[OpenSER-Users] Specifying IP Address for SIP Responses

[Iñaki Baz Castillo]

El Wednesday 09 April 2008 12:31:42 Bogdan-Andrei Iancu escribió:
> Hi Victor,
>
> if a UAC wants to have asymmetric signalling, just send from IP_A:PORT_A
> and put in top most via IP_B:PORT_B - via is used for routing back the
> reply.

Hi Bodgan, that will not work since the UAS transport layer will compare the 
IP in Via header wih the source IP and adds the source IP to "received" 
parameter. After processing the request UAS will always send response to the 
IP in "received" parameter:



http://tools.ietf.org/html/rfc3261#section-18.2.1
---------------------------------------------------
   When the server transport receives a request over any transport, it
   MUST examine the value of the "sent-by" parameter in the top Via
   header field value.  If the host portion of the "sent-by" parameter
   contains a domain name, or if it contains an IP address that differs
   from the packet source address, the server MUST add a "received"
   parameter to that Via header field value.  This parameter MUST
   contain the source address from which the packet was received.  This
   is to assist the server transport layer in sending the response,
   since it must be sent to the source IP address from which the request
   came.

   Consider a request received by the server transport which looks like,
   in part:

      INVITE sip:bob at Biloxi.com SIP/2.0
      Via: SIP/2.0/UDP bobspc.biloxi.com:5060

   The request is received with a source IP address of 192.0.2.4.
   Before passing the request up, the transport adds a "received"
   parameter, so that the request would look like, in part:

      INVITE sip:bob at Biloxi.com SIP/2.0
      Via: SIP/2.0/UDP bobspc.biloxi.com:5060;received=192.0.2.4
---------------------------------------------------

-- 
Iñaki Baz Castillo
ibc at in.ilimit.es