Zmodem uploads through terminal server are too slow
Benjamin Z. Goldsteen
V.32bis/V.42bis external FAXmodem running with a DTE of 19,200
(XON/XOFF flow control=AT\AT&K5). I connect to a UNIX machine through
a Zyplex (I think) terminal server with a Telebit Worldblazer modem via
TELNET. I want to transfer files using ZMODEM. Downloads work great,
but uploads are very slow (200-300cps). I am using RZSZ 3.17 on the
UNIX end and DSZ 5-28-93 on the DOS side.
If I take the defaults, it gives me a FLOW message at 3K or 4K and
then I have to wait a long time. If I try to use packets or something,
then DSZ sends a packet and there is this long delay before it is ACK'd
(maybe 3-4 seconds with "dsz z pl512" and 16+ seconds with "dsz z
pl4096") so it sends a few kilobytes and then has to wait. I tried
playing around with subpackets, handshakes, window-sizes, etc but I
can't seem to get this to work right.
Everything works fine both ways between BBSs at this speed. And
as I said, downloads work great too (~1400cps). Everything also works
fine when I connect directly to the UNIX machine with a 9600 baud
end-to-end connection (modems and serial ports locked at 9600 baud),
but a) I would like to use 14,400 and compression and b) the direct
connections are going to go away soon (the clincher).
Any help would be appreciated.
Thanks in advance,
P.S.I already tried zdoc0814.zip -- at least nothing I read helped.
--
Benjamin Z. Goldsteen
Hansang Bae
> I have a 386SX-20 w/16450 UARTS (I know...) and a Zoom
> V.32bis/V.42bis external FAXmodem running with a DTE of 19,200
> (XON/XOFF flow control=AT\AT&K5). I connect to a UNIX machine through
> a Zyplex (I think) terminal server with a Telebit Worldblazer modem via
> TELNET. I want to transfer files using ZMODEM. Downloads work great,
> but uploads are very slow (200-300cps). I am using RZSZ 3.17 on the
> UNIX end and DSZ 5-28-93 on the DOS side.
> If I take the defaults, it gives me a FLOW message at 3K or 4K and
> then I have to wait a long time. If I try to use packets or something,
> then DSZ sends a packet and there is this long delay before it is ACK'd
> (maybe 3-4 seconds with "dsz z pl512" and 16+ seconds with "dsz z
> pl4096") so it sends a few kilobytes and then has to wait. I tried
> playing around with subpackets, handshakes, window-sizes, etc but I
> can't seem to get this to work right.
> Everything works fine both ways between BBSs at this speed. And
> as I said, downloads work great too (~1400cps). Everything also works
> fine when I connect directly to the UNIX machine with a 9600 baud
> end-to-end connection (modems and serial ports locked at 9600 baud),
> but a) I would like to use 14,400 and compression and b) the direct
> connections are going to go away soon (the clincher).
We had the EXACT same problem. Some Zyplex term servers can handle
modem control AND RTS/CTS (hardware flowcontrol). Our model cannnot.
So we set it up for Xon/Xoff with modem control. At this speed,
xon/xoff is not good enought apparently. Our d/l's worked great, but
uploads would choke. The only solution that I found was to set the
typeahead buffer to ~ 2048k. This gives it enough buffer so that you
can get 1600cps throughput at 14.4 Our Modems are locked in at
38.4kbps. Also, you HAVE to used the windowed zmodem. So make sure
you type 'rz -w 2048' to start the u/l transfer. I also found that
large files transfer better if you log in at 19.2kbps.
hope this helped.
Hansang Bae --------------------------------------------------------
| hb...@unocdc.unomaha.edu | Data Communication EAB 110 |
| hb...@cwis.unomaha.edu | Voice: (402) 554-3769 FAX: (402) 554-3475 |
---------------------------------------------------------------------
R. Stewart Ellis
> hope this helped.
Some of the models that do support simultaneous hardware flow control and
modem control are 16x0 (where x is 0, 2 or 4), 810 and ?900?. You have to
have a different cable to support the cts signal for this as opposed to the
ring signal. There are several other settings in the Xyplex: an input flag
that should be set to immediate rather than buffered, a circuit timer should
be changed from the default of 80 down to 40. I changed my TCP window size
to 512 from default 256, and I moved my typeahead from 128 to 1024. My
upload stats went from about 400-600 cps for either text or compressed
binaries to 1200-1700 for compressed binaries or 2400 cps or so for text.
Uploads are still slower than downloads, but I am amazed how much difference
tuning made. I called Xyplex tech support with about 3 questions and they
answered two of my questions within a couple of hours. This one took a
couple of days. Each change made a little difference, but the biggest seems
to have been the typeahead. I am tempted to try even higher values.
If your Xyplex is the right model, you really ought to encourage your
computer center to get it setup right. I am so much happier since I took
over the responsibility of seeing why the Xyplex on our campus was
performing so poorly. Fixing it has been relatively easy. Many people who
manage serial communications facilities do not really understand all the
issues, so do not even know how to talk to tech support. Be gentle with
them, but show them these messages and perhaps everyone will be happier.
The poster who said some models do not support hardware handshake and modem
control was right, but even that system was helped by tuning to a very high
degree. The non hardware flow control models that I know of are 1500 and
1800.
Good luck.
--
R.Stewart(Stew) Ellis, Assoc.Prof., (Off)313-762-9765 ___________________
Humanities & Social Science, GMI Eng.& Mgmt. Inst. / _____ ______
Flint, MI 48504 el...@nova.gmi.edu / / / / / /
Gopher,News and sendmail maintainer, all around hack /________/ / / / /
Mike Andrews
>hb...@cwis.unomaha.edu (Hansang Bae) writes:
> >b...@rex.uokhsc.edu writes:
> >> I have a 386SX-20 w/16450 UARTS (I know...) and a Zoom
> >> V.32bis/V.42bis external FAXmodem running with a DTE of 19,200
> >> (XON/XOFF flow control=AT\AT&K5). I connect to a UNIX machine through
> >> a Zyplex (I think) terminal server with a Telebit Worldblazer modem via
> >> TELNET. I want to transfer files using ZMODEM. Downloads work great,
> >> but uploads are very slow (200-300cps). I am using RZSZ 3.17 on the
> >> UNIX end and DSZ 5-28-93 on the DOS side.
[munch]
To back up what's already been said; at Wittenberg we have a bunch of Xyplex
MX1520's, and they wouldn't do modem control and RTS/CTS at the same time.
We had to buy MX1600 servers to get RTS/CTS working. (We also have some
TS720 cards in a few Xyplex Network 9000 hubs, and RTS/CTS works OK there too)
HOWEVER, rumor has it that the new release of the server software (5.0; we
run 4.1.3 right now, use "show server" to get the version number) WILL do
RTS/CTS on the 1500 series, so don't go upgrading hardware just yet....
We've got Multitech 14.4's on our MX1600's, locked at 38400 bps. I had to
set the typeahead buffer up to 2048 to get uploading working. I didn't
try any of the other suggestions here (tcp window size, immediate/buffered
input, circuit timer and such, or any typeahead size smaller than 2048),
so your mileage will vary...
...but maybe those'll help me fix the problem I'm having with SLIP.
If anyone has run SLIP on a MX1600 and has gotten outbound FTP and SMTP
to work, I'd LOVE to hear from you! Inbound works, but outbound hangs
after about 20K... Help!! :-)
--
Mike Andrews
ro...@fragile.termfrost.org [NeXTmail OK]
kra...@wittenberg.edu (school) "This guy's pretty bizarre, Gus."
kra...@mik.uky.edu (hometown) -- Primus
Hansang Bae
> >b...@rex.uokhsc.edu writes:
[wrote about a xyplex term server not doing well on zmodem u/l's]
To which:
el...@nova.gmi.edu writes:
> Some of the models that do support simultaneous hardware flow control and
> modem control are 16x0 (where x is 0, 2 or 4), 810 and ?900?. You have to
> have a different cable to support the cts signal for this as opposed to the
> ring signal. There are several other settings in the Xyplex: an input flag
> that should be set to immediate rather than buffered, a circuit timer should
> be changed from the default of 80 down to 40. I changed my TCP window size
> to 512 from default 256, and I moved my typeahead from 128 to 1024. My
> upload stats went from about 400-600 cps for either text or compressed
> binaries to 1200-1700 for compressed binaries or 2400 cps or so for text.
> Uploads are still slower than downloads, but I am amazed how much difference
> tuning made. I called Xyplex tech support with about 3 questions and they
> answered two of my questions within a couple of hours. This one took a
> couple of days. Each change made a little difference, but the biggest seems
> to have been the typeahead. I am tempted to try even higher values.
^^^^^^^^^^^^^^^^^^^^^^
Becarefule about settin the typeahead buffer too high. I found that on
our model (which does NOT support hardware flow control), setting the
typeahead size to > 2048 resulted in diminishing returns. The speed
improvements were negligible. However, our model cannot be upgraded as
far as memory goes. So if you set your typeahead size to > 2048, make
sure that you monitor the server for the mem usage. You may have to
turn off some features like HELP.
BTW, thanks for the tcp window size (among others) tip. I'll have to
give it a shot.