SIP REFER Call Transfer UUI Relay
The SIP REFER Call Transfer User to User Information (UUI) Relay option assists in the transfer of caller details through using the information in the "Refer-To" header in a new "User to User" header in the INVITE to the Referred-to party. This feature only works when the refer-call-transfer option is enabled on the realm or session agent where the REFER is received. This behavior change is enabled by default. This option can be used by a Call Center application to transfer a call with user information to an agent.
A new INVITE is sent with the information about the calling user to the agent by way of the "Refer-To" header using the User to User Information. The product variable needs to relay this UUI as a separate header in the INVITE message while transferring the call to the destination. In this scenario, the product terminates the REFER message having captured the UUI and then sends an INVITE with the UUI to the agent. This feature works only when the refer-call-transfer option is enabled on the Realm or Session Agent where REFER is received. By default this option is enabled and thus needs to be specifically disabled in the configuration if not wanted.
SIP REFER UUI Relay
Refer-To Header
User to User Parameter in INVITE
User to User Header in REFER
INVITE Message Details
The following illustration shows the path of the call from the source to the destination by way of the product utilizing the User to User Information relay
The Oracle Communications Session Border Controller supports the format of User-to-User in the "Refer-To" header in the REFER message. The following example shows the new text after the IP address and port in the second to last line.
REFER sip:7325550000@192.168.28.10:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.29.1:5060;branch=z9hG4bK-10659-1-4 From: 7325550000 <sip:7325550000@192.168.29.1:5060>;tag=1 To: 7321110000 <sip:732111000@192.168.28.19:5060>;tag=1 Call-ID: 1-10679@192.168.28.1 ... Refer-To: <sip:9785550000@192.168.29.1:6062?User-to- User=56a390f3d2b7310023a%3Bencoding%3Dhex%3Bpurpose%3Disdn- interwork%3Bcontent%3Disdn-uui Content-Length:0
If the UUI is received in the "Refer-To" header in the REFER message, the Oracle Communications Session Border Controller adds the new UUI header in the INVITE message to the destination party. The system encodes the INVITE message as shown in the following example. All the escape characters received in the UUI parameter converts to plain text and all the UUI header parameters are relayed. In the example below, note the new UUI content below Content-Length and in the Supported fields.
INVITE sip:9785550000@192.168.29.1:6062 SIP/2.0 Via: SIP/2.0/UDP 192.168.29.20:5060;branch=z9hG4bKgkm8110090jmlvcfk80.1 From: 7321110000 <sip:7321110000@192.168.28.1:5060>;tag=1 To: <sip:9785550000@192.168.29.1:6062> Call-ID: 537e3302f02bbb0ddd8b8d7538f8b33030@192.168.28.1 CSeq: 2 INVITE Contact:<sip:sipp@192.168.29.20:5060;transport=UDP> Session-Expires: 3600;refresher=uac Max-Forwards: 69 Subject: Performance Test Content-Type: application/sdp Content-Length: 135 User-to-User:56a390f3d2b7310023a;encoding=hex;purpose=isdn- interwork;content=isdn-uui Supported: timer,uui Referred-By:<sip.7325550000@192.168.29.1:5060> Route:<sip:9785550000@core2:6020,lr> v=0 o=user153655765 2353687637 IN IP$ 192.168.28.1 s=- c=IN IP4 192.168.28.1 t= 0 0 m=audio 8000 RTP/AVP 8 a=rtpmap 8 PCMA/8000
The product supports the REFER header that replaces the default header with the UUI header in an attended call transfer.
Aug 4 10:09:10.233 On [256:0]192.168.12.1:5060 received from 192.168.12.2:5060 REFER sip:1000@192.168.12.1:5060 SIP/2.0 Via: SIP/2.0/udp 192.168.12.2:5060;branch=z9hG4bK-bob2alice-9 Max-Forwards: 10 From: bob <sip:2000@acme.com>;tag=bob-0 To: alice <sip:1000@acme.com>;tag=alice-1 Call-ID: 1-192.168.11.2 CSeq: 3 REFER Refer-To: <sip:3000@acme.com?Replaces=1-192.168.12.2%3Bto-tag%3Dcarol2bob-0%3Bfrom-tag%3Dbob2carol-2& User-to-User=56a390f3d2b7310023a%3Bencoding%3Dhex%3Bpurpose%3Disdn-interwork%3Bcontent%3Disdn-uui>
The Oracle Communications Session Border Controller adds the UUI parameter to the Supported header in the INVITE message to the Referred-to party. The Oracle Communications Session Border Controller encodes only one instance of the UUI header in the INVITE message to the Referred-to party. The Oracle Communications Session Border Controller will only process the first UUI parameter received in the "Refer-To" header. The Oracle Communications Session Border Controller supports a maximum of 128 octets hex content in the UUI header field, excluding parameters. The overall length of the header complies with RFC 3261. If the header length exceeds the maximum, the Oracle Communications Session Border Controller discards the UUI header and cannot relay the call.
