[SR-Users] reply code for lower cseq

[Andrew Pogrebennyk]

Hi Daniel,
See RFC 3261 section 12.2.2:

   If the remote sequence number was not empty, but the sequence number
   of the request is lower than the remote sequence number, the request
   is out of order and MUST be rejected with a 500 (Server Internal
   Error) response.

However, 400 or some 4xx response would seem more reasonable to me, to
let the UAC know it just did something wrong.
And I'm not the only one:
http://comments.gmane.org/gmane.ietf.sip-implementors/8970

On 04/24/2012 02:10 PM, Daniel-Constantin Mierla wrote:
> Hello,
> 
> I was wondering if someone here can point quickly where specs mention
> what is the right reply code to send when a request within dialog is
> received with lower cseq value than the previous request. I couldn't
> spot the part in the RFC yet, if any related exists.
> 
> Cheers,
> Daniel
>