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Re: LYNX-DEV http://www.flora.org/lynx-dev/html/month1297/msg00031.html


From: David Woolley
Subject: Re: LYNX-DEV http://www.flora.org/lynx-dev/html/month1297/msg00031.html
Date: Mon, 8 Dec 1997 08:24:47 +0000 (GMT)

> 
> KERMIT does it -- allow resumed downloads.

This was actually quite a late addition.  FTP probably came first, amongst
the common protocols, then Z Modem.  The restart feature in FTP requires
a transfer mode that allows embedding of restart point markers.  No
version I know of implements these, however....
> 
> Not so on a download from some OTHER computer, where
> you have NO friendly software to communicate with --

The FTP daemon's on most Unix systems are friendly.  Although they
don't implement the proper restart protocol, they infer a marker after
every byte, and label the marker with the byte number, so they can use
the restart protocol as though the explicit markers where being
transmitted, and it will work for binary stream representations of the
file in the filesystem.

Unfortunately, many new commercial sites are using Microsoft based
solutions, and the Microsoft FTP implementation doesn't implement this
sort of restart (the actual Microsoft software will only accept a restart
marker of 0).

HTTP/1.1 is also friendly, in that it allows byte ranges to be specified.

Basically restart is possible, in many cases (older sites not using
the latest fashion technology and sites using the latest generation web
servers); however, I still think that you should either use a downloading
tool, or investigate the cause of the dropouts.  In all cases one should
use a caching proxy at the ISP side.

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