[gu-l] (01/13/04) Origin of Packet-switching Technology
Takeshi Utsumi, Ph.D.
utsumi@columbia.edu
Tue, 13 Jan 2004 14:34:31 -0500
> This message is in MIME format. Since your mail reader does not understand
this format, some or all of this message may not be legible.
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<<January 13, 2004>>
Archived distributions can be retrieved by clicking "Correspondence" in our
home page at <http://www.friends-partners.org/GLOSAS/>.
For those after 2/27/01, see or bookmark:
<http://www.friends-partners.org/pipermail/gu-l/> and click on "Date,"
For example. The most recent archives are the bottom line.
Dr. Paul Baran
83 James Ave.
Atherton, CA 94027
650-328-0317
650-323-4053
paul@baran.com
Dear E-Colleagues:
(1) Pls visit our web at;
http://www.friends-partners.org/GLOSAS/GLOSAS_USA/Page/List_of_Activities.h=
t
ml
Then, go to =B3References=B2 to download the followings in =B3Origin of
Packet-switching Technology=B2;
1. Baran, P., =B3The Internet: Past, Present, and Future -- The Beginning of
Packet Switching: Some Underlying Concepts,=B2 IEEE Communications Magazine,
July 2002, pp 42-48 (IEEE copy.pdf, 8.8 MB)
2. Davies, D.W., =B3An Historical Study of the Beginnings of Packet
Switching,=B2 The Computer Journal, Vol. 44, No. 3, 2001, pp 152-162 (BCS
copy.pdf, 16.7 MB)=20
3. Malik, R., September 8, 1977, "In person: Packet-switching's unsung
hero," New Scientist
>> http://www.friends-partners.org/GLOSAS/Bookwriting/PART_I/Chapter_I/Tota=
l/Ins
>> ertions/Packet-switching/Paul_Baran/Paul_Baran.html
1. Guernsey, L., =B3An Unimaginable Emergency Put Communications to the Test,=
=B2
The New York Times, September 20, 2001 (MS/WORD filename: Paul Baram.doc,
38.3 KB) (see also ATTACHMENT I below)
(2) As you see in them, Dr. Paul Baran is the inventor of the
packet-switching technology, the very basic of the current Internet, which
made a profound paradigm shift from the circuit-switching technology of
analog Plain Old Telephone Service (POTS) network.
By the digitalization of telecom signal, this packet-switching technology
enables =B3sharing=B2 of valuable telecom media, compared with the exclusive
dominance of analog telecom media, thus realizing drastic cost reduction.
We are extending this =B3sharing=B2 concept to sharing of information, knowledg=
e
and wisdom by our Global University System and Globally Collaborative
Environmental Peace Gaming projects =8B see about them (in Part II for the
former and in Part IV for the latter) in our book =B3Global Peace Through The
Global University System=B2 at;
http://www.friends-partners.org/GLOSAS/Global_University/Global%20Universit=
y
%20System/UNESCO_Chair_Book/Bk_outline-D13.html
> Chinese proverb says, "Acquiring knowledge is a joy, and sharing knowledg=
e is
> an ultimate joy."
>=20
> The New York Times, Sunday Magazine, once said that it is ironic that the
> invention of the packet-switching technology to cope with the Soviet Unio=
n=B9s
> nuclear attack by ICBM missiles enables realization of egalitarian societ=
y in
> global scale, the dream of Karl Marx and Friedrich Engel.
(3) Dr. Baran has been one of our list members from almost its beginning
more than a dozen years ago, and a strong supporter of our GLOSAS projects.
Incidentally, we had an extraordinary privilege and honor to receive
generous financial support from Dr. Baran previously.
Dear Dr. Baran:
(4) Thank you very much for those information. I read them with great
interest.
I look forward to receiving your further information upon my return from ou=
r
trips to Bangladesh (from 1/18th to 24th) and Tokyo (from 1/25th to 2/8th).
Keep in touch.
Best, Tak
ATTACHMENT I=20
http://www.nytimes.com/2001/09/20/technology/circuits/20INFR.html?pagewante=
d
=3Dprint
=20
September 20, 2001
An Unimaginable Emergency Put Communications to the Test
By LISA GUERNSEY
N any given day, Dave Johnson knows far more than most people about the man=
y
phone calls that are crisscrossing the United States. Mr. Johnson, a
spokesman for AT&T (news/quote), works in the company's global network
operations center in Bedminster, N.J., where he and his colleagues monitor
141 vast projection screens that provide minute-by-minute details on the
state of the country's largest long-distance system. By watching
computerized maps of the United States, they can tell in an instant whether
there are any jams in long- distance traffic.
On an ordinary day, Mr. Johnson said, those maps are blissfully blank,
showing no unusual activity. But on Tuesday, Sept. 11, as soon as Mr.
Johnson and his colleagues saw the first television reports of the terroris=
t
attacks on New York and Washington, they knew that this would not be an
ordinary day.=20
"We all looked at each other and said, here we go," Mr. Johnson said. Withi=
n
minutes, the screens lighted up, showing tens of millions of calls =8B many
from worried relatives and friends =8B that threatened to clog the system.
"What started as a quite peaceful day," he said, "we instantly knew was not
going to be quiet and peaceful any longer."
In Manhattan, the threat to the phone system was not just traffic =8B it was
physical damage. The collapse of the World Trade Center crippled many of th=
e
connections that downtown Manhattan depended on, threatening crucial links
for the police and emergency crews. Cellular sites were knocked out. A
switching office for local service was badly damaged by falling debris and
burst water pipes. Fiber-optic transport equipment was crushed. Power
failures cut off high- speed Internet service for many companies across the
city.=20
By day's end, the telecommunications system in the country and particularly
in New York had experienced what was probably the biggest test ever of its
ability to withstand a physical attack and a national emergency.
So far, the results are encouraging. Several companies trucked in temporary
cellular towers. The 911 system was never disrupted. Long-distance lines
were kept open for New Yorkers who were calling out. For most people, the
Internet was slowed but intact.
Bruised and battered, the communications infrastructure persevered, but not
before providing lessons about how networks adapt to such extreme condition=
s
and what more can be done to preserve them in emergencies.
Verizon had to deal primarily with the effects of sheer destruction. The
company's office at 140 West Street was a central switching office for loca=
l
telephone traffic. Five stories of debris from 7 World Trade Center, which
collapsed Tuesday afternoon, fell against the building, which was also hit
by a massive steel girder from the North Tower. The basement is flooded wit=
h
water from shattered pipes, rendering the backup power generators useless.
The loss of all service at 140 West Street left as many as 175,000 customer=
s
in the area unable to make or receive calls. It also affected companies tha=
t
used as many as 3.5 million lines that carry Internet traffic and private
financial information through Lower Manhattan. Those lines, Verizon says,
were either damaged or were attached to switches that have no power. Severa=
l
companies had to use alternative communications channels to provide Interne=
t
access to their employees or subscribers.
"I suspect every business in Manhattan is in some way affected by the loss
of communication," said Ivan Seidenberg, co-chief executive of Verizon.
"Lower Manhattan is a pretty influential place in the entire scheme of
life."
Among the companies affected was Earthlink, which was unable to provide hig=
h
speed Internet service to more than 7,000 subscribers until Friday. The
effect rippled out to Washington, because Earthlink had been channeling som=
e
Washington subscribers through the New York center to balance its load.
Kevin Brand, the company's vice president for network operations, said that
to solve the problem the company rerouted traffic through several points in
the Northeast that are controlled by one of its partner companies.
Failures of backup power also hit several other network facilities around
downtown Manhattan. AT&T was unable to run telephone-switching equipment in
the World Financial Center because of power losses.
Many cables in the area are also in bad shape. When water mains broke after
buildings collapsed, the water seeped into cables that have since short
circuited, Verizon officials said. AT&T officials say they are certain that
they lost several pieces of sophisticated equipment in the basement of the
World Trade Center that were used to transport data over fiber-optic cables=
.
The phone system's losses were human as well. A half-dozen Verizon workers
are assumed to have perished in the trade center's destruction, among them
two technicians who were in the North Tower on a maintenance mission. They
had called their co- workers to tell them they were escaping to the roof
after they realized the extent of the fire caused by the first plane crash.
In the face of such horror, it is difficult to be heartened by the survival
of a communications network. But some communications experts said that the
ability of networks to adapt in such emergencies could be crucial to the
city's recovery.=20
Consider, for example, what happened that Tuesday in the AT&T operations
center in Bedminster, N.J. That day, AT&T handled 431 million voice calls =8B
20 percent more than usual and the most it had ever carried on a business
day. The morning of the attacks, blue lines pointing toward New York City
lighted up, indicating what the industry calls a "focused overload." Long-
distance calls cascading into New York's telephone system threatened local
callers' ability to reach emergency services.
The solution was to block some of the calls coming into the city. In
industry terms, the strategy is called "call gapping," and it was employed
with a few keystrokes by network managers at the control center. Managers
typed commands that automatically prompted the AT&T system to keep a
percentage of its circuits open for outbound long-distance calls. For peopl=
e
around the country who heard the message "All circuits are busy," call
gapping was a likely cause.
"People get emotional about this topic because they think we are
intentionally holding back their calls," said Mr. Johnson at AT&T. "The
local network in New York City is only going to handle so many calls."
Locally, Verizon was doing its part to make sure that emergency calls could
get through. The company provided nearly 2,400 spare circuits to city
government agencies (including the police and fire departments), about 900
circuits to the state government and more than 2,600 to federal agencies an=
d
the military.=20
The Internet also served its purpose as an efficient and relatively stable
network. Unlike traditional phone calls, which require an open circuit
between two people, data sent over the Internet travels in discrete packets
that move over hundreds of different channels at the same time and rejoin a=
t
their destination, in a process known as packet switching. For the most
part, that diverse distribution of the packets allows them to avoid
bottlenecks that result from blockages or damage to specific locations.
Many people, for example, had more luck sending e-mail and instant messages
than reaching people over the phone because the messages were automatically
stored when barriers were encountered and then forwarded to open routes.
Paul Baran, a former computer scientist at the RAND Corporation, who is
widely considered the co-inventor of packet switching, said that the
Internet's ability to stay up after the attacks was proof that the "route
around the trouble" model worked.
As planned, the telecommunications system also relied heavily on built-in
redundancies. Many companies, for example, have more than one line from
their offices to high-speed access points. But the disaster did expose some
of the limits of those contingency plans. Some of those multiple lines
travel the same conduits to the same routing centers. If something happens
to those conduits or routing centers =8B as did in many cases on Tuesday =8B al=
l
the redundancy in the world doesn't help: all the cables would be damaged.
Roy A. Maxion, director of the dependable-systems laboratory at Carnegie
Mellon University in Pittsburgh, has long preached the value of physical
diversity in networks. "I wouldn't want to be alarmist about this," he said=
,
"but what I think is interesting is how the system is not set up. A lot of
these contingency plans are not in place." He added that "as a nation we ar=
e
dangerously vulnerable."
Right now, telecommunications companies are focused on the task at hand:
getting power to buildings, clearing sites of debris, keeping lines up for
emergency crews, monitoring the networks that serve the stock exchanges and
running new cables for relocated businesses that had offices in the World
Trade Center.
"I've been trying to find a way to say it," Mr. Johnson said. "But there is
not a soft way to say that the businesses that were normally served are no
longer there."
Copyright 2001 The New York Times Company
Colored emphasizes were made by T. Utsumi.
**********************************************************************
* Takeshi Utsumi, Ph.D., P.E., Chairman, GLOSAS/USA *
* (GLObal Systems Analysis and Simulation Association in the U.S.A.) *
* Laureate of Lord Perry Award for Excellence in Distance Education *
* Founder and V.P. for Technology and Coordination of *
* Global University System (GUS) *
* 43-23 Colden Street, Flushing, NY 11355-3998, U.S.A. *
* Tel/Fax: 718-939-0928; (day time only--prefer email) *
* Email: utsumi@columbia.edu; Tax Exempt ID: 11-2999676 *
* http://www.friends-partners.org/GLOSAS/ *
**********************************************************************
--B_3156849272_1304897
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<HTML>
<HEAD>
<TITLE>(01/13/04) Origin of Packet-switching Technology</TITLE>
</HEAD>
<BODY>
<FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'><<January 13, 200=
4>> <BR>
Archived distributions can be retrieved by clicking "Correspondence&qu=
ot; in our home page at <a href=3D"http://www.friends-partners.org/GLOSAS/">&l=
t;http://www.friends-partners.org/GLOSAS/></a>. <BR>
For those after 2/27/01, see or bookmark: <BR>
<a href=3D"http://www.friends-partners.org/pipermail/gu-l/"><http://www.fr=
iends-partners.org/pipermail/gu-l/></a> and click on "Date," &n=
bsp;<BR>
For example. The most recent archives are the bottom line. <BR>
<BR>
Dr. Paul Baran<BR>
83 James Ave.<BR>
Atherton, CA 94027<BR>
650-328-0317<BR>
650-323-4053<BR>
paul@baran.com<BR>
<BR>
<BR>
<B><U>Dear E-Colleagues:<BR>
</U></B><BR>
(1) Pls visit our web at;<BR>
<a href=3D"http://www.friends-partners.org/GLOSAS/GLOSAS_USA/Page/List_of_Act=
ivities.html">http://www.friends-partners.org/GLOSAS/GLOSAS_USA/Page/List_of=
_Activities.html</a><BR>
<BR>
Then, go to “References” to download the followings in “O=
rigin of Packet-switching Technology”;<BR>
<BR>
</SPAN></FONT><OL><LI><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'>B=
aran, P., “The Internet: Past, Present, and Future -- The Beginning of=
Packet Switching: Some Underlying Concepts,” IEEE Communications Maga=
zine, July 2002, pp 42-48 (IEEE copy.pdf, 8.8 MB)=20
</SPAN></FONT><LI><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'>Davie=
s, D.W., “An Historical Study of the Beginnings of Packet Switching,&#=
8221; The Computer Journal, Vol. 44, No. 3, 2001, pp 152-162 (BCS copy.pdf, =
16.7 MB)=20
</SPAN></FONT><LI><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'>Malik=
, R., September 8, 1977, "In person: Packet-switching's unsung hero,&qu=
ot; New Scientist <BR>
</SPAN></FONT></OL><BLOCKQUOTE><BLOCKQUOTE><FONT FACE=3D"Verdana"><SPAN STYLE=
=3D'font-size:12.0px'><a href=3D"http://www.friends-partners.org/GLOSAS/Bookwrit=
ing/PART_I/Chapter_I/Total/Insertions/Packet-switching/Paul_Baran/Paul_Baran=
.html">http://www.friends-partners.org/GLOSAS/Bookwriting/PART_I/Chapter_I/T=
otal/Insertions/Packet-switching/Paul_Baran/Paul_Baran.html</a><BR>
</SPAN></FONT></BLOCKQUOTE></BLOCKQUOTE><OL><LI><FONT FACE=3D"Verdana"><SPAN =
STYLE=3D'font-size:12.0px'>Guernsey, L., “An Unimaginable Emergency Put =
Communications to the Test,” The New York Times, September 20, 2001 (M=
S/WORD filename: Paul Baram.doc, 38.3 KB) (see also <B><U>ATTACHMENT I</U></=
B> below)<BR>
</SPAN></FONT></OL><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'><BR>
(2) As you see in them, Dr. Paul Baran is the inventor of the packet-switch=
ing technology, the very basic of the current Internet, which made a profoun=
d paradigm shift from the circuit-switching technology of analog Plain Old T=
elephone Service (POTS) network.<BR>
<BR>
By the digitalization of telecom signal, this packet-switching technology e=
nables “sharing” of valuable telecom media, compared with the ex=
clusive dominance of analog telecom media, thus realizing drastic cost reduc=
tion.<BR>
<BR>
We are extending this “sharing” concept to sharing of informati=
on, knowledge and wisdom by our Global University System and Globally Collab=
orative Environmental Peace Gaming projects — see about them (in Part =
II for the former and in Part IV for the latter) in our book “Global P=
eace Through The Global University System” at;<BR>
<a href=3D"http://www.friends-partners.org/GLOSAS/Global_University/Global%20=
University%20System/UNESCO_Chair_Book/Bk_outline-D13.html">http://www.friend=
s-partners.org/GLOSAS/Global_University/Global%20University%20System/UNESCO_=
Chair_Book/Bk_outline-D13.html</a><BR>
<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0p=
x'>Chinese proverb says, "</SPAN></FONT><FONT SIZE=3D"5"><FONT FACE=3D"Time=
s New Roman"><SPAN STYLE=3D'font-size:18.0px'>Acquiring knowledge is a joy, an=
d sharing knowledge is an ultimate joy</SPAN></FONT></FONT><FONT FACE=3D"Verda=
na"><SPAN STYLE=3D'font-size:12.0px'>."<BR>
<BR>
The New York Times, Sunday Magazine, once said that it is ironic that the i=
nvention of the packet-switching technology to cope with the Soviet Union=
217;s nuclear attack by ICBM missiles enables realization of egalitarian soc=
iety in global scale, the dream of Karl Marx and Friedrich Engel.<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0=
px'><BR>
(3) Dr. Baran has been one of our list members from almost its beginning mo=
re than a dozen years ago, and a strong supporter of our GLOSAS projects. &n=
bsp;Incidentally, we had an extraordinary privilege and honor to receive gen=
erous financial support from Dr. Baran previously.<BR>
<BR>
<B><U>Dear Dr. Baran:<BR>
</U></B><BR>
(4) Thank you very much for those information. I read them with great=
interest.<BR>
<BR>
I look forward to receiving your further information upon my return from ou=
r trips to Bangladesh (from 1/18th to 24th) and Tokyo (from 1/25th to 2/8th)=
.<BR>
<BR>
Keep in touch.<BR>
<BR>
Best, Tak<BR>
<HR ALIGN=3DCENTER SIZE=3D"3" WIDTH=3D"95%">
</SPAN></FONT>
<P ALIGN=3DCENTER>
<FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'><B><U>ATTACHMENT I</U><=
/B>=20
</SPAN></FONT>
<P>
<FONT FACE=3D"Verdana"><SPAN STYLE=3D'font-size:12.0px'><BR>
<a href=3D"http://www.nytimes.com/2001/09/20/technology/circuits/20INFR.html?=
pagewanted=3Dprint">http://www.nytimes.com/2001/09/20/technology/circuits/20IN=
FR.html?pagewanted=3Dprint</a><BR>
<BR>
September 20, 2001<BR>
<BR>
<BR>
An Unimaginable Emergency Put Communications to the Test<BR>
<BR>
<BR>
By LISA GUERNSEY<BR>
<BR>
<BR>
N any given day, Dave Johnson knows far more than most people about the man=
y phone calls that are crisscrossing the United States. Mr. Johnson, a spoke=
sman for AT&T (news/quote), works in the company's global network operat=
ions center in Bedminster, N.J., where he and his colleagues monitor 141 vas=
t projection screens that provide minute-by-minute details on the state of t=
he country's largest long-distance system. By watching computerized maps of =
the United States, they can tell in an instant whether there are any jams in=
long- distance traffic.<BR>
<BR>
On an ordinary day, Mr. Johnson said, those maps are blissfully blank, show=
ing no unusual activity. But on Tuesday, Sept. 11, as soon as Mr. Johnson an=
d his colleagues saw the first television reports of the terrorist attacks o=
n New York and Washington, they knew that this would not be an ordinary day.=
<BR>
<BR>
"We all looked at each other and said, here we go," Mr. Johnson s=
aid. Within minutes, the screens lighted up, showing tens of millions of cal=
ls — many from worried relatives and friends — that threatened t=
o clog the system. "What started as a quite peaceful day," he said=
, "we instantly knew was not going to be quiet and peaceful any longer.=
" <BR>
<BR>
In Manhattan, the threat to the phone system was not just traffic — i=
t was physical damage. The collapse of the World Trade Center crippled many =
of the connections that downtown Manhattan depended on, threatening crucial =
links for the police and emergency crews. Cellular sites were knocked out. A=
switching office for local service was badly damaged by falling debris and =
burst water pipes. Fiber-optic transport equipment was crushed. Power failur=
es cut off high- speed Internet service for many companies across the city. =
<BR>
<BR>
By day's end, the telecommunications system in the country and particularly=
in New York had experienced what was probably the biggest test ever of its =
ability to withstand a physical attack and a national emergency. <BR>
<BR>
So far, the results are encouraging. Several companies trucked in temporary=
cellular towers. The 911 system was never disrupted. Long-distance lines we=
re kept open for New Yorkers who were calling out. For most people, the Inte=
rnet was slowed but intact.<BR>
<BR>
Bruised and battered, the communications infrastructure persevered, but not=
before providing lessons about how networks adapt to such extreme condition=
s and what more can be done to preserve them in emergencies. <BR>
<BR>
Verizon had to deal primarily with the effects of sheer destruction. The co=
mpany's office at 140 West Street was a central switching office for local t=
elephone traffic. Five stories of debris from 7 World Trade Center, which co=
llapsed Tuesday afternoon, fell against the building, which was also hit by =
a massive steel girder from the North Tower. The basement is flooded with wa=
ter from shattered pipes, rendering the backup power generators useless. <BR=
>
<BR>
The loss of all service at 140 West Street left as many as 175,000 customer=
s in the area unable to make or receive calls. It also affected companies th=
at used as many as 3.5 million lines that carry Internet traffic and private=
financial information through Lower Manhattan. Those lines, Verizon says, w=
ere either damaged or were attached to switches that have no power. Several =
companies had to use alternative communications channels to provide Internet=
access to their employees or subscribers.<BR>
<BR>
"I suspect every business in Manhattan is in some way affected by the =
loss of communication," said Ivan Seidenberg, co-chief executive of Ver=
izon. "Lower Manhattan is a pretty influential place in the entire sche=
me of life."<BR>
<BR>
Among the companies affected was Earthlink, which was unable to provide hig=
h speed Internet service to more than 7,000 subscribers until Friday. The ef=
fect rippled out to Washington, because Earthlink had been channeling some W=
ashington subscribers through the New York center to balance its load. Kevin=
Brand, the company's vice president for network operations, said that to so=
lve the problem the company rerouted traffic through several points in the N=
ortheast that are controlled by one of its partner companies.<BR>
<BR>
Failures of backup power also hit several other network facilities around d=
owntown Manhattan. AT&T was unable to run telephone-switching equipment =
in the World Financial Center because of power losses. <BR>
<BR>
Many cables in the area are also in bad shape. When water mains broke after=
buildings collapsed, the water seeped into cables that have since short cir=
cuited, Verizon officials said. AT&T officials say they are certain that=
they lost several pieces of sophisticated equipment in the basement of the =
World Trade Center that were used to transport data over fiber-optic cables.=
<BR>
<BR>
The phone system's losses were human as well. A half-dozen Verizon workers =
are assumed to have perished in the trade center's destruction, among them t=
wo technicians who were in the North Tower on a maintenance mission. They ha=
d called their co- workers to tell them they were escaping to the roof after=
they realized the extent of the fire caused by the first plane crash. <BR>
<BR>
In the face of such horror, it is difficult to be heartened by the survival=
of a communications network. But some communications experts said that the =
ability of networks to adapt in such emergencies could be crucial to the cit=
y's recovery. <BR>
<BR>
Consider, for example, what happened that Tuesday in the AT&T operation=
s center in Bedminster, N.J. That day, AT&T handled 431 million voice ca=
lls — 20 percent more than usual and the most it had ever carried on a=
business day. The morning of the attacks, blue lines pointing toward New Yo=
rk City lighted up, indicating what the industry calls a "focused overl=
oad." Long- distance calls cascading into New York's telephone system t=
hreatened local callers' ability to reach emergency services.<BR>
<BR>
The solution was to block some of the calls coming into the city. In indust=
ry terms, the strategy is called "call gapping," and it was employ=
ed with a few keystrokes by network managers at the control center. Managers=
typed commands that automatically prompted the AT&T system to keep a pe=
rcentage of its circuits open for outbound long-distance calls. For people a=
round the country who heard the message "All circuits are busy," c=
all gapping was a likely cause. <BR>
<BR>
"People get emotional about this topic because they think we are inten=
tionally holding back their calls," said Mr. Johnson at AT&T. "=
;The local network in New York City is only going to handle so many calls.&q=
uot;<BR>
<BR>
Locally, Verizon was doing its part to make sure that emergency calls could=
get through. The company provided nearly 2,400 spare circuits to city gover=
nment agencies (including the police and fire departments), about 900 circui=
ts to the state government and more than 2,600 to federal agencies and the m=
ilitary. <BR>
<BR>
The Internet also served its purpose as an efficient and relatively stable =
network. Unlike traditional phone calls, which require an open circuit betwe=
en two people, data sent over the Internet travels in discrete packets that =
move over hundreds of different channels at the same time and rejoin at thei=
r destination, in a process known as <FONT COLOR=3D"#FF0000"><B>packet switchi=
ng</B></FONT>. For the most part, that <FONT COLOR=3D"#0000FF"><B>diverse dist=
ribution of the packets allows them to avoid bottlenecks that result from bl=
ockages or damage to specific locations</B></FONT>.<BR>
<BR>
Many people, for example, had more luck sending e-mail and instant messages=
than reaching people over the phone because the messages were automatically=
stored when barriers were encountered and then forwarded to open routes. <B=
R>
<BR>
<FONT COLOR=3D"#FF0000"><B>Paul Baran</B></FONT>, a former computer scientist=
at the RAND Corporation, who is widely considered the <FONT COLOR=3D"#FF0000"=
><B>co-inventor</B></FONT> of packet switching, said that the Internet's abi=
lity to stay up after the attacks was <FONT COLOR=3D"#0000FF"><B>proof that th=
e "route around the trouble" model worked.<BR>
</B></FONT><BR>
As planned, the telecommunications system also relied heavily on built-in r=
edundancies. Many companies, for example, have more than one line from their=
offices to high-speed access points. But the disaster did expose some of th=
e limits of those contingency plans. Some of those multiple lines travel the=
same conduits to the same routing centers. If something happens to those co=
nduits or routing centers — as did in many cases on Tuesday — al=
l the redundancy in the world doesn't help: all the cables would be damaged.=
<BR>
<BR>
Roy A. Maxion, director of the dependable-systems laboratory at Carnegie Me=
llon University in Pittsburgh, has long preached the value of physical diver=
sity in networks. "I wouldn't want to be alarmist about this," he =
said, "but what I think is interesting is how the system is not set up.=
A lot of these contingency plans are not in place." He added that &quo=
t;as a nation we are dangerously vulnerable."<BR>
<BR>
Right now, telecommunications companies are focused on the task at hand: ge=
tting power to buildings, clearing sites of debris, keeping lines up for eme=
rgency crews, monitoring the networks that serve the stock exchanges and run=
ning new cables for relocated businesses that had offices in the World Trade=
Center.<BR>
<BR>
"I've been trying to find a way to say it," Mr. Johnson said. &qu=
ot;But there is not a soft way to say that the businesses that were normally=
served are no longer there."<BR>
<BR>
Copyright 2001 The New York Times Company<BR>
<BR>
Colored emphasizes were made by T. Utsumi.<BR>
<BR>
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* Takeshi Utsumi, Ph.D., P.E., Chairman, GLOSAS/USA  =
; &nb=
sp;*<BR>
* (GLObal Systems Analysis and Simulation Association in the U.S.A.) *<BR>
* Laureate of Lord Perry Award for Excellence in Distance Education *=
<BR>
* Founder and V.P. for Technology and Coordination of &nb=
sp; *<BR>
* Global University System (GUS) =
&nbs=
p; &n=
bsp; *<BR>
* 43-23 Colden Street, Flushing, NY 11355-3998, U.S.A. &n=
bsp; *<BR>
* Tel/Fax: 718-939-0928; (day time only--prefer email) &n=
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