Methods, systems, and computer readable media for optimized inter-session border controller (SBC) attended call transfer with re-use of transfer target session

A system for optimized attended inter-session border controller (SBC) call transfer with transfer target session re-use, the system comprising:

• a first SBC for establishing a first media session between a transferor and a transferee;
• and
• a second SBC, for, in response to a session initiation protocol (SIP) INVITE message initiated by the transferor and routed to the second SBC by a session router, establishing a second media session between the transferor and a transfer target;
• wherein the first SBC is configured for receiving a SIP REFER message from the transferor and including a dialog ID associated with the second media session and, in response, determining that the dialog ID does not correspond to a media session currently being handled by the first SBC and sending a SIP INVITE message to a plurality of SBCs, including the second SBC, that are in a load sharing group with the first SBC, the SIP INVITE message including the dialog ID associated with the second media session;
• wherein the second SBC is configured for receiving the SIP INVITE message sent by the first SBC, recognizing the SIP INVITE message sent by the first SBC as requesting an attended call transfer to the transfer target, and, in response, signaling with the transfer target and the first SBC to re-use the second media session to establish a media session between the transferee and the transfer target;
• wherein, in signaling with the first SBC and the transfer target to re-use the second media session to establish a media session between the transferee and the transfer target, the second SBC is configured for:
• sending a SIP Re-INVITE message to the transfer target;
• receiving a success response from the transfer target;
• and
• in response to receiving the success response from the transfer target, sending a success response to the first SBC;
• wherein the first and second SBCs are configured for establishing a media session between the first and second SBCs;
• and
• wherein the first SBC is configured for replacing an out-dialog of the first media session with an out-dialog of the media session between the first and second SBCs;
• and the second SBC is configured for replacing an in-dialog of the second media session with an in-dialog of the media session between the first and second SBCs.

A non-transitory computer readable medium having stored thereon executable instructions that when executed by a processor of a computer control the computer to perform steps comprising:

• at a first session border controller (SBC), establishing a first media session between a transferor and a transferee;
• at a second SBC, in response to a SIP INVITE message initiated by the transferor and routed to the second SBC by a session router, establishing a second media session between the transferor and a transfer target;
• receiving, at the first SBC, a SIP REFER message initiated by the transferor and including a dialog ID associated with the second media session and, in response, determining that the dialog ID does not correspond to a media session currently being handled by the first SBC and sending a SIP INVITE message to a plurality of SBCs, including the second SBC, that are in a load sharing group with the first SBC, the SIP INVITE message sent by the first SBC including the dialog ID associated with the second media session;
• at the second SBC, receiving the SIP INVITE message sent by the first SBC, recognizing the SIP INVITE message sent by the first SBC as requesting an attended call transfer to the transfer target, and, in response, signaling with the transfer target and the first SBC to re-use the second media session to establish a media session between the transferee and the transfer target, wherein signaling with the first SBC and the transfer target to re-use the second media session to establish a media session between the transferee and the transfer target includes:
• sending a SIP Re-INVITE message to the transfer target;
• receiving a success response from the transfer target;
• and
• in response to receiving the success response from the transfer target, sending a success response to the first SBC;
• establishing a media session between the first and second SBCs;
• at the first SBC, replacing an out-dialog of the first media session with an out-dialog of the media session between the first and second SBCs;
• and
• at the second SBC, replacing an in-dialog of the second media session with an in-dialog of the media session between the first and second SBCs.