Table of Contents

Cisco uBR924 Cable Access Router Description

Physical Description
Power Supply
Physical Specifications
Compliance with U.S. Export Laws and Regulations Regarding Encryption

Data Operations

Operating Modes
Data Specifications
Service Assignments
Provisioning
Provisioning Prerequisites
Downstream and Upstream Operations

Downstream
Upstream

IP Telephony

Voice Handling

H.323 Protocol Stack
SGCP Protocol Stack

Voice Specifications
Backup POTS Connection

Cisco IOS Release Images

Cisco IOS Release 12.0(4)XI Images
Cisco IOS Release 12.0(5)T Images

Installing the Router at the CMTS

Overview

This chapter describes the Cisco uBR924 cable access router and its interaction with the Cable Modem Termination System (CMTS)---the cable system headend equipment that enables data and digitized voice connectivity between Internet Protocol (IP) hosts and connected subscribers over the broadband infrastructure. The chapter provides physical and functional overviews of the Cisco uBR924 cable access router and its supported operating modes.

The chapter includes the following sections:

• Cisco uBR924 Cable Access Router Description

• Data Operations

• IP Telephony

• Cisco IOS Release Images

Cisco uBR924 Cable Access Router Description

The Cisco uBR924 cable access router gives residential or Small Office/Home Office (SOHO) subscribers high-speed Internet or Intranet access, and IP telephony services via a shared two-way cable system and IP backbone network. The router connects computers, telephone or fax equipment, and other customer premises devices at a subscriber site to the service provider's Hybrid/Fiber Coax (HFC) and IP backbone network.

The router is based on Data Over Cable Service Interface Specifications (DOCSIS) and interoperates with any bidirectional, DOCSIS-qualified CMTS. The router typically ships from the Cisco factory with a Cisco Internetwork Operating System (IOS) software image stored in nonvolatile memory (NVRAM) that supports DOCSIS-compliant bridging data operations. The Cisco  uBR924 cable access router functions as a cable modem---a modulator/demodulator at a subscriber site to convey data communications on the cable television system.

Based on the feature licenses your company purchased, other Cisco IOS images can be downloaded from Cisco Connection Online (CCO). Each Cisco uBR924 cable access router in your network can then be configured to support Voice over IP (VoIP) and/or other special operating modes based on your service offering and the practices in place for your network. The Cisco uBR924 can function as an advanced router, providing wide area network (WAN) data connectivity in a variety of configurations.

To ensure compliance with U.S. export laws and regulations for Data Encryption Standard (DES), refer to the "Compliance with U.S. Export Laws and Regulations Regarding Encryption" section of this chapter.

Updated Cisco IOS images can be downloaded to Cisco uBR924 cable access routers installed in the field. Refer to the "Provisioning" section of this chapter for an understanding of the processes to configure a Cisco uBR924 cable access router. Also refer to the "Cisco IOS Release Images" section of this chapter for identification of the Cisco IOS images and their supported operating modes. Refer to the "Downloading Specific Cisco IOS Images" section of Chapter 5 for a description on how to download an updated software image to a Cisco uBR924 installed in the field.

Physical Description

The Cisco uBR924 cable access router is a compact, easy-to-install device that contains:

• A single F-connector interface to the cable system.

• Four RJ-45 (10BaseT Ethernet) hub ports to connect computers or other Ethernet devices to the Ethernet hub ports at the rear of the unit:

  • Using Cisco IOS Release 12.0(4)XI or higher interim builds, up to three computers can be connected directly when in bridging mode. When in routing mode, four computers can be connected directly, or one of the Ethernet hub ports can be connected to an Ethernet hub which then connects additional devices at the site.

  • Using Cisco IOS Release 12.0(5)T or higher interim builds, up to four computers can be connected directly when in bridging or routing mode. One of the Ethernet hub ports can be connected to an Ethernet hub which then connects additional devices at the site. A maximum of 254 devices can be bridged. When configured for routing, no maximum limit exists.

• Two RJ-11 Foreign Exchange Station (FXS) ports to connect telephones and fax devices to the cable system and IP backbone; the router typically ships from the Cisco factory with the voice ports disabled.

• One RJ-11 port to connect to a standard, analog telephone line (optional) to provide a backup Plain Old Telephone Service (POTS) connection to the Public Switched Telephone Network (PSTN) should the Cisco uBR924 cable access router lose power.

• One RJ-45 console port (optional) to connect to a laptop PC or console terminal when locally configuring the router; the router ships from the Cisco factory with the console port enabled.

Figure 1-1 depicts the front of the Cisco uBR924 cable access router. Figure 1-2 shows the rear of the unit.

Figure 1-1: Cisco uBR924 Cable Access Router Front View

Cisco uBR924 Cable Access Router Rear View

As Figure 1-2 shows, the Cisco uBR924 contains two FXS VoIP ports that are labelled V1+V2 and V2 at the rear of the unit. These ports can be connected directly to telephones or fax devices, or to adapters that allow multiple telephones or fax devices to be connected to each of the two VoIP telephone lines. The Ringer Equivalence Number (REN) determines how many telephones or fax devices can be connected to a telephone line.

Five to ten voice devices can be connected to each of the two VoIP telephone lines, provided each telephone line does not exceed the 5 REN limit.

Typical length of telephone wire is 3,000 or more feet of 26 guage. Cisco uBR924 cable access routers, therefore, can support the number of telephones or fax devices typically found in small businesses.

The V1+V2 port on the Cisco uBR924 is a 4-wire port, with the second telco pair wired in parallel with V2. A two-line telephone can be connected, therefore, to the V1+V2 port.

Do not connect the V1+V2 and V2 ports to telephone wires that exit the building without appropriate agency-approved protection devices. This is a safety hazard.

Warning The REN assigned to each voice device denotes the percentage of the total load to be connected to a telephone loop which is used by the device to prevent overloading. The termination on a loop may consist of any combination of devices subject only to the requirement that the total REN of all the devices does not exceed five (5.0).

The Cisco uBR924 cable access router is designed to work with commercial security products, such as Kensington-compatible lock and cable devices, that attach to the router to prevent theft in small office applications. The router's rear panel contains generic lock and unlock symbols, identified as "Lock" in Figure 1-2.

The Cisco uBR924 cable access router contains no power switch. After the cable system technician installs, connects, powers on, and initializes the unit, it is intended to remain connected to the broadband network when operating normally.

Power Supply

The Cisco uBR924 cable access router uses an external AC-input power supply. Refer to Table 1-1 for the AC-input power supply power specifications, including input voltage and operating frequency ranges.

The same power supply supports both domestic (U.S.) and international operation. Different power cords are available, however, based on the country of operation.

Use only a Cisco-provided power supply and cord. Using any other vendors's power supply and cord can cause loss of data or permanent damage. Cisco uBR924 and Cisco uBR904 power supplies and cords are identical and interchangeable, provided the power cords are applicable to the country of operation.

Warning Read the installation instructions before you connect the system to its power source.

Physical Specifications

Table 1-1 lists the Cisco uBR924 cable access router physical specifications and power requirements.

Compliance with U.S. Export Laws and Regulations Regarding Encryption

The U.S. Government regulates products that perform encryption/decryption. Information regarding compliance with U.S. export laws and regulations follows:

• Products performing encryption/decryption are not authorized for use by persons located outside the United States and Canada that do not have export license authority from the U.S. Government.

• Products may not be exported outside the U.S. and Canada either by physical or electronic means without the prior written approval of the U.S. Government.

• Persons outside the U.S. and Canada may not reexport, resell, or transfer products by either physical or electronic means without prior written approval of the U.S. Government.

Data Operations

Figure 1-3 illustrates a broadband data cable system. Data transmitted to a Cisco uBR924 cable access router from the CMTS shares a 27 or 26 Mbps, 6 MHz data channel in the 88 to 860 MHz range. The Cisco uBR924 cable access router shares an upstream data rate of up to 10 Mbps on a 200 kHz-wide to 3.2 MHz-wide channel in the 5 to 42 MHz range.

Figure 1-3: Cisco Broadband Data Cable System Illustration

Operating Modes

The system uses multiple types of access control to ensure efficient use of bandwidth over a wide range of loading conditions. Advanced queuing techniques and service algorithms are used to define the acquisition and release of channels.

The Cisco uBR924 cable access router supports 64 or 256 Quadrature Amplitude Modulation (QAM) downstream, and Quadrature Phase Shift Keying (QPSK) or 16 QAM upstream transmission. This allows the CMTS system administrator to set the preferred modulation scheme based on the quality of the cable plant.

The system uses Transmission Control Protocol/Internet Protocol (TCP/IP) to transmit data. TCP/IP transmits data in segments encased in IP datagrams, along with checksums to detect data corruption and sequence numbers to ensure an ordered byte stream on the TCP connection between the Cisco uBR924 and the CMTS.

The Cisco uBR924 also supports multicast services---data streams sent to groups of subscribers. These applications utilize the User Datagram Protocol (UDP), instead of TCP. Since UDP does not mandate upstream acknowledgments, these applications can be very efficient in the network. Additionally, restricting upstream throughput will have no effect on downstream UDP streaming throughput.

Data Specifications

Table 1-2: Cisco uBR924 Cable Access Router Data Specifications

Description	Downstream Values	Upstream Values
Frequency Range	88 to 860 MHz	5 to 42 MHz
Modulation	64 QAM 256 QAM	QPSK 16 QAM
Data Rate	30 Mbps/64 QAM (27 Mbit/sec after FEC overhead) 42.8 Mbps/256 QAM (36 Mbit/sec after FEC overhead)	QPSK---320 Kbit/sec to 5 Mbit/sec 16 QAM---640 Kbit/sec to 10 Mbit/sec
Bandwidth	6 MHz	200K, 400K, 800K, 1.6M, 3.2 MHz
FEC	RS (122, 128) Trellis	Reed Solomon
One Channel	Receive level of digital signal -15 to +15 dBmV Note Most field measurements are of nearby or adjacent analog signal which is normally +6 to +10 dB (system specific) above the digital signal level	QPSK--- +8 to +58 dBmV 16 QAM--- +8 to +55 dBmV
Signal-to-Noise Ratio (SNR)	64 QAM: >23.5 dB @ BER<10^8 256 QAM*: >30 dB @ BER <10^-8 (For input level between +15 and -8 dBmV, SNR must be greater than 30 dB. For input level between -8 and -15 dBmV, SNR must be greater than 33 dB.) Note These performance numbers are in laboratory-controlled conditions, against statistically pure noise sources (AWGN). Since such conditions do not exist in practise, a 6 or more dB SNR margin is required for reliable operation. Check with your local system guidelines.	QPSK: >15 dB @ BER<10^-8 (QPSK will work at 98% successful ping rate for SNR>13 dB. An SNR of 15 dB will be needed to get almost optimal packets per minute transition.) 16 QAM: >22 dB @ BER <10^-8 (For 16 QAM, an SNR>22 dB makes the grade for 98% ping efficiency. To get good packet rate, you need SNR>25 dB) Note These measurements were done for 0 and -10 dBmV input to the CMTS, 1280 ksym/sec and 64 bytes packet size with a Cisco uBR904 and laboratory-controlled conditions.
Security	DES decryption: DOCSIS Baseline Privacy (BPI), 40 bit-, 56 bit- and 168 bit DES encryption, as controlled by the headend and configuration files. Note Cisco IOS images must contain encryption software at both the CMTS and the Cisco uBR924. Both routers must be enabled and properly configured to support encryption.	DES encryption

Service Assignments

Each Cisco uBR924 cable access router on the network is configured to receive data on a particular downstream channel. A downstream channel contains upstream segment(s). Each upstream segment typically serves more than one fiber node.

Partitioning the upstream plant into smaller segments significantly reduces the number of potential ingress sources and failure points. The CMTS divides the cable plant into downstream channels and upstream segments or clusters of nodes.

Provisioning

The Cisco uBR924 cable access router arrives from the Cisco factory with a unique identifier (UID) that consists of a serial number and Media Access Controller (MAC) address. You can find the factory-assigned values on a label at the bottom of the router. These values are also barcoded and can be scanned in.

The router ships from the Cisco factory ready to work in a DOCSIS-compliant bridging data mode. To enable the Cisco uBR924 voice ports and/or other special operating modes after you have purchased the appropriate software licences and downloaded the images from CCO, you can provision the Cisco uBR924 in a number of ways. If your billing and administrative system supports automatic feature upgrades, you can enter the MAC address of each Cisco uBR924 cable access router in your billing and administrative system, designate the feature set to support, and have the system download the required image. Alternatively, you can issue Cisco uBR924 cable access routers from your warehouse pre-configured with appropriate Cisco IOS release images. You can then use the configuration editor of your choice to create a configuration file to download to the Cisco uBR924 cable access router.

Figure 1-4 illustrates the router provisioning processes at a high level. For more detail, reference the DOCSIS 1.0 Radio Frequency Interface (RFI) specification.

Figure 1-4: Cisco uBR924 Cable Access Router Provisioning Overview

After downloading its configuration file, the router builds a registration request, inserts CoS parameters from this file, and sends this to the CMTS. The CMTS parses the registration request, extracts the CoS profile, verifies the profile with its local database, and converts the temporary SID into a data SID with a service class index that points to the applicable CoS profile. Based on the supported operating mode, the CMTS and router negotiate encryption/decryption as appropriate. Refer to the "Cisco IOS Release Images" section for a description of the feature sets. The router completes secondary ranging and is then operational.

Provisioning Prerequisites

Before a router can be provisioned:

• All required CMTS routing and network interface equipment must be installed, configured, and operational. This includes all headend routers, servers (DHCP, TFTP and TOD), network management systems, and/or other configuration or billing systems in use in your network.

• Based on the quality and capacity of your cable plant, your system administrator or network planner must have defined your network's IP address allocation plan; spectrum management plan outlining the recommended operating parameters to optimize performance; channel plan identifying the channels available to assign to specific Cisco uBR924 cable access routers; and dial plan based on the supported VoIP protocol.

• A CMTS Customer Service Representative (CSR) must have recorded all needed subscriber information, initiated a work order, and arranged an installation date with the subscriber. For subscriber sites that support multiple telephones or fax devices on a telephone line, all wiring associated with the telephone line extension must be in place. Inside wiring must be in compliance with the country of operation to prevent degradation of service.

• The CMTS system administrator or appropriate personnel must have specified the policy parameters for the Cisco uBR924 and all computers and other customer premises devices to be supported at the subscriber site. Reference Cisco's Network Registrar (CNR) product documentation.

• The CMTS system administrator or appropriate personnel must have defined and pushed DHCP and Cisco uBR924 configuration files to the appropriate servers such that each router, when initialized, can transmit a DHCP request, receive its IP address, obtain its TFTP and TOD server addresses, and download its configuration file (or updated Cisco IOS image).

• The CMTS system administrator must ensure appropriate databases are updated to activate and support the new subscriber account in the provisioning, billing and/or network management systems in place for your network once each router is registered with the CMTS.

Downstream and Upstream Operations

Downstream

When operating normally, the Cisco uBR924 receives data addressed to it from the CMTS. The router reads the address in the header of the message, filters the message and forwards it to the appropriate device at the subscriber site.

Upstream

The Cisco uBR924 uses a request/grant mechanism to obtain upstream bandwidth. The CMTS configures, via MAC messages, upstream parameters associated with transmissions from all Cisco uBR924 cable access routers on the system. Service class registration is granted based on class assignment and load provisioning. Upstream channels are time slotted and divided into basic scheduling time units.

The CMTS informs the Cisco uBR924 of minislot structures on the upstream channel. Some minislots are marked as contention-based---shared by routers to make bandwidth (timeslot) requests with the CMTS. Others are grouped together into unicast grants for specific routers to send their data bursts. Yet others are grouped together into maintenance slots for "keep alive" messages from routers to the CMTS.

IP Telephony

The Cisco uBR924 cable access router uses packets to transmit and receive digitized voice over an IP network. Voice signals are packetized and transported in compliance with H.323 or Simple Gateway Control Protocol (SGCP). H.323 is an International Telecommunications Union (ITU) standard that specifies call signaling and control protocols for a shared IP data network. SGCP is a Cisco/Bellcore-developed, out-of-band signaling protocol under review by the Internet Engineering Task Force (IETF).

Figure 1-5 illustrates a broadband cable system that supports VoIP transmission. Quality of Service (QoS) and prioritization schemes are used to enable real-time (voice) and non-real-time traffic to coexist on the same channel. The CMTS routes IP telephony calls, intermixed with other data traffic.

Figure 1-5: Simplified VoIP Network Illustration

Voice Handling

With IP telephony, telephone calls can be delivered at rates as low as 8 kbps in a packet format using compression algorithms. The Cisco uBR924 cable access router supports compression and decompression algorithms (CODECs) ranging from:

• G.711 A Law 64000 bps

• G.711 u Law 64000 bps

• G.723.1 5300 bps

• G.723.1 6300 bps

• G.726 16000 bps

• G.726 24000 bps

• G.726 32000 bps

• G.728 16000 bps

• G.729 Annex-A 8000 bps

• G.729 8000 bps --- Default CODEC for telephone calls

  Because voice is delay-sensitive, a well-engineered network is critical. Fine-tuning your network to adequately support VoIP typically involves a series of protocols and features geared to support QoS.

To achieve acceptable voice quality and reduce network bandwidth usage, several voice processing techniques are used. Digital Signal Processors (DSPs), in combination with DSP firmware in the Cisco uBR924 cable access router, provide the stream-to-packet and packet-to-stream conversion, as well as voice processing capabilities. Typical voice processing services include echo cancellation, voice compression, Voice Activity Detection (VAD) or silence compression, and Dual Tone Multi Frequency (DTMF) tone detection and generation.

The Cisco uBR924 cable access router is able to implement multiple classes of service on the cable interface. The router is based on DOCSIS 1.0 standards, but includes multiple QoS SID support. Cisco IOS Release 12.0(4)XI or higher headend images support multiple Classes of Service (CoS) per Cisco uBR924.

The system can treat VoIP and data traffic separately, keeping all data on a default class of service, while using a higher priority for the VoIP traffic that originates on the Cisco uBR924's telephone ports. This ensures voice traffic from the Cisco uBR924's telephone ports takes precedence over the data traffic coming from the Ethernet interface. Supporting separate classes of service provides the best available throughput for traffic.

The Cisco uBR924 cable access router supports the following service classes:

• The first CoS in the router's configuration file is configured as the "Tiered Best Effort Type Class" used by the router as the primary QoS for all regular data traffic. The class has no minimum upstream rate specified for the channel.

This service class results in the assignment of a primary SID for the router. In addition to being used as a data SID, the router uses this SID for all MAC message exchanges with the CMTS. Any SNMP management traffic from the network to the Cisco uBR924 will also use this SID.

While this class is strictly "best effort", data traffic within this class can be prioritized into eight different priority levels. The CMTS system administrator, however, must define the supported upstream traffic priority levels and include the traffic priority fields in the configuration file downloaded to the Cisco uBR924.

• The CMTS system administrator when creating a configuration for the Cisco uBR924 typically configures extra classes of service. These secondary classes of service are expected to be higher QoS classes and are used by higher priority traffic such as voice. These classes have a minimum upstream rate specified for the channel.

The multiple SID-per-router feature enables the Cisco uBR924 cable access router to use multiple SID queues for differentiated services. The Cisco uBR924 diverts voice call traffic to the higher QoS secondary SID, while forwarding "best effort" data from the Ethernet interface and MAC messages on the primary SID.

H.323 Protocol Stack

In architectures using the VoIP H.323 protocol stack, the session application manages two call legs for each call: a telephony leg managed by the voice telephony service provider and the VoIP leg managed by the cable system operator---the VoIP service provider. Use of the H.323 protocol typically requires a dial plan and mapper at the headend or other server location to map IP addresses to telephone numbers.

When both legs of the call have been setup, the session application creates a conference between them. The opposite leg's transmit routine for voice packets is given to each provider. The CMTS router passes data to the gateway and gatekeeper. The H.323 stack provides signalling via H.225 and feature negotiation via H.245.

To make and receive H.323 calls, the Cisco uBR924 cable access router must know:

• The IP address of the gateway for the destination dialed---In Cisco uBR924 IOS Release 12.0(4)XI or higher interim builds, you configure these IP addresses statically via the Command Line Interface (CLI) using voip dial peer group commands. When running Cisco IOS Release 12.0(5)T or higher on Cisco gatekeeper products, you can obtain these addresses dynamically from the gatekeeper using Registration, Admission, and Status (RAS).

• The telephone numbers of the attached devices---In Cisco IOS Release 12.0(4)XI or higher interim builds, you configure these IP addresses statically via the CLI pots port commands. When using Cisco Network Registrar (CNR) version 3.0 or higher with the relay.tcl and setrouter.tcl scripts, and Cisco gatekeeper products in your network running Cisco IOS Release 12.0(5)T or higher images, you can obtain these addresses dynamically from CNR. The telephone numbers of attached devices are then sent in DHCP response messages. When the Cisco uBR924 processes the DHCP response, it automatically creates the pots dial peer for each port, creates the voip dial peer for the RAS target, and starts the H.323 RAS gateway support.

SGCP Protocol Stack

In architectures using the SGCP protocol stack, the session application implements the gateway functionality defined to support both trunk and residential gateways. The Cisco uBR924 cable access router in this mode functions as a residential gateway with two endpoints.

The SGCP protocol stack provides signaling and feature negotiation via a remote call agent. SGCP eliminates the need for a dial plan mapper and static configuration on the router to map IP addresses to telephone numbers because this function is provided by the remote call agent.

Voice Specifications

Table 1-3: Cisco uBR924 Cable Access Router Voice Specifications

Metric	Value
Loss (between DCS and BTI gateway)	Nominal: 4 dB ±.5 dB (off hook) Nominal: 9 dB ±.5 dB (on hook)
Attenuation distortion: DCS <> BTI (200Hz-3.5kHz) BTI<> DCS (304 Hz-3004Hz) DCS -> BTI (204 Hz-3004 Hz)	Nominal: +1 dB/-3 dB ±0.5 dB ±0.5 dB0
Idle channel noise	<= 18 dBmC (noise shall not exceed)
Signal to C-notched noise	>= 35 dB
Inter-modulation distortion: R2 R3	>= 52 dB >= 52 dB
Single frequency interference: 0 to 12 kHz 0 to 4 kHz	<= -28 dBmO <= -40 dBmO
Frequency shift (offset)	<= ±0.2 Hz (max) <= ±0.1 Hz (99.5%)
Amplitude tracking (input Level, dBmO): -37 to 0 (on-hook) -37 to +3 (off hook) -50 to -37 (off-hook) -55 to -50 (off-hook)	Max Dev. Ave. Dev. <= ±.5 dB <= ±.5 dB <= ± .25 dB <= ±1.0dB <= ±.5 dB <= ± 3.0 dB <= ±1.5 dB
Crosstalk	<= -65 dBmO
Amplitude jitter 20-300 Hz 4-300 Hz	<= 2.5% Peak <= 2.9% Peak
Phase jitter 20 to 300 Hz 4 to 300 Hz	<= 1.5 P-P <= 1.8 P-P
Envelope delay distortion: 1704 Hz to 604 Hz 1704 Hz to 2804 Hz 1704 Hz to 204 Hz 1704 Hz to 3404 Hz	<= 350 usec <= 195 usec <= 580 usec <= 400 usec
Hybrid balance: Echo Return Loss (ERL) SRL	> 26 dB (standard test line) > 14 dB (station off hook) > 21 dB (standard test line) > 11 dB (station off hook)
Clipping: Speech segments <5 ms Speech segments > 5ms	< 0.5% 0.0%
Impulse noise: (>= 6 dB below receive signal)	0 in 93% of all 15 min intervals <= 1 count in all 30 min intervals
Phase hits (>= 10 deg)	0 in 99.75% of all 15 min intervals <= 1 count in all 30 min intervals
Gain hits (>= ± 3dB)	0 in 99.9% of all 15 min intervals <= 1 count in all 30 min intervals
Dropouts (>= 12)	0 in 99.9% of all 15 min intervals <= 1 count in all 60 min intervals

Backup POTS Connection

The Cisco uBR924 cable access router provides an RJ-11 port (Line) that connects to a standard analog telephone wall jack. In the event of a building power failure or a Cisco uBR924 power problem, the cutover port lets the subscriber dial out using the backup PSTN line. If the Cisco uBR924 router loses power while VoIP calls are in progress, the subscriber can re-establish one of the two connections---dialing out over the PSTN.

Cisco IOS Release Images

On power-on, the Cisco uBR924 cable access router boots from Read Only Memory (ROM) from the ROMMON partition of flash, extracts the system software image from flash, and begins execution. Software images in Cisco IOS Release 12.0(4)XI or higher interim builds, as well as Cisco IOS Release 12.0(5)T, are identified in Table 1-4, Table 1-5, and Table 1-6.

The Cisco uBR924 is capable of a TFTP transfer over the cable and Ethernet interface to obtain its configuration file. The configuration file can contain a vendor-defined attribute that lets the CMTS system administrator define a specific Cisco IOS release image to download to a remote Cisco uBR924 cable access router. When the Cisco uBR924 initializes, Cisco IOS software processes the router's configuration file. If the software upgrade option is present in the configuration file, and if the name of the Cisco IOS image in the configuration file differs from the image that is currently running on the Cisco uBR924, the router downloads the new Cisco IOS image from the TFTP server and automatically reboots.

Refer to Chapter 5, "Understanding Configuration Files" to obtain samples of Cisco uBR924 configurations. Also refer to the "Downloading Specific Cisco IOS Images" section of Chapter 5 for further information on downloading a Cisco IOS release image.

Cisco IOS Release 12.0(4)XI Images

Table 1-4 shows the two images available in Cisco IOS Release 12.0(4)XI or higher interim builds:

Cisco IOS Release 12.0(5)T Images

Table 1-5 lists the images that are available to support data and VoIP---fax and voice---in Cisco IOS Release 12.0(5)T and higher interim builds. Table 1-6 lists the images that are available to support data only. Brief descriptions of the features added in Cisco IOS Release 12.0(5)T follows Table 1-6.

The image subset legend for both Table 1-5 and Table 1-6 appears below:

• y5 = Reduced IP image with easy IP functionality (PAT/NAT/DHCP server): For Home Office Base IP Bridging image users, easy IP and routing are not supported.

• v4 = Voice set

• s = Plus set includes L2TP

• o = Firewall feature set

• k1 = DOCSIS baseline privacy

• 56i = 56-bit IPSec

• k2 = Triple DES

Key features added in Cisco IOS Release 12.0(5)T include:

• Baseline Privacy---Baseline privacy offers DOCSIS link level encryption/decryption to ensure the security of data over the cable system. When baseline privacy is enabled, the CMTS generates Traffic Encryption Keys (TEKs) for each SID. The router uses the keys to decrypt downstream data and encrypt upstream traffic. The router requests keys for unicast, broadcast, and multicast operation as appropriate. Keys are refreshed periodically and have a default lifetime of 12 hours.

• IPSec (56-bit encryption/decryption)---The system supports 56-bit encryption/decryption, as well as standard 40-bit encryption/decryption. IPSec involves encryption/decryption of IP packets, enabling customers to use network layer encryption.

• Triple DES (3DES)---In addition to 56-bit encryption, the system supports 168-bit encryption.

• Layer 2 Tunneling Protocol (L2TP) for Virtual Private Networking (VPN)---Service providers can increase revenues by offering secure, remote access to business subscribers. SOHO telecommuters can then securely access an Intranet or corporate data center using the cable and IP backbone network. The cable company can purchase remote access server equipment or pair with an Internet Service Provider (ISP) who owns this equipment and then host connections to remote clients.

Tunneling links two network devices so that the devices appear to exist on a common, private backbone. Encryption and user authentication provide security for data. With tunneling, the remote access server wraps the user data (payload) inside IP packets which are routed through the service provider's network or across the Internet to the tunnel endpoint where the tunneled packet is unwrapped and forwarded in its original form. Tunneling uses point-to-point session protocols, linking data addresses over a routed network.

• Cisco IOS Firewall---The Cisco IOS firewall-specific security feature offers:

  • Context-based Access Control (CBAC) which gives internal-to-the-firewall users secure, per-application-based traffic control across the Internet or Intranet.

  • Java blocking to protect against destructive Java applets.

  • Denial of service detection and prevention to protect access to the router, check packet headers and drop suspicious packets.

  • Real time alerts and audit trail capabilities to record and timestamp source and destination hosts.

Refer to the Cisco release IOS feature module descriptions and appropriate documents on CCO or CD-ROM for feature set or command descriptions, syntax and usage. Use the Cisco IOS Command Reference Master Index(s) to identify the Cisco IOS release that contains the feature set or to obtain document pointers for specific commands.

Installing the Router at the CMTS

To assist in field troubleshooting, the Cisco uBR924 cable access router can be mounted on an equipment shelf at the CMTS, provided the overall configuration permits safe installation and access at the headend near the CMTS.

Posted: Wed Aug 25 18:10:30 PDT 1999
Copyright 1989-1999©Cisco Systems Inc.