Subject: [Sip] comments for UPDATE method

From: "vishal" <[email-masked]>
Date: Tue, 7 May 2002 00:40:35 +0530

Hi ,

 I have following comments

regards, vishal

comments:

1. Timer handling section should be included. UPDATE response timer must be less than initial INVITE timer.Every time new UPDATE command is issued in early dialog,wait timer (of initial INVITE response) must be adjusted . 

2. UPDATE response is sent without prompting remote user .It requires UPDATE can be issued only from trusted party .It means user issuing UPDATE command MUST send authentication info along with UPDATE command .

3. In section 5.3 "Processing the UPDATE Response"

It is written that

"If a UA receives a non-2xx final response to a UPDATE, the session parameters MUST remain unchanged, as if no UPDATE had been issued.Note that, as stated in Section 12.2.1 of RFC BBBB [1], if the non-2xx final response is a 481 (Call/Transaction Does Not Exist), or a 408 (Request Timeout), or no response at all is received for the UPDATE (that is, a timeout is returned by the UPDATE client transaction), the UAC will terminate the dialog."

In case no response received for UPDATE then UAC SHOULD not terminate the dialog.Response to UPDATE may be delayed,lost,currupted due to many reasons

for ex. message was routed through many proxies OR UAS,proxy took more time in processing of authentication,locating user etc .Response to UPDATE received after timer expiry SHOULD be rejected and session parametre SHOULD remain unchanged .Dialog SHOULD not be terminated .

UPDATE failure MUST not affect ongoing dialog.

queries:

1. Can UPDATE be over TCP when initial INVITE was over UDP ,so that more UPDATEs can be sent over same TCP connection?

2. Can UPDATE be issued only for SDP modification purposes or it can be issued to modify contact info,call-id,allow fields etc.?

3. Can UPDATE be generated by other SIP entities(redirect server,proxies etc) if they want to enforce particular session parametres based dialog.?

SUGGESTION 

UPDATE should be used only for early dialogs .For confirmed dialogs ,re-INVITE MUST be used to avoid inconsistancy

Vishal ,
Knowledge Systems Pvt Ltd  ,INDIA
470, East End Main Road  
9th Block Jayanagar ,
Bangalore 560 069  
Telephone: +91-80-6545252