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The 

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supports Dialog Transparency which involves passing through "Call-ID", "From" tag, and "To" tag transparently in all the requests and responses. With a call traversing through multiple paths in an IMS VoLTE network, UEs and intermediate IMS entities need to correlate a call based on correct dialog information under various scenarios such as call transfer.

The dialogTransparencyflag under the Zone object passes dialogs transparently for SIP messages processed in that specified zone. If dialog transparency is disabled, SBC translates the dialog identifiers in the Target-Dialog header received in INVITE and REFER messages and sends the Target-Dialog header with translated dialog identifiers on the other leg. If dialog transparency is enabled, Target-Dialog header translation is not performed. However, the header is transparently passed if configured in transparency profile.

The dialogTransparency flag must be enabled on both ingress and egress zones because of the flag is only enabled on one zone, all calls and messages are rejected. In this situation, the sonusSbxDialogTransparencyMisConfiguredNotification alarm is raised on the zone in which the flag is disabled.

The following features are not supported on SBC when Dialog Transparency is enabled:

  • Support of local handling of REFER (REFER relay is supported)
  • Late media support 
  • Dialog Transparency support in REGISTER
  • NICE recording call flows
  • GW-GW support

SBC implements the SIP Dialog Identification internally based on certain SIP parameters. Manipulation of these parameters using the dialog scope SMM affects the intergrity of the dialog scope SMM functionality. The parameters to be considered differs based on whether the Dialog Transparency is enabled or not.

For Dialog Scope SMM without Dialog Transparency

If the advanced SMM is enabled in any adapter profile which applies to Trunk Group, manipulation of "From tag", "To tag" and "Call-ID header" is not supported for that Trunk Group. In rare cases where there is no other solution, manipulation of "To Tag" may be tested and implemented with the knowledge and support of Sonus Technical Support.

This only works for Basic Call Flows.

For Dialog Scope SMM with Dialog Transparency

If the advanced SMM is enabled in any adapter profile applying to a Trunk Group under a zone where the Dialog Transparency is enabled, manipulation of "branch parameter", "Call-Info parameter" or "Call-ID header" is not supported for that Trunk Group.

For example (no dialog transparency): consider a configuration where dialog scope variable is used in the inbound adapter profile applicable to Trunk Group TG_1 via Zone or Trunk Group. The SMM rules for an action specifying modification of "From-tag", "To tag" or "Call-ID" cannot be present in that inbound adapter as well as in the outbound adapter if one applies to "TG_1" via Trunk Group or Zone.

 

For CLI and EMA configuration details, see:

Dialog Transparency Call Flow

Only relevant headers are shown in this call flow.

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