ISDN BCAC and Round-Robin Channel Selection Enhancements

First Published: May 20, 2003

Last Updated: April 12, 2011

 

The ISDN BCAC and Round-Robin Channel Selection Enhancements feature allows more dynamic control of the ISDN B channels by providing the additional B-Channel Availability Control (BCAC) functionality for configuring message signaling and an enhanced channel selection scheme that adds a round-robin configuration to the existing ascending and descending channel selection schemes already available.

Finding Feature Information

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 for ISDN BCAC and Round-Robin Channel Selection Enhancements” section.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

Prerequisites for ISDN BCAC and Round-Robin Channel Selection Enhancements

You need to be familiar with the BCAC service message signaling procedure and the procedure for configuring ISDN PRI before configuring the commands described in this document. See the “Standards” section for a list of references.

Information About ISDN BCAC and Round-Robin Channel Selection Enhancements

BCAC Enhancements

BCAC is a service message signaling procedure used to control the availability of ISDN B channels. BCAC provides a coordinated capability between both ends of a PRI to simultaneously preclude selection of specified B channels for outgoing calls, and reject calls (if channel negotiation is employed, calls may go on another channel) for those same channels. The basic BCAC functionality for the handling of SERV and SERV ACK messages already exists on Cisco routers. In Cisco IOS Release 12.3(1), the software has been enhanced with the following BCAC functionality:

  • Provides improved processing of SERV and SERV ACK messages. Even though these messages are already handled in the Cisco IOS software, their processing has been enhanced to more closely align with the behavior described in the standards.
  • Provides a mechanism to allow the retransmission of SERV messages.
  • Handles SERV message collision cases.
  • Provides service status audits for various audit triggers.
  • Provides an option, that when set, triggers the exchange of service messages on all channels of the interface when the router is rebooted and when the signaling link comes up.
  • Provides a mechanism so that if there is a flood of service messages that need to be sent, the service messages can be throttled to avoid losing them.
  • Initializes the B-channel service status upon provisioning.

Round-Robin Selection Scheme for ISDN B Channels

ISDN enhancements introduced in Cisco IOS Release 12.3(1) enable you to select a B channel on a PRI or a nonfacility associated signaling (NFAS) interface in a round-robin fashion. This option is in addition to the ascending or descending channel selection schemes already available.

Logging of ISDN Events

ISDN enhancements introduced in Cisco IOS Release 12.3(1) support syslog logging of the following ISDN events:

  • ISDN Layer 2 Up and Down events at severity 3.
  • ISDN SERV, SERV ACK, Restart, Restart Ack, and Status Enq messages at severity 4.
  • ISDN SERV status audit messages for various triggers at different severities.

Additional ISDN Switch Types Supported for Network Emulation

ISDN enhancements introduced in Cisco IOS Release 12.3(1) extend network emulation capability to the Lucent 4ESS, 5ESS, and Nortel DMS-100 ISDN switch types. These switch types can be configured as network, but not all network-side features are supported.

How to Configure the ISDN BCAC and Round-Robin Channel Selection Enhancements

Configuring BCAC Service Audit Triggers

Perform this task to configure BCAC service audit triggers.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface serial port : channel

4. isdn bcac service audit

5. isdn bcac service audit trigger number

6. isdn bcac service audit interface

7. end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

interface serial port : channel

 

Router(config)# interface serial 2:23

Enters interface configuration mode on the specified serial port and channel.

Step 4

isdn bcac service audit

 

Router(config-if)# isdn bcac service audit

Enables BCAC service audits.

Step 5

isdn bcac service audit trigger number

 

Router(config-if)# isdn bcac service audit trigger 2

Enables individual BCAC service audit triggers.

Step 6

isdn bcac service audit interface

 

Router(config-if)# isdn bcac service audit interface

Specifies that BCAC service audits must be triggered on the entire interface.

Step 7

end

 

Router(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Configuring BCAC Service State Triggers

Perform this task to configure BCAC service state triggers.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface serial port : channel

4. isdn bcac service update provision

5. isdn bcac service update linkup

6. end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

interface serial port : channel

 

Router(config)# interface serial 2:23

Enters interface configuration mode on the specified serial port and channel.

Step 4

isdn bcac service update provision

 

Router(config-if)# isdn bcac service update provision

Enables the BCAC service status functionality for provisioning the B channels.

Step 5

isdn bcac service update linkup

 

Router(config-if)# isdn bcac service update linkup

Triggers updates of the BCAC service states between peer nodes through exchange of SERV and SERV ACK messages.

Step 6

end

 

Router(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Configuring BCAC Message Retransmission

Perform this task to configure retransmission of BCAC service messages.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface serial port : channel

4. isdn bcac service timer timer-value

5. isdn bcac service retry max retries

6. isdn bcac service retry in-serv-on-fail

7. end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

interface serial port : channel

 

Router(config)# interface serial 2:23

Enters interface configuration mode on the specified serial port and channel.

Step 4

isdn bcac service timer timer-value

 

Router(config-if)# isdn bcac service timer 600

Changes the value of the BCAC T3M1 or T323 service message timer.

  • Valid range is from 500 to 120000 ms, and the default is 120000 ms.

Step 5

isdn bcac service retry max retries

 

Router(config-if)# isdn bcac service retry max retries 5

Specifies the maximum number of times that a BCAC service message can be retransmitted when unacknowledged.

  • The default is 2 attempts, and you can enter a number from 0 to 127.

Step 6

isdn bcac service retry in-serv-on-fail

 

Router(config-if)# isdn bcac service retry in-serv-on-fail

Specifies that the BCAC service state of the channel needs to be changed to In-Service, because no acknowledgment message was received.

Step 7

end

 

Router(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Configuring B-Channel Selection Order

Perform this task to configure selection order of the ISDN B channels.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface serial port : channel

4. isdn bchan-number-order { ascending | descending } [ round-robin ]

5. end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

interface serial port : channel

 

Router(config)# interface serial 2:23

Enters interface configuration mode on the specified serial port and channel.

Step 4

isdn bchan-number-order { ascending | descending } [ round-robin ]

 

Router(config-if)# isdn bchan-number-order ascending round-robin

Configures an ISDN PRI interface to make outgoing call selection in ascending or descending order.

  • The optional round-robin keyword adds the round-robin selection functionality to the selection order.

Step 5

end

 

Router(config-if)# end

Exits interface configuration mode and returns to privileged EXEC mode.

Configuring ISDN Syslog Messages

Perform this task to configure logging of ISDN syslog messages.

SUMMARY STEPS

1. enable

2. configure terminal

3. isdn logging

4. end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

isdn logging

 

Router(config)# isdn logging

Enables logging of ISDN syslog messages.

Step 4

end

 

Router(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Configuration Examples for ISDN BCAC and Round-Robin Channel Selection Enhancements

Example: Configuring BCAC Service Audit Triggers

The following example shows how to enable service audits on serial interface 4:23:

interface serial 4:23
isdn bcac service audit
 

The following example shows how to disable service trigger 4 on serial interface 4:23:

interface serial 4:23
no isdn bcac service audit trigger 4
 

See the command page for the isdn bcac service audit trigger command for a list of triggers that can be disabled.

The following example shows how to configure service audits on the entire interface:

interface serial 4:23
isdn bcac service audit interface

Example: Configuring BCAC Service State Triggers

The following example shows how to enable the SERV status message for provisioning the B channels on serial interface 4:23:

interface serial 4:23
isdn bcac service update provision
 

The following example shows how to trigger service state updates on serial interface 4:23:

interface serial 4:23
isdn bcac service update linkup

Example: Configuring BCAC Message Retransmission

The following example shows how to configure an option whereby, on service message exchange failure, the service state of the concerned channel or channels will be set to In-Service:

interface serial 2:23
isdn bcac service retry in-serv-on-fail
 

The following example shows how to set the maximum number of service message retransmissions on serial interface 2:23 to 50:

interface serial 2:23
isdn bcac service retry max 50
 

The following example shows how to change the service timers to 600 ms on serial interface 2:23:

interface serial 2:23
isdn bcac service timer 600

Example: Configuring B-Channel Selection Order

The following example configures the outgoing B channel selection order on a PRI interface to be round-robin in ascending order:

interface serial 5:10
isdn bchan-number-order ascending round-robin

Example: Configuring ISDN Syslog Messages

The following example shows how to configure ISDN syslog logging:

isdn logging

Additional References

Related Documents

Related Topic
Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Dial commands

Cisco IOS Dial Technologies Command Reference

Fax, modem, and text support over IP configuration

Cisco IOS Fax, Modem, and Text Support over IP Configuration Guide

ISDN voice commands

Cisco IOS Voice Command Reference

ISDN voice configuration

Cisco IOS ISDN Voice Configuration Guide

Standards

Standard
Title

AT&T PRI

Technical Report 41459— AT&T ISDN Primary Rate Interface and Special Application Specification ; “User Network Interface Description,” 1999.

National ISDN Council (NIC) PRI

SR (Special Report)—NWT-002343— ISDN Primary Rate Interface Generic Guidelines for Customer Premises Equipment, June 1993.

SR-3887— National ISDN Primary Rate Interface Customer Premises Equipment Generic Guidelines, 1996.

Nortel PRI

NIS (Network Interface Specification)—A211-1— DMS100 ISDN Primary Rate Network User Interface, 1993.

MIBs

MIB
MIBs Link

None

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC
Title

None

—

Technical Assistance

Description
Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for ISDN BCAC and Round-Robin Channel Selection Enhancements

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

 

Table 1 Feature Information for ISDN BCAC and Round-Robin Channel Selection Enhancements
Feature Name
Releases
Feature Information

ISDN BCAC and Round-Robin Channel Selection Enhancements

12.3(1)

The ISDN BCAC and Round-Robin Channel Selection Enhancements feature allows more dynamic control of the ISDN B channels by providing the additional B-Channel Availability Control (BCAC) functionality for configuring message signaling and an enhanced channel selection scheme that adds round-robin configuration to the existing ascending and descending channel selection schemes already available.

The following commands were introduced or modified: isdn bcac service audit, isdn bcac service audit interface, isdn bcac service audit trigger, isdn bcac service retry in-serv-on-fail, isdn bcac service retry max, isdn bcac service timer, isdn bcac service update linkup, isdn bcac service update provision, isdn bchan-number-order, isdn logging, isdn protocol-emulate (dial).

Glossary

PBX —private branch exchange.

RESTART —restart message.

RESTART ACK —restart acknowledge message.

SERV —service message.

SERV ACK —service acknowledge message.

STATUS ENQ —status enquiry message.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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