X.25 Dual Serial Line Management
This feature was introduced.
This document describes the X.25 Dual Serial Line Management feature in Cisco IOS Release 12.2(13)T. It includes the following sections:
•Supported Standards and MIBs and RFCs
•X.25 Dual Serial Line Management Configuration Example
Telco service providers use data communications networks (DCNs) to provide communications between network management applications (also called operations support systems or OSSs) and network elements. The telco DCNs use the X.25 protocol (or a variation of X.25) to send network management information across the DCN.
Figure 1 shows a typical DCN that uses the BX.25 protocol developed by Bell Communications Research (now Telcordia Technologies). The Lucent 5ESS switch in this network uses the BX.25 protocol for monitoring, provisioning and collecting billing data.
Figure 1 Network Management Application Monitors Lucent 5ESS Switch over Datakit Network
The Datakit node provides the communications front end to a network management application and provides two links, SCC0 and SCC1, for link redundancy. One link is active and passes data across the network; the other remains in standby mode.
The Datakit node acts as a transport, so that to the network management application and the Lucent 5ESS switch, the node looks like it has two individual circuits. The network management application host is supplying leads on both interfaces but ignoring Set Asynchronous Balanced Mode (SABM) messages on the standby interface. If communication is lost on the active interface, the network management application host responds to the SABM messages on the standby interface and it becomes the active interface.
In the past, incumbent local exchange carriers (ILECs) have built either Lucent Datakit or X.25 networks to carry the network management data. Large ILEC customers are currently replacing the Lucent Datakit portion of the networks with Cisco IP core routers in their DCN. Figure 2 shows a typical migration path using X.25 over TCP/IP (XOT) and the Cisco Serial Tunneling (STUN) features.
Figure 2 Network Management Application Monitors Lucent 5ESS Switch Using XOT and STUN
Although the solution shown in Figure 2 eliminates some of the Lucent Datakit network elements in ILEC networks, the network still requires a Lucent Datakit node as a front end to the network management application from the Lucent 5ESS switch.
Additionally, competitive local exchange carriers (CLECs) do not have DCNs or have very limited ones. Furthermore, the CLECs are not interested in purchasing the legacy Lucent Datakit solution shown in Figure 1, nor do they want to install a network management application with a Lucent Datakit front end as shown in Figure 2.
Both the CLECs and the ILECs want the DCN based on IP intranet technologies shown in Figure 3.
Figure 3 Network Management Application Monitors Lucent 5ESS Switch over IP Network
As Figure 3 shows, Cisco offers solutions that allow telco service providers to reduce operating costs, translate and migrate existing X.25-based DCNs to IP-based DCNs, and bridge traditional telephony operations to newer ones. The X.25 Dual Serial Line Management feature is a part of the Cisco IOS Telco Feature Set, a bundle of applications specific to the DCN environment. Specifically, this feature supports X.25-to-TCP protocol translation, and provides dual serial interfaces to preserve the redundancy and monitoring capability available from the SCC0 and SCC1 links on the Lucent 5ESS switch in the DCN network.
The X.25 Dual Serial Line Management feature provides the following benefits:
•Preserves the redundancy and monitoring capability available from the SCC0 and SCC1 links on the Lucent 5ESS switch in the DCN network.
•Allows telco service providers to reduce operating costs by migrating existing X.25-based DCNs to IP-based DCNs.
Additionally, the Cisco IOS translate tcp command has been updated with the dynamic keyword for PVC options. The dynamic keyword provides a backup facility for PVC applications. Dynamic PVCs can be made part of an active backup configuration by using the dual serial line management feature.
The X.25 Dual Serial Line Management feature is used in DCN networks utilizing the Lucent 5ESS switch and running the X.25 protocol.
The chapter "Configuring X.25 and LAPB" in the Cisco IOS Wide-Area Networking Configuration Guide describes how to configure X.25.
The Cisco protocol translation feature is described in the Configuring Protocol Translation and Virtual Asynchronous Devices" chapter of the Cisco IOS Terminal Services Configuration Guide.
The translate command used for protocol translation is described in the Cisco IOS Terminal Services Command Reference.
The section "Switch Monitoring Networks: Cisco X.25 BAI OSS Connectivity Solution" in the Cisco Network Solutions for the Telco DCN: Telephone Switch Environments white paper provides tasks and examples for configuring a backup interface using dual serial lines in a telco DCN.
The "X.25 Record Boundary Preservation for Data Communications Networks" chapter of the Wide-Area Networking Configuration Guide provides related information about X.25 record boundary preservation.
Supported Standards and MIBs and RFCs
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
•Configuring X.25 Dual Serial Line Management (required)
•Verifying X.25 Dual Serial Line Management (optional)
•Troubleshooting Tips (optional)
•Monitoring and Maintaining X.25 Dual Serial Line Management (optional)
Configuring X.25 Dual Serial Line Management
To configure the X.25 Dual Serial Line Management feature, you must configure dual serial lines running the X.25 protocol, and activate a backup function on one of the interfaces. To enter these configurations, use the following commands beginning in global configuration mode:
Router(config)# interface serial x/y
Begins interface configuration on a serial interface (serial1/6, for example, which could be the primary interface).
Router(config-if)# backup active interface serial x/y
Assigns a serial interface (serial 1/7, for example) as backup or standby, for the primary serial interface.
Router(config-if)# encapsulation x25 dce
Specifies operation of a serial interface as an X.25 DCE device.
Router(config-if)# x25 address address
(Optional) Sets the X.121 address on the interface.
Refer to the documents listed in the "Related Documents" section for additional configuration information. The section "X.25 Dual Serial Line Management Configuration Example" also lists commands that you might enter to configure X.25 and X.25-to-TCP protocol translation.
Verifying X.25 Dual Serial Line Management
The verification process described in this section is based on the following configuration:
description connects to X.25 switch
ip address 10.10.0.15 255.255.255.0
backup active interface Serial0/1
To verify correct operation of the X.25 Dual Serial Line Management feature, perform the following steps in EXEC mode:
Step 1 Use the show backup command to display which interface is the active backup:
Primary Interface Secondary Interface Status
----------------- ------------------- ------
Serial0/0 Serial0/1 active backup
Step 2 Use the show interfaces command to monitor the serial interfaces. In the following display, serial interface 0/1 is up (active), and its backup interface is serial interface 0/0:
Router# show interfaces s0/1
Serial0/1 is up, line protocol is up
Hardware is PowerQUICC Serial
Description: connects to X.25 switch
Internet address is 10.10.0.30/24
Backup interface Serial0/0, failure delay 0 sec, secondary disable
kickin load not set, kickout load not set
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation X25, loopback not set
X.25 DCE, address 3034, state R1, modulo 8, timer 0
Defaults: idle VC timeout 0
input/output window sizes 2/2, packet sizes 128/128
Timers: T10 60, T11 180, T12 60, T13 60
Channels: Incoming-only none, Two-way 10-1024, Outgoing-only none
RESTARTs 2/0 CALLs 4+0/2+0/0+0 DIAGs 0/0
LAPB DCE, state CONNECT, modulo 8, k 7, N1 12056, N2 20
T1 3000, T2 0, interface outage (partial T3) 0, T4 0
VS 1, VR 1, tx NR 1, Remote VR 1, Retransmissions 0
Queues: U/S frames 0, I frames 0, unack. 0, reTx 0
IFRAMEs 130/130 RNRs 0/0 REJs 0/0 SABM/Es 2/1 FRMRs 0/0 DISCs 0/0
Last input never, output 1w3d, output hang never
Last clearing of "show interface" counters 2w2d
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
242 packets input, 4224 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
2 input errors, 0 CRC, 2 frame, 0 overrun, 0 ignored, 0 abort
183 packets output, 1337 bytes, 0 underruns
0 output errors, 0 collisions, 131 interface resets
0 output buffer failures, 0 output buffers swapped out
DCD=up DSR=up DTR=up RTS=up CTS=up
To troubleshoot operation of the X.25 Dual Serial Line Management feature, use the debug backup privileged EXEC command.
Monitoring and Maintaining X.25 Dual Serial Line Management
To monitor and maintain the X.25 Dual Serial Line Management feature, use the commands and steps listed in the "Verifying X.25 Dual Serial Line Management" section.
X.25 Dual Serial Line Management Configuration Example
In the following example, dual serial lines (serial 1/6 and 1/7) are configured for the X.25 protocol. Serial interface 1/6 is configured as the primary interface, and serial interface 1/7 is configured as the backup interface. X.25-to-TCP protocol translation is also configured.
backup active interface serial 1/7
x25 route ^66666666 interface Serial1/6
x25 route ^66666666 interface Serial1/7
translate tcp 172.20.21.188 port 1025 x25 66666666 pvc 1 dynamic max-users 1
translate tcp 172.20.21.188 port 1026 x25 66666666 pvc 2 dynamic max-users 1
translate tcp 172.20.21.188 port 1027 x25 66666666 pvc 3 dynamic max-users 1
translate tcp 172.20.21.188 port 1028 x25 66666666 pvc 4 dynamic max-users 1
translate tcp 172.20.21.188 port 1029 x25 66666666 pvc 5 dynamic max-users 1
translate tcp 172.20.21.188 port 1030 x25 66666666 pvc 6 dynamic max-users 1
translate tcp 172.20.21.188 port 1031 x25 66666666 pvc 7 dynamic max-users 1
data communications network—See DCN.
DCN—data communications network. An out-of-band network that provides connectivity between network elements and their respective operations support system (OSS). Its primary function is enabling the surveillance and the status of a telco network, yet it also facilitates network operations and management functions such as provisioning, billing, planning, and service assurance.
CLEC—competitive local exchange carrier. Company that builds and operates communication networks in metropolitan areas and provides its customers with an alternative to the local telephone company.
competitive local exchange carrier—See CLEC.
ILEC— incumbent local exchange carrier. The local telephone company that controls the cable that makes up the telephone network.
incumbent local exchange carrier—See ILEC.
Lucent 5ESS switch—A Class 5 local telephony switch that connects a local subscriber to a telephone network.
network element—A single piece of telecommunications equipment used to perform a function or service integral to the underlying network.
network management application—A application for managing elements in a service providers' network. For a Class 5 local telephony switch, the applications are used monitor the switch, provision the switch, collect call detail records, and collect traffic data. Examples of these applications include an OSS such as Lucent's Network Fault Management (NFM) application and Telcordia Technologies' Network Monitoring and Assurance (NMA) System.
operations support system—See OSS.
OSS—operations support system. DCN network management and operations applications.
SABM—Set Asynchronous Balanced Mode. Link Access Procedure, Balanced (LAPB) data link layer message that sets the operational mode of a link.
Set Asynchronous Balanced Mode—See SABM.
telco—Abbreviated form of the two words "telephone company."
X.25 protocol—ITU-T standard that defines how connections between data terminal equipment and data communications equipment are maintained for remote terminal access and computer communications in a network.
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
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