Subject: Re: rdist vs. sup
To: Ted Lemon , Randy Terbush <>
From: Ronald Khoo <ronald@cpm.COM.MY>
List: current-users
Date: 03/03/1995 10:39:30
In your message dated Mar  2, you write:

> My only complaint about sup versus rdist is that sup doesn't appear to
> CRC the files that it transfers, so if the IP checksum fails, you've
> got a corrupt file and no way of knowing that it's corrupt.

Um.  sup uses TCP, so an IP header checksum failure won't cause
a file corruption.  Note, IP only checksums its own header, not the
data.  However, I _have_ known TCP _data_ checksums to regularly
fail on a particularly bad link -- it took four or five tries to
get a 1 Meg file down across that link uncorrupted!  So even the TCP
checksum isn't really adequate if you're in a backwater of the Internet.
So, yes, a confidence CRC at the end of the whole file (or better
still something longer e.g. like an MD5 signature) would be useful.

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