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Date: Thu, 09 Mar 2000 22:11:50 -0500
From: Fred Goldstein <>
Newsgroups: comp.dcom.telecom
Subject: Re: The DLC Epidemic Spreads to the Northeast

Lest the dead horse be beaten too much, I can perhaps contribute some
background to this thread.  DLCs are not in and of themselves, bad things.
For instance, my house is 21 kilofeet from the CO, so I couldn't get ISDN
(18 kf loop limit) until I found somebody at New England Tel to admit to
the existence of a DLC only a few kilofeet away.  Said engineer looked at
the crufty old wire plant on my block and ordered a new cable job to the
DLC.  (He was a contractor, which accounted for his higher-than-NYNEX
standards.)  Now I have ISDN.  And if somebody could get into the manhole
(CEV), they could probably put in a DSLAM.

But as noted, there are two ways to do it.  "Universal" mode means
back-to-back  analog ports at the CO, putting an analog line into a CO
terminal.  This breaks modems badly.  (Not ISDN, though, or related
"switched digital" services.)  It's the only way to do it on an analog
switch, of course, but those are all gone here.  "Integrated" mode means
that there is a direct digital connection from the DLC into the CO, usually
T1 (E1 in Europe, of course).

There are two common standardized ways to do Integrated DLC in North
America.  Telcordia spec TR-008 maps each channel of the T1 to an
analog line.  There's no concentration; each T1 carries 24 lines from
CO to DLC.  It's essentially the protocol that AT&T (WECo) used
between the SLC-96 remote and CO terminals, using bit-robbed signaling
similar to other 1980s channel banks.  Telcordia's GR-303 is much
newer, having really come into its own within the last few years.  It
provides for line concentration; a group of 2-20 T1s supports as many
as 2000 lines, with channels assigned on demand.  ISDN-like signaling
and its own maintenance channel are required.  It's very slick when it
works and has become the standard way for CLECs to access the remote
terminals they put in ILEC CO collocation rooms.  (European equivalent
specs, totally different of course, are called V5.1 and V5.2

Universal needs a CO terminal (extra hardware) and analog line ports
(extra hardware), so it's hardly efficient.  It works worse than
Integrated mode.  So why is it the norm here in TheFormerNYNEXLand?

Some have speculated that it's intentional sabotage of modems.  Maybe
to some extent, given how much Bell Titanic detests Internet dial-up,
but I think that's more of a bonus, icing on their cake as it were.
More realistically, GR-303 is quite expensive.  Lucent and Nortel
charge big bucks for the software license ("right to use", or "RTU",
fee).  They'd rather have you use proprietary remote terminals.  Since
there are lots of old channel banks left around from the analog-switch
days, the universal-mode CO terminal is "free".

But the main reason, which I learned from a retired NYNEX executive,
is worse than that.  Within the telco hierarchy, there are two very
distinct departments, one in charge of "inside plant" (ISP), the other
in charge of "outside plant" (OSP).  The boundary is near the switch.
If there's a CO terminal for universal DLC, that's part of the OSP.
So if something breaks, they can pull off the jumper and see if the
switch or the DLC is broken.  If it were integrated, there would be no
clear demarc between the departments, so they'd have to cooperate
rather than point fingers at each other.  In telco corporate culture,
that's virtually unthinkable.

So your modem is broken because the manglers in Bell need a physical
break in their plant to mimic a hundred-year-old break in the org

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