by Mark Ollig
During President Eisenhower’s administration, a data
network intended to link together computers all across the country was being
designed.
The US Defense Department’s new network under their
Advanced Research Projects Agency (ARPA) would be called the ARPA Network, or
ARPANET.
The Department of Defense Directive 5105.15, which
officially began ARPA, was signed by Secretary of Defense Neil McElroy Feb.7,
1958.
ARPANET would support the wide-area packet switching
protocols to be used by computers across the country.
The ARPA network laid the groundwork for the “network
of networks,” which we today call the Internet.
It was 35 years ago this week, when this network had
the misfortune of crashing.
ARPANET stopped working Oct. 27, 1980, and remained out
of service for approximately four hours.
The outage was traced to the data routing tables, which
had become corrupted when an Interface Message Processor (IMP) malfunctioned.
An IMP would more commonly be identified today as an
Internet router, which is a device used to connect networks together. It also
passes data packets of information along the networks.
Further in this column, you will read how the IMP
influenced another event.
The cause of the 1980 outage was reportedly diagnosed
as a “high priority software process running out of control.”
Available resources were quickly used up in the
Interface Message Processors.
The underlining problem was said to be “a rather
freakish hardware malfunction . . . causing erroneous controlling data packets
to be generated.”
It took more than an hour just to figure out how to
restore the network.
Several more hours were needed to locate the
faulty-working Interface Message Processors, and get them stabilized so they
were operating and communicating with each other properly again over the
network.
Of course, many “Internet historians” out there will
want to correct yours truly by saying the actual “first crashing” of the early
Internet occurred in 1969.
Don’t worry; I’ve got it covered.
The first “host-to-host” messaging from one computer to
another, was being tried over the ARPA network Oct. 29, 1969.
The first computer node on the network, said to be the
size of a “one-bed-room apartment,” was the Scientific Data Systems (SDS)
Sigma-7 32-bit host computer. It was located at the University of California,
Los Angeles (UCLA).
This computer node was linked over the ARPA network
with the second node, an SDS-940 time-sharing host computer, located over 300
miles away at the Stanford Research Institute (SRI) in Menlo Park, CA.
Using serial communication protocol cabling, the
Sigma-7 computer was connected to what looked like a kitchen refrigerator, but
was in fact, the previously aforementioned: Interface Message Processor (IMP).
The IMP executed the hold and sending of the data
packets being transmitted over the 56kbps modem connected to leased telephone
lines.
The telephone lines served as the physical “transport
facility” to the second node in this network, the SRI host computer, which was
connected to its own an IMP.
The leased telephone lines also functioned as the
“data-line network” between the two IMPs.
Charley Kline, a programmer and student at UCLA, was
attempting to send the login command, “LOG” to the SRI SDS-940 computer from
his user teletype terminal connected to the Sigma-7 computer.
“I would type a character. It would go into my
computer. My software would take it, wrap around it all the necessary software
to send it to the IMP. The IMP would take it and say, ‘Oh, this is supposed to
go up to SRI,’” Kline said during a 2009 National Public Radio interview.
Kline typed the letters “L” and “O,” which the Sigma-7
computer successfully sent to the SRI SDS-940 computer.
Kline was on a headset, talking over the voice
telephone line with Bill Duvall, another programmer who was with the SDS-940
computer, at the SRI, in Menlo Park, CA.
Duvall confirmed to Kline the SDS-940 computer received
and recognized his typed characters “L” and “O.”
However, a problem occurred when Kline typed in “G.”
The SDS-940 computer did not receive the “G.”
Then, the network went down: it crashed.
Uh-oh.
A memory buffer at SRI had become full; causing the
ARPA network to crash.
Duvall, who was working the connections on the SRI
SDS-940 computer, knew why this happened.
One hour went by while he worked to increase the size
of a memory buffer.
Kline’s next “L-O-G” command message was sent, and
recognized by the SDS-940 computer without incident, (the SDS-940 computer
automatically filled-in the “I-N” to complete the “L-O-G-I-N” command).
Kline was now logged in to the SDS-940 computer, and
was able to issue commands within it.
The SRI SDS-940 computer in Menlo Park was treating
Kline’s UCLA SDS Sigma-7 32-user teletype terminal in Los Angeles, as if it was
a directly-connected user terminal.
This proved instead of needing a separate user terminal
on your desk with a dedicated connection to every computer you required access,
just one user terminal would be able to login or access, any interconnected
computer on the ARPANET.
The logbook by Charles Kline shows the very first
message sent over the ARPANET was Oct. 29, 1969, at 10:30 p.m.
Kline’s handwritten “IMP log” of this historic message
can be seen at: http://tinyurl.com/bytes-log1.
You can view a photo of an Interface Message Processor
here: http://tinyurl.com/bytes-IMP.
Here’s a diagram of the ARPANET with the UCLA and SRI
nodes: http://tinyurl.com/bytes-arpanet.
Could today’s entire Internet system stop working and
crash?
“It could never happen. There are too many redundancies
and alternate network routes which prevent the entire Internet from crashing,”
many will say.
However, I am reminded about an adage my mom
occasionally tells me; “Never say never.”
