Guest

Cisco IOS Software Releases 12.4 T

H.323 Gatekeeper-Based Load Balancing

  • Viewing Options

  • PDF (284.1 KB)
  • Feedback
H.323 Gatekeeper-Based Load Balancing

Table Of Contents

H.323 Gatekeeper-Based Load Balancing

Contents

Contents

Prerequisites for H.323 Gatekeeper-Based Load Balancing

Restrictions for H.323 Gatekeeper-Based Load Balancing

Information About H.323 Gatekeeper-Based Load Balancing

Tech-Prefix Based Routing

IP-to-IP Gateway Selection

Carrier-Based Routing

How to Enable H.323 Gatekeeper-Based Load Balancing

Enabling Capacity Based Gateway Selection

Examples

Verifying H.323 Gatekeeper-Based Load Balancing

Troubleshooting Tips

Configuration Examples for H.323 Gatekeeper-Based Load Balancing

H.323 Gatekeeper-Based Load Balancing: Example

Gateway Configuration for Trunk Groups: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

call-routing hunt-scheme

timer cluster-element

Feature Information for H.323 Gatekeeper-Based Load Balancing

Glossary


H.323 Gatekeeper-Based Load Balancing


First Published: November 17, 2006
Last Updated: November 17, 2006

The H.323 Gatekeeper-Based Load Balancing feature replaces random gateway selection with a selection process based on the capacity of the gateway (or endpoint). With this feature enabled, gateways with the capacity to support more calls than other gateways are routed more calls. Additionally, when the gateways in a zone are out of resources, calls are distributed randomly among all the gateways, and only not to gateways configured with priority 0.

Contents

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for H.323 Gatekeeper-Based Load Balancing" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS 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 H.323 Gatekeeper-Based Load Balancing

Restrictions for H.323 Gatekeeper-Based Load Balancing

Information About H.323 Gatekeeper-Based Load Balancing

How to Enable H.323 Gatekeeper-Based Load Balancing

Configuration Examples for H.323 Gatekeeper-Based Load Balancing

Additional References

Command Reference

Feature Information for H.323 Gatekeeper-Based Load Balancing

Glossary

Prerequisites for H.323 Gatekeeper-Based Load Balancing

This feature is supported on the following platforms Cisco AS5xxx, 3xxx/2xxx,17xx, and 7200.

Gateways that report call capacity (voice or H.323) of the trunks dynamically in RAS messages are preferred. If the gateways do not support this functionality, voice call-capacity must be statically configured in the Cisco gatekeeper. Load balancing can be achieved only if the gatekeeper receives periodic capacity updates from the gateway, or when the capacity of the gateway changes.

It is assumed that each call will consume only one bearer channel.

Capacity reporting from gateway in IRR, ARQ, and DRQ messages.

Tech-prefix, carrier-based, and trunk group-based routing are supported.

Restrictions for H.323 Gatekeeper-Based Load Balancing

Dynamic changes in capacities are not available to gatekeeper, which may affect load balancing. For instance, the gatekeeper may not know the exact utilization of capacity, when the DSO's are:

busied or shutdown

non-RAS calls

mixed protocols (SIP) are used in the gateway.

Voice interfaces, such as Foreign Exchange Stations (FXS) or Ephone do not support load balancing.

Load balancing depends on the capacity reporting from the gateways, which can be delayed. Therefore load balancing is achieved over a period of time, and not on a per-call basis.

Load balancing is not supported for E.164 registrations.

Configuration of endpoint max-calls command is not supported in conjunction with this feature.

IP-to-IP gateway selection should be explicitly specified through invia and outvia configurations in the gatekeeper.

If a gateway does not report call capacity, it will not be selected for termination when the load balancing is configured. Gateways that do not dynamically report the call capacity; configure the call capacity with the endpoint max-calls h323id command in the gatekeeper.


Note This configuration supports only voice call capacity. H.323 IP-to-IP call capacity is not supported.


The gatekeeper does not reject calls when the gateway exceeds maximum call capacity. Call rejection, when needed, is managed by the gateway.

The images used in the gatekeeper cluster should support load balancing for deterministic working. When only primary endpoints advertise their capacities periodically to other gatekeeper clusters, load balancing may be inaccurate.

Information About H.323 Gatekeeper-Based Load Balancing

This feature provides capacity-based gateway selection, and random gateway selection from all the gateways when an overload condition exists (except for gateways with priority 0). Load is calculated based on the number of calls being handled and the maximum call capacity of the gateway. The gateway with the least load is returned as the primary endpoint by the gatekeeper in ACF. Load balancing is extended to all types of call routing such as tech-prefix, carrier-based, and IP-to-IP gateway selection. Load balancing would be achieved over a period of time and should not be calculated on per-call basis.

To configure H.323 Gatekeeper-Based Load Balancing, you should understand the following concepts.

Tech-Prefix Based Routing

IP-to-IP Gateway Selection

Carrier-Based Routing

Tech-Prefix Based Routing

Tech-prefix based routing is used for routing calls based solely on the dialed prefix.

IP-to-IP Gateway Selection

The gatekeeper selects IP-to-IP gateway in a round-robin fashion.

Carrier-Based Routing

Carrier-based routing allows the gatekeeper to route calls based on the destination carrier. The destination carrier can be received from GKTMP server, from the ARQ in a Cisco IOS IP-to-IP gateway, or non-Cisco and third-party devices. The gatekeeper sorts the gateway based on the maximum available calls capacity (absolute) for each carrier. An algorithm returns maximum available gateway as the primary, and the rest of the gateways are reported as alternate endpoints in the order of the available capacity. With the exception of barring the endpoints marked as out-of-resources, the gatekeeper doesn't apply percentage based load-balancing based on the capacities.


Note In carrier based routing with multiple destination carriers, if all the endpoints in the first carrier are out of resources, one endpoint from that carrier is returned as the primary endpoint based on the least load. The endpoints from other carriers are alternates.


How to Enable H.323 Gatekeeper-Based Load Balancing

The H.323 Gatekeeper-Based Load Balancing feature monitors the current capacities of the gateway when multiple gateways are registered to the same zone and have the routing capability to handle the same call.

This section describes the following tasks:

Enabling Capacity Based Gateway Selection (required)

Verifying H.323 Gatekeeper-Based Load Balancing (optional)

Enabling Capacity Based Gateway Selection

Enabling this feature distributes gateways based on capacity utilization. To enable the selection of the gateway based on the relative size of the gateway, perform the following steps.

SUMMARY STEPS

1. enable

2. configure terminal

3. gatekeeper

4. call-routing hunt-scheme percentage-capacity-util

5. timer cluster-element resource-update seconds

6. exit

7. end

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2 

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3 

gatekeeper

Example:

Router(config)# gatekeeper

Enters gatekeeper configuration mode.

Step 4 

call-routing hunt-scheme percentage-capacity-util

Example:

Router(config-gk)# call-routing hunt-scheme percentage-capacity-util

Selects a terminating gateway based on capacity, even when an overload condition exists.

Step 5 

timer cluster-element resource-update seconds

Example:

Router(config-gk)# timer cluster-element resource-update 4

Dynamically sends capacity updates to an alternate gatekeeper in a cluster scenario.

Step 6 

exit

Example:

Router(config-gk)# exit

Exits gatekeeper configuration mode.

Step 7 

end

Example:

Router(config)# end

Exits global configuration mode.

Examples

Router> enable
Router# configure terminal
Router(config)# gatekeeper
Router(config-gk)# call-routing hunt-scheme percentage-capacity-util
Router(config-gk)# timer cluster-element resource-update 4
Router(config-gk)# exit
Router(config)# end

Verifying H.323 Gatekeeper-Based Load Balancing

Use the following show commands on both originating and terminating gateways to verify the implementation of the H.323 Gatekeeper-Based Load Balancing feature.

show gatekeeper status

In the following sample output the Hunt Scheme: Percentage Capacity Util line indicates that the load balancing feature is enabled:

Router# show gatekeeper status

    Gatekeeper State: UP
    Load Balancing:   DISABLED
    Flow Control:     DISABLED
    Zone Name:        GKB
    Accounting:       DISABLED
    Endpoint Throttling:        DISABLED
    Security:         DISABLED
    Maximum Remote Bandwidth:              unlimited
    Current Remote Bandwidth:              0 kbps
    Current Remote Bandwidth (w/ Alt GKs): 0 kbps
    Hunt Scheme: Percentage Capacity Util

show gatekeeper circuits

The following example shows sample debug output for maximum and utilized circuit capacity information for each trunk:

Router# show gatekeeper circuits 
 

                      CIRCUIT INFORMATION
                      ===================
Circuit       Endpoint   Max Calls Avail Calls Resources     Zone
-------       --------   --------- ----------- ---------     ----
XYZ
              Total Endpoints: 2
              TGW-1
                                                    23        16          Available
              TGW-2
                                                    46        31          Available

Troubleshooting Tips

Use the debug gatekeeper dns 10 command to verify domain name server information found on the gatekeeper.

To display all information related to the load balancing, the debug gatekeeper dns 10 command must be enabled before the debug gatekeeper endpoint 10 command.

Use the debug gatekeeper endpoint 10 command to verify that endpoint capacities are updated.

Use the debug gatekeeper gup asn1 command in a cluster scenario to verify that the new Gatekeeper Update Protocol (GUP) asn1 resourceUpdateIndication is used for updating the capacity of trunks or carries between the gatekeepers in the gatekeeper cluster.

Use the debug gatekeeper main 10 command to verify that the routing information used by the gatekeeper.

Use the debug h225 asn1 command to display the GUP events or Abstract Syntax Notation 1 (ASN.1) details.


Note For examples of show and debug command output and details on interpreting the output, see the following resources:

Cisco IOS Debug Command Reference, Release 12.4T

Cisco IOS Voice Troubleshooting and Monitoring Guide

Troubleshooting and Debugging VoIP Call Basics

Voice Multiservice Debug Lookup


Configuration Examples for H.323 Gatekeeper-Based Load Balancing

This section provides the following configuration examples:

H.323 Gatekeeper-Based Load Balancing: Example

Gateway Configuration for Trunk Groups: Example

H.323 Gatekeeper-Based Load Balancing: Example

gatekeeper 
zone local GK1 cisco.com 10.13.32.184
zone cluster local BGL-CL1 BGL-GK1 
element GK2 10.13.32.182 1719 
element GK3 10.13.32.183 1719 
! 
zone prefix GK1 9362* gw-priority 8 5850-GW4 GW1-5350 
zone prefix GK1 9362* gw-priority 2 GW2-3745 GW3-3845
zone prefix GK1 9845* gw-priority 6 5850-GW4 
zone prefix GK1 9845* gw-priority 4 GW3-3845 GW2-3745 GW1-5350
accounting 
timer cluster-element announce 10 
timer cluster-element resource-update 10 
no shutdown
call-routing hunt-scheme percentage-capacity-util 
server registration-port 1111

Gateway Configuration for Trunk Groups: Example

The following sample ouitput shows trunk group configuration for Analog, ISDN, and CAS voice interfaces on the gateway.

.
.
.
 trunk group  tg
 carrier-id ABC

voice-port 2/1/0
 trunk-group tg

interface Serial2:23
 trunk-group tg
 
controller T1 1/0
ds0-group 1 timeslots 1-10 type e&m-fgd
 cas-custom 1
 trunk-group tg 
.
.
.

Additional References

The following sections provide references related to the H.323 Gatekeeper Based Load-Balancing feature.

Related Documents

Related Topic
Document Title

General trunk and carrier-based routing

VoIP Gatekeeper Trunk and Carrier Based Routing Enhancements

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t11/feature/guide/ftgkrenb.html

VoIP Gateway Trunk and Carrier Based Routing Enhancements

http://www.cisco.com/en/US/docs/ios/12_2t/12_2t11/feature/guide/ftgwrepg.html


Standards

Standard
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.


MIBs

MIB
MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

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

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


RFCs

RFC
Title

No new RFCs are supported by this feature.


Technical Assistance

Description
Link

The Cisco Technical Support & Documentation website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, tools, and technical documentation. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/techsupport


Command Reference

This section documents new commands only.

call-routing hunt-scheme

timer cluster-element

call-routing hunt-scheme

To enable capacity-based load-balancing, use the call-routing hunt-scheme command in gatekeeper configuration mode. To disable this function, use the no form of this command.

call-routing hunt-scheme percentage-capacity-util

no call-routing hunt-scheme

Syntax Description

percentage-capacity-util

Selects the gateway with lowest percentage capacity utilized.


Command Default

This command is disabled.

Command Modes

Gatekeeper configuration

Command History

Release
Modification

12.4(11)T

This command was introduced.


Usage Guidelines

Use the call-routing hunt-scheme command to turn on load balancing based on the capacity of the gateway and verify that gateway capacity reporting is enabled.

Examples

The following example shows how to enable capacity-based load balancing:

Router(gk-config)# call-routing hunt-scheme percentage-capacity-util

Related Commands

Command
Description

timer cluster-element

Sets the length of time between capacity messages to the local gatekeeper.


timer cluster-element

To configure the length of time between dynamic capacity messages to the local gatekeeper, use the timer cluster-element command in gatekeeper configuration mode. To stop sending dynamic updates, use the no form of this command.

timer cluster-element {announce | resource-update} seconds

no timer cluster-element

Syntax Description

announce

Configures the lengh of time between announcement messages to the gatekeepers in the local cluster.

resource-update

Configures the lengh of time between resource update messages to gatekeepers in the local cluster.

seconds

Number of seconds between resource updates sent to the gatekeeper. The valid range is 1 to 60. There is no default value.


Command Default

Disabled by default.

Command Modes

Gatekeeper configuration

Command History

Release
Modification

12.4(11)T

This command was introduced.


Usage Guidelines

Use the timer cluster-element command to manage the length of time between resource updates and time between announcement messages sent to the gatekeeper.

Examples

The following example shows the time between resource update messages to gatekeepers in local cluster being set to 20 seconds:

Router(config-gk)# timer cluster-element resource-update 20

Related Commands

Command
Description

call-routing hunt-scheme

Enables capacity-based load-balancing.


Feature Information for H.323 Gatekeeper-Based Load Balancing

Table 35 lists the features in this module and provides links to specific configuration information. Only features that were introduced or modified in Cisco IOS Release 12.4(Pi5) or a later release appear in the table.

For information on a feature in this technology that is not documented here, see the "Cisco IOS H.323 Feature Roadmap."

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS 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 35 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.


Table 35 Feature Information for H.323 Gatekeeper-Based Load Balancing 

Feature Name
Releases
Feature Information

H.323 Gatekeeper-Based Load Balancing

12.4(11)T

H.323 Gatekeeper-Based Load Balancing feature balances calls based on the capacities of the gateway distribution of the calls when the gateways in a zone are considered to be in an overload condition.

The following commands were introduced or modified by this feature: call-routing hunt-scheme and percentage and timer cluster-element.


Glossary

GK—Gatekeeper.

GUP—Gatekeeper Update Protocol

GW—Gateway.

IRR—Information request.

GKTMP—Gatekeeper Transaction Message Protocol.

RAI—ResourcesAvailableIndicate.

ARQ—Admission request.

LRQ—Location request.

CME—Cisco Call Manager Express.

IPIPGW—IP-to-IP call functionality on VoIP gateways.


Note See Internetworking Terms and Acronyms for terms not included in this glossary.