From: vixen!jadams@uunet.UU.NET (26070-adams)
Newsgroups: comp.dcom.telecom
Subject: Re: AT&T SDN; New Calling Cards
Date: 31 Aug 92 13:15:48 GMT
Organization: Bellcore, Livingston, NJ
X-Submissions-To: telecom@eecs.nwu.edu
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X-Telecom-Digest: Volume 12, Issue 674, Message 7 of 10

In article <telecom12.652.6@eecs.nwu.edu>, drz@po.CWRU.Edu (David R.
Zinkin) writes:

> Question: what does SDN stand for anyway?  And what makes it different
                      ^^^ Software Defined Network (As of 1986ish!)

> from standard long distance service?

I believe SDN is a trademark of AT&T (possibly even registered).  I'm
a little hazy on this, but I believe SDN provides a multi-location
customer (read as big businesses) with an economical alternative to a
private voice network of dedicated trunks.  Using the intelligence of
AT&T's NCPs and LD net, all sorts of virtual numbering schemes are
possible (Corporate universal numbering plans for instance).

In article <telecom12.657.6@eecs.nwu.edu>, johnl@iecc.cambridge.ma.us
(John R. Levine) writes:

>> Question: what does SDN stand for anyway?  And what makes it different
>> from standard long distance service?

> It's Software Defined Network.  In Olden Days when long distance rates
> were much higher than now and switching was relatively much more
> expensive than it is now, large companies usually rented lots of fixed
> leased lines among their various facilities to carry intra-company
> traffic.  This saved money relative to toll rates and also sometimes
> avoided problems of not being able to get through at peak hours.

So far so good ...

> {STUFF DELETED}.        Once such hack is the "virtual private
> line" which is a long distance ringdown circuit -- whenever you pick

Are you sure about this?

> up the phone at one end it quickly calls the other end to give you
> pretty much the same effect as a leased line but at lower cost since
> they don't need to provide bandwidth when you're not asking for it.

> SDN is basically a bulk calling plan for large businesses that
> replaces networks of leased lines.  

It's a little more technical than a "calling plan".  It involves
called number routing manipulation based on all kinds of things (Day
of week, time of day, your telephone number, etc.).  The routing is
performed according to logic which resides in the Network Control
Points (NCP) which are simplisticly speaking, large databses of these
routing logic algorithms.

> One dials 10732 to make an SDN

This depends on your dialing plan of your LEC switch.

> call (and gets a message saying to call your account rep if it's not a
> line assigned to an SDN account) but as far as I know the calls are
> carried just like other AT&T calls.

In most applications of SDN, a second dial tone is played and the
number dialed is captured and sent to the NCP in the form of a query.
Based on your number, the number you dialed, and a lot of other stuff
(mentioned above), your call is routed to its destination via the AT&T
public switched telephone network.


Jack (John) Adams		| Bellcore RRC 4B-259
(908) 699-3447 {Voice}		| (908) 336-2871 {Facsimile}
jadams@vixen.bellcore.com	| kahuna@attmail.com