From: Kate Everitt (everitt@cs.washington.edu)
Date: Mon Oct 04 2004 - 09:44:30 PDT
The Design Philosophy of the DARPA Internet
David D. Clark. MIT
Synopsis: Katherine Everitt
<>
This paper discusses the goals involved in the design of the internet,
some design decisions based on these goals, and the success and failure
of the design decisions at supporting the goals. This is a very
important problem, as evidenced by internet use today. The protocol
authors discussed in the paper succeeded at their main goals quite well,
but found some of their decisions were not ideal in supporting some of
their secondary goals and some practical aspects of actual use.
The main design decision discussed in the paper was the use of a
datagram model over a packet switched network. The other main design
decision was to split TCP and IP, as TCP was too specific to support all
the needed types of service.
One of the most interesting things I felt about this paper was the
disparity between the design goals and the actual user goals. One of the
most obvious ones was the issue of trust of hosts. An unstated
assumption was that the hosts were trustworthy and part of the internal
model but in practice the Internet is a system where a host can
misbehave and hurt the network. This problem is still seen in the usage
of the internet today.
This opens up the question of how one designs a system that is flexible
enough to support shifting goals. This was partially addressed in the
use of a datagram network and the IP protocol. From this basic building
block, one can develop more sophisticated services which could give
different models of reliability, delay and bandwidth.
In general this paper helps in understanding the reasoning behind the
TCP/IP protocol, and is very valuable when proposing and evaluating
changes or the creation of similar protocols. It would be more effective
if it included a modified list of main goals based on what was learned
during the development of the protocol.
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