REFER-Initiated Call Transfer

In prior releases, the Oracle® Enterprise Session Border Controller supported REFER-initiated call transfer either by proxying the REFER to the other User Agent in the dialog, or by terminating the received REFER and issuing a new INVITE to the referred party. These static alternate operational modes could be configured for specific SIP interfaces, realms, or session agents.

Release S-C6.2.0 enhances support with an additional operational mode that determines on a call-by-call basis whether to proxy the REFER to the next hop, or terminate the REFER and issue an INVITE in its stead.

Note:

With the release of Version S-C6.2.0, support for REFER-initiated call transfer is no longer available for SIP interfaces; support must be configured for realms and/or session agents.

Version S-C6.2.0 provides a new configuration parameter dyn-refer-term, and a revised refer-call-transfer parameter (both available in realm-config configuration mode) that specify call transfer modes.

With the refer-call-transfer parameter set to disabled (the default), all received REFERs are simply proxied to the peer User Agent.

With the refer-call-transfer parameter set to enabled, the Oracle® Enterprise Session Border Controller terminates all REFERs, generates a new INVITE, and sends the INVITE to the address in the Refer-To header.

With the refer-call-transfer parameter set to dynamic (a new value introduced with Version S-C6.2.0), the Oracle® Enterprise Session Border Controller determines REFER handling on a call-by-call basis as follows:

1. Check the refer-call-transfer value for the session agent from which the REFER was received, or for ingress realm (the realm that received the REFER).

   If the value is disabled, proxy the REFER to the peer User Agent, to complete REFER processing.

   If the value is enabled, terminate the REFER and issue an new INVITE to the referred party, to complete REFER processing.

   If the value is dynamic, identify the next hop egress realm.

2. Check the dyn-refer-term value for the next hop egress realm.

   If the dyn-refer-term value is disabled (the default), proxy the REFER to the next hop to complete REFER processing.

   If the dyn-refer-term value is enabled, terminate the REFER and issue an new INVITE to the referred party to complete REFER processing.