IMPORTANT

The Transparency Profile is the recommended method of configuring transparency on the SBC Core for new deployments as well as when applying additional transparency configurations to existing deployments. Do not use IP Signaling Profile flags in these scenarios because the flags will be retired in upcoming releases.

Refer to the SBC SIP Transparency Implementation Guide for additional information.

The SBC acting as P-CSCF or IBCF in IMS deployment scenario supports 199 response code for early media termination using the support199OptionTag flag configurable from the egress IP Signaling Profile. If enabled, the SBC includes Option tag in Supported Header for the 199 Extension.

On the other hand, when SBC receives a progress response for INVITE, SBC checks for the response code received from the core; and if the response is 199, SIPSG consumes the response and does not relay to ingress trunk group.

For example, a User Agent Client (UAC) might receive multiple 18x responses from different destinations creating multiple early sessions, when a downstream entity forks the request. The forking entity, on receipt of final response from one of the forked branch, it can use 199 response code (i.e. if the UAC supports 199) to indicate the termination of that particular early dialog. The forking SIP entity might wait for ‘best response code’ and hence cannot send a final response upstream yet. A 199 early session termination indication will help the UACs to release any resources associated with corresponding early session immediately.

The CLI syntax to enable the support199OptionTag is shown below:

% set addressContext <address context name> zone <zone name> sipTrunkGroup <TG name> signaling support199OptionTag <disabled|enabled>

Note

If the flag support199OptionTag is enabled, the SBC adds a 199 option tag to the Supported header for an egress INVITE. The SBC relays a 199 option tag received on the ingress, which is controlled by the Supported/Require Profile. The SBC releases resources associated with an early dialog if a 199 response is received. This behavior is independent of the configuration of the flags support199OptionTag and dialogTransparency.

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