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000402_fdc@panix.com_Sun Aug 20 16:07:53 2006.msg
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Path: reader2.panix.com!reader1.panix.com!panix!not-for-mail
From: Frank Da Cruz <fdc@panix.com>
Newsgroups: comp.protocols.kermit.misc
Subject: Re: extremely high latency channel
Date: Sun, 20 Aug 2006 19:58:50 +0000 (UTC)
Organization: PANIX Public Access Internet and UNIX, NYC
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Message-ID: <slrneehfnq.j1o.fdc@panix2.panix.com>
References: <1155239757.815134.180170@74g2000cwt.googlegroups.com> <1155277449.917953.181880@h48g2000cwc.googlegroups.com>
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Xref: panix comp.protocols.kermit.misc:15534
On 2006-08-11, tomviolin <rock_spambust_violin@yahoo.com> wrote:
: As a followup, I have found that using Zmodem protocol over the link
: works slowly but reliably when timeouts are disabled using the -O
: parameter.
:
Sorry for the delay in getting to this; I have to go out of my way to
check netnews these days.
Zmodem is a streaming protocol. You can make C-Kermit stream too if you
want to try it. This technique is appropriate for error-free connections
such as over TCP/IP networks, but it can also work when you have an
error-free serial connection, such as you should have when using
error-correcting modems and hardward flow control. See:
http://www.columbia.edu/kermit/ckermit70.html#x4.20
See especially section 4.20.2.4, "Streaming on Dialup Connections".
Of course both Kermit partners must support streaming. For example,
C-Kermit 7.0 or later and Kermit 95 1.1.19 or later.
The problem with streaming is that it's all-or-nothing. Any error will
stop the transfer dead. Of course you can always keep partial files
and use the RESEND/REGET feature to continue from that point.
: I would still much rather use the Kermit protocol, but every attempt I
: have made to adjust the parameters of the protocol (I'm transferring
: C-Kermit to C-Kermit here) result in indefinite delays or unbelievably
: slow performance (would you believe 2 CPS -- that's TWO (period) CPS,
: while Zmodem at least broke the 20CPS barrier and averaged about 21
: CPS, which is acceptable. But again, I'd rather use the Kermit
: protocol and its nice features like "set send move-to" and countless
: other advantages.
:
Thanks :-)
For the past 10 years or so, timeouts have been "dynamic" -- calculated on
the fly based on the behavior of the connection. That's why your SET SEND
and SET RECEIVE timeout commands seemed to have no effect. Here's the
text from "help set send":
SET SEND TIMEOUT number [ { DYNAMIC [ min max ] ], FIXED } ]
Number of seconds to wait for a packet before sending NAK or
retransmitting. Include the word DYNAMIC after the number in the
SET SEND TIMEOUT command to have Kermit compute the timeouts dynamically
throughout the transfer based on the packet rate. Include the word FIXED
to use the "number" given throughout the transfer. DYNAMIC is the
default. After DYNAMIC you may include minimum and maximum values.
It should also say, a negative timeout value means "don't time out,
wait forever":
SET SEND TIMEOUT -1 FIXED
Does this help?
- Frank