Subject: Re: Gateways and registration

From: Sean Olson <[email-masked]>
Date: Fri, 7 Jan 2000 13:32:57 -0600 (CST)

> > 
> > Although not required by the SIP standard, there is absolutely nothing to
> > keep you from doing this other than the fact that there are better
> > mechanisms. TRIP might be one avenue to consider.
> > 
> 
> The slight difficulty is that SIP registers users, so a gateway
> "representing" phone numbers would have to register a lot of individual
> users. This is another reason TRIP is preferable, since it has
> mechanisms to aggregate reachability information. It is not clear to me
> that creating a wildcard user, with all the possible permutations, would
> be wise. Obviously, if you know your proxy server, nothing prevents you
> from registering
> 
> 415*@gateway
> 
> or whatevever format you choose.
> 
> Henning
> 

True, it would require some interesting syntax but I believe the semantics
he had in mind are different. The problem he is trying to solve is not
registering a gateway that is capable of answering for a set of users, but
more simply, registering the fact that a given gateway is up and in service.
The set of users that a given gateway can support would then have to be
either statically configured or negotiated through some different protocol
such as TRIP. 

sean

---

From: Henning Schulzrinne <[email-masked]>
Date: Fri, 07 Jan 2000 14:40:35 -0500

> either statically configured or negotiated through some different protocol

However, registration of a gateway only shows that the gateway was
available, say, an hour ago, unless the gateway is kind enough to "sign
out" before it crashes. If you already know that you want to send a call
to the gateway and you only have one, you might as well try and find out
quickly whether it's up or not. If there's a choice of gateways, you
presumably need something like TRIP to determine the correct one, in the
absence of information which "users" (phone #) each gateway handles.