Subject: [Sip] End to end ACKs

From: De Leo Walter <[email-masked]>
Date: Wed, 12 Dec 2001 11:04:11 -0300

I have a doubt with end to end ACKs
1) Line 1797 of bis 05 says:
"Once the ACK has been constructed, the procedures of Section 24 are used to
send it."

2) In section 24 lines 4185 to 4190 say
"Once a next hop is successfully contacted, that same next hop address MUST
be used for all subsequent
messages that share the same Call-ID. More specifically, once a request is
delivered successfully to a par-
ticular next hop, all subsequent requests with the same Call-ID MUST be
delivered to that next hop. Once a
response is delivered successfully to a particular next hop, all subsequent
responses with the same Call-ID
MUST be delivered to that next hop. However, if that next hop fails, the
selection algorithms MUST be re-run
for the top." 

3) But in lines 438 to 444 it is said:
"Note that in this example, the ACK is sent directly from Alice to Bob,
bypassing the two proxies. This is due to 
the fact that through the INVITE/200 OK exchange, the two SIP user agents
have learned each other's IP
address through the Contact header fields, something which was not known
when the initial INVITE was 
sent. The lookups performed by the two proxies are no longer needed, so they
drop put of the call flow. This
completes the INVITE/200/ACK three way handshake used to establish SIP
sessions, and is the end of the transaction."

Aren´t this the first two paragraphs contradictory with the third?

_______________________________________________
Sip mailing list  http://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 18 Dec 2001 13:34:45 -0500

> Aren´t this the first two paragraphs contradictory with the third?

What the second is trying to say is that for the same URI, all requests 
with the same call-id go to the same place. THis needs to be clarified 
in the text, since based on the literal interpretation you are correct 
that they are inconsistent. However, if, as a result of the various SRV 
open issues, we require consistent usage of the same server only within 
a transaction, this point becomes moot, since the ACK-200 is a separate 
transaction.

-Jonathan R.
-- 
Jonathan Rosenberg, PhD                 72 Eagle Rock Avenue
Chief Scientist                         First Floor
dynamicsoft                             East Hanover, NJ 07936
[email-masked]                 FAX: (973) 952-5050
http://www.jdrosen.net                  PH: (973) 952-5000
http://www.dynamicsoft.com