Hello,

Contact header is not used for routing of current message, it is there to indicate to the receiver where to send back follow up requests.

As I can see in the trace you attached, the request URI doesn't have any transport parameter, which means to use UDP, the transport that kamailio uses for relaying.

You can enforce a transport for kamailio, by adding transport parameter to uri or using some dedicated functions -- see the readme of tm module.

Cheers,
Daniel

On 17/11/14 23:48, Andrew Mason wrote:

Hi All,

I am testing SIP messages through the proxy from one client to another and the sender specifies TCP as the transport but Kamailio seems to overwrite this and chooses UDP (TCP is specified in the contact header).

The receivers are manually registered using kamctl ul add so i am not sure if this is forcing UDP or something else - I have redirected the messages to wireshark and attached an example of Kamailio adding its VIA headers but specifying UDP (taken from destination).

Basically I am getting TCP to Proxy the UDP from Proxy to Dest?

Thanks

Andrew
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