[SIPForum-discussion] Sequence of Via headers

[Karan Thakur]

Hi Abhishek

It is very much valid till the time the ordering of via headers field in
response is same as in the request. (Single VIA header containing multiple
VIA header field values or Multiple VIA headers with respective Header
field value...Whatever syntax you use, ordering should be correct)
If we change the ordering then it can be issue because in order to traverse
the response through same route as the request, we need to order the VIA in
same order as in request.

Section 8.2 UAS behavior: "The Via header field values in the response MUST
equal the Via header field values in the request and MUST maintain the same
ordering"
Section 16.7: Response Processing by UAS



On Fri, Jul 5, 2013 at 5:22 PM, Abhishek Gupta <
gupta.kumar.abhishek at gmail.com> wrote:

> Hi,
>
> This is related to the sequence of Via headers. We all know that it is
> copied from the request in the same order while forming the response and
> sent to the topmost Via order. How valid is the below mentioned 180
> response (having Via headers at different places) -
>
> INVITE sip:1002 at 10.44.104.117:5060;transport=udp SIP/2.0
> Record-Route: <sip:10.44.104.156;lr=on>
> Via: SIP/2.0/UDP 10.44.104.156;branch=z9hG4bK7805.472b72f2.0
> Via: SIP/2.0/UDP 10.44.104.119:32986
> ;branch=z9hG4bK-d8754z-fdbc5e3d0e2c5a3d-1---d8754z-;rport=32986
> Max-Forwards: 16
> Contact: <sip:1001 at 10.44.104.119:32986;transport=udp>
> .
> .
> Content-Length: 216
>
>
> SIP/2.0 180 Ringing
> *Via: SIP/2.0/UDP 10.44.104.156;branch=z9hG4bK7805.472b72f2.0*
> From: "1001"<sip:1001 at 10.44.104.156>;tag=87b60828
> To: <sip:1002 at 10.44.104.156>;tag=331752176
> Contact: <sip:1002 at 10.44.104.117:5060;transport=udp>
> Call-ID: NTY3ZmQyZDgzM2JiMjQ5MjI3MDZjZDc5MDFiMjBjZmY
> CSeq: 1 INVITE
> Content-Length: 0
> *Via: SIP/2.0/UDP 10.44.104.119:32986
> ;rport=32986;branch=z9hG4bK-d8754z-fdbc5e3d0e2c5a3d-1---d8754z-*
> Record-Route: <sip:10.44.104.156;lr=on>
> Allow: ACK, BYE, CANCEL, INVITE, MESSAGE, NOTIFY, OPTIONS, PRACK, REFER,
> UPDATE
>
>
> Regards,
> Abhishek
>
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