RFC 3665, "Session Initiation Protocol (SIP) Basic Call Flow Examples", December 2003

Errata ID: 4516
Status: Rejected
Type: Technical
Publication Format(s) : TEXT
Reported By: Fritz
Date Reported: 2015-10-30
Rejected by: Ben Campbell
Date Rejected: 2015-11-01

Section 3.2 says:

   F3 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74b43
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>;tag=3flal12sf
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0

It should say:

   F3 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK12345
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>;tag=3flal12sf
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0

Notes:

ACK is a new transaction and need a new value for via-branch
--VERIFIER NOTES--
The flow in the RFC is correct. ACK is only a new transaction if the final response to the INVITE was in the 2xx class. In this case, the final response was a 407 - this ACK is hop-by-hop, and is part of the INVITE transaction.

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