[VoIP] Real-time dialling and tandem stacking

[John R. Covert]

>Establishment of direct interoffice trunk groups between offices

Globally, we don't have to do to anything special to create a direct
inbound trunk group in any office.  We already have all that we need
in the current infrastructure.

ENUM as currently configured will respond just as well to a "selector
level" as to a full seven digit number.

Anyone can publish selector levels in the directory, just as they
currently publish seven digit numbers, at least at the 1-NXX-X level,
and for the 1-NXX level, just use a throw-away letter.

On the incoming side, you just configure your Asterisk to handle
the number of digits you're sent (taking the possibility of a
throw-away letter into account if you accept four digits inbound
rather than one, two, or three).

On the outbound side, you code the trunk to operate on seizure,
which is a standard feature in Asterisk, and based on the interface
that was selected, do the ENUM lookup of the partial number, and
connect.  The remaining digits can be sent inband.  You better have
a really good connection to your ISP and a good ISP if you expect
inband MF or SF to work.

For a switch, an outbound trunk group would seem to go to just a
single other CNET switch.  But the inbound trunk group would be
reachable by anyone who can properly signal into it.

/john