gutierrez@noc.arc.nasa.gov (Robert Michael Gutierrez) (11/04/90)
In another article in this issue, I wrote I would explain what the
carrier access code 10732. That was in an article by Barton F. Bruce
(BRUCE@ccavax.camb.com) in which he was asking for help in trying to
find the source for some fraudulent calls originating on his outgoing
trunks.
10732 is an access code used by AT&T, but not for its normal L.D.
network as you would describe, but rather for it's Software Defined
Network (SDN). A SDN is a network that you as it's customer,
literally sets up (or has AT&T set it up for you) with your own "phone
numbers". Depending on how large the network would be, they can
either be 7 digit or 10 digit numbers, and they can be literally
anything (assuming following normal NPA/NXX configurations, for a
reason...). MCI and Sprint also offer the same service (under the
names V-Net [MCI] and Sprint ??? Network).
In a virtual network like this, you need access to the switch that
knows how to route calls, and obviously, routes them along. Normally,
this access is provided by dedicated lines (either private lines for
single trunks or T-1 access for multiple trunks) that go directly into
the switch, since it is the AT&T (or other L.D. carrier) switch that
has the information to route the call (or "translation"). In
actuality, the switch consults with a central database somewhere that
does the "translation" so the call can be routed.
If this private network is all dedicated lines and T-1 spans, that's
all fine and dandy. But what if a customer has a few offices in some
far away place, each with just a few phones, and the idea of
installing private lies to that place is just too expensive??? Are
those places S.O.L. (that's "S*** Out of Luck," BTW).
In a Software Defined Network, it would be no problem to place those
phones in the network to _receive_ calls (just provide good ol' POTS
translations in the database), but that still leaves the problem to
dial into the network itself from those same phones.
AT&T used the carrier access code 10732 to designate SDN calls. The
AT&T switch sees that the call comes in on that access code ("just
another class of service"), and instead of routing the call based on
the number it received, it queries the SDN database, saying
"415-732-2000 is calling 202-976-7883", and the SDN database replies
that it actually translates to "Trunk Type 1010 in switch Cheyenne-1,
Port 1", the NORAD Hot Line instead of 976-STUD in Washington, D.C. :-)
MCI uses a similiar method, in which their V-Net calls are prefixed
with 700 (ie: 1-700-XXX-XXXX if your default carrier is MCI). With
this method, MCI appears to be limited to seven digit numbers, but
they rely on the switch itself to carry the class of service info for
that particular number (loaded on there by each region's Database
Group, daily). So, no matter what call comes into that switch, if
it's been marked as V-Net, it will do a database lookup for every call
from that number. MCI, though, is willing to do any translation your
heart desires on any number you want, and regularly does routing
translations for it's V-Net customers, routing calls around rotten
paths (ie: analog or known bad digital microwave paths) for regular
long distance calls on V-Net.
This concludes today's seminar, Virtual Networks 101 :-)
Robert Michael Gutierrez
NASA Science Internet Office - Network Operations Center.
Ames Research Center, Moffett Field, California. USA.