Subject: [SIP] UAC Record Routing in draft-ietf-sip-call-flows-01.txt

From: Neil Deason <[email-masked]>
Date: Fri, 03 Nov 2000 13:33:45 +0000

The way the UAC builds the Route on a final 200 response 
in 3.1.2 of the call flows draft doesn't look quite 
right ...

3.1.2 Successful SIP to SIP through two proxies

   User A          Proxy 1          Proxy 2          User B
     |                |                |                |
     |   INVITE F1    |                |                |
     |--------------->|                |                |
     |     407 F2     |                |                |
     |<---------------|                |                |
     |     ACK F3     |                |                |
     |--------------->|                |                |
     |   INVITE F4    |                |                |
     |--------------->|   INVITE F5    |                |
     |    (100) F6    |--------------->|   INVITE F7    |
     |<---------------|    (100) F8    |--------------->|
     |                |<---------------|                |
     |                |                |     180 F9     |
     |                |    180 F10     |<---------------|
     |     180 F11    |<---------------|                |
     |<---------------|                |     200 F12    |
     |                |    200 F13     |<---------------|
     |     200 F14    |<---------------|                |
     |<---------------|                |                |
     |     ACK F15    |                |                |
     |--------------->|    ACK F16     |                |
     |                |--------------->|     ACK F17    |
     |                |                |--------------->|

F14 200 OK Proxy 1 -> A

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP here.com:5060
   Record-Route: <sip:[email-masked];maddr=ss2.wcom.com>,
    <sip:[email-masked];maddr=ss1.wcom.com>
   From: BigGuy <sip:[email-masked]>
   To: LittleGuy <sip:[email-masked]>;tag=314159
   Call-ID: [email-masked]
   CSeq: 1 INVITE
   Contact: LittleGuy <sip:[email-masked]>
   Content-Type: application/sdp
   Content-Length: 134

   v=0
   o=UserB 2890844527 2890844527 IN IP4 there.com
   s=Session SDP
   c=IN IP4 110.111.112.113
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   F15 ACK A -> Proxy 1

   ACK sip:[email-masked] SIP/2.0
   Via: SIP/2.0/UDP here.com:5060
   Route: <sip:[email-masked];maddr=ss2.wcom.com>,
    <sip:[email-masked];maddr=110.111.112.113>
   From: BigGuy <sip:[email-masked]>
   To: LittleGuy <sip:[email-masked]>;tag=314159
   Call-ID: [email-masked]
   CSeq: 1 ACK
   Content-Length: 0

The UAC should build the Route header in the ACK by 
copying the 200 response Record-Route header, 
reversing the order and then adding the Contact as 
the last entry. (Note the 1st entry in the Route is
subsequently removed when the client actually sends F15).
But in this case the last entry has become an IP address. 
Shouldn't the UAC just copy the Contact and not try 
and do any resolution of it?

Cheers,
Neil.
-- 
Ubiquity Software Corporation, UK        http://www.ubiquity.net

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