Path: utzoo!utgpu!water!watmath!clyde!att!mtuxo!mtgzy!mtgzz!drutx!dvac
From: dvac@drutx.ATT.COM (Daniel Vachon)
Newsgroups: comp.sys.apple
Subject: Re: Streaming Protocols
Summary: Streamers
Message-ID: <8868@drutx.ATT.COM>
Date: 4 Oct 88 16:33:34 GMT
References: <8809251636.AA04554@crash.cts.com> <8605@smoke.ARPA>
Organization: AT&T, Denver, CO
Lines: 30

In article <8605@smoke.ARPA>, gwyn@smoke.ARPA (Doug Gwyn ) writes:
> 
> However, there is one circumstance where this half-duplex mode of
> operation (one direction at a time) does present a problem, and
> that is with some "9600bps" modems that aren't really 9600bps when
> operated as full-duplex (simultaneous transmission in both
> directions)....
> 
> There are several ways to set up protocols that make effective use
> of such brain-damaged modems. 

  Maybe brain damaged, but how much more do you gain out of FDX 9600?
  Most on-line sessions are half duplex anyways...As for data transfers,
  the only thing the slow speed channel need be used for is ACK's and 
  NAK's...Why pay twice the price for those?!  Just get a true streaming
  protocol...  What it means is a protocol that has the ability to 
  go back and re-transmit a specific block...So, while the sender is
  cranking out these blocks of data (1..2..3...4..5...etc...25..26), say
  the receiver didn't get a good block 24, so it sends a NAK-24, and the
  transmitter will re-transmit block 24... This of course requires some
  more elaborate headers and larger buffer space, but memory is cheaper
  than hardware too... So, if we are talking about hobbyist data transfers
  (of which I assume we are), most hobbyists would rather spend the money
  on a new computer or something instead of getting some over-priced full
  duplex 9600 baud monster... Thats why the USR HST is pretty much the only
  9600 baud modem that Apple hobbyists use.

Later - Dan Vachon -   !ihnp4!drutx!dvac    

Disclaimer: These opinions are mine....who else would want em?!