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000218_news@newsmaster….columbia.edu _Sat Jun 20 08:55:12 1998.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: Z-Modem vs FTP: Is the following an accurate comparison?
Date: 20 Jun 1998 12:55:09 GMT
Organization: Columbia University
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References: <35867DA0.A4FB2608@interlog.com> <6m7s57$s99$1@apakabar.cc.columbia.edu> <uXGi1w8Z7ijP092yn@netcom.com>
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In article <uXGi1w8Z7ijP092yn@netcom.com>,
Jeffrey Hurwit <jhurwit@netcom.com> wrote:
: In article <6m7s57$s99$1@apakabar.cc.columbia.edu>,
: jaltman@watsun.cc.columbia.edu (Jeffrey Altman) wrote:
:
: > PPP adds a great deal of overhead. On a dial-up
: >connection there is no additional overhead. So Zmodem will be faster.
:
: Interesting... I download a fair number of reasonably large
: compressed .zip files from various software archives. On my Unix
: shell account, there are generally two ways I do this: 1) run a PPP
: emulator (SLiRP) on my shell and use Netscape for my FTP client, or
: 2) use lynx over a terminal session (to bring the file to my
: provider's machine), then use Kermit to transfer it to my own over
: the dialup connection. Given that I'm using recent Kermit versions
: tuned for speed (long packets, sliding windows, 8-bit dialup
: connection, minimal control character prefixing, block-checking 3),
: which method would be faster overall?
:
You should measure it and see for yourself. FTP has less protocol overhead
than Kermit, but that's because it relies on the underlying protocols (TCP,
IP and/or PPP) to provide the error checking, sequencing, fragmentation and
reassembly, and recovery. Kermit has more protocol overhead at the file
transfer level, but when you use it over a straight dialup, there is nothing
underneath it adding anything extra -- except whatever protocol the modem is
using, but that's the same in both cases.
The next round of Kermits (K95 1.1.16, already out; C-Kermit 6.1 and MS-DOS
Kermit 3.16, both current in Beta test) add a new Kermit protocol option
called streaming, that takes advantage of an underlying reliable transport.
- Frank