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H.323 Trunk Group Services

The 'h323TrunkGroup' object binds an H.323 trunk to an H.323 Trunk group and assigns a name and properties to this binding.

The administrative state of the H.323 service is by default disabled, inactive, and configurable. When enabled, the H.323 service is active. Temporarily remove and restore this service by toggling its operational state between “inService” and “outOfService”. Since removing service in this manner may disrupt existing calls, a confirmation prompt displays to verify your intent.

For configuration details, refer to Zone - H323 Trunk Group - CLI or Trunk Group - H323 Trunk Group (EMA) pages.

For deployment scenarios, refer to H.323 Deployment Scenarios.

SIP-H.323 Interworking Function for Video

SIP-H.323 Interworking Function (IWF) is a logical entity allowing interworking between SIP and H.323 protocols. IWF can be implemented as part of a VoIP network server such as an H.323 Gatekeeper, a SIP Proxy, or an external SIP-H.323 signaling gateway. The SBC Core supports SIP-H.323 IWF as an external SIP-H.323 signaling gateway.

An IWF includes the following functionality:

  • Mapping of the call setup and tear down sequences
  • Registering H.323 and SIP endpoints with SIP registrars and H.323 gatekeepers
  • Resolving H.323 and SIP addresses
  • Maintaining the H.323 and SIP state machines
  • Negotiating terminal capabilities
  • Opening and closing media channels
  • Mapping media-coding algorithms for H.323 and SIP networks
  • Reserving and releasing call-related resources
  • Processing of mid-call signaling messages
  • Handling of services and features

H.323 Overlap Dialing Support

The SBC Core supports H.323 overlap dialing, when configured, to process an incoming H.323 call request with incomplete called party digits in the initial SETUP message and subsequent digits in INFO messages to complete the dial sequence resulting in a successful route. When configured on the egress side, a SETUP message is sent without sufficient called party digits and forwards extra digits as it receives them from the ingress side in INFO messages to complete the call.

To configure H.323 overlap dialing service, see Zone - H323 Trunk Group - CLI or H323 Trunk - Services - Advanced - Overlap Dialing.

H.323 Signaling Agent

The SBC acts as SIP/SIP-I Back-to-Back User Agent (B2B UA) for packet-to-packet calls, and as a H.323 Gateway based on the following:

  • H.323
  • H.225
  • H.245
  • H.450

H.323 Redundancy

The SBC supports H.323 redundancy on a best effort basis depending upon the TCP activity of the endpoint. Stable calls with endpoints that do not send any TCP activity (most audio-only calls) will survive a switchover independent of the call rate. Endpoints that do use short TCP keep-alive packets, or are chatty based on their application (such as video), most likely will not survive a switchover.

H.323-SIP and SIP-H323 Calls

When using H.323-SIP and SIP-H.323 call flows, an additional re-INVITE/Update may get generated towards the SIP side. To suppress this, enable the IP Signaling Profile (IPSP) flag Minimize Relaying Of Media Changes From Other Call Leg at SIP side.

For CLI IPSP flag details, refer to Flags - CLI.

For EMA IPSP flag details, refer to Common IP Attributes - Flags.


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