Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!pacbell.com!tandem!zorch!hico2!sonyd1.Broadcast.Sony.COM!blilly.UUCP!bruce
From: bruce@balilly (Bruce Lilly)
Newsgroups: comp.sys.3b1
Subject: Re: Why 3 and 7? (was Re: patching uucico)
Message-ID: <1991Jun8.160126.28884@blilly.UUCP>
Date: 8 Jun 91 16:01:26 GMT
References: <1991Jun3.024220.19047@netcom.COM> <1991Jun7.050757.18586@fithp>
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Organization: Bruce Lilly, Flushing, NY
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In article <1991Jun7.050757.18586@fithp> mhw@fithp (Marc Weinstein) writes:
>From article <1991Jun3.024220.19047@netcom.COM>, by gandrews@netcom.COM (Greg Andrews):
>> 
>> 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.
>
>Is it that there isn't sufficient buffer space for more than 7 packets?

3 bits are allocated to describe the number of windows; 7 is the absolute
maximum.

The packet size can be up to 4096 bytes (in powers of 2), but it's not
easy to change by patching the uucico binary (reason: the code uses an
immediate load instruction (2 bytes) which cannot load a larger number
than 64 without problems due to sign extension).

There is a published description of the uucp g protocol; consult it for
more details (it has been posted to comp.mail.uucp many times, and should
be available at several archive sites).

-- 
	Bruce Lilly		bruce%balilly@sonyd1.Broadcast.Sony.COM