Table Of Contents
ISDN BCAC and Round-Robin Channel Selection Enhancements
Prerequisites for ISDN BCAC Enhancements
Information About the ISDN BCAC and Round-Robin Channel Selection Enhancements
Round-Robin Selection Scheme for ISDN B Channels
Additional ISDN Switch Types Supported for Network Emulation
How to Configure the ISDN Enhancements
Configuring BCAC Service Audit Triggers
Configuring BCAC Service State Triggers
Configuring BCAC Message Retransmission
Configuring B-Channel Selection Order
Configuring ISDN Syslog Messages
Configuration Examples for ISDN BCAC and Round-Robin Channel Selection Enhancements
isdn bcac service audit interface
isdn bcac service audit trigger
isdn bcac service retry in-serv-on-fail
isdn bcac service update linkup
isdn bcac service update provision
ISDN BCAC and Round-Robin Channel Selection Enhancements
The ISDN BCAC and Round-Robin Channel Selection Enhancements feature allows more dynamic control of the ISDN B channels by providing 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.
Feature Specifications for the ISDN BCAC Enhancements
Finding Support Information for Platforms and Cisco IOS Software Images
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Contents
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Prerequisites for ISDN BCAC Enhancements
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Prerequisites for ISDN BCAC Enhancements
You need to need to be familiar with the BCAC service message signaling procedure and configuring ISDN PRI before configuring the commands described in this document. See the "Standards" section for a list of references.
Information About the ISDN BCAC and Round-Robin Channel Selection Enhancements
The following functionality is introduced in the ISDN BCAC and Round-Robin Channel Selection Enhancements:
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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:
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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 Non-Facility 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:
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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 no additional changes were made and not all network-side features are supported.
How to Configure the ISDN Enhancements
This section contains the following procedures. Each procedure is optional and depends upon the settings required for your network.
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Configuring BCAC Service Audit Triggers
Perform this task to configure BCAC service audit triggers:
SUMMARY STEPS
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DETAILED STEPS
Examples
The following example shows how to enable service audits on serial interface 4:23:
interface serial 4:23isdn bcac service audit
The following example shows how to disable service trigger 4 on serial interface 4:23:
interface serial 4:23no isdn bcac service audit trigger 4See the command page for the isdn bcac service audit trigger command for a list of the triggers that are set.
The following example shows how to configure service audits on the entire interface:
interface serial 4:23isdn bcac service audit interfaceConfiguring BCAC Service State Triggers
Perform this task to configure BCAC service state triggers:
SUMMARY STEPS
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5.
DETAILED STEPS
Examples
The following example shows how to enable the SERV status message for provisioning the B channels on serial interface 4:23:
interface serial 4:23isdn bcac service update provisionThe following example shows how to trigger service state updates on serial interface 4:23:
interface serial 4:23isdn bcac service update linkup
Configuring BCAC Message Retransmission
Perform this task to configure retransmission of BCAC service messages:
SUMMARY STEPS
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DETAILED STEPS
Examples
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 2:23isdn bcac service retry in-serv-on-failThe following example shows how to set the maximum number of service message retransmissions on serial interface 2:23 to 50:
interface serial 2:23isdn bcac service retry max 50The following example shows how to change the service timers to 600 ms on serial interface 2:23:
interface serial 2:23isdn bcac service timer 600Configuring B-Channel Selection Order
Perform this task to configure selection order of the ISDN B channels:
SUMMARY STEPS
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DETAILED STEPS
Examples
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-robinConfiguring ISDN Syslog Messages
Perform this task to configure logging of ISDN syslog messages:
SUMMARY STEPS
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DETAILED STEPS
Examples
The following example shows how to configure ISDN syslog logging:
isdn loggingConfiguration Examples for ISDN BCAC and Round-Robin Channel Selection Enhancements
See the examples following each task in the preceding sections, for ideas about how the ISDN CBAC enhancements and other new ISDN features can be introduced into your network.
Additional References
For additional information related to the ISDN enhancements, see the following sections:
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Related Documents
Standards
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.
1 Not all supported standards are listed.
MIBs
None
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
Technical Assistance
Command Reference
This section documents the following new and modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.3 command reference publications.
New Commands
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Modified Commands
isdn bcac service audit
To enable service audits on an interface configured for B-Channel Availability Control (BCAC), use the isdn bcac service audit command in interface configuration mode. To disable service audits, use the no form of this command.
isdn bcac service audit
no isdn bcac service audit
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
This commands starts service audits for all triggers. Use the isdn bcac service audit trigger command to selectively enable and disable audit triggers.
Examples
The following example shows how to configure service audits on serial interface 2:23:
interface serial 2:23isdn bcac service auditRelated Commands
isdn bcac service audit interface
To specify that B-Channel Availability Control (BCAC) service audit needs to be triggered on the entire interface, use the isdn bcac service audit interface command in interface configuration mode. To change or remove the specification, use the no form of this command.
isdn bcac service audit interface
no isdn bcac service audit interface
Syntax Description
This command has no arguments or keywords.
Defaults
The default can be to trigger audits on a single channel, a group of channels, or the entire interface, depending upon the type of trigger set. See the "Usage Guidelines" section for the isdn bcac service audit trigger command for the list of triggers.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command when the service audit needs to be triggered on the entire interface when a condition to trigger the service audit is triggered for any channel.
Examples
The following example shows how to configure service audits on serial interface 2:23:
interface serial 2:23isdn bcac service audit interfaceRelated Commands
isdn bcac service audit trigger
To re-enable individual B-Channel Availability Control (BCAC) service triggers, use the isdn bcac service audit trigger command in interface configuration mode. To disable individual service triggers, use the no form of this command.
isdn bcac service audit trigger number
no isdn bcac service audit trigger number
Syntax Description
number
A number from 1 to 6 that disables specific service triggers; see a list of these triggers in the "Usage Guidelines" section.
Defaults
All triggers are configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
The service audit procedure can be used by the either the user or network side to bring both ends of the interface into agreement about the service status through an exchange of SERV and SERV ACK messages.
Following is the list of triggers with the conditions that cause them. Triggers 1 through 4 are triggered by single-channel audits. Trigger 5 occurs on the entire interface. Trigger 6 applies to a group of channels, which in some cases may apply to the entire interface.
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Examples
The following example shows how to disable service trigger 4 on serial interface 2:23:
interface serial 2:23no isdn bcac service audit trigger 4Related Commands
isdn bcac service retry in-serv-on-fail
To specify that the B-Channel Availability Control (BCAC) service state of the channel needs to be changed to In-Service because no acknowledgment was received, use the isdn bcac service retry in-serv-on-fail command in interface configuration mode. To change or remove this specification, use the no form of this command.
isdn bcac service retry in-serv-on-fail
no isdn bcac service retry in-serv-on-fail
Syntax Description
This command has no arguments or keywords.
Defaults
Original service state is maintained.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command when there is a need to change the service state of a channel to In-Service when no acknowledgment is received, even after retransmitting the service message the maximum number of allowed times. If this command is not configured, the original service state is maintained.
Examples
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 2:23isdn bcac service retry in-serv-on-failRelated Commands
isdn bcac service retry max
To specify the maximum number of times a B-Channel Availability Control (BCAC) service message can be retransmitted when unacknowledged, use the isdn bcac service retry max command in interface configuration mode. To remove or change the specification, use the no form of this command.
isdn bcac service retry max retries
no isdn bcac service retry max retries
Syntax Description
retries
A number from 0 to 127 that determines the maximum number of times that a service message can be retransmitted when unacknowledged. Default is 2.
Defaults
Maximum retransmissions is 2.
Command Modes
Interface configuration
Command History
Usage Guidelines
When a SERV message is sent to the far side, SERV message timer T3M1 or T323 is started. If no SERV ACK message is received before these timers expire, the SERV message is retransmitted. This command determines how many times retransmission occurs.
Examples
The following example shows how to set the maximum service message retransmissions on serial interface 2:23 to 50:
interface serial 2:23isdn bcac service retry max 50Related Commands
isdn bcac service timer
To change the value of the B-Channel Availability Control (BCAC) T3M1 or T323 service message timer, use the isdn bcac service timer command in interface configuration mode. To change the timer value, use the no form of this command.
isdn bcac service timer timer-value
no isdn bcac service timer timer-value
Syntax Description
timer-value
Length, in milliseconds (ms), of the T3M1 or T323 service message timer. Valid range is from 500 to 120000 ms; default is 120000 ms.
Defaults
The T3M1 or T323 service message timer defaults to 120000 ms.
Command Modes
Interface configuration
Command History
Usage Guidelines
The T3M1 or T323 service message timer is started when a SERV message is sent to the far side.
Examples
The following example shows how to change the service timers to 600 ms on serial interface 2:23:
interface serial 2:23isdn bcac service timer 600Related Commands
isdn bcac service update linkup
To trigger updates of the B-Channel Availability Control (BCAC) service states between peer nodes through exchange of SERV and SERV ACK messages, use the isdn bcac service update linkup command in interface configuration mode. To disable triggering of updates, use the no form of this command.
isdn bcac service update linkup
no isdn bcac service update linkup
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command updates the service states of all the channels to the far side of the interface by exchanging SERV and SERV ACK messages whenever Layer 2 comes up.
Examples
The following example shows how to trigger service state updates on serial interface 2:23:
interface serial 2:23isdn bcac service update linkupRelated Commands
isdn bcac service update provision
To enable functionality of service status for provisioning the ISDN B channels, use the isdn bcac service update provision command in interface configuration mode. To disable provisioning, use the no form of this command.
isdn bcac service update provision
no isdn bcac service update provision
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command enables functionality of service status for provisioning the B channels, which for the Cisco implementation happens only on reboot.
Examples
The following example shows how to enable the service service status for provisioning the B channels on serial interface 2:23:
interface serial 2:23isdn bcac service update provisionRelated Commands
isdn bchan-number-order
To configure an ISDN PRI interface to make outgoing call selection in ascending descending, or round-robin order, use the isdn bchan-number-order command in interface configuration mode. To restore the default, use the no form of this command or reconfigure the interface with the new value.
isdn bchan-number-order {ascending | descending} [round-robin]
no isdn bchan-number-order
Syntax Description
Defaults
Selection default is ascending for the network side; descending for the user side.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command supports ascending, descending, and round-robin B-channel selection schemes. This command is for PRI configuration only.
This command supports ascending and descending B-channel selection by instructing the router to select the lowest or highest available B channel starting at either channel B1 (ascending) or channel B23 for a T1 and channel B31 for an E1 (descending).
In the ascending B-channel selection scheme, for example, if the channel selected for the last call was channel 14, then if channel x, where x is any channel number less than or equal to 14, becomes available by the time a channel is selected for the next call, that channel will be selected for the call.
In the round-robin B-channel selection scheme, the next channel selected is the current channel number x plus 1 for ascending, or current channel number x minus 1 for descending configuration.
When the channel selection software routine reaches channel 1 (the bottom for descending) or channel 23 for T1 and channel 31 for E1 (the top for ascending), the software routine wraps around. An example for a descending configuration: After reaching channel 1, the routine goes back to channel 31 or 23 and then decrements the count from there.
Examples
The following example configures the outgoing B-channel order on a PRI interface to be in ascending order. The router will select the lowest available B channel beginning with channel B1.
interface serial 5:10 isdn bchan-number-order ascendingThe following example configures the outgoing B-channel order on a PRI interface to be round-robin in ascending order.
interface serial 4:23 isdn bchan-number-order ascending round-robinisdn logging
To enable logging of ISDN syslog messages, use the isdn logging command in global configuration mode. To disable logging, use the no form of this command.
isdn logging
no isdn logging
Syntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Global configuration
Command History
Usage Guidelines
This command supports syslog logging of the following ISDN events:
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Examples
The following example shows how to configure ISDN syslog logging:
isdn loggingRelated Commands
isdn protocol-emulate (dial)
To configure the Layer 2 and Layer 3 port protocol of a BRI voice port or a PRI interface to emulate NT (network) or TE (user) functionality, use the isdn protocol-emulate command in interface configuration mode. To restore the default (user), use the no form of this command.
isdn protocol-emulate {user | network}
no isdn protocol-emulate
Syntax Description
user
Specifies Layer 2 and Layer 3 port protocol operation as TE (port functions as QSIG slave).
network
Specifies Layer 2 and Layer 3 port protocol operation as NT (port functions as QSIG master).
Defaults
The port functions as QSIG slave.
Command Modes
Interface configuration
Command History
Usage Guidelines
You can use this command to configure the Cisco AS5300 PRI interface to serve as either the primary QSIG slave or the primary QSIG master. To disable QSIG signaling, use the no form of this command.
If you use the no isdn protocol-emulate command, the Layer 2 and Layer 3 protocol emulation defaults to user.
Examples
The following example configures the Layer 2 and Layer 3 function of T1 PRI interface 23 to act as the QSIG master (NT):
interface serial 1:23isdn protocol-emulate networkThe following example configures the Layer 2 and Layer 3 function of a BRI voice port to operate as QSIG slave (TE):
interface bri 1isdn protocol-emulate userThe following example configures the Layer 2 and Layer 3 function of an E1 PRI interface to operate as QSIG slave (TE):
interface serial 4:23isdn protocol-emulate userRelated Commands
Glossary
PBX—private branch exchange.
RESTART—restart message.
RESTART ACK—restart acknowledge message.
STATUS ENQ—status enquiry message.
SERV—service message.
SERV ACK—service acknowledge message.
Note
Guest
