Newsgroups: comp.mail.uucp
Path: utzoo!lsuc!jim
From: jim@lsuc.on.ca (Jim Mercer)
Subject: Re: 'g' protocol over X.25 - why not?
Message-ID: <1990Sep5.204922.8506@lsuc.on.ca>
Organization: Law Society of Upper Canada, Toronto
References: <6706.26e3ab4f@ccvax.ucd.ie>
Date: Wed, 5 Sep 90 20:49:22 GMT

In article <6706.26e3ab4f@ccvax.ucd.ie> ctwomey@ccvax.ucd.ie writes:
>Another question about uucp over X.25!
>
>My understanding of the difference between the 'g' and 'f' protocols
>is that the 'f' protocol does a minimal amount of data checking and the
>'g' protocol does a lot of packetising and data checking.

generally, yes

>Now assuming that I have two machines linked via modems and PADs using an
>X.25 connection, and the connection is such that the PADs ignore all 
>interpretation of characters essentially entering binary mode, why exactly
>does the 'f' protocol work and the 'g' protocol not?  (Remember ^P is being
>ignored by the PADs.)

it's not that 'g' doesn't work, you just have to mung the X.28 parameters
appropriately and maybe adjust your uucico window variable.

i did extensive playing with this on a past project and finally achieved
an average of 160 cps over 2400 baud X.25 links.

two tricks:

1) under SCO Xenix 2.2, we adjusted the windows variable in uucico (using
adb, yech!) from the default of 3 to 7.  this means that as many as 7
(formerly 3) packets could be sent before the protocol would wait
for an ACK from the first packet.  opening the window allowed the ACK's
to return before the protocol timed out.

2) X.28 parameters must be set to as transparent a mode as possible.
no forwarding characters, forward on timer or full packet.
also watch those flow control parameters.  depending on the network
(private, DataPAC, Tymnet, Telenet, etc) these parameters may change.

'g' over X.25 may not be as efficient as 'f', but at least 'g' is available
in almost all uucp implementations.

a pleasant request to postmaster@avcoint may get you in touch with someone
who continued the effort (using X.25 on Hayes V series modems).
ask for chris williams.

-- 
[ Jim Mercer  jim@lsuc.On.Ca  || ...!uunet!attcan!lsuc!jim    +1 416 947-5258 ]
[ Systems Facilitator - Law Society of Upper Canada, Toronto, Ontario, CANADA ]
[ Standards are great. They give non-conformists something to not conform to. ]
[      The opinions expressed here may or may not be those of my employer     ]