On Mon, Nov 06, 2006 at 11:03:01AM +0100, Fredrik Thulin wrote:

> What if you type in an address of "sip:[EMAIL PROTECTED];transport=udp" in 
> your user agent, but example.org has NAPTR/SRV records giving precedence 
> to TCP? When your user agent sends the request to your YXA proxy 
> (presumably using UDP), what transport should the YXA server use after 
> it resolves the NAPTR/SRV records of example.org and sees that the UAC 
> has requested one protocol, but example.org prefers to be contacted 
> using another?
> I'll have to think about that at least over lunch.
> /Fredrik

I assume that the user agent is configured with a pre-set route set
(AKA outbound proxy), otherwise the user agent should send the request
directly to the example.org server.

Section 4.1 "Selecting Transport Protocol" in RFC 3263 is completed if
the URI contains a transport parameter. There is no reason to select
transport protocol using NAPTR. And you should only lookup SRV records for
the selected transport protocol.

Btw, when using NAPTR you should select the most preferred transport
protocol, and not use all.

RFC 3263 4.1
   The NAPTR processing as described in RFC 2915 will result in the
   discovery of the most preferred transport protocol of the server that is
   supported by the client, as well as an SRV record for the server.


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