Thanks, Bodgan-Andei.

But unfortunelly, for UDP, that only work for the transport port. For example, if I send the request from IP_A:PORT_A and I specify IP_B:PORT_B in top most via, the reply is sent to IP_A:PORT_B.

2008/4/9, Bogdan-Andrei Iancu bogdan@voice-system.ro:

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.

regards, Bogdan

Victor Cartes wrote:

...

Thanks, Iñaki. But It is not what I really need.

I need to send to an UAS a SIP Request, like OPTIONS, and tell it to send the reply to a different transport address (IP Addr + Port) than the source address of the request.

This is, basically, in order to perform NAT discovering and typing from the server.

Thanks in advance,

Víctor

2008/4/7, Victor Cartes <ietf.sip@tivatechnologies.com mailto: ietf.sip@tivatechnologies.com>:

Actually not. What I need the UAS exactly to do is to send the SIP reply to a different IP address than the source of the SIP Request that it is replying to. Just how it sends the replies to the UDP port specified in top most Via HF.

2008/4/7, Bogdan-Andrei Iancu <bogdan@voice-system.ro mailto:bogdan@voice-system.ro>:

   Hi Victor,

   Not sure I got your question correctly, but you mean like
   something like "received" via param used to route back the
   replies?

   Regards,
   Bogdan

   Victor Cartes wrote:

       Hello to all,

       About SIP/UDP: Is there any way to specify the IP address
       for SIP responses, in a similar fashion as port specified
       on top most Via HF?

       Thanks in advance,

       Víctor

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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@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@Biloxi.com SIP/2.0 Via: SIP/2.0/UDP bobspc.biloxi.com:5060;received=192.0.2.4 ---------------------------------------------------