[Asterisk-Users] New Asterisk bounty: SIP simultaneous

[Sunrise Ltd]

in response to Olle's excellent post, ...

in particular ...

>Asterisk is *not* a SIP proxy. It's a SIP registrar and
location server.
>It's a very clever SIP UA. It wants to be in the middle
of the call
>and wants to be in control of each device. This
device-slave view >doesn't match the SIP architecture.

and ...

>I've spent a considerable amount of time investigating
support for
>multiple registrations on one Asterisk sip [peer] account
and after
>learning about Asterisk's architecture come to the
conclusion that
>it is not an easy or even a desirable feature to
implement.

and ...

>It may be possible, but will probably lead to a lot of
changes to
>Asterisk, both core and applications, that no other
channel will
>benefit from. A quick hack to support it may lead to a
lot of
>confusion on how to handle other apps. And it's a lot
more work
>than the bounty will cover. I suggest that you use a
forking SIP
>proxy in conjunction with Asterisk to get this
functionality.

Precisely! A fairly simple and elegant solution.

For those rare occasions where one would really need
multiple concurrent SIP registrations I'd say one should
consider running Asterisk in combination with a SIP proxy.
Since SER is a free download, this wouldn't seem to be
such a big deal IF IT WASNT for the fact that one will
then need to run two boxes.

It would make a lot of sense to provide support for an
easy-to-configure set up where Asterisk can live together
with another SIP speaking piece of software on the same
box.

Something along the lines of ...

(ip1:5060)---[*]---[portswapper]---(ip1:5061)---[SER]---(ip2:5060)

Something like this should allow you to run Asterisk on
one address (ie LAN side) and SER on another (ie WAN
side), so you get the best of both Asterisk and a SIP
proxy all in one box.

This would also make it possible to run a SIP softphone
alongside Asterisk on a notebook, so it would solve two
birds with one stone.

I'd like to emphasise however, that most of the problems
described in this thread are NOT good reasons for multiple
concurrent SIP registrations. Those problems have other
solutions. Let's take a look at them.

1) Call centre scenario

Problem: multiple agents should receive calls on the same
phone number

Solution: assign a number to a call queue and let the call
queue distribute incoming calls to the agents on different
SIP phones, each of which should have unique logins for
reasons of accounting and quality assurance.

multiple concurrent registrations on the same SIP account
in call centres is a BAD IDEA.

2) Overworked admin scenario

Problem: asterisk admin doesn't want to deal with support
calls for adding additional SIP phones

Solution: a simple self provisioning system, either web
based or even IVR based.

3) Dual line desk phone scenario

Problem: dual line desk phone requires multiple
registrations, one per line

Solution: let the phone register on two different SIP
accounts, which is how any conventional PBX handles dual
line phones: one extension per line.

4) Call group scenario

Problem: multiple phones to ring on the same extension

Solution: use the call group feature or use the dial
command with multiple SIP peers


For the avoidance of doubt, I am not saying there is no
situation for which multiple concurrent SIP registrations
may be the right solution, but the problems described so
far are *not*.

But if anybody has a problem that truly warrants parallel
forking, then I propose you look into sponsoring somebody
to work on the little port swapping trick to run SER
concurrently on your Asterisk box.

rgds
benjk


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