Re: my broken TCP is faster on broken networks

Albert D. Cahalan (acahalan@cs.uml.edu)
Fri, 11 Sep 1998 08:54:32 -0400 (EDT)


jamal writes:

> It is extremely rude to make suggestions on how to break TCPs
> net-friendliness. I dont see the hack value in it; neither does
> it prove anything smart on your part. Infact i dont think what you are
> suggesting will improve anything.

Clearly it _does_ improve his network performance, and there is
something very wrong with exponential backoff on the Internet.
Congestion is not a temporary problem that can be fixed in such
a simple manner. Even if every client does the backoff (hah!)
there will be plenty of packets to which it does not apply.

Real users do not ever tolerate 2 minute delays. Don't be silly.
They hit the "Stop" button after 2 _seconds_ and start a new
connection to avoid the stall. They kill the window and telnet again.
In general, humans know to kill and restart a slow network connection.

New connections means _more_ network traffic, not less. It sure
seems that exponential backoff was designed for local 10base2
with no collision detection. Perhaps a greedy algorithm would
make more sense on the Internet.

In any case, delays beyond 2 seconds make congestion worse.
Since real users will restart such connections, it is very bad
to let the backoff grow so much. Never mind the pure theory.
We have _humans_ involved, and they don't wait 2 minutes.

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