CMTS for CM initialization, registration, and "service denied."
One Cisco uBR7246 universal broadband router can pass 48000 homes; more by increasing the fiber nodes per segment or by increasing subscribers per node. Topology and configurations increase the server and provisioning load, increasing the likelihood that CMs will go offline and online.
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Note Based on the subscriber profiles for the area to service—residential versus telecommuter users, and the mix of service classes for the area—Cisco recommends you partition your network so that no more than 1,000 CMs per downstream port are supported. |
Cisco recommends the following:
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Note A DOCSIS-compliant HFC plant should ensure that a 25 dB C/N is maintained at all times. |
The remainder of this section describes some system engineering calculations.
(Number of downstream channels) * (Number of CMs per downstream)
In general, this would be:
(Number of CMs per downstream) / (Number of upstream channels per downstream)
In theory, the maximum number of SIDs is 8175 downstream, rather than 8191.
Cisco recommends 1000 CMs per cable modem card or downstream port. An explanation follows:
SIDs (IDs are 12 bits long, and each CM has at least one unique SID.)
The Cisco CMTS consumes approximately 1 Kbyte of DRAM for each active SID in the chassis. Each physical CM (not SID) is typically ranged at least once every 30 seconds. This ranging is in a polled format, and consumes 50 microseconds of time on the wire.
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Note Slower data rates will lengthen this time. Faster data rates will remain the same. |
Thus, 30 seconds / 50 * 10-6 seconds = 600,000 modems per upstream at 100% wire utilization.
A cable modem card with four upstreams and one downstream would create a quiescent keepalive upstream traffic rate of about 35% when there are 8191 CMs (DOCSIS-specified total) connected to the associated downstream; 8 MB of DRAM would be used for this card. A chassis with four such cards, would consume 32 MB of DRAM, consume 35% of all upstream bandwidth, and perhaps 85 to 95% of all CPU time to handle this. Configurations such as this would be optimized for low data rate per user applications such as Pay Per View CATV set top box control.
These applications would not be used for residential Internet access services. You would be too constrained with RF path impairments on the upstream to possibly connect enough homes, such that there would be more than 1000 CMs on a single upstream interface. At 20% customer penetration, this is 5,000 homes passed per upstream. Twenty percent penetration is considered very high for Internet residential subscription.
In theory, this would be 8191 CMs as interpreted from DOCSIS. In reality, because of physical plant limitations, this number would be less—1,000 CMs per downstream channel or cable modem card.
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Note The Cisco CMTS has no software limitations that prohibit it from running the full DOCSIS limit. Cisco recommends 1,000 CMs per cable modem card for the reasons given earlier. |
The distance limit is based on the length of the CM insertion interval.
The speed of light through HFC is:
0.75 * 3.0 X 10^^10 meters/sec in coax
0.66 * 3.0 X 10^^10 meters/sec in fiber
You can assume that the coax will be less than 3000 meters in most cases, and the remaining distance will be fiber. If there are two consecutive grants for CM insertion interval, and the CMTS is able to deal with a response in either time interval, or spread across the middle (software), then this distance is doubled.
Other things can be done as a result of the variable interleaver delay option. This permits up to a 4 msec round trip in the cable system. Greater distances, however, make for poor performance/response time underload.
The Cisco CMTS routers support DOCSIS 1.0 QoS definitions. You can configure service class profiles to support a specific QoS profile number, traffic priority, maximum upstream bandwidth, guaranteed upstream bandwidth, maximum downstream bandwidth, maximum transmit burst length, and ToS overwrite byte.
The Cisco CMTS routers also support DOCSIS 1.0 extensions. The routers support multiple service classes per CM and dynamic service identifiers. This allows the Cisco CMTS to dynamically allocate and delete service flows for VoIP transmissions originating from RF CPE devices containing integrated telephony CMs.
The CMTS also supports QoS profile enforcement to override interference from cable modems that might be improperly rate limited. The CMTS system administrator can assign a default DOCSIS 1.0 service class that overrides a pre-existing service class on the modem. The CMTS can do traffic shaping based on the QoS profile the administrator enforces.
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Note These capabilities are described in more detail in the sections that follow. For additional information on general Cisco IOS QoS, refer to the Quality of Service Solutions Configuration Guide. |
Cisco CMTS routers let you create multiple service class profiles with the following characteristics:
Using these service class profiles, you can define a guaranteed-rate service queue to store bandwidth requests from CMs subscribing to a class with minimum upstream rate on the upstream channel, and a "best effort" service queue for CMs subscribing to a class with no minimum upstream rate on the upstream channel.
The Cisco CMTS software supports multiple service identifiers (SIDs). This provides the following functionality:
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Tips Best effort service involves requests with no minimum upstream rate on the channel. The CMTS treats the primary and secondary SIDs independently for issuing grants. Channel access for each SID is independent of the other. |
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Caution Reliable operation with voice requires multiple SIDs—at least two per cable modem to separate voice from data traffic. In DOCSIS 1.0, SIDs are set up statically. When supporting extensions to DOCSIS 1.0 or DOCSIS 1.1, SIDs can be set up either statically or dynamically. Both the CMTS and CM must support the feature set. |
DOCSIS 1.0 supports tiered best effort and CIR-type service. To better support the delay/jitter requirements of real time VoIP traffic, the QoS/MAC code is enhanced in Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, or higher images. The Cisco CMTS now supports a mechanism to dynamically initiate and terminate MAC level scheduling for voice calls and to specify exactly what QoS parameters to use for a voice call.
The Cisco CMTS routers support dynamic voice/fax service addition and deletion. In addition to DOCSIS 1.0 MAC messages, the Dynamic Service Addition (DSA) and Dynamic Service Deletion (DSD) are supported to allow RF CPE devices with integrated telephony CMs to activate or tear down special scheduling requirements from the CMTS MAC scheduler.
In DOCSIS 1.0, the CM explicitly requests upstream bandwidth—either in contention or piggyback to grant minislots—for every single packet it wishes to send upstream. This limits the maximum upstream data throughput that a CM can receive due to the inherent "request to grant" roundtrip latency each packet incurs on the cable system.
To support this per-CM upstream throughput increase, the Cisco CMTS software is enhanced. The CMTS can now receive a concatenated burst of multiple MAC frames from the same CM.
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Note Both the CMTS and CM must support this capability. |
This feature promotes better control of voice calls, permitting per-SID bandwidth requests and grants. Profiles can be customized for scheduling parameters required at subscriber sites for the service offering. The show interface cx/0 upstream number now supports a verbose option that displays:
DOCSIS 1.0 provides QoS, based on the SID. Each QoS profile carries a parameter maximum downstream rate which is used to provide peak rate limiting and traffic shaping on the downstream.
When voice and data traffic are combined for a particular CM, rate-exceeded data packets might shut down or delay voice packets, thereby degrading voice quality. IP precedence bits can be used as a basic differentiator to provide independent rate limits for different traffic streams.
The administrator-defined service class is enforced on CMs attempting to register with the CMTS. The service class has no upstream or downstream rate limits.
When the CM sends data upstream, it makes bandwidth requests without throttling or dropping packets because of its own rate-policing algorithm. The CMTS does traffic shaping based on the QoS profile enforced by the operator.
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Note By default, the system will not enforce a specific QoS profile on the cable modem. The QoS profile assigned to the cable modem will depend on the class of service parameters provisioned in the cable modem's DOCSIS configuration file. |
Tag Switching is a Cisco-developed technology that implements a next-generation architecture for the Internet backbone and large intranets. Tags placed on the fronts of packets contain forwarding information used for making switching decisions and applying network services.
Tag Switching has become the foundation for flexible Layer 3 virtual private networks (VPNs), QoS handling, and traffic engineering. It also forms the basis for the emerging IETF standard for Multiprotocol Label Switching (MPLS).
A Tag Switching infrastructure combines with advanced routing protocol capabilities to define IP VPNs by selectively advertising IP reachability information to just those subscribers within the same VPN or extranet, thus keeping different VPN traffic logically separate. The subscribers are then all connected via Tag switch paths (TSPs).
Forwarding is based entirely on the assigned Tag values (rather than IP destination prefixes), eliminating the requirement for uniqueness in the IP addresses that are used. This feature means subscribers to different VPNs do not have to concern themselves with the problems that would otherwise occur when connecting networks with different subnetworks into an integrated network.
NetFlow switching is a high-performance, network-layer switching path that provides administrators with access to "call detail recording" information from their networks. This information includes details such as user, protocol, port, type of service information, and the duration of the communication. This data can be used for a variety of purposes, including billing, enterprise accounting, network planning and performance analysis, QoS bandwidth management, security policies, and data warehousing.
The collected NetFlow data is sent out via UDP packets to a workstation running the Netflow Flowcollector server, which can collect data from multiple routers for later analysis by a user running the Netflow Flowanalyzer application. Through the NetFlow Data Export feature, traffic information can also be passed to external applications that perform functions such as billing or network performance analysis.
NetFlow also provides a mechanism that can process security access lists without incurring the same performance penalty as other available switching methods. In conventional switching at the network layer, each incoming packet is handled on an individual basis with a series of functions to perform access list checks, capture accounting data, and switch the packet. In contrast, after NetFlow switching identifies a flow and processes the access list for the flow's first packet, all subsequent packets are handled on a "connection-oriented" basis as part of the flow. This avoids further access list checks on the flow. Packet switching and statistics capture are performed in tandem.
This feature enables you to specify traffic handling policies to maximize throughput under congestion conditions. Random early detection (RED) works in conjunction with TCP to intelligently avoid network congestion. WRED combines IP precedence and RED capabilities to provide differentiated performance characteristics for different classes of service, thus providing preferential traffic handling for higher priority traffic. You can define minimum and maximum queue depth thresholds and drop probabilities for each class of service.
This feature performs priority output queuing and custom queuing to grant resources to important sessions when network bandwidth is saturated. It is typically used for digitized voice packets to help reduce delay. WFQ provides expeditious handling for high priority traffic, requiring low delay, while fairly sharing the remaining bandwidth between lower priority traffic. WFQ divides link traffic into high and low priority flows based on metrics including IP precedence and traffic volume.
This feature works in conjunction with WFQ; it helps the router establish a weight for different types of packets that affect the order in which the packets enter the output queue and are placed on the cable network for transmission. Voice packets are routed through the interface with a QoS method that allows the packets to receive priority over standard data frames. A router that supports RSVP gives priority to packets that fall into a reservation within RSVP.
This feature provides the means to allocate and limit bandwidth to traffic sources and destinations, and specify policies to handle traffic exceeding the bandwidth allocation. CAR policies can be utilized at the ingress or egress of the network. CAR uses token bucket filters to measure traffic load and limit sources to bandwidth allocations.
The Cisco CMTS support mapping SIDs to subinterfaces. This mapping is created by gleaning DHCP reply messages meant for the PC. The cmts_glean() function is modified for that purpose. The IP address stored in the DHCP reply is matched for its subnet value against the subnet value configured for each of the subinterfaces over a physical interface or a cable bundle. The subnet information can be derived by the IP address and the mask value available in the software IDB structure. The linked list of software IDBs can be accessed from the hardware IDBs associated with the physical interface or the interface configured as a bundle master.
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Note The SID to subinterface mapping can be made user configurable. Current Cisco IOS releases bind SID to subinterface, based on DHCP-assigned IP address. |
The Cisco CMTS supports multiple-SIDs-per CM (single ISP case) and multiple SIDs per CM (multiple ISP case). When multiple SIDS are assigned to a CM, either statically or dynamically, the SID instance pointer corresponding to the non-primary SID is obtained first. This is used to obtain the address of the primary SID instance. The primary SID instance stores the software IDB pointer to be used.
Each packet arriving over the cable interface will have a SID prepended to it. The SID will be extracted from the packet and used as an index in the array of SID instance pointers.
The paktype structure for a downstream packet will have a software IDB of the subinterface. This software IDB will point to the associated hardware IDB. In case of a bundled interface, it is the IDB of the bundle master.
The destination MAC address is used to look up the associated entry in the MAC buckets created at the time of IP address assignment via DHCP. If the MAC address entry is not found, then the destination IP address will be used to perform ARP over the sub-interface.
The Cisco CMTS routers support DOCSIS baseline privacy (BPI). The Cisco CMTS software supports both 40-bit and 56-bit encryption/decryption.
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Note When BPI is enabled, 56-bit encryption/decryption is the default. Both the Cisco CMTS routers and the cable modem must contain software and be configured to support encryption/decryption. |
A configuration command allows an administrator to manually force the Cisco CMTS to generate a 40-bit DES key, where the DES key that is generated and returned masks the first 16-bits of the 56-bit key to zero in software. The Cisco CMTS router generates keys for unicast, broadcast, and multicast operation as appropriate. Keys are refreshed periodically and have a default lifetime of 12 hours.
The Cisco CMTS routers can be configured for CM and multicast authentication using the Remote Authentication Dial-In User Service (RADIUS) protocol—an access server authentication, authorization, and accounting protocol that Livingston, Inc. developed. The Cisco CMTS also supports additional vendor-proprietary RADIUS attributes.
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Note An Internet Engineering Task Force (IETF) draft standard, RFC 2138, defines the RADIUS protocol. RFC 2139 defines the corresponding RADIUS accounting protocol. Additional RFC drafts define vendor-proprietary attributes and MIBs that can be used with an SNMP manager. |
When a CM comes online or when an access request is sent through a multicast data stream, the Cisco CMTS sends relevant information to RADIUS servers for CM/host authentication. This feature can be configured on a per-interface basis.
This feature has been enhanced to provide additional authentication information, allowing an administrator to determine whether a subscriber dialed a number that requires special billing arrangements (such as a toll-free number). If a telco return customer is being authenticated by a TACACS+ or RADIUS server, and if the number dialed by the CM is being redirected to another number for authentication, the system can include the original number in the information sent to the authentication server. The original number can be sent as a Cisco Vendor Specific Attribute (VSA) for TACACS+ servers and as RADIUS Attribute 93 (Ascend-Redirect-Number) for RADIUS servers.
This feature prevents the spoofing of IP addresses. Using the CLI, administrators can determine the IP and MAC address of a given cable modem, and the SID number that shows the IP and MAC addresses of all devices learned in the cable modem's MAC table.
The CMTS verifies the source IP address against the MAC address for the CM. CM and PC IP addresses are verified to ensure SID and MAC addresses are consistent. A PC behind a cable modem is assigned an IP address from the DHCP server. If a user on a second PC/cable modem statically assigns the same IP address to a PC, the Cisco CMTS reports this. Using customer databases, administrators can cross reference the spoofing CM and PC to prevent further usage.
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Note The cable source-verify [dhcp] cable interface command specifies that DHCP lease query requests are sent to verify any unknown source IP address found in upstream data packets. The feature requires a DHCP server that supports the LEASEQUERY message type. Cisco Network Registrar (CNR) supports the LEASEQUERY message type in software release 3.01(T) and greater. The feature requires a DHCP server that supports the new LEASEQUERY message type. |
This feature enables Cisco CMTS routers to manipulate the GIADDR field of DHCPDISCOVER and DHCPREQUEST packets with a Relay IP address before they are forwarded to the DHCP server. By modifying the GIADDR field based on whether the source is a CM or a host, the Cisco CMTS provides hints to the DHCP server as to where—on which IP subnet—the server should allocate addresses to the requesting client.
Per-modem and per-host access lists allow Cisco CMTS routers to filter incoming packets from individual hosts or cable modems based on the source Media Access Controller (MAC) or Internet Protocol (IP) address. This allows access lists to be specified on a per-interface or a per-address basis.
You can pre-configure the filters by using the CLI following standard IOS access list and access group configuration procedures. You can assign these filters to a user or modem by using the CLI or Simple Network Management Protocol (SNMP). The feature also supports traps to inform the CMTS about the online/offline status of modems.
This feature provides support for a basic wiretap facility as required by the United States Federal Communications Assistance for Law Enforcement Act (CALEA). The feature is controlled by the cable intercept command, which requires a MAC address, an IP address, and a UDP port number as its parameters.
When activated, the Cisco CMTS examines each packet for the desired MAC address. When a matching MAC address is found—for either the origination or destination endpoint—a copy of the packet is encapsulated into a UDP packet. The packet is then sent to the specified server at the given IP address and port.
The Cisco CMTS routers support Network Address Translation (NAT) and firewall functionality.
This feature reduces the chance that information will be retransmitted to hosts on the HFC network, and therefore, conserves bandwidth. Without traffic shaping, the Cisco CMTS software drops bandwidth requests from CMs found to be exceeding their configured peak upstream transmission rate. Dropping bandwidth requests (and eventually upstream packets) from rate-exceeding cable modem causes TCP-related timeouts which cause the host sending the information to retransmit its information.
The Cisco CMTS supports the following traffic shaping features:
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Note Packets that contain ToS bytes that have not been configured for downstream data rates continue to use the common data rate limits. |
This feature allows all cable modems on the HFC network to identify themselves via unique downstream channel IDs, instead of their downstream frequencies. CMs communicate their downstream ID when making a connection, not their downstream frequency. This feature allows system administrators to enter a configurable downstream channel ID to a value other than the default. Thus, each downstream channel ID can be unique on a cable network.
Cisco CMTS routers are able to change the downstream frequency for any or all CMs, overriding the DOCSIS configuration file settings.
Cisco CMTS routers can report and limit the number of CPEs per CM using the CLI or SNMP.
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Note This feature is separate from the ability of a CM to support multiple CPE devices. For example, depending on the Cisco IOS software release being used, Cisco's uBR900 series cable access routers can support a maximum of either 3 or 254 CPE devices. |
For each modulation profile configuration, Cisco CMTS routers will support burst profile number, burst profile interval usage code, burst type, preamble length and unique word length, differential encoding enable/disable, forward error correction (FEC) correctable bytes value, FEC code word length, scrambler seed value, maximum burst size, guard time size, last code word shortened/lengthened, and scrambler enable/disable.
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Note Multiple modulation profiles are supported on the MC11C, MC12C, MC14C, MC16B, MC16C, MC16S, and MC16E cable modem cards. Only one profile is supported on the MC11-FPGA card. |
The Cisco IOS software CLI can be used to configure the Cisco cable modem card for correct operation on the HFC network. Perform the following tasks to configure the Cisco cable modem card.
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Note For tasks marked optional below, default settings are adequate to configure the system typically; choosing values different than the defaults should be done with care. |
The first step in configuring the Cisco CM interface is to configure the downstream cable interface. Configure the downstream frequency, symbol rate, compression, and modulation. Configuring the downstream cable interface consists of the following tasks:
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Note In most applications, default values for the commands used in these configuration steps are adequate to configure the Cisco CMTS. You do not need to specify individual parameters unless you want to deviate from system defaults. |
To activate a downstream port on a Cisco CMTS cable modem card for digital data transmissions over the HFC network, complete the steps in Table 3-1.
| Step | Command | Purpose |
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1. | | Enter enable (privileged EXEC) mode. Enter the password. You have entered privileged EXEC mode when the prompt displays the pound symbol ( |
2. | | Enter global configuration mode. You have entered global configuration mode when the prompt displays This command can be abbreviated to config t. |
3. | | Enter cable interface configuration mode. In this example, the interface is downstream port 0 on the cable modem card installed in slot 6 of the Cisco CMTS. |
4. | | Default. Activate downstream digital data from the Cisco CMTS. |
5. | | Place the downstream port in the "admin up" state. |
6. | | Return to privileged EXEC mode. |
To determine if the downstream carrier is active (up), enter the show controllers cable command for the downstream port that you just configured.
The sample below is for NTSC 6 MHz operations:
CMTS01# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
The sample below is for EuroDOCSIS 8 MHz operations using the MC16E cable modem card:
CMTS01# show controllers cable 3/0 downstream
Cable3/0 Downstream is up
Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate
6.952000 Msps
FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17
Downstream channel ID: 0
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Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers. |
Downstream frequency is an information-only parameter that should match the digital carrier frequency—the center frequency of the downstream RF carrier (the channel) for a particular downstream port. The configuration controlling the digital carrier frequency is performed in the IF-to-RF upconverter that must be installed in the downstream path from the Cisco CMTS. Refer to the upconverter's manufacturer's instructions for information about configuring the upconverter.
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Note The Cisco CMTS cable downstream frequency command has no effect on external upconverters. It is informational only. |
| Command | Purpose |
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| Enter the fixed center frequency for your downstream RF carrier in Hz. |
To verify the current value of the center frequency, enter the show controllers cable command for the downstream port that you have just configured:
router#show controllers cable 6/0 downstream Cable6/0 Downstream is up Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4 Downstream channel ID: 0
Router# show controllers cable 3/0 downstream Cable3/0 Downstream is up Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate 6.952000 Msps FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17 Downstream channel ID: 0
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency is not set. Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0
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Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you have calculated and entered the center frequency for your router accurately. |
| Command | Purpose |
|---|---|
| Specify the downstream channel ID. Acceptable range is 0 to 255. |
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Note This command must be used with the cable downstream frequency <54000000-1000000000> Broadcast Frequency - H command. |
The commands are used in instances where you want to send multiple downstream frequencies to a single region that contains CMs that can only connect to upstream ports on the same cable modem card. You must configure unique channel IDs for each downstream that any CM is capable of receiving. The downstream frequency setting must match the setting on the upconverter.
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Caution After defining unique downstream IDs, test the CMs for correct operation. Cisco recommends when using this feature that you re-test each subsequent software release of CM code to verify correct operation and ensure reasonable acquisition time for new installations. Failure to use these commands in conjunction or to test the involved CMs can result in customer service outages of indefinite duration. |
To verify the downstream channel ID, enter the show controllers cable command for the downstream port you have just configured.
For NTSC operations, a sample appears below:
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 1
For EuroDOCSIS operations, a sample appears below:
Router# show controllers cable 3/0 downstream Cable3/0 Downstream is up Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate 6.952000 Msps FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17 Downstream channel ID: 2
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Tips Annex B is the DOCSIS MPEG framing format standard for North America. Annex A is the European standard, supported only when using the Cisco MC16E cable modem card and Cisco CMTS images that support EuroDOCSIS Annex A operation. |
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Note Annex A or B framing format is automatically set when configuring Cisco cable modem cards. The cable modem card's downstream ports and the connected CMs on the network must be set to the same MPEG framing format and support either DOCSIS or EuroDOCSIS operations as appropriate. |
| Command | Purpose |
|---|---|
| Set the downstream MPEG framing format. |
To verify the downstream MPEG framing format setting, enter the show controllers cable command for the downstream port you have just configured.
A sample output appears below for NTSC operations:
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
Downstream channel ID: 0
A sample output appears below for EuroDOCSIS operations:
Router# show controllers cable 3/0 downstream Cable3/0 Downstream is up Frequency 669.0000MHz, Channel Width 8MHz, 64-QAM, Symbol Rate 6.952000 Msps FEC ITU-T J.83 Annex A, R/S Interleave I=12, J=17 Downstream channel ID: 0
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Note Setting a downstream modulation rate of 256-QAM requires approximately a 6 dB higher signal-to-noise ratio (SNR) than 64-QAM at the subscriber's cable modem. If your network is marginal or unreliable at 256-QAM, use the 64-QAM format instead. Also, consider the significance of your data. |
To set the downstream modulation, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
| Set the downstream modulation. The standard DOCSIS modulation rate (and the Cisco default) is 64 QAM. |
To verify the downstream modulation setting, enter the show controllers cable command for the downstream port you have just configured. A sample is shown below:
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
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Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; the downstream carrier is active using the cable downstream if-output command; you have selected the default if you are not certain about the modulation rate needed. |
Set the interleave depth for the downstream port on the Cisco cable modem card. A higher interleave depth provides more protection from bursts of noise on the HFC network; however, it will increase downstream latency.
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Note The valid values are 8, 16, 32 (default), 64, and 128 for MC16C, MC16S and older cable modem cards other than the MC11 FPGA. This command is not applicable to the MC16E cable modem card. |
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable downstream interleave-depth | Set the downstream interleave depth in milliseconds. |
To verify the downstream interleave depth setting, enter the show controllers cable command for the downstream port you have just configured:
router# show controllers cable 6/0 downstream
Cable6/0 Downstream is up
Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps
FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4
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Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; the downstream carrier is active using the cable downstream if-output command. |
Specify an IP address of a DHCP server where UDP broadcast (DHCP) packets will be sent. You can specify a DHCP server for UDP broadcast packets from cable modems and a DHCP server for UDP broadcast packets from hosts.
| Step | Command | Purpose | ||
|---|---|---|---|---|
1. |
| Set the downstream helper address to the DHCP server at IP address 10.x.x.x for UDP broadcast packets from cable modems.
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2. | | Set the downstream helper address to the DHCP server at IP address 172.56.x.x for UDP broadcast packets from hosts. |
To verify the downstream helper address setting, enter the show running-config command and look for cable helper-address in the cable interface configuration information:
CMTS01# show running-config Building configuration... Current configuration: ! interface Cable4/0 ip address 10.254.254.254 255.0.0.0 no ip directed-broadcast cable helper-address 192.168.1.1 no keepalive
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Tips If you are having trouble: Check the cables, upconverters, RF levels, and frequencies if the cable modems do not find a downstream signal. Check the cables, RF levels, and upstream frequencies, and enter a no shut command if the cable modems find a downstream signal, but not an upstream signal. Check the provisioning servers, ping the DHCP server using the source IP address option—the primary IP address of a cable interface, check IP routing if the cable modems acquire an RF upstream and downstream lock, but do not stay up. Check DHCP options and the IP address of the TOD server, ping the TOD server using the source IP address option, check IP routing, verify that the TFTP filename is correct, verify the TFTP file is in the correct directory on the TFTP server, ensure the TFTP file has read privileges, ping the TFTP server using the source IP address option, and check IP routing if the cable modems acquire an RF and a DHCP, but fail on TOD or TFTP. |
Downstream rate limiting enables you to use the token bucket policing algorithm with traffic shaping options or the weighted discard policing algorithm to buffer, shape, or discard packets that exceed a set bandwidth. Downstream rate limiting is disabled by default.
To enable downstream rate limiting for a downstream port on a Cisco cable modem card, use one of the following commands in Table 3-8 in cable interface configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | | Enable rate limiting on the downstream port using the token bucket policing algorithm. With this command, the Cisco CMTS will automatically drop packets in violation of the allowable bandwidth. |
2. | | Enable rate limiting on the downstream port using the weighted packet discard policing algorithm and assign a weight for exponential moving average of loss rate. Acceptable values are 1 to 4. |
3. | CMTS01(config-if)# | Exit back to EXEC mode so that you can verify the steps. |
To determine if downstream rate limiting is configured and activated, enter the show running-config command and look for the cable interface configuration information. If downstream rate limiting is configured and enabled, a rate limiting entry is displayed in the output. If downstream rate limiting is disabled, no rate limiting entry is displayed.
CMTS01# show running-config Building configuration... Current configuration: ! interface Cable4/0 ip address 10.254.254.254 255.0.0.0 no ip directed-broadcast cable helper-address 192.168.1.1 no keepalive cable downstream rate-limit token-bucket shaping cable downstream annex B cable downstream modulation 64qam
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected the default if you are not certain about the modulation rate needed; the downstream carrier is active using the cable downstream if-output command. |
Upstream cable interface commands configure the frequency and input power level of the upstream signal, in addition to error detection and correction of the upstream signal. The configuration of the upstream cable interface depends on the characteristics of your plant.
|
Note For some tasks below, default values are adequate to configure the device. |
Perform the following tasks to configure the upstream cable interface:
The upstream channel frequency of your RF output must be set to comply with the expected input frequency of your Cisco cable modem card. To configure upstream channel frequencies, either:
You can also select a default that does not set a specific fixed value.
|
Note The upstream port is frequency-agile. The frequency can change while the interface is up and carrying traffic if you define spectrum groups. |
A modulation profile consists of a table of physical layer characteristics for the different types of upstream bursts; for example, initial maintenance, long grant, request/data, request, short grant, and station maintenance.
|
Note The upstream cable interface will not operate until you either set a fixed upstream frequency or create and configure a spectrum group. Refer to the "Configuring Hot Standby 1+1 Redundancy" section. If you are setting a fixed upstream frequency, make sure that the frequency selected does not interfere with the frequencies used for any other upstream applications running on the cable plant. |
|
Note If you are using the first version of the MC11 cable modem card, you cannot define an alternative upstream modulation profile. |
To set a fixed upstream frequency, use the following commands in cable interface configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config-if)# cable upstream usport frequency up-freq-hz | Enter the fixed center frequency for your upstream RF carrier in Hz. Valid range for usport is from 0 to 5 if you are using a Cisco MC16 cable modem card. |
2. | CMTS01(config-if)# no cable upstream usport shutdown | Place the upstream port in the "admin up" state. |
|
Tips For NTSC operations, valid ranges are 5000000 to 42000000 Hz. For PAL or SECAM operations using the MC16E, the valid range is 5000000 to 65000000 Hz. |
|
Caution Some cable systems cannot reliably transport frequencies near these band edges. The wider the upstream channel (in MHz), the more difficulty you might have. Enter a center frequency between 20 and 38 MHz if you have difficulty. |
|
Note You can also select a default that does not set a specific fixed value. The Cisco CMTS will command the cable modems to use this frequency as the center frequency. |
To verify the current value of the upstream frequency, enter the show controllers cable command for the upstream port you have just configured:
CMTS01# show controllers cable 6/0 u0
Cable6/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
|
Note The upstream frequency displayed in the show controllers cable command output might not match the frequency that you entered when you set the upstream frequency. The Cisco CMTS might select an upstream frequency close to the frequency you entered that offers better performance. The minimum upstream frequency step size on the MC16C is 32 kHz. The Cisco CMTS selects the closest frequency available. |
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you have selected a valid frequency for your router. |
Enter the channel width in hertz (Hz). For NTSC operations, valid values are 200000 Hz (160 kilosymbols per second [ksps]), 400000 Hz (320 ksps), 800000 Hz (640 ksps), 1600000 Hz (1280 ksps), and 3200000 Hz (2560 ksps). The default is 1600000 Hz.
Using the MC16S cable modem card, you have advanced spectrum management capability to scan the upstream spectrum for clean channel widths of varying sizes. By entering an optional second channel width value in the appropriate command line, you instruct the MC16S to hierarchically search for clean upstream channels of 3.2 MHz, 1.6 MHz, 800 kHz, 400 kHz, and 200 kHz width. The spectrum management card on the MC16S will scan the upstream spectrum for clean (usable) channels of the greatest specified width.
If no acceptable channels of the specified width are found, the spectrum management card automatically begins to scan the upstream spectrum for the next largest available channel width; for example if the spectrum management card is unable to find a usable 1.6 MHz upstream channel, it automatically begins searching for usable 800 kHz channels.
|
Note To ensure that only one specified upstream channel width is ever used in a given upstream segment leading to an MC16S, enter the same channel width twice in the appropriate command line. If you change the channel width, the symbol rate changes accordingly (symbol rate = 1.25 channel width). |
|
Caution Higher symbol rates are more susceptible to RF noise and interference. If you use a symbol rate or modulation format beyond the capabilities of your HFC network, you might experience packet loss or loss of cable modem connectivity. |
|
Note For QAM-16 channel widths of 400 kHz (320 ksps) or greater, Cisco recommends that you use 16-QAM modulation for long and short data, and that you use QPSK for request, initial, and station communications. For QAM-16 channel widths of 200 kHz (160 ksps), all communication must be able to use 16-QAM. That is, 160 ksps with 16-QAM requires an exceptional signal-to-noise ratio (SNR) in your upstream channel(s). When you use QAM-16 for request, initial, and station maintenance messages with channel widths greater than 400 kHz, the QAM-16 preamble and message data take longer to transmit than the QPSK format. |
To set the upstream channel width, use the following commands in cable interface configuration mode.
| Step | Command | Purpose |
|---|---|---|
1 | CMTS01(config-if)# cable upstream usport channel-width width | Enter the channel width for your upstream RF carrier in Hz. |
2 | CMTS01(config-if)# no cable upstream usport channel-width | Return the channel-width to its default setting of 1600000 Hz. |
Using an MC16S to specify an upstream channel width, use the cable upstream channel-width interface configuration command. Use the no form of this command to set the channel width to 1600000 for a port number. See the examples below:
cable upstream portnum channel-width width1 width2
no cable upstream portnum channel-width
Table 3-11 shows the syntax description for the MC16S-based hardware spectrum management enhancements.
| Syntax | Valid Values |
width1 | Specifies upstream channel width in hertz (Hz). Valid values are 200000 (160000 symbols/sec), 400000 (320000 symbols/sec), 800000 (640000 symbols/sec), 1600000 (1280000 symbols/sec), and 3200000 (2560000 symbols/sec). |
width2 | Specifies the smallest width in hertz (Hz) for this upstream channel. Valid values are 200000 (160000 symbols/sec), 400000 (320000 symbols/sec), 800000 (640000 symbols/sec), 1600000 (1280000 symbols/sec), and 3200000 (2560000 symbols/sec). |
To verify the current value of the upstream channel width, enter the show controllers cable command for the upstream port you just configured. A sample appears below:
CMTS01# show controllers cable 6/0 u0
Cable6/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
|
Tips If you are having trouble: Use a valid combination of modulation format (QPSK/QAM-16), minislot size, frequency, and no shutdown. Use a recommended or previously tested modulation profile. It is not uncommon to create a modulation profile that does not allow cable modem-to-headend communication. Since each message type is individually specified, some messages may not work. Verify using IP ping packets of varying lengths (64 to 1500 bytes). Ping from the headend to the cable modem. Verify with your cable modem vendor that CM software is fully certified or compatible with DOCSIS 1.0 or DOCSIS 1.0 extensions as appropriate. |
The Cisco CMTS controls the output power levels of CMs to meet the desired upstream input power level. The nominal input power level for the upstream RF carrier is specified in decibels per millivolt (dBmV). The default setting of 0 dBmV is the optimal setting for the upstream power level.
The valid range for the input power level depends on the data rate. At 1.6 MHz, the valid range is -10 dBmV to 25 dBmV. If your power levels operate at greater than the maximum valid level, use an inline attenuator to bring the power level to within the valid range.
|
Caution If you increase the input power level, CMs on your HFC network will increase their transmit power level. This increases the carrier-to-noise ratio (C/N) on the network, but also increases distortion products. Composite Second Order Beat (CSO) and Composite Triple Beat (CTB) values worsen by 2 dB for every 1 dB-increased C/N. The return path laser immediately enters a non-linear mode called clipping and all communication is no longer reliable. Many return lasers send "short" bursts above the clipping thresholds and fail on longer or successive bursts. You should not adjust your input power level by more than 5 dB in a 30-second interval. If you increase the power level by more than 5 dB within 30 seconds, cable modem service on your network will be disrupted. If you decrease the power level by more than 5 dB within 30 seconds, cable modems on your network will be forced offline. |
|
Note When you run cable upstream 0 power-level, Cisco recommends that the adjacent channel not have a large variation. The recommended maximum input power variance is 5 to 6 dBmV. |
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport power-level dbmv | Enter the upstream power level in dBmV. |
To verify the current value of the upstream input power level, enter the show controllers cable command for the upstream port you have just configured:
CMTS01# show controllers cable 6/0 u0
Cable6/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 0.800 MHz, QPSK Symbol Rate 0.640 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
|
Tips If you are having trouble, verify that the upstream amplitude of an optimal RF carrier injected at the fiber node reference input point reaches the cable modem card input point at a consistent level (node-to-node and port-to-port), and that this absolute level as installed matches both the design and software settings on the Cisco uBR7200 series. |
|
Note Software adjustments of 1 to 3 dB can be used to adjust for minor variations in measurement or setup and port-to-port calibration differences. These adjustments can significantly improve cable modem performance, especially in marginal situations. Larger adjustments should be made in conjunction with spectrum analyzer-support at the headend or distribution hub. |
The admission control is set as a percentage of the specified upstream channel capacity. The acceptable range is from 10 to 1000 percent. Admission control is disabled by default.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport admission-control percentage | Set the admission control as a percentage of the upstream channel capacity. Valid range is from 10 to 1000 percent. |
To determine if upstream admission control is configured and activated, enter the show running-config command in privileged EXEC mode and look for the cable interface configuration information. If upstream admission control is configured and enabled, an admission control entry is displayed in the show running-config output, indicating the user-defined percentage of upstream channel capacity allowable. If upstream admission control is disabled, no admission control entry is displayed in the output.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
The Cisco uBR7200 series uses forward error correction (FEC) to attempt to correct any upstream data that might have been corrupted. FEC is activated by default and should not be disabled. When FEC is activated, all cable modems on the network also activate FEC.
|
Note Although it is an option, Cisco recommends that you use upstream FEC. |
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport fec | Enable FEC. This is the default setting. |
To verify if FEC is activated or deactivated, enter the command more system:running-config and look for the cable interface configuration information. If FEC is enabled, an FEC entry is displayed in the show running-config output. If FEC is disabled, no FEC entry is displayed in the output. If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport minislot-size size | Specify the minislot size in ticks for the selected upstream interface. Acceptable values are 2, 4, 8, 16, 32, 64, and 128. |
To verify upstream minislot size, enter the show controllers cable 6/0 u0 command for the upstream port you have just configured:
CMTS01# show controllers cable 6/0 u0
Cable6/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0xFFFF, rev_id=0xFF, rev2_id=0xFF
nb_agc_thr=0x0000, nb_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 64
Bandwidth Requests = 0xFE
Piggyback Requests = 0xD
Invalid BW Requests= 0x2
Minislots Requested= 0x2963
Minislots Granted = 0x2963
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
The scrambler on the upstream RF carrier enables cable modems on the HFC network to use built-in scrambler circuitry for upstream data transmissions. The scrambler circuitry improves reliability of the upstream receiver on the cable modem card.
To activate the upstream scrambler, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport scrambler | Enable the scrambler. This is the default. |
To determine if the upstream scrambler is activated, enter the command more system:running-config and look for the cable interface configuration information.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable upstream usport differential-encoding | Enable differential encoding. This is the default. |
To determine if upstream differential encoding is activated, enter the show running-config command and look for the cable interface configuration information. If upstream differential encoding is enabled, a differential encoding entry is displayed in the show running-config output. If upstream differential encoding is disabled, no differential encoding entry is displayed in the output.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
Upstream rate limiting allows upstream bandwidth requests from rate-exceeding cable modems to be buffered without incurring TCP-related timeouts and retransmits. This enables the CMTS to enforce the peak upstream rate for each cable modem without degrading overall TCP performance for the subscriber CPEs. Upstream grant shaping is per cable modem (SID).
Token bucket policing with shaping is the per-upstream default rate-limiting setting at the CMTS. Shaping can be enabled or disabled for the token-bucket algorithm.
| Step | Command | Purpose |
|---|---|---|
1. | | Enable rate limiting for the specified upstream cable interface. |
2. | CMTS01(config-if)# | Exit back to the EXEC mode so that you can verify upstream rate limiting. |
To disable upstream traffic shaping for an upstream port, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport rate-limit
To determine if upstream rate limiting is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream rate limiting is configured and enabled, a rate limiting entry is displayed in the show running-config output. If upstream rate limiting is disabled, no cable upstream rate-limit is displayed in the output.
You can also perform the following tasks to verify that rate limiting is enabled on the upstream channel:
Step 2 Use a regular rate-limiting algorithm on the upstream without rate shaping and see the drops of the excess bandwidth requests from this cable modem when it exceeds its peak upstream rate.
Use the show interface cx/y sid counters command to see the bandwidth request drops. See that the upstream rate received by that modem is in fact less than its configured peak rate due to the timeouts and backoffs produced by the drop in bandwidth requests. Enter the show interface cx/y sid command to see the input rate at CMTS in bps.
Step 3 Enable grant shaping on the upstream channel by using the new shaping keyword extension to the token-bucket algorithm CLI command.
Step 4 Make the cable modem exceed its peak upstream rate by generating upstream traffic and see the effect of grant buffering (shaping) at the CMTS. If you use cable modem-to-CMTS pings, you will see a perceivable slowing down of the pings.
Let the pings run for a while to let averages at the CMTS settle; then view the upstream rate received by this single modem. Use the show interface cx/y command and see the input rate in bps. This value should be close to the modem's peak upstream rate. Also see the drop counts for the modem's SID by using the show interface sid counters command and see that the CMTS no longer drops the bandwidth requests from the cable modem.
The bandwidth request drop count (from previous non-shaping test) remains unchanged when upstream rate shaping is used, indicating that the CMTS is actually shaping (buffering) the grants for the modem. See that the input rate at the CMTS (from the single rate-exceeded CM) stabilizes close to the configured peak rate of 128 Kbps.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
| Step | Command | Purpose |
|---|---|---|
1. | | Set the minimum number of frequency adjustment packets required to justify changing the upstream frequency adjustment method as a percentage. Acceptable range is 10 to 100 percent. |
2. | | Return to enable (privileged EXEC) mode. |
To return the automatic upstream frequency adjustment percentage to the default value of 30 percent, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport frequency-adjust averaging
To determine if upstream frequency adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream frequency adjustment is enabled, frequency adjustment entries are displayed in the show running-config output. If frequency adjustments are disabled, no frequency adjustment entry is displayed in the output.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers; you selected a valid frequency for your router. |
| Step | Command | Purpose |
|---|---|---|
1. | | Set the minimum power adjustment in dB that will allow continued ranging status. Valid values are 2 to 15 dB. Default = 2 dB. |
2. | | Set the minimum number (percentage) of power adjustment packets required to justify changing the upstream power rating. Valid values are 10 to 100 percent. Default = 30 percent. |
3. | | Set the power adjustment threshold in dB. Valid values are 0 to 2 B. Default = 1 dB. |
4. | | Return to enable (privileged EXEC) mode. |
To return the automatic upstream power adjustment ranging value to the default of 2 dB, enter the following command in cable interface configuration mode:
CMTS01(config-if)#no cable upstream usport power-adjust continue
To return the automatic upstream power adjustment noise value to the default of 30 percent, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport power-adjust noise
To return the upstream power adjustment threshold value to the default of 1 dB, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport power-adjust threshold
To determine if upstream power adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream power adjustment is enabled, any or all three of the continue, noise, and threshold power adjustment entries are displayed in the show running-config output. If all three continue, noise, and threshold upstream power adjustments are disabled, no power adjustment entry is displayed in the show running-config output.
| Step | Command | Purpose |
|---|---|---|
1. | | Set the minimum timing adjustment that will allow continued ranging status. Valid values are 2 to 64 seconds. Default = 2 seconds. |
2. | | Set the timing adjustment threshold value in seconds. Valid values are 1 to 32 seconds. Default = 1 second. |
3. | | Return to enable (privileged EXEC) mode. |
To return the upstream time adjustment ranging value to the default of 2 seconds, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport time-adjust continue
To return the upstream time adjustment threshold value to the default of 1 second, enter the following command in cable interface configuration mode:
CMTS01(config-if)# no cable upstream usport time-adjust threshold
To determine if upstream timing adjustment is configured and activated, enter the show running-config command and look for the cable interface configuration information. If upstream timing adjustment is enabled, either or both of the continue and threshold timing adjustment entries are displayed in the show running-config output. If both the continue and threshold upstream timing adjustments are disabled, no timing adjustment entry is displayed in the show running-config output.
|
Tips If you are having trouble, make sure the cable connections are not loose or disconnected; the cable modem card is firmly seated in its chassis slot; the captive installation screws are tight; you have entered the correct slot and port numbers. |
Each upstream port must be activated to enable upstream data transmission from the cable modems on the HFC network to the Cisco CMTS.
|
Note The upstream cable interface will not operate until you either set a fixed upstream frequency or create and configure a spectrum group. Refer to the "Set the Upstream Frequency" section or the "Create Spectrum Groups" section for details. |
To activate the upstream ports, use the following commands in global configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# interface cable slot/port | Specify a cable interface and enter cable interface configuration mode. |
2. | CMTS01(config-if)# no cable upstream usport shutdown | Enable upstream data traffic. |
To determine if the upstream ports are activated or deactivated, enter the show interface cable command for the upstream port just configured:
router# show interface cable 6/0
Cable6/0 is up, line protocol is up
Hardware is BCM3210 FPGA, address is 00e0.1e5f.7a60 (bia 00e0.1e5f.7a60)
Internet address is 1.1.1.3/24
MTU 1500 bytes, BW 27000 Kbit, DLY 1000 usec, rely 255/255, load 1/255
Encapsulation, loopback not set, keepalive not set
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:25, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sea, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
10878 packets input, 853740 bytes, 0 no buffer
Received 3679 broadcasts, 0 runts, 0 giants, 0 throttles
3 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
5401 packets output, 645885 bytes, 0 underruns
0 output errors, 0 collisions, 9 interface resets
0 output buffer failures, 0 output buffers swapped out
The DOCSIS-specified method of contention resolution for cable modems wanting to transmit data or requests on the upstream channel is a truncated binary exponential backoff, with the initial backoff window and the maximum backoff window controlled by the CMTS. The Cisco CMTS specifies backoff window values for both data and initial ranging, and sends these values downstream as part of the Bandwidth Allocation Map (MAP) MAC message.
The values are configurable on the Cisco CMTS and are power-of-two values. For example, a value of 4 indicates a window between 0 and 15; a value of 10 indicates a window between 0 and 1023. You can set fixed start and end values for data backoff on the upstream ports, or you can set the upstream ports for automatic data backoff. You have the same options for ranging backoff. For both backoff windows, the default start value is 0; the default end value is 4. Valid values are from 0 to 15.
|
Note Cisco does not recommend you adjust default values, but enable the automatic dynamic backoff algorithm. Also refer to "Configure Dynamic Contention Algorithms (Cable Insertion Interval, Range, and Data Backoffs)" section. |
| Step | Command | Purpose |
|---|---|---|
1. |
| The automatic setting is optimized for up to 250 cable modems per upstream port. Set manual values for data backoff windows only when operating with more than 250 cable modems per upstream port. |
2. |
| The automatic setting is optimized for up to 250 cable modems per upstream port. Set manual values for data backoff windows only when operating with more than 250 cable modems per upstream port. |
When considering whether to adjust backoff values, keep the following in mind:
|
Note Upstream segments serving a relatively large number of cable modems (for example, more than 1600 or so) might suffer recovery times greater than 10 minutes. |
To verify backoff window settings, enter the show controllers cable 6/0 u0 command for the upstream port you have just configured:
CMTS01# show controllers cable 6/0 u0
Cable6/0 Upstream 0 is up
Frequency 24.016 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps
Spectrum Group is overridden
SNR 33.2560 dB
Nominal Input Power Level 0 dBmV, Tx Timing Offset 2288
Ranging Backoff automatic (Start 0, End 3)
Ranging Insertion Interval automatic (60 ms)
Tx Backoff Start 0, Tx Backoff End 4
Modulation Profile Group 1
part_id=0x3137, rev_id=0x03, rev2_id=0xFF
nb_agc_thr=0x0000, nb_agc_nom=0x0000
Range Load Reg Size=0x58
Request Load Reg Size=0x0E
Minislot Size in number of Timebase Ticks is = 8
Minislot Size in Symbols = 64
Bandwidth Requests = 0xFE
Piggyback Requests = 0xD
Invalid BW Requests= 0x2
Minislots Requested= 0x2963
Minislots Granted = 0x2963
Minislot Size in Bytes = 16
Map Advance = 4000 usecs
UCD Count = 32964
DES Ctrl Reg#0 = C000C043, Reg#1 = 0
|
Note Both the CMTS and the CM must support baseline privacy and have BPI enabled. |
To configure baseline privacy (deviating from default values), follow procedures in this section:
A gracetime KEK can be set from 300 to 1,800 seconds. A lifetime KEK can be set from 86,400 to 6,048,000 seconds. If you do not set a KEK value, the default values are used.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable privacy kek grace-time seconds | Set the cable privacy KEK gracetime in seconds. Valid values are from 300 to 1800 seconds. Default = 600. |
To verify the KEK lifetime or gracetime values that are set, enter the show cable privacy kek command:
CMTS01# show cable privacy kek
Configured KEK life time value = 750000
Configured KEK grace time value = 800
|
Tips If you are having trouble, make sure you have entered a valid value for gracetime or lifetime. |
A gracetime TEK can be set from 300 to 1,800 seconds. A lifetime TEK can be set from 1,800 to 604,800 seconds. If you do not set a TEK value, the defaults are used.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable privacy tek grace-time seconds | Set the cable privacy TEK grace time in seconds. Valid values are from 300 to 1800 seconds. Default = 600. |
To verify the TEK lifetime or gracetime values that are set, enter the show cable privacy tek command:
CMTS01# show cable privacy tek
Configured TEK life time value = 56000
Configured TEK grace time value = 900
BPI is activated by default when using an image that supports baseline privacy. Commands in the cable interface configuration mode are described below.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config-if)# cable privacy enable | Activate cable privacy. This is the default. |
2. | CMTS01(config-if)# cable privacy mandatory | Activate cable privacy and do not allow access for any unencrypted cable modem connections. |
To determine if baseline privacy is activated, enter the show interface privacy command. When using a Cisco CMTS "k1" image, cable privacy is enabled by default and can only be disabled with the no cable privacy command. The cable modem must also be configured to support baseline privacy.
|
Tips If you are having trouble, make sure you entered a valid value for gracetime or lifetime for KEK and TEK privacy. |
|
Note If you entered the cable privacy mandatory command, then cable modems will not operate unless the cable modem configuration file specifies that privacy is on. |
No configuration tasks are required to configure or activate the clock card after it is installed in the Cisco uBR7246 VXR chassis. When the clock card is present, it becomes the midplane TDM clock reference source.
Refer to the following sections for optional configuration tasks:
To select the external timing reference for the clock card when it is in holdover mode, perform the following optional task in global configuration mode.
| Command | Purpose |
|---|---|
Router(config)# cable clock force {primary|secondary}
| Overrides the default behavior of the clock card to allow you to select the external timing source, when the clock card is in holdover mode. |
Use show commands to verify that the clock card is installed and operating correctly. Use the show version command to display the hardware configuration:
Router# show version ---- cut ---- cisco uBR7246VXR (NPE300) processor (revision B) with 122880K/40960K bytes of memory. Processor board ID SAB0329005N R7000 CPU at 262Mhz, Implementation 39, Rev 1.0, 256KB L2, 2048KB L3 Cache 6 slot VXR midplane, Version 2.0 Last reset from power-on X.25 software, Version 3.0.0. National clock card with T1 controller 1 FastEthernet/IEEE 802.3 interface(s) 2 Cable Modem network interface(s) 125K bytes of non-volatile configuration memory. ---- cut ----
|
Note The Cisco clock card displays as "national clock card". |
Use the show cable clock command to display the status of the external clock sources. Verify that the primary and secondary sources are present and whether the clock card is in holdover or free-running mode.
Router# show cable clock Clockcard primary input is present Clockcard secondary input is present Cable clock reference is clockcard primary input Cable3/0 Timestamp clock reference is from Clockcard Cable4/0 Timestamp clock reference is from Clockcard
Use the show controllers clock-reference command to display hardware information, register values, and current counters for the clock card. The example below shows that the primary external timing source is available, and the secondary source is not.
Router# show controllers clock-reference National clock card with T1 controller Control register :0x4 Status register :0x54 LIU Config Register 0:0x0 LIU Config Register 1:0x0 1 events reported in 266636 seconds Primary active:1, LOS :0 Secondary active :0, LOS :1 Holdovers :0, HW faults :0
Display the running configuration file with the show running-config command. Verify that the configuration is accurate for the system and for any optional clock card commands.
Use the following commands to monitor and maintain the cable clock card.
| Command | Purpose |
|---|---|
Router# show cable clock | Displays the clock reference status information for the clock card. |
Router# show controllers clock-reference | Displays hardware information, register values, and current counters for the clock card. |
Router# cable clock clear-counters | Resets the counters that are displayed with the show controllers clock-reference command. |
| Command | Purpose | |||
|---|---|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. | ||
Step 2 | Router(config-if)#hccp 2 protect 2 10.1.2.3 | Specifies that cable interface 0 on the cable modem card installed in slot 4 will be assigned to protect member 2 of group2 and will transmit and receive redundancy status messages at IP address 10.1.2.3.
| ||
Step 3 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp 1 working 1 | Specifies that cable interface 0 on the cable modem card installed in slot 4 will be a working interface designated to be member 1 of group1. |
Step 3 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp ds-switch 1 wavecom 1.1.11.3 2 1.1.11.3 1 | Specifies module 2 on a Wavecom upconverter at IP address 1.1.11.3 as the host upconverter module connected to Working CMTS 1 and module 1 on the same Wavecom upconverter (with the same IP address location) as the peer or remote switch module connected to the Protect CMTS. |
Step 3 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp 1 authenticate md5 | Specifies MD5 as the authentication algorithm for group 1, which will provide automatic key-chain encryption. |
Step 3 | Router(config-if)#hccp 1 authenticate key-chain cisco1 | Enables authentication using the MD5 algorithm and defines the authentication key "cisco1" for group 1. |
Step 4 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp 2 timers 750 3000 | Configures the HELLO interval and hold time on a Protect CMTS in group 2 to 750 and 3000 milliseconds, respectively. |
Step 3 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp 2 track | Enables automatic failover behavior based on cable interface state for interfaces in group 2. When the interface state of the cable modem card interface in question moves from "up" to "down," failover will automatically take place. |
Step 3 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)#interface cable 4/0 | Enters interface configuration mode for cable interface0 on a cable modem card installed in slot4 of a CiscouBR7200series chassis. |
Step 2 | Router(config-if)#hccp 2 revert | Enables reversion capability on cable interfaces that are members of group 2. |
Step 3 | Router(config-if)#hccp 2 reverttime 15 | Specifies the time before a Working CMTS that has experienced system failover will wait before automatically switching back to a Working CMTS to 15 minutes. |
Step 4 | Router(config-if)# | Exits back to EXEC mode so you can perform verification steps. |
| Command | Purpose |
|---|---|
Router#hccp 2 switch 2 | Allows you to manually configure a Protect CMTS or Working CMTS to switchover with its peer. |
| Command | Purpose |
|---|---|
Router#hccp 2 lockout | Prevents a Working CMTS that is currently sending and receiving data and voice traffic from automatically switching to a Protect CMTS in the same group. |
Router#hccp 2 unlockout | Makes a Working CMTS that has been manually placed in "lockout" state using the hccp lockout command available for automatic or manual switchover to a Protect CMTS. |
Step 2 Enter interface configuration mode for the cable interface referred to in Step 1 by entering the interface cable interface number command at the privileged EXEC prompt.
Step 3 Shut down the working cable interface by issuing the shutdown command.
Step 4 Type ^Z to exit back to privileged EXEC mode.
Step 5 Enter the show hccp detail command at the privileged EXEC prompt to display all 1+1 redundancy information configured on the Cisco uBR7200 series.
| Command | Purpose | |||
|---|---|---|---|---|
Step 1 | Router(config)# configure terminal | Enters configuration mode. | ||
Step 2 | Router(config)# cable modulation-profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff pre-len last-cw uw-len | Creates a modulation profile. A modulation profile is a collection of six burst profiles sent out in a UCD message to configure a modem's transmit parameters for the upstream message types: request, initial maintenance, station maintenance, short grant, and long grant. profile = Modulation profile number. iuc = Interval usage code or upstream burst type. Valid entries are: initial, long, request, short, or station.
fec-tbytes = The number of bytes that can be corrected per FEC code word. Valid values are from 0 to 10, where 0 means no FEC. fec-len = FEC code word length. Valid values are from 16 to 253. burst-len = Maximum burst length in minislots. Valid values are from 0 to 255, where 0 means no limit. guard-t = Guard time in symbols. The time between successive bursts. mod = Modulation. Valid entries are 16qam and qpsk. scrambler = Enable or disable scrambler. Valid entries are scrambler and no-scrambler. | ||
| Turning the scrambler off can cause packet loss, and is only used in lab testing environments. Errors or incompatible configurations in the burst profile(s) cause modems to either drop connectivity, drop short or long data packets, or even fail to connect to the network. It is possible to build a burst profile set for which no implementation of a DOCSIS receiver is capable of receiving the modem's transmission. 160 Ksymbol/sec and 2560 Ksymbol/sec data rates are highly sensitive to unique word length, preamble length, and FEC sizing. Incorrect choices for these values can cause poor or no connectivity at these symbol rates. seed = Scrambler seed in hexidecimal format. Valid values are from 0x0000 to 0x7FFF. diff = Enable or disable differential encoding. Valid entries are diff and no-diff. pre-len = Preamble length in bits. Valid values are from 2 to 128. last-cw = Handling of FEC for last code word. Valid entries are fixed for fixed code word length and shortened for shortened last code word. uw-len = Upstream unique word length. Enter uw8 for 8-bit unique words or uw16 for 16-bit unique code words. | |||
Step 3 | Router(config)# interface type slot/port | Configures the interface where: | ||
Step 4 | Router(config-int)# cable upstream port-number modulation-profile primary-profile-number secondary-profile-number | Adds the modulation profile to the interface. port-number = port number on cable modem slot (port numbers begin with a 0) primary-profile-number = The primary modulation profile added to the interface. secondary-profile-number | ||
Step 5 | Router(config-int) # exit | Enter exit to go back to the configuration mode. |
Router# show running-config
To review changes you make to the configuration, use the show startup-config command to display the information stored in NVRAM.
Step 2 Use the show cable modulation-profile privileged EXEC command to display modulation profile group information.
Router# show cable modulation-profile [profile] [iuc-code]
profile—(Optional) Profile number. Valid values are from 1 to 8.
iuc-code —(Optional) Internal usage code.
Valid options are:
***TBD***
***NEED MORE INFORMATION***
The command used to create the subinterface-over-cable interface or cable bundle is:
interface cable x/y.n
where x is slot number, y is port number, and n is subinterface number.
When bundling cable interfaces only, the interface configured to be the bundle master is allowed to have subinterfaces. An attempt to create a subinterface over non master cable interface will result into a warning message and command will fail. An interface that has subinterface(s) defined over it will not be allowed to be part of a bundle.
Generic cable interface configuration such as source verify or ARP handling will apply to subinterface as well.
In case of physical interface going down the associated sub-interface will also go down as well. But if subinterface is defined over the cable bundle and bundle master is shut down or removed then no data packets will be sent to any of the sub-interfaces defined over it. Packets will still be received from non-master interfaces but will be dropped. This behavior is same as described in cable bundling functional spec[1]. In case of non-bundle interface going down a part of the sub-interface will be really going down because cable modems connected to different cable interface will get their IP address from the same subnet.
Set upstream port frequency to a fixed value during system installation and testing. Choose this value from your frequency allocation plan for the RF plant segment connected to the upstream.
When the system has reached sufficient stability, the RF domain topology can be entered into the configuration file to enable spectrum management. Spectrum management or frequency agility is configured and activated using spectrum groups.
Frequency-hopping policies supported on all Cisco cable modem cards include combined blind and scheduled specifications, as well as guided frequency hops. The MC16S cable modem card offers additional spectrum management capabilities.
|
Note The cable interface will not operate until you either create and configure a spectrum group or set a fixed upstream frequency. From the interface configuration prompt, an interface is assigned membership in a spectrum group. From the interface point of view, the spectrum group also represents the set of upstreams connected to the same group of fiber nodes. This allows the spectrum manager to know if upstream frequencies need to be managed together. |
To configure and activate frequency agility, perform the following tasks:
Following is an example topology for a Cisco uBR7223 with combiner groups designated A through J. Combiner groups C and E have multiple upstream ports. These should be configured in a shared spectrum group. The other upstreams should be configured in a non-shared spectrum group.
In this example, ten combiner groups are served with frequency hop tables from three spectrum groups:
Cable3/0 DS +-----+ Upconverter +----- laser group 1 U0 +----- combiner group A U1 +----- combiner group B U2 +------combiner group C U3 +------combiner group C U4 +----- combiner group D U5 +------combiner group E Cable4/0 DS +-----+ Upconverter +----- laser group 2 U0 +------combiner group E U1 +----- combiner group F U2 +----- combiner group G U3 +----- combiner group H U4 +----- combiner group I U5 +----- combiner group J
The laser group term refers to the set of fiber nodes that share the same downstream signal. An optical splitter is often used to create individual feeds-per-node.
In the downstream direction, two 6 MHz channel slots are assigned. All fiber nodes in combiner groups A-E should have a channel slot containing the downstream signal from Cable3/0. Combiner groups A-E are said to belong to "laser group 1."
All fiber nodes in combiner groups E-J should have a channel slot containing the downstream signal from Cable4/0. Combiner groups E-J are said to belong to "laser group 2."
Because combiner group E belongs to two laser groups, there should be two different downstream channel slots for Cable3/0 and Cable4/0.
To create a spectrum group, use one of the following general commands in global configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable spectrum-group group-number type scheduled daily | Create a scheduled spectrum group that can change its frequency and power level at the same time every day. |
2. | CMTS01(config)# cable spectrum-group group-number type scheduled periodic-sec seconds | Create a scheduled spectrum group that can change its frequency and power level at a specified interval in seconds. |
Frequency agility is configured and activated using spectrum groups. You can create from 1 to 32 spectrum groups for each cable modem card upstream port.
To create spectrum groups, specify a list of upstream frequencies and nominal power levels that each spectrum group can use when an upstream frequency change is necessary. Each spectrum group should have its own list of upstream frequencies.
After you have created one or more spectrum groups, you can add characteristics to them, providing more definitive control over frequency usage and frequency hopping. See the "Configure and Activate Spectrum Groups" section.
To verify that a spectrum group is created, enter the show cable spectrum-group command:
CMTS01# show cable spectrum-group spectrum-group 1 spectrum-group 2 spectrum-group 3
|
Tips If you are having trouble, make sure you have entered a valid spectrum group number and type. |
After you create a spectrum group, configure a list of upstream frequencies and optional nominal power levels that each spectrum group can use when an upstream frequency change is necessary. Each spectrum group should have its own list of upstream frequencies.
|
Note Valid frequencies are 5,000,000 to 42,000,000 Hz for NTSC operations and 5,000,000 to 65,000,000 for EuroDOCSIS 8 MHz operations. |
To configure and activate a spectrum group, use the following commands in global configuration mode.
| Step | Command | Purpose | ||
|---|---|---|---|---|
1 | CMTS01(config)# cable spectrum-group group-number [time day hh:mm:ss] [delete] frequency ctr-freq-hz [power-level-dbmv] | Add the upstream frequency to the list of valid frequencies with a default power level for a spectrum group.
The power level value should only be changed if you want to change the power level as part of spectrum management. The standard power level is 0 dBmV. |
|
Note Configuring a spectrum group enables frequency agility and disables the fixed upstream frequency setting. |
|
Tips You must repeat the command above for each frequency or power level that you want to add to a spectrum group's list of valid values. |
If your cable plant has an upstream noise characteristic on a weekly cycle, use time-scheduled spectrum allocation:
CMTS01(config)# cable spectrum-group 1 time Mon 08:00:00 frequency 21600000
Deletion is performed using the delete keyword:
CMTS01(config)# cable spectrum-group 1 time Mon 18:00:00 delete frequency 21600000
Below is an example of a spectrum group configuration that is designed to perform minor equalization as a function of frequency.
CMTS01(config)# cable spectrum-group 1 frequency 21600000 CMTS01(config)# cable spectrum-group 1 frequency 24800000 1 CMTS01(config)# cable spectrum-group 1 frequency 28000000 2
In this example, the upstream port nominal receive power at 21.6 MHz is 0 dBmV, at 24.8 MHz is 1 dBmV, and at 28.0 MHz is 2 dBmV. At any time, the power level set in the interface configuration overrides the spectrum group power level.
The example below enables spectrum management for all upstream ports, assuming that all combiner groups use the frequency band from 20-26 MHz:
CMTS01(config)# cable spectrum-group 1 band 20000000 26000000 CMTS01(config)# cable spectrum-group 2 shared CMTS01(config)# cable spectrum-group 2 band 20000000 26000000 CMTS01(config)# cable spectrum-group 3 shared CMTS01(config)# cable spectrum-group 3 band 20000000 26000000 CMTS01(config)# interface Cable3/0 CMTS01(config-if)# cable spectrum-group 1 CMTS01(config-if)# cable upstream 2 spectrum-group 2 CMTS01(config-if)# cable upstream 3 spectrum-group 2 CMTS01(config-if)# cable upstream 5 spectrum-group 3 CMTS01(config-if)# exit CMTS01(config)# interface Cable4/0 CMTS01(config-if)# cable spectrum-group 1 CMTS01(config-if)# cable upstream 0 spectrum-group 3
A description of the spectrum groups 1 through 3 follows:
Upstream Port RF Domain Cable3/0 U0 combiner group A Cable3/0 U1 combiner group B Cable3/0 U4 combiner group D Cable4/0 U1 combiner group F Cable4/0 U2 combiner group G Cable4/0 U3 combiner group H Cable4/0 U4 combiner group I Cable4/0 U5 combiner group J
Upstream Port RF Domain Cable3/0 U2 combiner group C Cable3/0 U3 combiner group C
Upstream Port RF Domain Cable3/0 U5 combiner group E Cable4/0 U0 combiner group E
For the 20-26 MHz band of each RF domain, the spectrum is channelized according to the channel width settings of each member port. For example, if the ports U2 and U3 of Cable3/0 are set to 3.2 MHz and 1.6 MHz channel widths, respectively, then spectrum group 2 uses the following channelization:
> Channel Width Start Stop Center > (Mhz) (Mhz) (Mhz) (Mhz) > 1 3.2 20.0 23.2 21.6 > 2* 1.6 20.0 21.6 20.8 > 3* 1.6 21.6 23.2 22.4 > 4 1.6 23.2 24.8 24.0
|
Note Channels 2 and 3 are not available when channel 1 is in use. |
Because the group is shared, ports U2 and U3 will be assigned channels 1 and 4, respectively, to prevent overlap.
|
Note There are no alternate frequency assignments for either port and bandwidth is wasted from 24.8-to-26.0 MHz. To create alternate channels, increase the upper boundary from 26.0-to-28.0 MHz. |
> Channel Width Start Stop Center > (Mhz) (Mhz) (Mhz) (Mhz) > 1 3.2 20.0 23.2 21.6 > 2 3.2 23.2 26.4 24.8 > 3 1.6 20.0 21.6 20.8 > 4 1.6 21.6 23.2 22.4 > 5 1.6 23.2 24.8 24.0 > 6 1.6 24.8 26.4 25.6 > 7 1.6 26.4 28.0 27.4
Care should be taken to reduce the spectrum allocation when used with small channel widths. Otherwise, there will be a large number of upstream channel slots.
For example, if the allocation is from 20.0-to-28.0 MHz and an upstream port has its channel width set to 0.2 MHz, then there will be 40 possible slots for that channel width. Blind frequency hopping may require quite a long time to find the clean slot since it will try each available slot, one at a time for several seconds each try.
To verify if spectrum groups are configured and activated, enter the show cable spectrum-group command:
CMTS01# show cable spectrum-group
22:07:46: %SYS-5-CONFIG_I: Configured from console by console
Group Frequency Upstream Weekly Scheduled Power Shared
No. Band Port Availability Level Spectrum
(Mhz) From Time: To Time: (dBmV)
1 5.000-15.000 0 Yes
1 12.000 0 Yes
1 22.000 7 Yes
2 29.000 6 No
2 26.000 0 No
3 35.000-41.000 0 No
3 16.000-19.000 5 No
5* 5.000-10.000 Thu 21:50:00 Thu 21:45:00 0 Yes
To verify frequency hopping on the Cisco CMTS, note the following:
After you have established basic operation, inject a tone to the upstream port. For example, if the upstream frequency is currently 22.4 MHz, inject a 22.4 MHz tone at approximately the same power level as the modem. If the power level at the modem is 40 dBmV, set the tone power to 40 dBmV. The interfering carrier should shut down the channel and cause the frequency to change to the next configured value. In this example, it would be 24.0 MHz.
If you do not have an RF tone generator, use another cable modem card and modem that carries traffic. Connect the upstream to the same combiner group, and use the data carrier as an interfering signal by setting it to the same frequency. For example, to test frequency hopping on c3/0, install c4/0 and connect both upstreams together using a combiner. If the upstream frequency of c3/0 is currently 22.4 Mhz, set c4/0 to 22.4 MHz while c4/0 is carrying traffic. This should force c3/0 to change the frequency to the next configured value.
|
Tips If you are having trouble, make sure you entered a valid spectrum group number, time, frequency, and input power level. When defining your spectrum, avoid frequencies with known ingress problems such as amateur radio bands or short-wave bands and spectrum below 20 MHz; allow extra bands for frequency hopping; place upstream ports in the same combiner group in a shared spectrum group; use the receive power level setting to perform slight equalization adjustments. |
Once you have created one or more spectrum groups, add characteristics to them. As stated in Section 6.3.2.2 of the DOCSIS RFI specification, RF channel migration occurs by broadcasting a change in the upstream channel descriptor (UCD) message to all cable modems. The UCD message contains the upstream frequency and transmission parameters associated with an upstream channel.
The speed of channel migration via the UCD message is typically less than 20 milliseconds (ms). During this time, upstream transmission is interrupted until the cable modem transmitter adjusts to its new frequency. Data is stored in the cable modem's buffers during this time and is sent when the frequency hop is complete.
Also, per the DOCSIS RFI, station maintenance intervals are used to perform per-modem keepalive polling. The Cisco CMTS routers poll each cable modem. When ingress noise causes loss of keepalive messages from a configurable percentage of all cable modems, resulting in those cable modems going offline, a new frequency is selected from the allocation table and a UCD update is performed.
|
Note Also see the "Polling Cable Modems" section. |
The migration time is 10 seconds (maximum) for the decision and 20 ms for the frequency hop. The percentage threshold method prevents a single failing cable modem from affecting service to other good cable modems. The system will not hop endlessly because one cable modem is generating 90% of the errors and 90% of the traffic.
The minimum period between frequency hops is also configurable, with a default setting of 300 seconds. If the destination channel is expected to be impaired, the minimum period between frequency hops can be reduced to a small value such as 10 seconds. This allows the frequency hop to continue more rapidly until a clear channel is found. If excessive frequency hop is a concern, the minimum period between hops can be increased.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable spectrum-group groupnum hop threshold percent | Set the percentage of all cable modems losing keepalive messages (going offline) that will cause a frequency hop. |
2. | CMTS01(config)# cable spectrum-group groupnum hop period seconds | Set the minimum time between frequency hops in seconds. Valid values are from 1 to 3600 seconds. |
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable spectrum-group groupnum shared | Specifying a given spectrum group as "shared" tells the Cisco uBR7200 series that you want to be sure that upstream frequencies assigned to upstream interfaces are not assigned to additional upstream interfaces. |
Table 3-33 describes the spectrum group parameters.
| Syntax | Valid Values | ||||
group number | Specifies the spectrum group for which you are specifying a parameter value or specifies the number of the spectrum group you wish to remove from your router configuration. Valid range is from 1 to 32. | ||||
parameter | The spectrum group values that can be changed or added are:
| ||||
value | The corresponding parameter value for the parameter you are defining for a given spectrum group. |
|
Note Using Cisco IOS Release 12.0(7)XR2 and Cisco IOS Release 12.1(1a)T1 or higher, a band parameter is added to enable the frequency range scanning capabilities of the MC16S cable modem card. |
Examples are provided to configure differing spectrum groups:
Use the example below to configure spectrum group 1 with an upstream frequency of 6,500,000 Hz and a default power level of 0 dBmV:
Router(config)# cable spectrum-group 1 frequency 6500000
Use the example below to add the upstream frequency 7,000,000 Hz to the list of valid frequencies with a default power level of 0 dBmV for spectrum group 1:
Router(config)# cable spectrum-group 1 frequency 7000000
Use the example below to configure spectrum group 2 with an upstream frequency 7,500,000 Hz and change the power level to 5 dBmV:
Router(config)# cable spectrum-group 2 frequency 7500000 5
Use the example below to configure spectrum group 3 with an upstream band of 12,000,000 to 18,000,000 Hz and default power level of 0 dBmV:
Router(config)# cable spectrum-group 3 band 12000000 18000000
Use the example below to add the upstream band 20,000,000 to 24,000,000 Hz to the list of valid bands with a change in the power level of 13 dBmV for spectrum group 3:
Router(config)# cable spectrum-group 3 band 20000000 24000000 13
Use the example below to configure a continuous band between 5,000,004 and 40,000,000 Hz for scheduled spectrum group 4 with a default power level of 0 dBmV. The spectrum group will be available to the spectrum group starting at 12:00 p.m. local time each Monday:
Router(config)# cable spectrum-group 4 time Monday 12:00:00 band 5000004 40000000
Use the example below to add the upstream frequency 9,500,000 Hz to the list of valid frequencies and change the nominal power level to 5 dBmV. The spectrum manager adjusts frequencies and power levels on this group at 2:00 a.m. local time each day:
Router(config)# cable spectrum-group 3 time 02:00:00 frequency 9500000 5
Use the example below to configure the minimum period before which a frequency hop can occur in seconds:
Router(config)# cable spectrum-group 3 hop period 800
Use the example below to configure the threshold value (expressed as a percentage) of the number of "offline" modems identified before the Cisco uBR7200 series initiates an automatic frequency hop:
Router(config)# cable spectrum-group 3 hop threshold 40
Use the example below to configure a particular spectrum group as a shared RF spectrum group. Specifying a given spectrum group as "shared" tells the Cisco uBR7200 series that you want to be sure that upstream frequencies assigned to upstream interfaces are not assigned to additional upstream interfaces:
Router(config)# cable spectrum-group 3 shared
Use the example below to remove a specified spectrum group from your configuration:
Router(config)# no cable spectrum-group 3
To verify spectrum group characteristics and to determine if a spectrum group is shared, use the show cable spectrum-group command:
CMTS01# show cable spectrum-group
22:07:46: %SYS-5-CONFIG_I: Configured from console by console
Group Frequency Upstream Weekly Scheduled Power Shared
No. Band Port Availability Level Spectrum
(Mhz) From Time: To Time: (dBmV)
1 5.000-15.000 0 Yes
1 12.000 0 Yes
1 22.000 7 Yes
2 29.000 6 No
2 26.000 0 No
3 35.000-41.000 0 No
3 16.000-19.000 5 No
5* 5.000-10.000 Thu 21:50:00 Thu 21:45:00 0 Yes
|
Tips If you are having trouble, make sure you entered a valid spectrum group number and typein global cable configuration mode. |
After determining which upstream ports you want assigned to a combiner group, perform the following steps to configure a frequency hop table.
| Step | Command | Purpose |
|---|---|---|
| 1 | CMTS01(config)# interface cable slot/port | Enter cable interface configuration mode for the interface to which you wish to assign a spectrum group. |
| 2 | CMTS01(config-if)# cable spectrum-group usport | Assign the spectrum group to the interface. |
| 3 | CMTS01(config-if)# cable upstream number spectrum-group usport | Assign the upstream ports to the spectrum group for the interface. |
4 | CMTS01(config-if)# no cable upstream slot/port shutdown | Place the upstream port in the "admin up" state. |
| 5 | CMTS01(config-if)# exit CMTS01# test cable hop c3/0 CMTS01# test cable hop c3/0 | Exit configuration mode and force the system to hop. |
Use the show cable spectrum-group command to display the current allocation table and frequency assignments.
Use the following command in the configuration command mode to override hop decisions using the MC16S cable modem card:
router(config-if)# cable upstream interface number hopping blind
To stop blind hopping, enter the no form of this command:
router(config-if)# no cable upstream interface number hopping blind
|
Note The interface number specifies the number of the upstream cable interface for which blind frequency hopping is activated. By default, this is disabled. |
|
Caution Do not use this command unless you have a specific reason to disable MC16-based spectrum management enhancements. For example, if you are experimenting with an MC16S card, you can use this command to enforce blind hopping on individual upstream channels. |
Address Resolution Protocol (ARP) is an Internet protocol used to map IP addresses to MAC addresses on computers and other equipment installed in a network. You need to activate ARP requests on the cable interface so that the Cisco uBR7200 series can perform IP address resolution on the downstream path.
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Note The default values for the commands used in this configuration step are adequate in most cases to configure the Cisco CMTS. |
To activate ARP requests, use the following command in cable interface configuration mode:
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable arp | Enable ARP. This is the default. |
To verify if cable ARP is activated, enter the more system:running-config and look for the cable interface configuration information. If ARP is activated, it does not appear in this output. If ARP is deactivated, it appears in the output as no cable arp as shown below:
CMTS01#more system:running-config Building configuration... Current configuration: ! interface Cable6/0 ip address 1.1.1.1 255.255.255.0 no keepalive
no cable arp cable downstream annex B cable downstream modulation 64qam cable downstream interleave-depth 32 cable downstream symbol-rate 5056941 cable upstream 0 frequency 15008000 no cable upstream 0 shutdown
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Tips If you are having trouble, make sure you entered the correct port and cable modem card slot number when you activated ARP and when you entered the show interface cable command. |
Cable proxy ARP allows the Cisco uBR7200 series to issue cable ARP requests on behalf of cable modems on the same cable network subnet.
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Note Because the downstream and upstreams are separate interfaces, modems cannot directly perform ARP with other modems on the cable plant. |
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Note The default values for the commands used in this configuration task are adequate in most cases to configure the Cisco CMTS. |
To activate cable proxy ARP for host-to-host communications, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable proxy-arp | Enable proxy ARP on the cable interface. This is the default. |
To verify if cable proxy ARP has been activated or deactivated, enter the more system:running-config and look for the cable interface configuration information. If cable proxy ARP has been activated, it does not appear in the output. If cable proxy ARP has been deactivated, it appears in the output as no cable proxy-arp as shown below:
CMTS01#more system:running-config Building configuration... Current configuration: ! interface Cable6/0 ip address 1.1.1.1 255.255.255.0 no keepalive
no cable proxy-arp cable downstream annex B cable downstream modulation 64qam cable downstream interleave-depth 32 cable downstream symbol-rate 5056941 cable upstream 0 frequency 15008000 no cable upstream 0 shutdown
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Tips If you are having trouble, make sure you entered the correct port and cable modem card slot number when you activated cable proxy ARP. |
The cable relay agent is for use with DOCSIS-based DHCP servers that utilize option 82 to automatically map the Ethernet MAC address of a host (subscriber PC) with the cable modem to which it is connected.
With the cable relay agent activated, the Cisco uBR7200 series inserts the cable modem MAC address into a DHCP packet when the packet is received from a cable modem or another host. The Cisco uBR7200 series then forwards the packet to the DHCP server.
To activate the cable relay agent, use the following command in cable interface configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable relay-agent-option | Activate the cable relay agent. This is the default. |
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Tips If you are having trouble, make sure you entered the correct port and cable modem card slot number when you activated the cable relay-agent-option. |
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Note A DOCSIS-based DHCP server is required. The DHCP server verifies that the defined IP address, if any, returned to the host is valid for the IP subnet on that downstream interface. The IP address must be unique and valid in the subnet for the subscriber to obtain connectivity. |
Configure the Cisco uBR7200 series so it will either assign primary addresses to cable modems and remote hosts, or assign primary addresses to cable modems and secondary addresses to remote hosts.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable dhcp-giaddr primary | Enable cable DHCP giaddr functionality so that primary addresses are assigned to both cable modems and remote hosts.
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To disable cable DHCP giaddr functionality (the default) after it has been enabled, enter the no cable dhcp-giaddr command in cable interface configuration mode.
To determine if DHCP giaddr is activated, enter the show running-config command and look for the cable interface configuration information. If DHCP giaddr is activated, a notation appears in this output. If DHCP giaddr is deactivated, no entry appears in this output.
To activate Time-of-Day (ToD) service for the Cisco uBR7200 series, use the following command in global configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable time-server enable | Enable Time-of-Day (ToD) service for the Cisco CMTS |
To disable ToD service (the default) after it has been enabled, enter the no cable time-server command or the cable time-server disable command in global configuration mode.
To determine if ToD service is activated, enter the show running-config command and look for the global cable configuration information. If ToD service is activated, an entry appears in this output. If ToD service is deactivated, no entry appears in this output.
You can set additional IP parameters to enable downstream echoing of upstream data. To configure these optional IP parameters, perform the following tasks:
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Note The default values for the commands used in these configuration steps are adequate in most cases to configure the Cisco CMTS. |
The Cisco uBR7200 series echos IP multicast packets by default. To activate IP multicast echo if it has been previously disabled, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable ip-multicast-echo | Enable IP multicast echo. This is the default. |
To disable IP multicast echo, enter the no cable ip-multicast-echo command in cable interface configuration mode.
To determine if IP multicast echo isactivated or deactivated, enter the more system:running-config and look for the cable interface configuration information. If IP multicast echo is activated, there is no notation in the output since this is the default setting. If IP multicast echo is deactivated, a notation appears in the output as shown below:
CMTS01#more system:running-config Building configuration... Current configuration: ! interface Cable6/0 ip address 1.1.1.1 255.255.255.0 no keepalive
no cable ip-multicast-echo cable downstream annex B cable downstream modulation 64qam cable downstream interleave-depth 32 cable upstream 0 frequency 15008000 no cable upstream 0 shutdown
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Tips If you are having trouble, make sure that you have entered the correct slot and port numbers when you entered cable interface configuration mode. |
By default, the Cisco uBR7200 series does not echo IP broadcast packets. To activate IP broadcast echo, use the following command in cable interface configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable ip-broadcast-echo | Enable IP broadcast echo. |
To disable IP broadcast echo once it is enabled, enter the no cable ip-broadcast-echo command in cable interface configuration mode.
To determine if IP broadcast echo is activated or deactivated, enter the more system:running-config and look for a notation in the cable interface configuration information as shown in the excerpt below:
CMTS01#more system:running-config Building configuration... Current configuration: ! interface Cable6/0 ip address 1.1.1.1 255.255.255.0 no keepalive
cable ip-broadcast-echo cable downstream annex B cable downstream modulation 64qam cable downstream interleave-depth 32 cable upstream 0 frequency 15008000 no cable upstream 0 shutdown
To activate packet intercept functionality, use the following commands in cable interface configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config-if)# cable intercept xxxx.xxxx.xxxx | Specify a MAC address on the cable network for which interception capabilities are to be activated. A limit of 10 MACs exist. |
CMTS01(config-if)# no cable intercept xxxx.xxxx.xxxx | Disable interception after it is enabled. |
To configure cable profiles (deviating from defaults), perform the following as necessary:
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Note Also refer to the "Monitor and Maintain QoS for Voice" section. |
In this step, you are defining the elements used in a cable modulation profile. The Cisco CMTS supports up to 8 cable modulation profiles. Profile 1 is the default.
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Caution If you modify a cable modulation profile from default parameters, you are changing the physical layer. Changing physical layer characteristics affects router performance and function; therefore, only an expert should perform this task. |
The following modulation profile values are configurable:
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable modulation-profile profile iuc fec-tbytes fec-len burst-len guard-t mod scrambler seed diff pre-len last-cw uw-len | Create a new cable modulation profile with a profile number or modify an existing profile.
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In the following example, the request burst for cable modulation profile 2 is defined to have 0 fec-tbytes, 16 kbytes fec-len, a burst-len of 1, a guard time of 8, a mod value of qpsk, scrambler enabled with a seed value of 152, differential encoding disabled, a preamble length of 64 bits, a fixed code word length, and 8-bit unique words for upstream unique word length.
CMTS01(config)# cable modulation-profile 2 request 0 16 1 8 qpsk scrambler 152 no-diff 64 fixed uw8
To remove a cable modulation profile, use the no cable modulation-profile profile command in global configuration mode. You can use this command to remove all modulation profiles except for modulation profile 1.
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Tips Entering no cable modulation-profile 1 sets all of the parameters in profile 1 to the default values. |
To determine if a cable modulation profile is created, enter the show cable modulation-profile command.
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Tips The earlier show cable burst-profile command is removed using Cisco IOS Release 12.0(7)XR2 or higher. |
A sample output is shown below:
CMTS01# show cable modulation-profileMo IUC Type Preamb Diff FEC err FEC Scrambl Max Guard Last Scrambl Preamb
length enco correct T seed B time CW offset
bytes size size short1 request qpsk 64 no 0x0 0x10 0x152 1 8 no yes 56
1 initial qpsk 128 no 0x5 0x22 0x152 0 48 no yes 0
1 station qpsk 128 no 0x5 0x22 0x152 0 48 no yes 0
1 short qpsk 72 no 0x5 0x4B 0x152 0 8 no yes 48
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Note If you're using Cisco IOS Release 12.0(7)XR2 or higher, and if you have CBR scheduling parameters and IP precedence rate limits defined in the QoS profile, the command output reveals this. Refer to the "Monitor and Maintain QoS for Voice" section. The show cable modulation-profile and show interface cable commands are enhanced to reflect the state of the new MAC scheduler for the specified upstream port. |
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Tips If you are having trouble, make sure you are in global configuration mode and that you typed the correct modulation profile number and elements when you used the command. |
The Preamble Offset is calculated from the modulation profile entries. The preamble offset is the distance the CMTS looks into the preamble to determine where the preamble starts. The CMTS does not need to look at the entire preamble in all instances. A shorter preamble has less overhead and time associated with that type of burst request. In general, you will want an offset of "0" for initial/station maintenance because you will want to seperate these packets as distinctly as possible.
The offset for QPSK is shorter because of the way DOCSIS specifies the preamble. For QPSK, it only takes a preamble length of 256 bits to separate frames, whereas with 16 QAM, the date rate is much higher. Utilization of a larger preamble is necessary.
The Cisco CMTS supports multiple QoS profiles. QoS profile 1 is used during cable modem registration and QoS profile 2 is the default QoS profile. Both of these profiles are preconfigured and cannot be removed. However, you can modify these profiles and create additional Q0S profiles for various traffic flows.
| Step | Command | Purpose |
|---|---|---|
1. | CMTS01(config)# cable qos-profile groupnum | Create a new QoS profile with a profile number of groupnum , or modify an existing profile.
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2. | CMTS01(config)# cable qos-profile groupnum ip-precedence bits | Set the bits in the Type of Service (ToS) byte that enable you to configure individual data rate limits on a per-modem basis. Valid values are from 0 to 7. |
3. | CMTS01(config)# cable qos-profile groupnum guaranteed-upstream rate | Set the guaranteed minimum upstream rate in kbps. Valid values are from 0 to 100000 kbps. Default = 0 (no reserved rate). |
4. | CMTS01(config)# cable qos-profile groupnum max-burst size | Set the maximum upstream transmit burst size in minislots that the cable modem can send for any single transmit burst. Valid values are from 0 to 255 minislots. Default = 0 (no limit). |
5. | CMTS01(config)# cable qos-profile groupnum max-upstream rate | Set the maximum upstream data rate in kbps that a cable modem using this QoS profile will send. Valid values are from 0 to 100000 kbps. Default = 0 (no upstream rate limit.) |
6. | CMTS01(config)# cable qos-profile groupnum max-downstream rate | Set the maximum downstream data rate in kbps that a cable modem using this QoS profile will receive. Valid values are from 0 to 100000 kbps. Default = 0 (no downstream rate limit.) |
7. | CMTS01(config)# cable qos-profile groupnum priority number | Assign a relative priority number for the upstream traffic associated with this QoS profile. Valid values are from 0 to 7, with 7 being the highest priority. Default = 0. |
8. | CMTS01(config)# cable qos-profile groupnum tos-overwrite value | Overwrite the ToS byte in the IP datagrams received on the upstream before forwarding them downstream. Set the mask bits to a hexadecimal value to help the CMTS identify datagrams for QoS on the backbone. |
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Note You can use a single cable qos-profile command to configure multiple parameters for the selected QoS profile number. |
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Tips Use the no cable qos-profile groupnum command to remove an optional QoS profile, or in the case of QoS profiles 1 and 2, to return the parameters to their default values. |
To determine if a QoS profile has been created, and to see how it is configured, enter the show cable qos profile command:
CMTS01# show cable qos profile
Service Prio Max Guarantee Max Max tx TOS TOS Create B IP
class upstream upstream downstream burst mask value by priv prec
bandwidth bandwidth bandwidth enab enab
1 0 0 0 0 0 0x0 0x0 cmts no no
2 0 64000 0 1000000 0 0x0 0x0 cmts no no
3 0 3120 31200 0 0 0x0 0x0 cmts yes no
4 7 87200 87200 0 0 0x0 0x0 cmts yes yes
5 0 256000 128000 1000000 0 0x0 0x0 cm no yes
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Tips If you are having trouble, make sure you typed the correct QoS profile number and profile elements when you used the command in global configuration mode. |
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Note Cable modems that register continuously and fail consume more resources than cable modems that stay registered. Assign customers who do not pay for service to QoS profile 3. |
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Caution DOCSIS 1.0-certified cable modems that are given a short max-burst size may be unable to transmit large packets to the headend. |
The Cisco CMTS supports the creation of QoS table entries by SNMP or by CM registration requests. You can also configure a Cisco CMTS to dynamically update QoS table entries via SNMP.
To set QoS table access, use one or more of the following commands in global configuration mode.
| Step | Command | Purpose |
|---|---|---|
1. | | Enable SNMP access to create entries in the QoS tables. |
2. | | Enable SNMP access to dynamically update entries in the QoS tables. |
3. | | Enable QoS table entries to be created via CM registration requests. |
4. | | Disable both SNMP access and CM registration access to the QoS tables. |
To verify QoS permissions, enter the show cable qos permission command:
CMTS01# show cable qos permission Create by SNMP Update by SNMP Create by modems no no yes
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Tips If you are having trouble, make sure you typed the correct QoS profile number and profile elements in global configuration mode. |
|
Note QoS profiles can be changed dynamically, permitting service tiers that are time-sensitive. This provides more bandwidth during business hours than on weekends for telecommuter applications. |
To override the provisioned QoS profile of a CM and enforce a CMTS-specified QoS profile, use the following command in global configuration mode.
| Command | Purpose |
|---|---|
CMTS01(config)#cable qos permission enforce index | Assigns the QoS profile, specified by the index number, to all CMs attempting to connect to theCisco CMTS. |
Notice that the CMs are getting their provisioned class of service as indicated by the show cable modem and show cable qos profile commands.
Step 2 Configure any QoS profile at the CMTS with a specific index number (for example index 1) by using the SNMP/CLI.
Step 3 Enter the global command cable qos permission enforce 1.
Step 4 Enter the clear cable modem all reset global configuration command to force the CMs to reregister with the CMTS.
Notice that the CMs are assigned temporarily the CMTS-defined PRE_REGISTRATION QoS profile with index 2 until the CMs register with the CMTS.
Step 5 Use the debug cable reg command to see that the provisioned QoS parameters of the CMs are overwritten at the CMTS during registration. Notice that at the end of the registration, the CM gets the user-enforced QoS profile as indicated by the show cable modem and show cable qos profile commands.
This feature describes the software enhancements to support QoS for voice. These enhancements include improving support for:
| Step | Command | Purpose |
|---|---|---|
1. | Router(config)# cable qos-profile n name | Assigns a name to the QoS profile. |
2. | Router(config)# cable qos-profile n priority | Sets the upstream traffic priority. |
3. | Router(config)# | Sets the maximum upstream traffic rate. |
4. | Router(config)# | Sets the guaranteed upstream traffic rate. |
5. | Router(config)# | Sets the size for unsolicited grants. |
6. | Router(config)# | Sets the interval for unsolicited grants. |
7. | Router(config)# | Sets the maximum rate for upstream transmission bursts. |
8. | Router(config)# | Sets the mask bits to overwrite the Type of Service byte. |
9. | Router(config)# | Sets the maximum downstream traffic rate. |
10. | Router(config)# | Enables baseline privacy. |
11. | Router(config)# | Downstream settings are based on IP precedence. |
| Command | Purpose |
|---|---|
Router# show cable qos profile n | Displays the configuration for the specified profile. |
Router# show interface cable x/y sid | Displays each QoS profile configured for the specified cable interface. |
Router# show interface cable x/y upstream | Displays QoS statistics for the upstream channel. |
The following example shows how the cable router (mgmt) creates a CM with a QoS profile 30:
router(config)# cable qos profile 30 name qostest
router(config)# cable qos profile 30 grant-int 55
router(config)# cable qos profile 30 grant-size 100
router(config)# cable qos profile 30 guaranteed 60000
router(config)# cable qos profile 30 ip-prec 7
router(config)# cable qos profile 30 max-bur 256
router(config)# cable qos profile 30 max-down 3000
router(config)# cable qos profile 30 max-up 6000
router(config)# cable qos profile 30 prior 7
router(config)# cable qos profile 30 privacy
router# show cable qos profile 30
ID Prio Max Guarantee Max Max ToS ToS Create B IP prec.
upstream upstream downstream tx mask value by priv rate
bandwidth bandwidth bandwidth burst enab enab
30 7 6000000 60000000 100000000 256 0x0 0x0 mgmt yes no
To configure a QoS profile, enter the cable qos profile global configuration command. To set default values for profile group numbers 1 or 2, or to remove the QoS profile if no specific parameters remain, enter the no form of this command.
cable qos profile {groupnum | grant-interval {interval} | grant-size {size} | guaranteed-upstream {rate} | ip-precedence {value} | max-burst {rate} | max-downstream {rate} | max-upstream {rate} | name {string} | priority {value} | privacy | ToS-overwrite {value}}Table 3-49 describes the syntax and values for these commands.
| Syntax | Valid Values |
groupnum | QoS profile group number. Qos profiles 1 and 2 are required by the system. QoS profile 1 is used during registration, and QoS profile 2 is the default QoS profile. Both profiles are preconfigured and cannot be removed. However, you can modify these profiles. |
grant-interval | The periodic interval in microseconds at which the CM wants to send the fixed-sized upstream MAC frames. It is used to compute the period between constant bit rate (CBR) slots for the CM. Valid range is 0 through 65535. |
grant-size | The size of the DOCSIS MAC frame the CM wants periodically to send on the upstream transmission. This value in bytes does not include any PHY layer overhead. It includes the complete fixed MAC frame size starting from the frame control byte to the CRC of the protocol data unit (PDU). This parameter is used by the CMTS to set the size of the periodic CBR slot for the CM after adding the PHY overhead. |
guaranteed-upstream | Guaranteed minimum upstream rate in kilobytes per second. Valid values are 0 through 100000. Default value is 0 (no reserved rate). |
ip-precedence | Bits in the ToS byte that enable you to configure individual data rate limits on a per modem basis. Valid values are 0 through 7. |
max-burst | Maximum upstream transmit burst size in bytes that the modem can send for any single transmit burst. Valid values are from 0 to 65535 bytes. Default value is 0 (no limit). |
max-downstream | Maximum downstream data rate in kilobytes per second that a modem using this QoS profile receives. Valid values are from 0 through 100000. Default value is 0 (no downstream rate limit). |
max-upstream | Maximum upstream data rate in kilobytes per second that a modem using this QoS profile receives. Valid values are from 0 through 255. Default value is 0 (no upstream rate limit). |
name | QoS name string. |
priority | Relative priority number assigned to upstream traffic by this QoS profile. Valid values are from 0 through 7 with 7 being the highest priority. Default value is 0. |
privacy | Enables cable baseline privacy. |
ToS-overwrite | Overwrite the ToS field in the IP datagrams received on the upstream before forwarding them downstream (or IP backbone). This parameter sets the hexadecimal mask bits to a hexadecimal value, thereby helping the CMTS identify datagrams for QoS on the backbone. Valid range is from 0x0 to 0xFF. |
value | The value substituted for the ToS value. See ToS-overwrite. |
Refer to the example below to configure QoS profile 4 with guaranteed upstream of 2 kbps, maximum transmission burst of 2, an IP precedence of 7, a maximum downstream rate of 300 kbps, with a priority of 4, cable baseline privacy set, and a ToS-overwrite mask and value byte (in hex) of 0x7:
Router(config)# cable qos profile 4 name Mondayqos Router(config)# cable qos profile 4 guaranteed-upstream 2 Router(config)# cable qos profile 4 max-burst 2 Router(config)# cable qos profile 4 ip-precedence 7 max-downstream 300 Router(config)# cable qos profile 4 priority 4 Router(config)# cable qos profile 4 ToS-overwrite 0x7
To display QoS profiles, use the show cable qos profile privileged EXEC configuration command.
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Note For Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, or higher CMTS images, an optional "verbose" parameter is added: show cable qos profile qos profile index [verbose]. The qos profile index option displays the index of the specified QoS profile. The verbose option displays all details for the specified QoS profile index. |
The following example shows the full QoS table for profile 30:
router# show cable qos profile 30 verbose Profile Index 30 Name test Upstream Traffic Priority 7 Upstream Maximum Rate (bps) 6000000 Upstream Guaranteed Rate (bps) 60000000 Unsolicited Grant Size (bytes) 100 Unsolicited Grant Interval (usecs) 55000 Upstream Maximum Transmit Burst (bytes) 256 IP Type of Service Overwrite Mask 0x0 IP Type of Service Overwrite Value 0x0 Downstream Maximum Rate (bps) 100000000 Created By mgmt Baseline Privacy Enabled yes IP precedence rate limits IP precedence 2 Rate Limit 100000
Table 3-49 describes the fields shown in the show cable qos profile displays.
| Field | Description |
|---|---|
Profile Index | Profile number. |
Name | The name string for this profile. |
Upstream Traffic Priority | Priority level for upstream traffic. |
Upstream Maximum Rate (bps) | Maximum upstream transmission rate in bits per second. |
Upstream Guarantee Rate (bps) | Guaranteed minimum upstream rate in bits per second. |
Unsolicited Grant Size (bytes) | Number of grant-size parameters in bytes. Grant Size is used by the CMTS to set the size of the periodic CBR slot for the CM after adding the PHY overhead. |
Unsolicited Grant Interval (usecs) | Number of unsolicited grant intervals in microseconds. The grant-interval parameter is used to compute the period between CBR slots for the CM. |
Upstream Maximum Transmit Burst (bytes) | Maximum transmit burst size in bytes. |
IP Type of Service Overwrite Mask | Hex value of the mask bits. |
IP Type of Service Overwrite Value | Value of the mask byte. This is the value the CMTS will overwrite into the ToS field (after masking bits specified in the ToS-mask parameter) of the IP datagram before forwarding the datagram into IP backbone/downstream. The IP ToS overwrite feature helps to propagate cable access QoS onto the IP backbone. |
Downstream Maximum Rate (bps) | Minimum upstream transmission rate in bits per second. |
Created by | Identity of the profile creator. |
Baseline Privacy Enabled | Reports yes if Baseline Privacy is enabled for this QoS profile. Reports no if Baseline Privacy is not enabled for this Qos profile. |
IP Precedence rate limits | Value of the IP precedence and the transmission rate limit in bits per second. |
Command | Description |
|---|---|
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In the sample show cable qos profile output response, note the added IP precedence column:
CMTS01# show cable qos profile
Service Prio Max Guarantee Max Max tx TOS TOS Create B IP
class upstream upstream downstream burst mask value by priv prec
bandwidth bandwidth bandwidth enab enab
1 0 0 0 0 0 0x0 0x0 cmts no no
2 0 64000 0 1000000 0 0x0 0x0 cmts no no
3 0 3120 31200 0 0 0x0 0x0 cmts yes no
4 7 87200 87200 0 0 0x0 0x0 cmts yes yes
5 0 256000 128000 1000000 0 0x0 0x0 cm no yes
The software provides QoS based on the CM SID. Every QoS profile carries a parameter maximum downstream rate which is used to provide peak rate limiting and traffic shaping on the downstream. When the particular CM supports combined voice and data traffic, rate exceeded data packets might shut out or delay voice packets, degrading voice quality. As a solution, IP precedence bits are used as a basic differentiator to provide independent rate limits for different traffic streams as desired.
The show interface cable <x>/<y> upstream <port #> command is also enhanced to reflect the current state of the new MAC scheduler for the specified upstream port as shown below:
cmts#show interface cable 3/0 upstream 0
Cable3/0: Upstream 0 is up
Received 68 broadcasts, 0 multicasts, 20811 unicasts
0 discards, 99 errors, 0 unknown protocol
20879 packets input, 0 corrected, 0 uncorrectable
99 noise, 0 microreflections
Total Modems On This Upstream Channel : 2 (2 active)
Default MAC scheduler
Queue[Cont Mslots] 2/104, fifo queueing, 0 drops
Queue[Rng Polls] 0/20, fifo queueing, 0 drops
Queue[CIR Grants] 0/20, fair queueing, 0 drops
Queue[BE Grants] 0/30, fair queueing, 0 drops
Queue[Grant Shpr] 0/30, calendar queueing, 0 drops
Reserved slot table currently has 5 CBR entries
Req IEs 176103, Req/Data IEs 0
Init Mtn IEs 540, Stn Mtn IEs 101
Long Grant IEs 10042, Short Grant IEs 405
Total channel bw reserved 200000 bps
CIR admission control not enforced
Current minislot count : 2099853 Flag: 1
Scheduled minislot count : 2100020 Flag: 1
The show interface sid command is also enhanced to display the type of SID—whether it is "Static" versus "Dynamic".
cmts# show interface cable <x>/<y> sid
Sid | Prim Sid | Type | Online State | Admin Status | QoS | Create Time | IP Address | MAC Address |
2 |
| stat | online | enable | 4 | 12:10:25 | 1.11.51.37 | 0010.7b6b.722d |
4 | 2 | dyn | online | enable | 5 | 12:10:30 | 1.11.51.37 | 0010.7b6b.722d |
You can optimize the physical layer parameters on an upstream channel. An example is provided for physical layer parameters that can be used on the CMTS for upstream channels expected to support high VoIP call density. These parameters minimize the physical layer overhead encountered for each fixed sized (89 bytes) voice packet. The resulting fine tuning gives a direct improvement in the number of CBR voice connections that can be admitted on a single upstream channel.
Configure the following settings for the upstream channel to maximize the number of CBR
connections:
To configure the above modulation profile at the CMTS, use the following commands:
Create a new qpsk modulation profile template <m> with all default parameters, except the "short grant" profile which has special parameters as given below:
cmts(config)#cable modulation-profile <m> qpsk cmts(config)#cable modulation-profile <m> short 2 52 16 8 qpsk scrambler 152 diff 72 shortened uw8
Configure upstream port <n> on a given interface to use minislot size of 8 ticks and above modulation profile template <m>:
cmts(config-if)#cable upstream <n> minislot-size 8 cmts(config-if)#cable upstream <n> modulation-profile <m>
To turn concatenation off or on from the CMTS, use the cable upstream concatenation interface configuration command. To turn off concatenation from the default state of on, use the no form of this command.
cable upstream n concatenation |
Note Concantenation is part of DOCSIS 1.0 extension support. Concatenation must be supported at both the CMTS and the CM. When enabled on both the CMTS and the CM, the CMTS can receive a concatenated burst of multiple MAC frames from the CM. |
| Step | Command | Purpose |
|---|---|---|
1. | Router(config-if)# no cable upstream n concatenation | Turns off concatenation on the specified channel. |
2. | Router(config-if)# cable upstream n concatenation | Turns on concatenation on the specified channel. |
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Tips Concatenation is enabled by default for current cable modem cards. |
|
Caution Turning off concatenation instructs the CM that the CMTS does not want the CM to concatenate. It is actually up to the CM not to concatenate. If the CM concatenates even after the no cable upstream number concatenation interface command is issued, it may concatenate incorrectly. Such a CM is considered noncompliant. |
| Command | Purpose |
|---|---|
Router# show controller cable slot/port | Displays the current status of concatenation for the specified slot and port. |
The following display indicates that concatenation is turned off.
Lab-CMTS#show controller cab 3/0
Interface Cable3/0
Hardware is BCM3210 FPGA
idb 0x6182BE18 MAC regs 0x3D900000 PLX regs 0x3D800000
rx ring entries 1024 tx ring entries 128 MAP tx ring entries 128
Rx ring 0x4B09A400 shadow 0x61849408 head 359
Tx ring 0x4B09C440 shadow 0x6184A478 head 85 tail 85 count 0
MAP Tx ring 0x4B09C880 shadow 0x6184A8E8 head 7 tail 7 count 0
MAP timer sourced from slot 4
throttled 0 enabled 0 disabled 0
Rx: spurious 341 framing_err 0 hcs_err 2 no_buffer 0 short_pkt 2
no_enqueue 0 no_enp 1 miss_count 0 latency 16
invalid_sid 0 invalid_mac 0 bad_ext_hdr_pdu 0 concat 0 bad-concat 0
Tx: full 0 drop 0 stuck 0 latency 1
MTx: full 0 drop 0 stuck 0 latency 9
Slots 68056 NoUWCollNoEngy 15 FECorHCS 2 HCS 0
Req 1803579865 ReqColl 1 ReqNoise 276120 ReqNoEnergy 0
ReqData 0 ReqDataColl 0 ReqDataNoise 0 ReqDataNoEnergy 0
Rng 143099 RngColl 0 RngNoise 3891
FECBlks 0 UnCorFECBlks 0 CorFECBlks 0
MAP FIFO overflow 0, Rx FIFO overflow 0, No rx buf 0
DS FIFO overflow 0, US FIFO overflow 0, US stuck 0
Bandwidth Requests= 0xFFC9
Piggyback Requests= 0xA1D
Ranging Requests= 0x22039
Timing Offset = 0x0
Bad bandwidth Requests= 0x31BC No MAP buffer= 0x0 Cable3/0 Downstream is up Frequency not set, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4 Downstream channel ID: 0 Cable3/0 Upstream 0 is up Frequency 20.208 MHz, Channel Width 1.600 MHz, QPSK Symbol Rate 1.280 Msps Spectrum Group is overridden SNR - Unknown Nominal Input Power Level 0 dBmV, Tx Timing Offset 4667 Ranging Backoff automatic (Start 0, End 3) Ranging Insertion Interval automatic (60 ms) Tx Backoff Start 0, Tx Backoff End 4 Modulation Profile Group 1
concatenation is disabled
The command to create a subinterface over a cable interface is the same as that defined by Cisco IOS for other software applications:
interface cable x/y.nwhere x is the slot number, y is the port number, and n is the subinterface number.
Each created subinterface is assigned a software IDB. The layer 3 packet arriving over a physical cable interface must be assigned an appropriate software IDB to which it belongs. Since each packet that is received over a cable interface is prepended with its associated SID, this can be extracted from the packet and used as the key to find the associated software IDB. The defined cmts_sid_instance_t structure holds information pertaining to the SID and is extended to include the associated software IDB pointer.
The IP address stored in the DHCP reply is matched for its subnet value against the subnet value configured for each of the subinterfaces over the physical cable interface. The subnet information is derived by combining the IP address and the mask value available in the software IDB structure.
The linked list of software IDBs can be accessed from the hardware IDB associated with the physical cable interface. At the time of CM registration, the software IDB address is initialized to null as the mapping is unknown at first.
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Tips In current releases of software, the SID-to-subinterface mapping is done based on the DHCP-assigned IP address and is not user configurable. |
To reduce the number of subnets consumed per Cisco CMTS, cable interface bundling is used. Multiple cable interfaces can share a single IP subnet. An IP subnet is required for each bundle. You can bundle all cable interfaces on a Cisco CMTS into a single bundle.
Using the CLI, first configure a master interface for a cable interface bundle. The master interface has an IP address assigned and is visible for IP routing functionality. After you configure the master interface, add additional cable interfaces to the same interface bundle. Those interfaces must not have an IP address assigned. You can also configure multiple bundle interfaces.
Use the following commands in Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1 or higher, to configure and view cable interface bundles:
[no] cable bundle n masterUp to four interface bundles can be configured. In each bundle, specify exactly one interface as the master interface, using the "master" keyword. In the case of a subinterface over a cable bundle, `x' is the interface number of the bundle master [1]. The subinterface number starts from 1.
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Caution Configure an IP address on the master interface only. An attempt to add an interface to a bundle will be rejected if an IP address is configured and the interface is not specified as a master interface. When bundling cable interfaces, only the interface configured to be the bundle master is allowed to have subinterfaces. An interface that has subinterface(s) defined over it will not be allowed to be part of a bundle. MIB objects on cable interface bundles are not supported as of the date of this publication. |
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Tips Generic cable interface configuration such as source verify or ARP handling will apply to subinterfaces as well. |
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Note If a physical interface goes down, the associated subinterface will also go down. If the subinterface is defined over the cable bundle and the bundle master is shut down or removed, no data packets will be sent to any of the subinterfaces defined over it. Packets will still be received from non-master interfaces, but will be dropped. |
| Command | Purpose |
|---|---|
Router(config-if)# cable bundle n master | Configures the interface n to be the master interface in a bundle. Valid range is 1 to 255. |
| Command | Purpose |
|---|---|
Router# show cable bundle n forwarding-table | Displays the forwarding table for the specified interface. |
This section provides the following configuration examples:
Router(config-if)#cable bundle ? <1-255> Bundle number Router(config-if)#cable bundle 25 ? master Bundle master <cr> Router(config-if)#cable bundle 25 master ? <cr> Router(config-if)#cable bundle 25 master Router(config-if)# 07:28:17: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to down 07:28:18: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to up Router#show cable bundle 25 forwarding-table MAC address Interface 0050.7366.17ab Cable3/0 0050.7366.1803 Cable3/0 0050.7366.1801 Cable3/0
Use the cable bundle interface configuration command to configure a cable interface to belong to a bundle. Specify the bundle identifer—1 to 255. Optionally define the specified interface as the master.
Specify IP networking information, including IP address, routing protocols, and switching modes, on the bundle master. Do not specify generic IP networking information on bundle slave interfaces.
If you attempt to add an interface to a bundle as non-master interface and an IP address is assigned to this interface, the command will fail. You must remove the IP address configuration before you can add the interface to a bundle.If you have configured an IP address on a bundled interface and the interface is not the master interface, a warning message appears.
Specify generic (that is, not downstream or upstream related) cable interface configurations, such as source-verify or ARP handling, on the master interface. Do not specify generic configuration on non-master interfaces.
If you configure an interface as part of a bundle and it is not the master interface, all generic cable configuration for this interface is removed. The master interface configuration will then apply to all interfaces in the bundle.
If you shut down or remove the master interface in a bundle, no data packets are sent to any of the interfaces in this bundle. Packets will still be physically received from non-master interfaces which have not been shut down, but those packets will be discarded. This means that CMs connected to those interfaces will not be disconnected immediately, but CMs coming online will not be able to obtain an IP address, download their DOCSIS configuration file, or renew their IP address assignment if the DHCP lease expires.
If you shut down a slave interface, only the specific interface is affected. See the following example to configure interface 25 to be the master interface:
Router(config-if)#cable bundle 25 master Router(config-if)# 07:28:17: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to down 07:28:18: %UBR7200-5-UPDOWN: Interface Cable3/0 Port U0, changed state to up
The following example shows an error message you receive if you try to configure an interface with an IP address that is not the master interface:
Router(config-if)#cable bundle 5 Please remove ip address config first then reenter this command
To display the forwarding table for a specified interface, use the show cable bundle privileged EXEC command. A sample is shown below:
Router#show cable bundle 25 forwarding-table MAC address Interface 0050.7366.17ab Cable3/0 0050.7366.1803 Cable3/0 0050.7366.1801 Cable3/0
Cisco CMTS routers support DOCSIS-based telco return communication from remote CMs.
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Note DOCSIS telco return is supported only in Cisco CMTS IOS software images that contain a "t" in the file name or in the feature set description.Telco return is supported in Cisco CMTS 12.0(5)T1 and higher. The third-party telco-return CM must also be DOCSIS telco-return compliant. |
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Tips The Cisco IOS Release 12.0 SC train does not support telco return. If you do not have a software image that supports telco return, download the software from Cisco Connection Online (CCO). |
The example below shows how to configure a Cisco uBR7200 series router to support telco return:
ubr7223#conf t Enter configuration commands, one per line. End with CNTL/Z. ubr7223(config)#int c2/0 #cable telco-return enable ubr7223(config-if)#cable telco-return spd 1 factory-default ubr7223(config-if)#cable telco-return spd 1 phonenum 8005551212 ubr7223(config-if)#cable telco-return spd 1 phonenum 4085551212 ubr7223(config-if)#cable telco-return spd 1 phonenum 6505551212 ubr7223(config-if)#cable telco-return spd 1 service-provider norcal ubr7223(config-if)#cable telco-return spd 1 dhcp-server 172.172.172.172 ubr7223(config-if)#cable telco-return spd 1 username joe ubr7223(config-if)#cable telco-return spd 1 password password ubr7223(config-if)#cable telco-return spd 1 dhcp-authenticate ubr7223(config-if)#cable telco-return spd 1 threshold 5 ubr7223(config-if)#cable telco-return spd 1 ppp-authenticate both ubr7223(config-if)#cable telco-return spd 1 manual-dial ubr7223(config-if)#cable telco-return spd 1 dial-timer 7200
Key telco-return commands include:
To enable telephone return support, use the cable telco-return enable interface configuration command. Use the no form of this command to disable the feature:
ubr7233(config-if)# cable telco-return enableThe command has no arguments or keywords. The cable telco-return enable command enables or disables the telco return feature. The cable telco-return interval defines the interval for sending Telephony Channel Descriptor (TCD) and Termination System Information (TSI) messages.
To specify the intervals for sending TCD enrollment messages and TSI messages, use the cable telco-return interval interface configuration command. Use the no form of this command to set the time interval to the default:
ubr7233(config-if)# cable telco-return interval secondsThe seconds specifies the number of seconds for TCD or TSI messages. Valid range is from 2 to 60 seconds with 2 seconds being the default.
To set the DHCP authenticate parameter in TCD messages as TRUE, which specifies the DHCP server that must be used, use the cable telco-return spd dhcp-authenticate interface configuration command. Use the no form of this command to set the DHCP authenticate parameter to the default value and remove the parameter from subsequent TCD messages:
ubr7223(config-if)# cable telco-return spd number dhcp-authenticateThe spd number specifies the Service Provider Descriptor (SPD) number; the default is False (0). The DHCP authenticate parameter, which is an optional parameter, is expressed as a boolean value. The cable telco-return spd dhcp-server specifies the IP address of the DHCP server parameter in TCD messages. The cable telco-return spd dial-timer specifies the Demand Dial Timer TCD parameter for TCD messages. The cable telco-return spd factory default indicates the factory default service provider descriptor (SPD) used by CMs. The cable telco-return spd ppp-authenticate specifies the PPP authentication parameter in TCD messages. The cable telco-return spd phonenum specifies the telephone numbers parameter in TCD messages. The cable telco-return spd threshold specifies the connection attempt rhreshold parameter for TCD messages.
To specify the IP address of the DHCP server parameter in TCD messages, use the cable telco-return spd dhcp-server interface configuration command. Use the no form of this command to set the default value and remove the parameter from subsequent TCD messages:
cable telco-return spd number dhcp-server ip address To specify the demand dial timer TCD parameter for TCD messages, use the
cable telco-return spd dial-timer EXEC command. Use the no form of this command to set the default value and remove the dial-timer parameter from subsequent TCD messages:
The spd number specifies the SPD number. The dial-timer seconds specifies the number of seconds of the Demand Dial Timer parameter for TCD messages; valid range is from 0 to 4294967295.
To indicate the SPD used by CMs during the factory default procedure, use the cable telco-return spd factory-default interface configuration command. Use the no form of this command to disable this feature:
cable telco-return spd number factory-defaultTo specify the manual dial parameter in TCD messages, use the cable telco-return spd manual-dial interface configuration command. Use the no form of this command to remove the parameter from subsequent TCD messages:
cable telco-return spd number manual-dialTo specify the login password parameter in TCD messages, use the cable telco-return spd password interface configuration command. Use the no form of this command to remove the parameter from subsequent TCD messages:
cable telco-return spd number password stringThe string parameters specify the log in password.
To specify the telephone numbers parameter in TCD messages, use the
cable telco-return spd phonenum interface configuration command. Use the no form of this command to delete any or all previously entered telephone numbers:
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Tips You can enter up to three telephone numbers that are mapped to the telephone numbers parameters (in TCD messages). The phone numbers appear as phone number 1, phone number 2, and phone number 3 in the order in which you enter them. |
To specify the PPP authentication parameter in TCD messages, use the
cable telco-return spd ppp-authenticate EXEC command. Use the no form of this command to remove the parameter from subsequent TCD messages:
| Syntax | Valid Values |
spd number | Specifies the Service Provider Descriptor (SPD) number. |
both | Specifies PAP and CHAP authentication. |
chap | Specifies CHAP authentication. |
pap | Specifies PAP authentication. |
To specify the RADIUS Realm Service Provider Descriptor (SPD) parameter in TCD messages, use the cable telco-return spd radius-realm interface configuration command. Use the no form of this command to remove the parameter from subsequent TCD messages:
cable telco-return spd number radius-realm stringTo specify the Service Provider Name parameter in TCD messages, use the cable telco-return service-provider interface configuration command. Use the no form of this command to remove the parameter from subsequent TCD messages:
cable telco-return spd number service-provider string (where string specifies the service provider name)To specify the connection attempt threshold parameter for TCD messages, use the cable telco-return spd threshold interface configuration command.
Use the no form of this command to set the default threshold:
cable telco-return spd number threshold number
| Syntax | Valid Values |
spd number | Specifies the SPD number. |
threshold number | Specifies the connection attempt threshold. Valid range is from 1 to 255. |
To specify the login username parameter in TCD messages, use the cable telco-return spd username interface configuration command. Use the no form of this command to remove the parameter from subsequent TCD messages:
cable telco-return spd number username stringThe following debug commands apply to telco-return:
To display debug messages for telco-return events, use the debug cable telco-return EXEC command. Use the no form of this command to disable debugging output.
To display debug messages for telco-return events, use the debug cable telco-return msg EXEC command. Use the no form of this command to disable debugging output.
To verify that the subscriber modem can log in to the CMTS in telco-return mode:
Step 2 Allow the subscriber modem to complete telco registration (will take several minutes).
Step 3 Enter the show cable modem command on the Cisco CMTS to verify that the CM in the list contains the letter "T." This indicates that the CM supports telco-return.
A sample appears below:
ubr7246-1#show cable modem
Interface Prim Online Timing Rec QoS CPE IP address MAC address
Sid State Offset Power
Cable4/0/U0 2 online 2848 -0.50 5 1 10.2.0.3 0010.7b6b.53d5
Cable4/0/T 3 offline 0 0.00 2 1 10.2.0.101 0020.4001.4af6
Cable4/0/U0 4 online 2852 -0.75 5 1 10.2.0.6 0010.7b6b.7255
Cable4/0/U0 5 online 2850 0.25 5 1 10.2.0.7 0010.7b6b.5669
Cable4/0/U0 6 online 2851 0.00 2 1 10.2.0.4 0010.7b6b.53c9
Cable4/0/T 7 offline 0 0.00 2 0 10.2.0.102 0020.4001.4b32
Step 4 Ping the CM from the Cisco CMTS to ensure the Cisco CMTS receives the echo reply packets.
Posted: Mon Oct 2 13:17:33 PDT 2000
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