[asterisk-dev] SIP: So you mean you want to be able to *dial* something?

[Joshua Colp]

Hey all,

I've been tackling the area of outbound session creation in the new SIP 
work and the concept of location in general. I've experimented with 
stuff and ended up breaking it into two parts:

* Note #1: all of this is in a branch and has not yet been put up for 
review. I'd just like to hold a discussion about the usage aspect.
** Note #2: you can still dial straight up SIP URIs regardless of this work.

Storage

There's a new small and straight forward API in the SIP work for 
location. It allows querying for an AOR, getting contacts, adding 
contacts, and updating contacts. It's really a thin wrapper around the 
new sorcery API that adds automatic expiration of expired contacts and 
also static contacts. Since it's using sorcery all of this can be stored 
wherever someone wants it (flat file, local database, remote database, 
etc). Yes, you can have multiple contacts for an AOR. The underlying API 
does not forbid this. For external manipulation (a device registering) 
then the registrar would use this API and enforce any restrictions on 
contacts.

Usage

When I say usage I'm referring to actually using the above information 
for the purposes of setting up a session. I've sort of 
demoed/accomplished this twofold:

The GULP_DIAL_CONTACTS dialplan function produces a properly formatted 
dial string which creates a channel for each contact on an AOR. This can 
be pretty expensive, since you've got an Asterisk channel + RTP instance 
+ SIP internal structure + pjsip internals, but it works!

You can dial just the AOR. This uses a single Asterisk channel, a single 
SIP internal structure, a single RTP instance, but multiple pjsip 
internal structures. It's not as heavy as GULP_DIAL_CONTACTS but 
accomplishes the same thing in the end and yes, it works. This was 
really a *can I do this* thing and a few hours later it was up and running.

So really, my questions are:

1. Do we want my current usage options to go into the new SIP work?

2. If not, how do we want to expose multiple contacts on an AOR?

3. If we don't want to, then do we even want to support multiple 
contacts (for different targets) on an AOR?

4. What would *you* like usage of this to be like?

Cheers,

-- 
Joshua Colp
Digium, Inc. | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at:  www.digium.com  & www.asterisk.org