Path: utzoo!utgpu!watserv1!maytag!xenitec!zswamp!root
From: root@zswamp.fidonet.org (Geoffrey Welsh)
Newsgroups: comp.dcom.modems
Subject: Re: Can we back up a sec?
Message-ID: <2837.272D1738@zswamp.fidonet.org>
Date: Mon, 29 Oct 90 11:19:29 EDT
Organization: Izot's Swamp BBS - Kitchener, Ontario

George Robbins (grr@cbmvax.commodore.com ) wrote: 

 >The only way that V.32 can "slow down" is via repeated retraining, or posibly
 >fallback to 4800 BPS.

   Not if you're using UUCP-g protocol, in which case a performance limiting 
factor is how long it takes to transport the packets; since a 7*64 byte packet 
takes about half a second or less at 9600+ bps, it's possible that the 
transmitter might stop while waiting for the ACK on the oldest packet before 
continuing. This isn't a problem with UUCP-spoofed PEP, but might provide a 
real pain in the proverbial posterior when you're on a LD connection that's 
carried half a continent north on wireline, piped to microwave for a few 
hundred miles, uplink to sattelite to cross the continent, and the same (in 
reverse) on the other coast. Now the ACK packet must do the same on the return 
path... this could easily push the response time from, say, .5 seconds to .6; 
if that .1-second pause happens after every packet, you're spending more time 
waiting for ACKs than actually transmitting, hence very low efficiency 
figures.

DISCLAIMER: This is speculation. I know not of the technology, nor the 
real-life figures. I go into this only because Mr. Robbins seems to be under 
the impression that V.32 throughput should be the same at all times because of 
the fixed-baud carrier. That may be valid for XMODEM, but it sure ain't for 
UUCP-g!
 

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