|
|
This chapter describes the commands needed to configure X.25 over the B (bearer) channel and the D (demand) channel. The commands described in this chapter require the X.25 Cisco 700 series router software image. The image is posted on CCO; it does not ship with the router.
Basic Rate Interface (BRI) is an ISDN interface consisting of two B channels (B1 and B2) and one D channel. The B channels are commonly used to transfer data, voice, and video. The D channel is commonly used to carry signal and call setup information.
X.25 virtual circuits define an end-to-end, logical connection between two network endpoints. Each circuit uses a logical channel number (LCN) between the endpoint and the network. Therefore, a single circuit requires two LCNs, one at each end of the network. Virtual circuits are available in two forms, permanent virtual circuits (PVCs) and switched virtual circuits (SVCs).
PVCs are always present when the network and the link to the network are present. The advantages of permanent circuits are as follows:
Deployment of PVC-based circuits tends to be less common due to the cost and delay, and PVCs are not supported on Cisco 700 series routers.
SVCs are established at the start of a session and maintained until the communication is complete. Billing for SVCs is often based on hold time (the duration the circuit is up), call establishment events, and data volume.
The D-channel packet service pipes the D-channel packet data to the carrier's packet data network. As a result, the carrier can control which D-channel packet service is allowed. To limit the erosion of existing packet data network business, policy-based restrictions are usually placed on packet-based services.
Some ISDN service providers allow subscribers to use some or all of the D-channel bandwidth to transport X.25 packets over the link. The bandwidth available depends on the volume of signaling traffic, and in some cases, it is limited to 9600 bps.
The Transaction Processing/D-channel Processing (TP/DCP ) service can be divided into the following subsections, as shown in Figure 13-1. (See the section "TP Communications Processing" for more information.)
Packet services on the D channel are considered a special routing function because of the restrictions. A transaction processing communication function called D-channel Policy Routing (DCPR) qualifies IP frames from the LAN for transmission over the D channel. DCPR defines and implements policies that control D-channel traffic. Definition of the policies is based on the destination host address and a variety of packet-specific parameters such as protocol and port number.
DCPR qualification occurs before normal routing functions. DCPR enables traffic not qualified for the D channel to be transported over the B channel. For example, periodic transaction requests can be transmitted over the D channel. Other operations, such as transmitting inventory transfer data between the same two hosts, are transported over the B channel.
Packets that qualify for D-channel transportation are queued according to priority. If an SVC to the destination is up, the packet is encapsulated and sent over the D channel at the earliest opportunity. If an SVC is not up, the system brings up the circuit and sends the packet. Packets returning from the host over established SVCs are unencapsulated and sent to the LAN interface.
Local communications occur between the Cisco 700 series router and a local host over the Ethernet link, using one or more of the protocols in the TCP/IP protocol suite. There is no D-channel-specific limit on the number of POS terminals that can be supported.
This section defines the features the Cisco 700 series router supports for TP/DCP.
Priority transaction queuing is provided on a per-SVC (or host) basis. Four queues are available for each SVC, providing low, normal, medium, and high-priority queuing. Traffic is always taken from the highest priority queue first.
Queue assignment is configurable on a per-SVC basis, based on the following elements:
The following parameters can be assigned by the user to the router:
The router maintains and displays queue usage statistics since the previous reset. This data is not stored in nonvolatile RAM (NVRAM) and is reset if the router is reset or rebooted.
With D-channel policy routing, you can specify which traffic can be transported over the D channel. Four policy definitions are supported, one for each SVC:
Packets that qualify for transport over the D channel are encapsulated and queued for transmission according to the priority queuing scheme.
Communications over the WAN link, specifically the D-channel packet service, are carried on SVCs. (Other X.25 bearer services, such as PVCs and fast packets are not supported at the application layer and therefore are not available.)
The Cisco 700 series router does not accept inbound X.25 calls. Inbound calls are refused with a suitable X.25 call response, such as busy.
A maximum of four concurrent SVCs are supported. An SVC is established when the presence of qualified data and a configuration are detected. The duration that the SVC is maintained (held up) is based on the presence of data and the circuit hold time. The circuit hold time specifies how long an SVC can be maintained without traffic.
The user can specify the destination host X.25 address (X.121 format) and the Network User Identifier (NUI) used to place the call. These can be specified on a per-host basis.
If the SVC setup fails, the data destined for that SVC is dropped. The event type and the reason the SVC was dropped is logged. IP packets are encapsulated for transportation over SVCs in accordance with the Multi-Protocol Over X.25 specification.
Only one SVC is established for an X.25 address. Specifying two policies with the same X.25 address causes both queues to be sent over the same SVC alternately.
The router maintains statistics for traffic and the WAN (SVCs). These statistics are stored in RAM and are not maintained if the Cisco 700 series router is power cycled or reset. All statistical information can be displayed on the console.
The priority queuing service collects traffic statistics that reflect the usage for each queue. This information includes the total packets (per queue) and overflow (discarded) packets.
WAN statistics are collected on the X.25 link and each SVC. This information includes:
To reset the X.25 D channel parameters, use the reset x25d policy command.
REset X25d POlicy LSvc=x | ALl
LSvc | Reset the logical switched virtual circuit (LSVC) number, where x is an LSVC number from 1 to 4. |
ALl | Reset all logical switched virtual circuits. |
None
System mode
Removes the policy definition for a specific LSVC or all LSVCs.
The following example resets all of the LSVCs:
Host> reset x25d policy all
set x25d policy
show x25d policy
To turn AO/DI on, use the set aodi command.
SEt AOdi ON | OFf [NUA=nua] [POwerupenable] [REversechargerequest ON | OFf]
ON | AO/DI is configured. |
|---|---|
OFf | AO/DI is not configured. |
NUA | The X.121 address of the destination. This is a required parameter if AO/DI is on. |
POwerupenable | The D channel X.25 SVC established at power up. The SVC is established only for active profiles. |
REversechargerequest | Reverses the charges (makes a call collect) when set to on. The default is off. |
Off
System or profile mode
The Always On/Dynamic ISDN (AO/DI) networking service provides an always-available connection to packet-based services through the WAN. For the user, AO/DI reduces costs by using the D channel to make low-speed data transfers. For service providers, AO/DI removes a significant amount of data traffic from the voice network.
The D channel is an always-available, packet-oriented link between the remote office and the central office. The customer premises equipment (CPE) can use the D channel to pass Multilink Point-to-Point and TCP/IP protocols encapsulated in X.25. The D-channel X.25 packets are handled at the central office by the X.25 packet handler, so these packets can be routed without crossing the circuit-switched switch fabric.
When D-channel bandwidth exceeds a defined threshold, the router places one or more ISDN B-channel calls to increase bandwidth. When bandwidth requirements fall below a defined threshold, the B channels are released.
A maximum of four switched virtual circuits (SVCs) can be used for AO/DI. If a D-channel connection is not available, the router uses the first available B channel for a call. After the D channel PPP link is established, it is not torn down. If Bandwidth Allocation Control Protocol (BACP) is configured, Bandwidth on Demand (BOD) is negotiated by using BACP.
Performance of the Multilink Protocol declines when the bandwidth of the underlying links varies widely; therefore, the router idles the D channel when the B channels are in use. (Packets that can be redirected using the multilink procedure are described in RFC 1990.) After the number of links drops to one and that link is idle, the router returns to normal operation.
To disconnect from the D-channel link, use the disconnect command.
The set link auto on command (where link = D) brings the D channel up on demand. By default the D-channel link is set to OFF.
To configure AO/DI, Multilink PPP has to be configured first. Any available SVC can be used for the AO/DI call. The demand and timeout commands configure three links when AO/DI is configured.
If AO/DI is enabled when a call is made, the channel number for the first link of the call is 3. If AO/DI is disabled, the channel number is 1 or 2.
When configuring the demand command parameters for the D channel, the syntax is as follows:
DEmand D [THreshold=kbs] [DUration=seconds] [SOurce=LAn | WAn | BOth]The default demand command parameters are as follows:
| Link | Auto | Threshold | Duration | Source |
|---|---|---|---|---|
D | On | 0 kbps | 1 | LAN |
1 | On | 7.5 kbps1 | 1 | BOTH |
2 | On | 48 kbps | 1 | BOTH |
| 1The value of 7.5 kbps for bringing up the first B channel is based on an assumption of 1.5 kbps per SVC. If the queue cannot be cleared in 5 seconds, B-channel bandwidth is used. |
When configuring the timeout command parameters for the D channel, the syntax is as follows:
TImeout D [THreshold=kbs] [DUration=seconds] [SOurce=LAn | WAn | BOth]The timeout parameter for the D-channel link is set to off by default.
This feature is available only on the X.25 images.
The following example turns AO/DI on for the address of the remote device:
Host> set aodi on nua 14082221000
show aodi
show config
show connection
show demand
show status
show timeout
To set the virtual circuit ranges, use the set x25 command.
SEt X25 [LIc | HIc | LTc | HTc | LOc | HOc] vc_number
LIc | Lowest incoming virtual circuit number. |
|---|---|
HIc | Highest incoming virtual circuit number. |
LTc | Lowest two-way virtual circuit number. |
HTc | Highest two-way virtual circuit number. |
LOc | Lowest outgoing virtual circuit number. |
HOc | Highest outgoing virtual circuit number. |
vc_number | Virtual circuit number. Valid value ranges are from 0 to 4095. |
The default value for lic, hic, ltc, and htc is 0. The default value for loc and hoc is 1024.
System level
When you change the virtual circuit ranges, the new values are not effective until the router is rebooted.
The router verifies that the highest virtual circuit number is larger than the lowest virtual circuit number; it sets the highest virtual circuit number first.
This command is also available for X.25 over the D channel; therefore, the values of LTC and HTC must match the LSVC number.
The following example sets hoc and loc to 1024:
Host> set X25 hoc 1024 Host> set X25 loc 1024
set x25d
show x25
To set the host parameters to perform the TCP/IP relay function between Ethernet and X.25 D channel connections, use the set x25d command.
SEt X25d LSvc=x NUA=nua [NUI=nui] IDle=xxx
LSvc | Logical switched virtual circuit (LSVC) number, where x is an LSVC number from 1 to 4. |
NUA | Network X.121 address. |
NUI | Network user identifier, from 1 to 15 digits. |
IDle | Hold-time in seconds before the X.25 link shuts down because there is no traffic. |
None
System mode
The command adds an entry to the X.25 D channel host table. Up to four entries are allowed.
The following example sets the network user address for LSVC 1 to 100102 and sets an idle time of 60 seconds:
Host> set x25d lsvc=1 nua=100102 idle=60
reset x25d policy
set x25d policy
show x25d policy
To route a specific IP packet to the target IP host through an X.25 D channel and provide the parameters needed for a X.25 D channel connection, use the set x25d policy command.
SEt X25d POlicy LSvc=x HOst IP address [TCP | UDP | ICMP] [Port xx] [REversechargerequest ON | OFf]
LSvc | Logical switched virtual circuit (LSVC) number, where x is an LSVC number from 1 to 4). |
HOst IP address | IP address of the host. |
TCP, UDP, and ICMP | Protocols supported by the X.25 D channel. |
Port xx | Port number, where xx is the port number. (See the "Port Assignments and NetBIOS Names" appendix for a list of port numbers.) |
REversechargerequest | Makes X.25 calls collect calls (added in software Release 4.2(3.5)). |
None
System mode
The connection between the electronic point of sale (POS) site and the router is restricted to LAN Ethernet TCP/IP; T3POS/TPAD implementation is not available. The router does not require knowledge of POS transaction formats or protocols.
The software supports four policy definitions, one for each LSVC. Packets that qualify for transport over the D channel are encapsulated and queued for transmission according to the priority queuing scheme.
The following example sets the policy host IP address to 10.10.10.1, using TCP and the Telnet port (23).
Host> set x25d policy host ip 10.10.10.1 TCP port 23
reset x25d policy
set x25d
set x25d tei
show x25d policy
To specify a subprotocol and port number within IP packets or to assign a priority to IP packets greater than or less than a specific size, use the set x25d priorityqueue command.
SEt X25d PRiorityqueue LSvc=x IP [HIgh | MEdium | NOrmal | LOw]
LSvc | Logical switched virtual circuit (LSVC) number, where x is the LSVC number (1 through 4). |
IP | Priority level (high, medium, normal [default], and low). |
TCP, UDP, and ICMP | Protocols supported by the X.25 D channel. |
Port | Port number, where xx is the port number. (See the "Port Assignments and NetBIOS Names" appendix for a list of port numbers.) |
PKtsize | Size of the packet. GReater than the value in xxxx or LEssthan the value in xxxx. |
DEfault | Default priority (high, medium, normal [default], and low) for a logical switched virtual circuit (LSVC). |
None
System mode
Priority queueing improves the responsiveness of the D channel link. X.25 is a flow-controlled, nonbroadcast multiaccess (NBMA) protocol. A high-priority packet might not be transmitted first, even when it is eligible. With priority queueing, data can be put into one of the four priority queues: high, medium, normal, and low. Packets with the same priority are sent on a first-in-first-out basis.
The following sets the priority for IP packets greater than 1024 to a low priority for LSVC 1:
Host> set x25d priorityqueue lsvc=1 ip low pksize greater 1024
set x25d priorityqueue lsvc default
set x25d priorityqueue lsvc limit
show x25d priorityqueue
To set the Terminal Endpoint Identifier (TEI) number, use the set x25d tei command.
SEt X25d TEI [ON | OFf | nnn]
ON | TEI has a value of 255. |
OFf | TEI has a value of 0. |
nnn | TEI number or the support level. |
None
System mode
If set to OFF, there is no X.25 D channel support. If set to ON, the value is 255; the central office assigns the TEI number dynamically. If nnn is less than 255 and greater than 0, the value for nnn is assigned to TEI. This command is not effective until the router is rebooted.
The following example sets the TEI number to 2:
Host> set x25d tei 2
reset x25d policy
set x25d policy
show x25d policy
To specify the limit (maximum depth) of the queue for a logical switched virtual circuit (LSVC), use the set x25d priorityqueue lsvc limit command.
SEt X25d PRiorityqueue LSvc=x LImit HIgh | MEdium | NOrmal | LOw xx
LSvc | LSVC number, where x is the LSVC number (1 through 4). |
LImit | Priority of any packet not previously assigned a priority (high, medium, normal, or low). |
LOw | Depth (maximum number of packets) a queue can have. |
None
System mode
The following example limits to 20 the number of packets the normal priority queue for LVSC 1 can have:
Host> set x25d priorityqueue lsvc=1 limit normal 20
set x25d priorityqueue default
set x25d priorityqueue ip
show x25d priorityqueue
To change the X.121 address, use the set x25d x121host command.
SEt X25d X121host address
address |
None
System mode
The X.121 address can be added to packets sent over the D channel. This address is the calling DTE address for all X.25 D channel packets. The length of the X.121address must not be greater than 16 decimal digits. After setting the X.121address, the router must be rebooted for the change to take effect. The set defaults command sets the X.121address to an empty string.
The X.121 address is used only for X.25 D channel. The X.25 B channel packets do not contain the X.121 address because calling DTE address suppression is required for TPAD operations (on X.25 over the B channel).
The following example sets an X.121 address:
host> set x25d x121host 1234567890
set defaults
upload
To display the parameters for AO/DI, use the show aodi command.
SHow AOdiSystem or profile mode
The following example displays the AO/DI parameters:
Host> show aodi AODION or OFF NUA686887987 REVERSE CHARGE REQUESTON or OFF
show config
show connection
show demand
show status
show timeout
To display the X.25 parameters, use the show x25 command.
SHow X25None
System or profile mode
The output shows whether or not X.25 was initialized properly, the mode of operation, and the virtual circuit ranges.
The following example shows the output of the command:
Host> show x25 X25 is running in DTE MODE. VC Ranges - current value (new value after reboot): lic 0 (0), hic 0 (0), ltc 0 (0), htc 0 (0), loc 1024 (1024), hoc 1024 (1024)
reset x25d policy
set x25
set x25d
show x25d policy
To show the X.25 D channel parameters, use the show x25d policy command.
SHow X25d POlicyNone
System or profile mode
The following example shows the output of the command:
Host> show x25d policy LSVCNUANUIIP AddressProtPort Idle Reverse ------------------------------------------------------------------------ 112345678901234192.168.253.128 ALL1234 3000 ON 212345678901234192.168.253.128 ALL03000 OFF 312345678901234192.168.253.128 ALL03000 OFF 412345678901234192.168.253.128 ALL03000 OFF
reset x25d policy
set x25d
set x25d policy
To show the configuration statistics of priority queues, use the show x25d priorityqueue command.
SHow X25d PRiorityqueue COnfig | STatistics
COnfig | Show the configuration. |
STatistics | Show the statistics. |
None
System mode
Priority queue is only available to IP (and its subprotocols); other protocols, such as IPX, are not supported.
The following example shows the configuration output of the command:
Host> show x25d priorityqueue config LSVC1DefaultPriorityNORMAL PriorityQueueProtocolOptionsMaxSizeDrops --------------------------------------------------------------------- HIGHIP400 MEDIUMIP400 NORMALIP400 LOWIP400 LSVC 2 Default Priority NORMAL PriorityQueueProtocolOptionsMaxSizeDrops --------------------------------------------------------------------- HIGHIP400 MEDIUMIP400 NORMALIP400 LOWIP400
The following example shows the statistical output of the command:
Host> show x25d priorityqueue statistics LSVCNUANUIIPAddressProtocolPortIdle ----------------------------------------------------------------------- 114085763301192.168.100.1ALL060 214085763301192.168.100.3ALL0120
set x25d priorityqueue default
set x25d priorityqueue ip
set x25d priorityqueue limit
To show the statistics for X.25 D channel, use the show x25d statistics command.
SHow X25d STatisticsNone
System or profile mode
The following example shows the output of the command:
Host> show x25d statistics LSVC 1 Outbound Requests: 0 Outbound Failed: 0 SVC Errors: 0 Out Packets: 0 In Packets: 0 LSVC 2 Outbound Requests: 0 Outbound Failed: 0 SVC Errors: 0 Out Packets: 0 In Packets: 0
reset x25d policy
set x25d
set x25d policy
To show the terminal endpoint identifier (TEI) number, use the show x25d tei command.
SHow X25d TEiNone
System or profile mode
The following example shows the output of the command:
Host> show x25d tei TEI 255
reset x25d policy
set x25d
set x25d tei
The X.121 address can be added to packets sent over the D channel using the set x25d x121host x121address command. To view the X.121 address set in the router, use the show x25d x121host command.
System or profile mode
This command shows the X.121 host address. The value of the X.121 address entered using the command set x25d x121host command.
The following example displays the x121host address:
700> show x25d x121host X25D X121HOST 14081763269
set x25d x121host
Posted: Thu Jul 8 12:52:58 PDT 1999
Copyright 1989-1999©Cisco Systems Inc.