On 04 Apr 2016, at 10:02, Grant Bagdasarian <gb@cm.nl> wrote:

Hi Daniel,
 
You mentioned below about this issue not being complaint with the RFC.
Our supplier is telling us this is normal behavior and that they went through the RFC and found this was normal behavior.
 
If it’s not too much work, could you tell me in which part of the RFC this is described?
 
8.2.6.2 Headers and Tags


   The From field of the response MUST equal the From header field of
   the request.  The Call-ID header field of the response MUST equal the
   Call-ID header field of the request.  The CSeq header field of the
   response MUST equal the CSeq field of the request.  The Via header
   field values in the response MUST equal the Via header field values
   in the request and MUST maintain the same ordering.



RFC 3261 basics. The UAS copies ALL Via:s from the request into the response. This is how we route responses through
a SIP network, so without all headers, communication will likely be very broken.

/O