Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.unix.sysv386
Subject: Re: Equinox question
Message-ID: <1991Feb21.142804.26980@virtech.uucp>
Date: 21 Feb 91 14:28:04 GMT
References: <27B79130.5C72@telly.on.ca> <1991Feb13.170319.13308@virtech.uucp> <1991Feb15.165755.3231@pcserver2.naitc.com> <1991Feb20.202915.21242@eci386.uucp>
Organization: Virtual Technologies Inc.
Lines: 50

woods@eci386.uucp (Greg A. Woods) writes:
>However, in certain circumstances when receiving a file via UUCP with
>this setup, I can see that the uucico may lose packets if there is no
>hardware flow control.  Maybe the uucico is swapped out.  Maybe the

The only time you should loose packets is if the buffers between the
host and the modem cannot hold a window's worth of packets (8 packet
window with 64 bytes per packet == 512 bytes of buffering are needed).

Between the Clists and the buffers on the I/O card, there should be
no reason to loose a packet.

>system has a load average of 15.  Remember, UNIX isn't a real time
>O/S.  Any lost packets will mean timeouts in the uucico.  That's
>probably why Conor is seeing only an average of 1000 cps input.  I'd
>be real disappointed if that's all I was seeing on my system.

I hadn't seen any higher numbers from other people when accessing
UUNET, so you haven't convinced me that we have a problem.  In fact,
running uucico with debug turned on show NO TIMEOUTS (no alarm messages)
which does indicate that we are NOT loosing packets.

>Now, for any other devices, i.e. non-spoofing modems, hardware flow
>control will be required when sending *or* receiving files with UUCP.

Again, the only thing that is needed is enought room to store a window's
worth of packets on the recieving end (then the transmitting end will 
wait for the acknowledgement of the first packet).

>cps to 90 cps at 2400 bps.  All you folks running single user 33 Mhz
>386's and 16 Mb RAM won't have to worry, but the rest of us do.

We have a 33MHZ 386 with 16MB of ram, but we still don't loose packets
even when we are processing news from the last download, running a system
backup and I am logged in on my 4 or 5 xterms compileing/editing verry
slowly because in this environment we are usually swapping).

>Finally, I don't care how fast that little Equinox card can receive
>characters, if I can't get them safely onto my disk, all the speed in
>the world won't help.  I.e. can I cat from each port into separate
>files, and receive every byte without any flow control?  That's

Remember that there is a built-in flow control in UUCP (that 8 packet
window), so you don't need hardware flow control on top of it unless
your recieve buffers cannot hold 8 packets.

-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170