[SIPForum-discussion] SIP/2.0 400 Out-of-order request

[Prasad G]

      6. The registrar checks whether the request contains the Contact
         header field.  If not, it skips to the last step.  If the
         Contact header field is present, the registrar checks if there
         is one Contact field value that contains the special value "*"
         and an Expires field.  If the request has additional Contact
         fields or an expiration time other than zero, the request is
         invalid, and the server MUST return a 400 (Invalid Request) and
         skip the remaining steps.  If not, the registrar checks whether
         the Call-ID agrees with the value stored for each binding.  If
         not, it MUST remove the binding.  If it does agree, it MUST
         remove the binding only if the CSeq in the request is higheruve
         than the value stored for that binding.  Otherwise, the update
         MUST be aborted and the request fails.


The above  snippet is from the RFC.

For each contact or the binding, the registrar first checks for the call-id
and if the call-id is same then it checks for the cseq and it must be more
than the previous register message to accept this message.

in your case i think the cseq is less than the previous one hence you are
getting this response.

Read more: http://www.faqs.org/rfcs/rfc3261.html#ixzz0elNARjYZ


On Fri, Feb 5, 2010 at 11:43 AM, SIP Babie <sipbabie at gmail.com> wrote:

> Hi All,
>
> Could anybody explain me why "SIP/2.0 400 Out-of-order request" is been
> sent. As shown below, I received this response for the REGISTER request sent
> below.
>
> REGISTER sip:softswitch.com SIP/2.0^M
> Via: SIP/2.0/UDP 100.2.3.4:2198;branch=z9hG4bK*0003-000004d1^M
> From: <sip:mediaserver at softswitch.com <sip%3Amediaserver at softswitch.com>
> >;tag=0000041f^M
> To: <sip:mediaserver at softswitch.com <sip%3Amediaserver at softswitch.com>>^M
> Call-ID: 3 at softswitch.com^M
> CSeq: 92601 REGISTER^M
> Contact: <sip:mediaserver at 100.2.3.4:2198>^M
> Expires: 3600^M
>
>
>
> SIP/2.0 400 Out-of-order request^M
> Via: SIP/2.0/UDP 100.2.3.4:2198;branch=z9hG4bK*0003-000004d1^M
> From: <sip:mediaserver at softswitch.com <sip%3Amediaserver at softswitch.com>
> >;tag=0000041f^M
> To: <sip:mediaserver at softswitch.com <sip%3Amediaserver at softswitch.com>
> >;tag=b72e12N264b6d055c-49a3^M
> Call-ID: 3 at softswitch.com^M
> CSeq: 92601 REGISTER^M
> Contact: <sip:mediaserver at 100.2.3.4:2198>;expires=3133^M
> Contact: <sip:media at 100.2.3.4:2198>;expires=2664^M
> Expires: 3600^M
> Content-Length: 0^M
> ^M
>
> Regards,
> SIPBABIE
>
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