Xref: utzoo comp.mail.uucp:4902 comp.dcom.modems:6394
Path: utzoo!dciem!tim
From: tim@dciem.dciem.dnd.ca (Tim Pointing)
Newsgroups: comp.mail.uucp,comp.dcom.modems
Subject: Re: What use is Trailblazer compression -- Summary of replies (long)
Message-ID: <3397@dciem.dciem.dnd.ca>
Date: 1 Aug 90 19:32:40 GMT
References: <1990Jul4.195351.9324@tsa.co.uk> <1990Jul19.154334.27957@tsa.co.uk> <1990Jul29.020727.20158@lokkur.dexter.mi.us>
Reply-To: tim@dretor.dciem.dnd.ca (Tim Pointing)
Followup-To: comp.mail.uucp
Organization: Defence and Civil Institute of Environmental Medicine
Lines: 26

In article <1990Jul29.020727.20158@lokkur.dexter.mi.us> scs@lokkur.dexter.mi.us (Steve Simmons) writes:
>I post this with hesitance, as it's based on three-year-old memories
>of a casual conversation.  So take it with a big grain of salt: Peter
>Honeyman said that when you add in the overhead of the PEP protocol
>and the uucp conversations on both ends, maximum uucp thruput on a
>pair of trailblazers is in the high 14000s.

Hmmm... that seems awfully close to the bit-rate of the modems (maximum of
about 14400 bit/sec.) Just a coincidence? I don't think so.

UUCP's "g" protocol seems to take up about 10% of the bandwidth (witness
110 bps over 1200 bps modems.) If one connects the TB to the hosts at
19200 bps, you should be able to get ~ 90% * 19200 = 17280 bps (that's
bits of real user-data). This is higher than the bit-rate of the TB modems,
I hear you say. If, however, the compression in the TB runs fast enough,
and only text is sent (not already-compressed) data, you should be able to
get a theoretical maximum information-transfer-rate of around 28000 bps
[14400 / (1.0 - 0.5) ...  the "0.5" being the compression factor - 50% is
about right for text.] Thus, you *should* be limited by the 19200 bit-rate
to the modems. Again, this assumes very fast compression on straight text
or news.
-- 
	Tim Pointing, DCIEM
	{decvax,attcan,watmath,...}!utzoo!dciem!tim
        uunet!csri.toronto.edu!dciem!tim or nrcaer!dciem!tim
	tim%ben@zorac.dciem.dnd.ca or tim@ben.dciem.dnd.ca