Transcoding Framework

1
Transcoding Framework

• draft-ietf-sipping-transc-framework-01.txt
• Gonzalo.Camarillo_at_ericsson.com

2
Status

• Framework defines two models
• 3pcc already approved
• B2BUA under discussion

3
Callers Invocation using 3pcc

• A T
  B
• 
  
• 
  
• -------(1) INVITE SDP A----gt
  
• 
  
• lt----(2) 200 OK SDP TATB---
  
• 
  
• ----------(3) ACK----------gt
  
• 
  
• --------------------(4) INVITE SDP
  TA-------------------gt
• 
  
• lt--------------------(5) 200 OK SDP
  B--------------------
• 
  
• -------------------------(6)
  ACK------------------------gt
• 
  
• --------(7) INVITE---------gt
  
• 
  
• lt---(8) 200 OK SDP TATB --
  
• 
  

4
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

5
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

6
Comparison

• Conference model
• INVITE T
• ltURI-listgt
• callee
• lt/URI-listgt

• Route model
• INVITE callee
• Route T

7
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