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From: wcs@ho95e.UUCP (#Bill_Stewart)
Newsgroups: net.news,net.micro.mac,net.sources.d
Subject: Re: Backbone automatic news-compression question ...
Message-ID: 
Date: Sun, 21-Sep-86 01:34:34 EDT
Article-I.D.: ho95e.857
Posted: Sun Sep 21 01:34:34 1986
Date-Received: Tue, 23-Sep-86 07:48:42 EDT
References: 
Reply-To: wcs@ho95e.UUCP (Bill Stewart 1-201-949-0705 ihnp4!ho95c!wcs HO 2G202)
Organization: AT&T Bell Labs, Holmdel NJ
Lines: 38
Keywords: question [regarding] compression [of] news [for] transmission
Xref: mnetor net.news:2043 net.micro.mac:7140 net.sources.d:528

In article  werner@ut-ngp.UUCP (Werner Uhrig) writes:
<discussion of whether to compress or not, since the backbone sites
<mostly compress news anyway, and double-compression tends to be
<counter-productive.

I've seen this done in two areas -
	Binary programs for PCs
	Very large text files (e.g. the Senate bill)

Binary programs have to be processed by a program such as BinHex or
uuencode to make them safe to transmit; my guess is that compressing
them *before* Binhexing would not have much effect on the results of
compress.  Two comments: for PC programs, the most popular compression
seems to be ARC, which is shareware.  Compress is PD, its behavior
is better known, and source is available from mod.sources; is there
any reason to prefer ARC?  Also, the "btoa" program that comes with
compress expands files by 20% instead of the 33% for uuencode; this
can be significant, if more people would use it.

For large text files, it's normally not appropriate, because of the
double-compression problem.  However, the Senate Bill was >64K
before compression/uuencoding, and significantly smaller afterwards.
This allowed it to survive braindamaged mailers, at the expense of
being more work to read, and the redundancy added by uuencode was
probably exploited by compress on the backbone.

On the subject of compression for transmission, if a backbone site is
transmitting a given message to 24 other sites, does it compress each
outgoing message once, or does it do it 24 times?  This is obviously
moot on a broadcast network (like Stargate, or ihnp4->rest of IH),
but could have a major CPU impact on an overloaded machine like
ucbvax, ihnp4, or allegra.  If I were designing "C News", I'd consider
storing all articles in compressed form, with special pre-defined
tokens for the common header items; this would have major disk space
and transmission savings, and would probably have low CPU impact for
news reading programs.
-- 
# Bill Stewart, AT&T Bell Labs 2G-202, Holmdel NJ 1-201-949-0705 ihnp4!ho95c!wcs