Video Conferencing Support for Polycom Terminals

The Enterprise SBC includes support for Polycom video conferencing that implements messaging properly and presents proper addressing information for session billing, as described below.

The Enterprise SBC supports operations in a video conferencing environment with Polycom H323 terminals and a Polycom MCU (Multipoint Conferencing Unit) by relaying H.239/H.245. The Enterprise SBC implements the following messages appropriately:

  • Miscellaneous command message with subtype such as multiPointModeCommand, cancelMultipointModeCommand
  • Conference Indication message with subtype such as terminalNumberAssign, terminalYouAreSeeing

The Enterprise SBC can also resolve a video conference billing issue caused by a NAT device. NAT devices change the sourceCallSignalAddress in a Setup message to the IP address of the NAT device. Deployments that rely on this address in CDRs to bill for the service need this address to be that of the original station behind the NAT. The user sets the addSrcCallSignalAddr option in the h323-stack that receives the incoming Setup to cause the Enterprise SBC to present the desired address.

The srcCallSignalAddress field in the admissionRequest message received by the Enterprise SBC often contains the transportAddress of the calling endpoint. This field is optional for the admissionRequest message. If configured with the option and presented with this field, the Enterprise SBC saves the address for later use in outgoing Setup messages. If the srcCallSignalAddress field in the admissionRequest message is not present, or is equal to 0.0.0.0, the Enterprise SBC does not save it.

Having stored this address, the Enterprise SBC uses it following the steps below. Note that the Setup message in this scenario is preceded by the admission request and confirmation messages from the gatekeeper for the call.

  1. Add the srcCallSignalAddress, saved from the admissionRequest message, into the sourceAddress field of the outgoing Setup message. The Enterprise SBC adds this address in the format of an AliasAddress of type transportID after any other AliasAddresses that are normally included from the incoming Setup sourceAddress field.
  2. Add the remote transport address of the incoming Q.931 TCP connection, into the sourceAddress field of the outgoing Setup message. The Enterprise SBC adds this address in the format of an AliasAddress of type transportID, after the alias that was added in step 1.

The call flow diagram below depicts the Enterprise SBC adding addresses in accordance with this feature.

The Enterprise SBC managing a video conference for a Polycom terminal.

Use the syntax below to set this option on the h323-stack receiving the incoming Setup. 

(h323-stack)# options +addSrcCallSignalAddr

The user can find this process confirmed in the log.h232d log file.