TELECOM Digest OnLine - Sorted: Re: Non-Bell ESS?

Re: Non-Bell ESS?

Fred Goldstein (
Wed, 13 Jul 2005 23:23:02 -0400

On Wed, 13 Jul 2005 17:11:22 -0400, John Stahl <> wrote,

>> ... The basic pattern was the same-an unexplained deluge of
>> electronic messages shutting down a computer built by DSC
>> Communications Corp. of Plano, Texas ...

DSC made Signal Transfer Points (STPs), which are the routers, packet
switches, in the Signaling System 7 network. Their STPs may have had
a problem ... at one point over a decade ago, a bug in the code did
bring down some SS7 networks. I think that's what the allusion was to.

One of the SS7 network crashes happened when there was a bug in some C
code (this might have been AT&T/Lucent's? DSCs?) that exited a loop in
a manner that the programmer hadn't intended (the CPU not having a "do
what I mean" instruction!). This was executed during congestion, and
would cause the link to fail over to its paired link (everything in
SS7 is paired), but that would now have congestion from queued
messages, so it would execute the flawed code, and the switch at the
other end of the line would get the burst of traffic, and if it had
that load of code, it would fail over.... nicely metastatic!

> To the best of my memory, DSC, whose name was mentioned in the archive
> you added (above), never made any type of an ESS switch, which the
> original essage questioned a non-Bell switch. DSC, now owned by
> Alcatel (France), made a whole line of CPE including multi-line
> systems and even some FO based equipment.

DSC made toll switches (Class 4), the DEX family, which was the
backbone of various LD networks including much of Worldcom. Late in
the 1990s, they added some Class 5 features, mainly for CLECs, but
never really became competitive in that space. They do get some use
for CLEC applications like ISDN PRI, used for dial-in modems, among
other things.

> So I'm pretty sure in relating again that the (only) non-Bell #5ESS
> switch back then was made by AGCS which was the creation of GTE and
> AT&T to get around the FCC regulations about Bell selling their
> equipment into the ILEC market. I do remember something about a couple
> of CO fires which were attributed to these switches but seem to recall
> there was some lightening connected with the stories.

AGCS was the old Automatic Electric, the company that first sold
Strowger switches in the 1890s. It was owned by GTE for decades, and
built the GTD-5, a digital central office switch that long-time Digest
readers will recall was somewhat less stable than a 5E or DMS... at
least in some places. GTE used a lot of them in house, though it was
becoming largely a Nortel shop. By the mid-1990s, GTE was tired of
AE, so they sold a majority stake in it to AT&T (what became Lucent).
This was AGCS. They stopped making GTD-5s, but had a few products of
their own (like Roameo and Superline), and eventually became a
marketing channel of Lucent, selling Lucent kit to the "independent"
ILECs. This had nothing to do with the FCC though; it was just a
marketing decision.

Fred Goldstein k1io fgoldstein "at"
ionary Consulting

Post Followup Article Use your browser's quoting feature to quote article into reply
Go to Next message: Thor Lancelot Simon: "Re: Non-Bell ESS?"
Go to Previous message: "Enterprise Numbers Still in Use?"
May be in reply to: "Non-Bell ESS?"
Next in thread: Thor Lancelot Simon: "Re: Non-Bell ESS?"
TELECOM Digest: Home Page