On Tue, 2010-03-02 at 16:39 -0600, Josh Patten wrote:
> Is there or will there be any way in the future to set the call pickup 
> timeout to less than 1 second? Old school key system user get really 
> frustrated when they start talking immediately after dialing the pickup 
> sequence only to realize it takes a full second to connect the call. Is 
> there a technical reason why this can't be less?

There are some interactions between how we implement the feature and
what it actually does for the user.

The essence of the implementation is that when the INVITE for the call
pick-up call gets to the Registrar, the Registrar sits on it.

The Registrar then sends a SUBSCRIBE targeted to the number that is to
be picked up.  That SUBSCRIBE propagates through sipXecs to (hopefully)
all the phones that are registered for the number.  Each phone responds
with a NOTIFY containing the details of all calls on the phone, and in
particular, all calls ringing on the phone.  Those NOTIFYs propagate
back through sipXecs to the Registrar.

After a selected time period, the Registrar collates all the information
that it got from the NOTIFYs and selects the call which has been ringing
the *longest*, and modifies the original INVITE to pick up that call, on
the phone on which it is ringing.  It then sends the INVITE onward,
which completes the pick-up operation.

The problem revolves around the specification of call pick-up to pick up
the call that has been ringing longest.  Because of that, the Registrar
needs to have complete information about what calls are ringing on what
phones with the given line number.  Or at least, it needs to get
complete information maybe 90% of the time.  So it has to wait for some
period of time -- it can't just jump on the first ringing call that it
gets information about.  Conversely, it takes a certain amount of time
for the SUBSCRIBE and NOTIFY messages to propagate through sipXecs and
be acted upon by the phones.

Perhaps if we're lucky, 1/2 second is long enough, though.  Can you
please file an issue on this, so we have a place holder for the work
needed to improve the feature?

Dale


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