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This document describes the Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature that was introduced in Cisco IOS Release 12.1(2)T. This document contains the following sections:
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature supplements the existing support for alternate gatekeepers and adds support for the alternate gatekeeper field (altGKInfo) to the admission rejection (ARJ). This allows a gateway to move between gatekeepers during the admission request (ARQ) phase.
The altGKInfo consists of two subfields: the alternateGatekeeper and the altGKisPermanent flag. The alternateGatekeeper is the list of alternate gatekeepers. The altGKisPermanent is a flag that indicates whether the gatekeepers in the associated alternateGatekeeper field are permanent or temporary.
If the current permanent gatekeeper becomes nonresponsive and the altGKisPermanent flag is set to FALSE, the gateway sets the internal state of the altGKisPermanent flag to TRUE. This allows the gateway to accept the alternate gatekeeper list from one of the gatekeepers in the existing alternate gatekeeper list.
When the gateway accepts the alternate gatekeeper list from first the ARJ message, the gateway retransmits an ARQ message to a gatekeeper on the alternate gatekeeper list. The selection is based on priority of the alternate gatekeepers.
The retransmission of the ARQ message depends on the current state of the altGKisPermanent flag and the current state of the needToRegister flag of each alternate gatekeeper as follows:
If the gateway receives an ARJ message without the AltGKInfo field, it accepts the rejection.
If the gateway exhausts the list of alternate gatekeepers without receiving any response from an alternate gatekeeper, the gateway returns to the RRQ phase.
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature allows gateways to move between gatekeepers without requiring a reconfiguration of the gateway or a gatekeeper failover in the gateway.
Gateways can be configured to switch from their primary gatekeeper to an alternate gatekeeper if a failure or outage occurs. If an outage occurs and gateways move from one gatekeeper to another, there may be an imbalance in the number of gateways registered to each gatekeeper. The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 helps to restore the balance (when the outage has been corrected) by allowing some of the gateways to be moved back to their proper gatekeepers.
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature has the following restrictions and limitations:
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature is related to the H.323 VoIP Gateway for Cisco Access Platforms feature and the Gateway Support for Alternate Gatekeepers feature.
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature is supported on any existing IOS gateway platforms, including the following:
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on CCO.
RFCs
No new or modified RFCs are supported by this feature.
The Ecosystem Gatekeeper Interoperability Enhancements, Phase 2 feature requires the Cisco H.323 VoIP Gateway for Cisco Access Platforms feature.
There are no configuration tasks for the Ecosystem Gatekeeper Interoperability Enhancements, Phase 2.
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Note If you configure static gatekeepers from the command line interface (CLI), they will still be inserted into the alternate gatekeeper list during the admission confirmation (ACF) phase. |
Because there are no configuration tasks, no configuration examples are provided.
ACF---An RAS message sent as an admission confirmation.
ARJ---An RAS message sent as an admission rejection.
ARQ---An RAS message sent as an admission request.
gatekeeper---A gatekeeper maintains a registry of devices in the multimedia network. The devices register with the gatekeeper at startup, and request admission to a call from the gatekeeper.
The gatekeeper is an H.323 entity that provides address translation and control access to the network for H.323 terminals and gateways. The gatekeeper may provide other services to the H.323 terminals and gateways, such as bandwidth management and locating gateways.
gateway---A gateway allows H.323 terminals to communicate with non-H.323 terminals by converting protocols. A gateway is the point at which a circuit-switched call is encoded and repackaged into IP packets.
A H.323 gateway is an endpoint that provides real-time, two-way communications between H.323 terminals on the network and other ITU-T terminals in the WAN, or to another H.323 gateway.
GCF---An RAS message sent as a gatekeeper confirmation.
GRJ---An RAS message sent as a gatekeeper rejection.
GRQ---An RAS message sent as a gatekeeper request.
E.164---ITU-T recommendation for international telecommunication numbering, especially in ISDN, BISDN, and SMDS. An evolution of standard telephone numbers.
H.323---An International Telecommunication Union (ITU-T) standard that describes packet-based video, audio, and data conferencing. H.323 is an umbrella standard that describes the architecture of the conferencing system, and refers to a set of other standards (H.245, H.225.0, and Q.931) to describe its actual protocol.
LRQ---A RAS message sent as a location request.
POTS---Plain old telephone service. Basic telephone service supplying standard single line telephones, telephone lines, and access to the PSTN.
PSTN---Public switched telephone network. PSTN refers to the local telephone company.
RAS---Registration, admission, and status protocol. This is the protocol that is used between endpoints and the gatekeeper to perform management functions. The RAS signaling function performs registration, admissions, bandwidth changes, status, and disengage procedures between the VoIP gateway and the gatekeeper.
RCF---An RAS message sent as a registration confirmation.
RRJ---An RAS message sent as a registration rejection.
RRQ---An RAS message sent as a registration request.
VoIP---Voice over IP. The ability to carry normal telephone-style voice over an IP-based Internet with POTS-like functionality, reliability, and voice quality. VoIP is a blanket term which generally refers to Cisco's standards-based (H.323, etc.) approach to IP voice traffic.
Posted: Wed May 31 11:45:19 PDT 2000
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