[Asterisk-Users] SIP extension "busy" when not available ??

[Olle E. Johansson]

Rich Adamson wrote:

>>How come * says 1010 is BUSY in the trace below? I would have guessed
>>"UNAVAILABLE" since 1010 is not logged on/registered.
Sounds right to me.
> 
> That's what has been programmed in the asterisk code and has been that way
> since the beginning of time. 
Is that right? I was afraid it was the result of a recent patch to prevent
problems when calling two SIP devices simultaneously.

> The logical response really should be Unavailable, but apparently there must
> be a reason why no one has changed this. It would appear part of the reason
> behind this is that asterisk stores the last known status of each sip phone's
> Register in a database entry (which is what gets displayed in the "sip show
> registry" command), and should the logical connection to that SIP phone be 
'Sip show registry' only shows outbound registrations, i.e. when you use
Asterisk as a SIP client to register with other SIP proxies.

The registration status is shown for dynamic hosts in 'sip show peers'.
If there's no active registration, there is no IP address known.

> Although the current logic does not require a sip phone to register, it would
> seem like the asterisk logic should be something like:
>  a. call is attempted to sip x1234,
>  b. if * knows the extn is in use, return busy, or,
>  c. if not busy, asterisk attempts to contact x1234 across the wire,
>  d. if no contact, return Unavailable
Or if not registred.

The problem is 'b'. If we have a limit (the missing outgoinglimit) we could force
busy. Otherwise Asterisk doesn't know anything about the status of the client, if
it's busy or not. It's the nature of the SIP protocol, that SIP devices have their
own lifes. We just have to place a call to the device. The device may answer 'busy'
and then we'll answer busy.

> The sip phone could be busy since it could actually have another call in progress
> with some other sip proxy other then asterisk, so I'm sure there is far more
> logic required then what meets this non-programmers eye.
Right.

/O