I'm going to try to explain this to Jiri and the list. I've changed the subject since it will diverge from the original.

What we're trying to do is set something up in SER which allows a single URI/phone # to be called, and have it ring multiple user's phones, which, if they go unanswered, will go to the original dialed user's voice mail box (which is a 'common' VM account that multiple users have access to). It also needs to be flexible in that any user can put themselves on and take themselves off the 'list' of users whose phones will ring when this number is dialed. And lastly, but not leastly, it also needs to be very user friendly, so users with no knowledge of SER/SIP can add/remove themselves from this list.

I'd like to do this with as little custom programming as possible. Preferably, none. I've been trying to get this working with SER/SERWeb/Asterisk/SEMS "natively". I realize this may not be possible without some coding, and that SER wasn't meant to do everything every user wanted 'out of the box' without coding, etc.

The main problem is, with the current setup of SEMS/SERWeb, and the current examples of voice mail setup, there is a presumption that the original called URI is the same person, and rings one or more of this same person's phones. But as explained above, we want to dial one user, and have it actually ring a bunch of other users phones, which can change dynamically.

The simplest way to implement this is to have whoever wants to receive the calls have their phones register themselves as the "main" user. This actually works fine with existing setups. The problem with this is that it's not very user friendly or practical, since not all SIP phones allow multiple user registration, which would require each user who wants to do this to have a separate phone reserved for this purpose. It's also somewhat inconvenient for a user with multiple phones to add/remove themselves from the registration for this "main" user on every phone every time they need to do it (like when they go to lunch, etc). It's far nicer for a user to be able to log into a central location and add their personal URI there, and have their already registered phones ring. I've though of hacking SERWeb and adding some functionality which would look up the users' current contacts in location and simply add them to the "main" user's contact list, but then realized that they'd have to update this every time they turned off a phone, added a new phone, etc.

We tried doing this by having the users register their contacts via SERWeb by logging into the "main" user's account and adding contacts like "user1@domain.tld", "user2@domain.tld". I call these sorts of locations entries "indirect contacts", since they're not destined for a different SIP domain, but they're also not pointing at the users' phones. Instead, they point back at other SER location entries which in turn point to the actual phones (hence, indirect). They wind up causing SER to relay the call back to itself. Example: main@domain.tld -> user1@domain.tld -> user1@<phoneIP:port>. These sorts of location entries would actually work for ringing the phones, etc, but would fail when it timed out to voice mail, for reasons both clear and unclear when the SIP messages were analyzed.

Analyzing the SIP messages, the failure reasons varied depending on whether there was a single contact, multiple contacts, and which "time-out method" was used, etc. For the case of multiple contacts, the routing logic wound up doing multiple failure_routes for voice mail for the same phone call, etc, which is bad. If there was a single contact, and we were using the failure_route method of timing out, SER would send a CANCEL message to the VM system within a second of issuing the INVITE from the added VM branch (as if it couldn't differentiate between the original URI, indirect contact, and final contact branches of the call, and the added VM branch, or was simply choosing the wrong ones to CANCEL).

However, if the "have Asterisk wait" method of timing out were used with a single contact, SER would be fine and the call would be answered by the VM system (unfortunately not for the original URI user, but for the "ringing phone" user, which makes sense when the routing logic is examined). If the call involved multiple contacts, this method would fail, not because of SER, but because Asterisk would misinterpret SER's CANCEL message for one user for another, and stop responding to the call it just issued an OK for. This is likely because a double INVITE was issued (for each branch of the final destination set), and confused Asterisk.

The problem is, for this sort of set up is that there's no easy 'native' way to 'mark' the particular original URI, and resulting indirect URIs for the special treatment by the routing logic without hard coding them into ser.cfg, or using exec_dset() and some other of database of special users, etc, for which their would need to be a UI front end written (and which could be an expensive operation because of the "exec_dset").

The new approach I'm implementing right now is to use special prefixes for these types of users so that SER will treat them differently in the routing logic, and "do the proper thing". I'm hoping this will result in SER keeping its cookies, etc, and CANCELing the right calls when VM picks up.

Another stumbling block I see already is the case of handling "indirect contacts" which don't have a final location entry. E.g., the user logged out of the SIP domain, but didn't remove his indirect contact entry. When SER relays the call back to itself, and goes to lookup the location, it won't find one and normally it'd issue a "404". The desired action in this case is to forget about that particular contact, and just ring any other contacts that exist without having it tear down the entire call, or instantly shunt it off to voice mail (unless of course, there are no 'final contacts' available to ring). Tricky, especially since I'm still learning all this stuff.

Hopefully this will explain what I'm trying to do, the problems I've been having, etc. Perhaps I'm taking a completely wrong approach and someone will just say "just do it this way dummy!". :-)

- Jim

Jiri Kuthan wrote:

At 02:39 AM 12/20/2003, Jim Burwell wrote:

For instance, if you have a locations entry that points a user to another user, or more than one user (e.g. <mailto:mainline@domain.com>mainline@domain.com -> <mailto:receptionist@domain.com>receptionist@domain.com -> receptionist@<phone-IP:port>), SER seems to get confused and sends a CANCEL to the voice mail system you've just triggered the INVITE to in your failure_route.


Whats is exactly the issue? I mean SER sends CANCEL when timeout strikes or when some of the 
branches completes. If you decide to forward to voice mail, other pending branches will be 
cancelled and it is good so. If you maintain the CANCEL is sent to voice mail (as opposed to
pending branhces), send me your message dumps.

-jiri

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