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List:       sip-implementors
Subject:    Re: [Sip-implementors] Reg Cseq value for processing 3xx responses.
From:       Paul Kyzivat <pkyzivat () alum ! mit ! edu>
Date:       2012-06-05 13:20:00
Message-ID: 4FCE0780.10305 () alum ! mit ! edu
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On 6/5/12 1:31 AM, kiran kumar wrote:
> Hi all,
>
> I have a doubt regarding Cseq value while processing 3xx responses.
> According to RFC 3261 8.1.3.4 the new invite request for the redirected
> address can use the same Cseq value.

It actually says SHOULD.

> According to RFC 3665 3.6 call flows, the CSeq value is incremented for the
> new invite request while processing the 3xx response.
> Is it mandatory to increment the CSeq value in this scenario ?

Note that 3665 isn't normative. So when in doubt you must follow a 
normative source - 3261 in this case.

While not clear in 3261, there are two distinct situations here:

- recursion by the UAC, such as in 3665 6.3
- recursion by a proxy

When a proxy is doing the recursion, it MUST retain the CSeq value. 
Otherwise the UAC would be confused.

When the UAC is doing the recursion it really doesn't matter.

	Thanks,
	Paul
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