RFC - Informational
(September 1982; No errata)
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RFC 872 (Informational)
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RFC 872 September 1982
THE MITRE CORPORATION
The sometimes-held position that the DoD Standard
Transmission Control Protocol (TCP) and Internet Protocol (IP)
are inappropriate for use "on" a Local Area Network (LAN) is
shown to be fallacious. The paper is a companion piece to
M82-47, M82-49, M82-50, and M82-51.
M. A. Padlipsky
It is the thesis of this paper that fearing "TCP-on-a-LAN"
is a Woozle which needs slaying. To slay the "TCP-on-a-LAN"
Woozle, we need to know three things: What's a Woozle? What's a
LAN? What's a TCP?
The first is rather straightforward :
One fine winter's day when Piglet was brushing away the
snow in front of his house, he happened to look up, and
there was Winnie-the-Pooh. Pooh was walking round and round
in a circle, thinking of something else, and when Piglet
called to him, he just went on walking.
"Hallo!" said Piglet, "what are you doing?"
"Hunting," said Pooh.
"Tracking something," said Winnie-the-Pooh very
"Tracking what?" said Piglet, coming closer.
"That's just what I ask myself. I ask myself, What?"
"What do you think you'll answer?"
"I shall have to wait until I catch up with it," said
Winnie-the-Pooh. "Now look there." He pointed to the
ground in front of him. "What do you see there?
"Tracks," said Piglet, "Paw-marks." he gave a little
squeak of excitement. "Oh, Pooh! Do you think it's a--a--a
Well, they convince each other that it is a Woozle, keep
"tracking," convince each other that it's a herd of Hostile
Animals, and get duly terrified before Christopher Robin comes
along and points out that they were following their own tracks
all the long.
In other words, it is our contention that expressed fears
about the consequences of using a particular protocol named "TCP"
in a particular environment called a Local Area Net stem from
misunderstandings of the protocol and the environment, not from
the technical facts of the situation.
RFC 872 September 1982
The second thing we need to know is somewhat less
straightforward: A LAN is, properly speaking , a
communications mechanism (or subnetwork) employing a transmission
technology suitable for relatively short distances (typically a
few kilometers) at relatively high bit-per-second rates
(typically greater than a few hundred kilobits per second) with
relatively low error rates, which exists primarily to enable
suitably attached computer systems (or "Hosts") to exchange bits,
and secondarily, though not necessarily, to allow terminals of
the teletypewriter and CRT classes to exchange bits with Hosts.
The Hosts are, at least in principle, heterogeneous; that is,
they are not merely multiple instances of the same operating
system. The Hosts are assumed to communicate by means of layered
protocols in order to achieve what the ARPANET tradition calls
"resource sharing" and what the newer ISO tradition calls "Open
System Interconnection." Addressing typically can be either
Host-Host (point-to-point) or "broadcast." (In some environments,
e.g., Ethernet, interesting advantage can be taken of broadcast
addressing; in other environments, e.g., LAN's which are
constituents of ARPA- or ISO-style "internets", broadcast
addressing is deemed too expensive to implement throughout the
internet as a whole and so may be ignored in the constituent LAN
even if available as part of the Host-LAN interface.)
Note that no assumptions are made about the particular
transmission medium or the particular topology in play. LAN
media can be twisted-pair wires, CATV or other coaxial-type
cables, optical fibers, or whatever. However, if the medium is a
processor-to-processor bus it is likely that the system in
question is going to turn out to "be" a moderately closely
coupled distributed processor or a somewhat loosely coupled
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