Subject: [Simple] Presence & SRV - Problem solved?

From: "Ryan Chapman" <[email-masked]>
Date: Tue, 29 Oct 2002 10:12:51 -0800

Hello all,

I'm writing a SIMPLE-based presence infrastructure, but I'm having some difficulty determining exactly how to deal with a presence URI (e.g., pres:[email-masked]).

In the CPIM draft, we are told to query _im._sip.example.com for im:[email-masked], and then that the "choice of IM transfer protocol is a local configuration option for each system."  Given this, which SRV RR should my SIP layer query?  If I translate my presence URI to a SIP URI as specified (somewhere!) in the mailing archive by simply replacing "pres" with "sip", then what good was my first SRV lookup?  In other words, my SIP layer would simply lookup _sip._udp.example.com, ignoring whatever results my previous query returned.

One way that I can see to solve this problem is to use the first lookup as a mechanism for determining the domain name associated with the URI.  In other words, pres:[email-masked] would generate a lookup for _pres._sip.somewhere.com, which would give me an RR for the presence service.  Using this result, I would generate a SIP URI that would look something like sip:[email-masked].  At this point, the SIP layer would query _sip._udp.sippresenceserver.somewhere.com, yielding the desired results.

My primary goal is to have my presence server be decoupled from our proxy/registrar, so the presence URI should send the message to a different location than a normal SIP URI would.

Thanks in advance,

Ryan Chapman
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