Path: utzoo!attcan!uunet!umich!wuarchive!usc!jarthur!ucivax!gateway
From: vcerf@NRI.Reston.VA.US
Newsgroups: comp.protocols.iso.x400
Subject: Re: DATA Compression and X400 standards
Message-ID: <9010290828.aa22293@NRI.NRI.Reston.VA.US>
Date: 29 Oct 90 13:42:02 GMT
References: <Your message of Mon>,
	<531*Eppenberger@verw.switch.ch>
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Approved: usenet@ICS.UCI.EDU
Autoforwarded: true

Urs,

your view strikes me as potentially off the mark in the
sense that compression methods may vary in their usefullness
depending on the kind of material and encoding employed.
As a result, it may be important to perform the compression
with knowledge of the type of content. This tends to place
the application of compression rather high in the protocol
architecture rather than below the level of X.400, for
example.

Just to give you one example, I recently got a message
advising I could pick up a compressed postscript file
via FTP from Germany. The compression took place "above"
the level of FTP and decompression is applied after
receipt of the file. I suppose you could argue this
should have somehow been done at a lower layer, but I
think the argument is not convincing on its surface.

I appreciate your apparent distress with all the various
body types. I suppose this will get worse over time as
people want to convey proprietary objects. Best guess
is that things will settle down as we discover particular
encodings and object types which seem to be the most useful.

Vint Cerf