Transcoding Framework draft-ietf-sipping-transc-framework-01.txt Gonzalo.Camarillo@ericsson.com

Status Framework defines two models 3pcc: already approved B2BUA: under discussion

Caller’s Invocation using 3pcc A T B | | | |-------(1) INVITE SDP A---->| | |<----(2) 200 OK SDP TA+TB---| | |----------(3) ACK---------->| | |--------------------(4) INVITE SDP TA------------------->| |<--------------------(5) 200 OK SDP B--------------------| |-------------------------(6) ACK------------------------>| |--------(7) INVITE--------->| | |<---(8) 200 OK SDP TA+TB --| | |--------------------(9) INVITE SDP TA------------------->| |<-------------------(10) 200 OK SDP B--------------------| |-------------------------(11) ACK----------------------->| |------(12) ACK SDP A+B----->| | | ************************** | ************************** | |* MEDIA *|* MEDIA *|

Motivation for a New Model A lot of messages over the air User agents using slow radio links Many UAs will not support 3pcc New model needed Fewer messages over the air Simpler for UAs

Proposals so far Treat the transcoder like a simple conference Use the URI-list service for INVITE requests mechanism Address the transcoder as if it was a proxy Using the Route header field Use a new mechanism

Comparison Conference model INVITE T <URI-list> callee Route model INVITE callee Route: T

Comparison (2) Conference model + Recipient of the SDP identified by the Request-URI - Requires UAs to support list bodies Route model + Trivial to support by UAs - Impossible to tell who is the recipient of the SDP by inspecting a message