Subject: [SIP] Errors handling on session description in ACK

From: "Piotr S. Kossowski" <[email-masked]>
Date: Wed, 01 Nov 2000 13:26:52 +0100

Hello,

When UAC send session description in INVITE request, UAS send 200 OK
if it supports them or 606 Not Acceptable if not. Clear.
(I assume ideal situation: no 1xx, etc.)

When UAC doesn't send session description in INVITE (what means
that it's going to do that in ACK), UAS' 200 OK contains description.
Next, UAC sees that it will not be able to support capabilities
of UAS. Does it send session descr. as if it would send in INVITE,
regardless of this failed handshake ? This scenario will fail,
because there is no way of negotiation after UAC has sent ACK,
since ACK doesn't generate response.

More generaly:
1. When UAC has an error and doesn't send session descr. in ACK (
   INVITE did NOT contain session descr. as well), Should
   UAS just ignore such ACK and treat it as *not received* ?

2. Should garbage in body of type application/sdp generate
   4xx response (which one ?) or 606 with appropriate code in 
   Warning header (which one ?)

By the way,

I've compared bis-02 with draft-ietf-mmusic-sip-new-00.ps (August '99).

Section 10.5.1 Unreliable Transport Protocols (bis-02):

"(...)Response retransmissions cease when (...) the response has been
 RETRANSMITTED seven times."

Section 10.5.1 (draft-ietf-mmusic-sip-new-00.ps):

"(...)Response retransmissions cease when (...) the response has been
 TRANSMITTED seven times."

Is it Typo or it must have been realy changed ?
If it's only typo, bis-02' the section should be like in old draft or:

"(...)Response retransmissions cease when (...) the response has been
 RETRANSMITTED SIX times."

Comment?

Best regards,
Piotr

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