On 04-Apr-12 03:14, Adam H. Kerman wrote:
Stephen Sprunk wrote:
On 03-Apr-12 14:49, Adam H. Kerman wrote:
Stephen Sprunk wrote:
PBX trunks aren't numbered.

If outbound trunks aren't numbered, how does ANI work?

For a trunk, both called and calling number are explicitly signaled at
the start of each call in either direction.

So they are numbered.

There is not a 1:1 correspondence between trunks and numbers, as there
is with POTS lines. That is what makes them trunks!

If I have a block of 1000 directory numbers, all of them are routed to
the entire trunk group, so no trunk can be said to have any particular
number. Same if I only have one (high-volume) number: it is routed to
the entire trunk group, so all trunks have the "same" number, which also
means they don't have unique numbers.

Of course, trunks still have _circuit_ numbers for tracking and billing
purposes, but those are not dialable _directory_ numbers, which is what
we were discussing. For POTS lines, the directory number _is_ the
circuit number.

Inbound calls to a number (or set of numbers, eg. DID) are routed to any
available trunk in the trunk group.

Right. ANI must be passed along to the PBX so it knows what extension
to connect to.

DNIS (called number) is the opposite of ANI (calling number). The very
_need_ to signal the called number proves the trunk itself doesn't have
a fixed directory number. If it did, there would be no need for DNIS!

S

--
Stephen Sprunk "God does not play dice." --Albert Einstein
CCIE #3723 "God is an inveterate gambler, and He throws the
K5SSS dice at every possible opportunity." --Stephen Hawking