Newsgroups: news.software.b
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Anyone interested in end-to-end checksums in news?
Message-ID: <1989Nov16.173359.22435@utzoo.uucp>
Organization: U of Toronto Zoology
References: <14594@well.UUCP>
Date: Thu, 16 Nov 89 17:33:59 GMT

In article <14594@well.UUCP> Jef Poskanzer <jef@well.sf.ca.us> writes:
>Seems like we could add an end-to-end checksum to netnews articles in
>an upward compatible fashion.  Add a new header field, "Checksum: ",
>based on the entire article except the Path: and Checksum: headers.
>Modify the news software to add the checksum to locally-posted
>articles, and check it if present on articles from elsewhere.

Such a scheme existed in an early version of C News.  We eventually
abandoned it.  The problem is, what do you do when you receive an
article with a bad checksum?  The underlying difficulty is that news
not infrequently travels via networks that corrupt the data in "benign"
ways, e.g. substituting spaces for tabs.  Throwing away such articles
means you don't see perfectly-readable news.  Keeping them and reporting
on them just increases the noise level in the sysadmin's mailbox, since
all too often the responsible parties won't (or can't) fix their software.
We thought about checksumming only non-blank characters, but that drives
the cost up considerably, and there's still the question of what to do
with a bad article.  It just didn't seem worth it.

>Note that this means no more gratuitous header re-writing.  Bet Henry
>like it for this reason...

Alas, not so.  Since it is *necessary* to rewrite the Path header, the
checksum has to be recomputed every time anyway.
-- 
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
