Why 3 and 7? (was Re: patching uucico)

Greg Andrews gandrews at netcom.COM
Mon Jun 3 12:42:20 AEST 1991

In article <1991Jun2.224048.7111 at ingres.Ingres.COM> rog at Ingres.COM (Roger Taranto) writes:
>How were the 3 and 7 chosen?  Is there any research on the optimal
>number of un-ack'ed packets?  Why not raise it to 16 or 32 or ...?

Certain decisions in the initial design of the protocol determined the
maximum window size and the default window size, along with the default
packet length.

The protocol's design limits the maximum window size to 7.  The default size
of 3 was probably just the figure that the designers found to be optimal
for transfer:  Kept the data flowing in a steady stream, and didn't hog the
system resources too much.

The designers only had 1200 and 2400 bps modems to work with at the time
(78 or 79, I believe), and not the same modems as many folks use today.
As such, somebody with a different type of modem may not get the same
results.  They may need to adjust the protocol's operation to get optimal

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