Telephone Multiplexer failures, power outages, and VOIP firewall Risks/Problems.
- From: cerberus.perillo@xxxxxxxxx
- Date: Fri, 29 Jun 2007 15:46:35 -0700
Emmanuel (E***) has asked me to post on 2600 for along time now,
but now posting because I am semi-retired and this will not raise
eyebrows. While I was asked to take pictures of Pay Phones in the
Middle East especially Riyadh, Saudi, I was told not to pack a camera
because they would think I was a spy, which was ridiculous because
everybody had camera's, though a friend of mine was questioned by
police for taking pictures of sand dunes.
These Telecommunications Risk's/Problem's questions arose out of
an Washington, DC and George Washington University (GWU) sponsored ACM
meeting on Computer Security with former AT&T/Bell Labs Steve
Bellovin, that became heated Telecommunications arguments at a local
bar in Foggy Bottom close to GWU.
The discussion morphed into the question of SLiC's (Subscriber
Line Interface Circuits), or Pair-Gains, essentially multiplexers to
convert a one copper pair line to multiple lines, due to a long line
repairman in our group. (I do not know why we wandered off of Computer
Security?)
He was stating that when you had an AC power failure, the
batteries in the SLiC's only last for about 8 hours, then everything
will go dead. This confused me because as someone with limited
experience with SLiC's only at the cross-connects near the
Demarc, the F2, or the F3 (Demarc), that these things ran off of CO
48V battery, and usually there was no electric power to be had at the
F2, or F3. Through an alcoholic haze when he started to talk about
large currents it finally dawned on me that he was talking about
SLIC's used around the Central Office (CO) or F1 that split one pair
into
thousands of lines? And I was talking about SLiC's that split one line
into 2, 4, 8, or 16, so that an extra copper line did not have to be
added on the street (F1 to F2), or from the F2 to the residence. With
the glut of broadband, I was under the impression that all CO to CO,
or CO to F1 traffic was done via optical fiber, so I'm not sure if
these devices are still in use? And if this is a real risk?
I do know that during the massive East Coast long lasting power
failure, blackout, in August 2003, that while there was no problem
with landline telephone service due to CO 48V generation, the Key
Telephone Sets (KTS) in all the New York City firehouses which are
used to route the calls within the firehouse were dependent on AC
power and only had batteries that lasted about 8 hours. So while the
telephone lines coming in to the buildings were working, the phones on
the desks stopped working after 4 to 8 hours. I believe this has now
been fixed?
Both Cell Phone Towers and Cell Switches immediately failed when
AC Power went out, causing long queue's at the Pay Phones around the
city. This problem to my knowledge has not been fixed?
I do not consider putting some generators at some cell towers
the solution, obviously this did not work in the Blackout of August
2003 when Senator Hillary Clinton had to discard all her cell phones,
and personal communications devices, because they stopped working
immediately, and queue up in line to use the Pay Phones. As far as I
know the Cell Switches have no generators, and what about turning the
generators on, and keeping
them supplied with fuel? To solve this problem, Cell Providers should
come up with an alternate/separate power generation system similar to
CO 48V "Battery" used by the old Ma Bell, the land-line carriers.
Obviously they are refusing to do this.
The Long-line repairman who changed our discussion from computer
security to these issues also questioned my technical knowledge, but I
think it comes from different perspective of Telecommunications? As
some of this group knows I started building PBX's as a pre-teenager
with used steppers, LineFinders, Selectors, and Connectors obtained
from Canal Street, and also built Multi-Frequency Trunk Operator tone
sets. Taught Telephony and Data Systems Technician courses at Great
Lakes. And was involved in the development of the STU-III, Advanced
Narowband Digital Voice Terminal (ANDVT), Unit Level Circuit Switch
(ULCS), and Unit Level Message Switch
(ULMS).
The residential SLiC's or Pair-Gains that I was talking about
do have a very high failure rate. Recently a friend of mine was
constantly losing service at his Co-opt, Verizon did at least five
service calls and kept on telling him that nothing was wrong and it
had to be "inside wiring" if that. He asked me to look at it. It turns
out that
when the previous tenant wanted an extra line for his apartment,
instead of running the line from the complex's basement junction box,
which is normally the Demarc, Verizon added a 4 line SLIC in the
closet of the co-opt apartment. When my friend moved in they still
kept his single line through the SLiC, and that started failing. I
disconnected the SLIC from the circuit and everything started working
fine, when I got Verizon out there, they agreed, but had no record of
the SLiC that they installed, including on the Line Maintenance
Configuration System (LMCS) computer?
Since these Residential SLiC's are powered off of Central
Office (CO) 48V "Battery", and probably do not have batteries in them?
Therefore their high failure rates are not explained by "battery
problems".
One item that is relevant that Prof. Steve Bellovin, the father
of Firewalls, talked about, is that current Internet Firewalls do not
handle VOIP very well, are not suited or designed for voice, and there
are many security problems with VOIP. The industry is well aware of
this problem and has tried to develop standards for a specialized
Firewall just for Voice, VOIP, called a "Boundary System", which is
based on Telephony technology and terminology. For some reason Steve
has not participated in this effort.
This long-line repairman, and a pretty girl from the commerce
department, mentioned that you can get very cheap VOIP service from
Latin American and Caribbean countries, such as Venezuela?, because
their Internet Voice, Voice over IP (VOIP) implementations are not
setup for, and bypasses the various Tariffs, Taxes, and Fee's
associated with the normal PTT Telephone service? I am sure that this
has been brought up before on this group? And this is one of the
reasons that European PTT's have insisted on keeping their X.25
Networks as front ends into the conventional Internet. X.25 has
various fields for carrier usage charging of Tariffs, Taxes, and
Fee's.
(VOIP is difficult to understand, maintain, and troubleshoot because
telephony technology and terminology is morphed into a the arcane TCP/
IP, i.e. the telephone # becomes a series of IP addresses)
Robert J. Perillo
Principal Telecommunications Engineer
dockmaster_perillo@xxxxxxxxx
.
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