On Thu, 2005-11-10 at 05:46 +0000, venu yadlapalli wrote:
> "If a SIP proxy, redirect server, or registrar is to be contacted
> through the lookup of NAPTR records, there MUST be at least three
> records - one with a "SIP+D2T" service field, one with a "SIP+D2U"
> service field, and one with a "SIPS+D2T" service field."
> 
> Could any body explain what could be the reason.

The authors of RFC 3263 wanted to ensure that all proxies support TCP
and TLS.  (Sadly, many proxies do not support TLS.)

> "All proxies must implement both UDP and TCP, along with TLS over TCP,
> so that there is always an intersection of capabilities."
> 
> So when processing NAPTR, to contact a proxy we must check for all the three
> even though we are supporting only UDP. 

No.  The proxy is required to provide all three, but the UA is not
required to check that the proxy provides all three.

Dale


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