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List:       sip-implementors
Subject:    Re: [Sip-implementors] Query on Forking
From:       Ravi Kumar <ravikumar () huawei ! com>
Date:       2010-08-27 6:51:23
Message-ID: 001501cb45b2$973e0330$2301120a () china ! huawei ! com
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Hi All,
	
As per rfc 2543 section 6.37 
	The UAS or redirect server copies the To header field into its
   response, and MUST add a "tag" parameter if the request contained
   more than one Via header field.
	
	If request has only one via that means it has not traveled any
proxy. So UAC should not receive multiple 2xx or 1xx response. 
	If UAC receive multiple 2xx or 1xx response then it has travel
through at least one proxy. So UAS should add To-Tag.

Thanks & Regards,
Ravi Kumar
	 


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-----Original Message-----
From: sip-implementors-bounces@lists.cs.columbia.edu
[mailto:sip-implementors-bounces@lists.cs.columbia.edu] On Behalf Of Paul
Kyzivat
Sent: Thursday, August 26, 2010 8:26 PM
To: Brett Tate
Cc: sip-implementors@lists.cs.columbia.edu
Subject: Re: [Sip-implementors] Query on Forking

I don't have 2543 committed to memory and am not motivated to go read it 
right now. But as Brett says, I think you can get a 180 w/o to-tag from 
a 2543 compatible UAS. If you subsequently get a 1xx with a to-tag then 
I guess you have two early dialogs. (But I'm not certain 2543 had the 
notion of early dialogs.) Presumably you could get a 200 w/o to-tag, and 
another with to-tag. In that case you would have to confront two dialogs.

But are there any UAs out there today that support 2543 and not 3261? 
Its been a *looooog* time.

	Thanks,
	Paul

Brett Tate wrote:
>> Is 180 response received without TO tag a forked response?
> 
> A 18x without To tag is non compliant; see rfc3261 section 8.2.6.2.  Thus
the UAC has to decide how it wants handle the abnormal situation.
> 
> RFC 2543 did not always require tags to form dialogs; however RFC 3261
does.  Thus various vendors likely handle the abnormal situation
differently.  
> 
> 
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