Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

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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.

The figure below 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. The figure below 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 the figure above 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 the first figure above, nor do they want to install a network management application with a Lucent Datakit front end as shown in the second figure above.

Both the CLECs and the ILECs want the DCN based on IP intranet technologies shown in the figure below.

Figure 3

Network Management Application Monitors Lucent 5ESS Switch over IP Network

As the figure above 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.

• Benefits
  
• Restrictions
  
• Related Documents
  

• Configuring X.25 Dual Serial Line Management
  
• Verifying X.25 Dual Serial Line Management
  
• Troubleshooting Tips
  
• Monitoring and Maintaining X.25 Dual Serial Line Management
  

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.

interface Serial1/6
 description SCC0
 backup active interface serial 1/7
 encapsulation x25 dce
 x25 address 66666666
 x25 ltc 8
 x25 ips 256
 x25 ops 256
 clockrate 9600
!
interface Serial1/7
 description SCC1
 encapsulation x25 dce
 x25 address 66666666
 x25 ltc 8
 x25 ips 256
 x25 ops 256
 clockrate 9600
!
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.