I believe that a CSeq of 2 is perfectly valid for the second INVITE 
(resubmitted with credentials). The RFC 3261 is clear that it should have the 
same Call-ID and from-tag.  The CSeq number space is per dialog. This second 
INVITE is not part of any dialog, therefore its CSeq should not be compared 
with any previous dialog.

If a UA does keep CSeq state for a Call-ID it should be independent of the 
dialog CSeq state, and not updated by in-dialog requests.

cheers,
(-:bob

-----Original Message-----
From: Jeroen van Bemmel [mailto:[EMAIL PROTECTED]
Sent: Friday, January 18, 2008 3:02 AM
To: Christer Holmberg
Cc: [email protected]; Paul Kyzivat
Subject: Re: [Sip] Interesting problem with PRACK and resent INVITEs

Christer,
>> .
>>
>>
>> Regarding from tags there is no explicit text, but 22.2 says:
>>
>> When a UAC resubmits a request with its credentials after receiving a
>> 401 (Unauthorized) or 407 (Proxy Authentication Required) response,
>> it MUST increment the CSeq header field value as it would normally
>> when sending an updated request.
>>
>
> So, I guess that means that the second INVITE in Dale's example should
> have Cseq => 3.

I interpreted this as "MUST increment (relative to the INVITE being
challenged)". I guess for initial INVITEs the minimal requirement is
that the CSeq be different, else merged request detection (8.2.2.2)
could kick in and prevent the call from succeeding. So both 2 or 3 are
valid, the text is ambiguous

Regards,
Jeroen


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