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Date:      Fri, 26 Oct 2001 13:33:11 +0100 (BST)
From:      Andrew Gordon <arg-bsd@arg1.demon.co.uk>
To:        Martin Husemann <martin@duskware.de>
Cc:        <freebsd-isdn@FreeBSD.ORG>
Subject:   Re: RFC1974 (STAC) 
Message-ID:  <20011026132510.N36971-100000@server.arg.sj.co.uk>
In-Reply-To: <200110260716.f9Q7Gju04711@night-porter.duskware.de>

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On Fri, 26 Oct 2001, Martin Husemann wrote:

> Excuse me if I'm a bit behind with reality (in catch-up mode now) - I just
> noticed one of the big german ISPs, t-online, now offers STAC compression
> (RFC 1974) for their ISDN access. Do we have support for that already? Anyone
> looked at it?

I don't know of implementation for use with I4B.

The information necessary to implement it is publicly available - RFC1974
gives the PPP packet encapsulation, and the compression algorithm itself
is in X3.241, available from ANSI (it's only 14 pages).

There appears to be a linux implementation (I've not tried it):

http://www.ibh.de/~beck/stuff/lzs4i4l/


However, STAC holds patents on the compression algorithm, so the legal
status of any implementation would be questionable.

It is also not clear that it offers much advantage in typical use, since
many things are already compressed (graphics on web pages, .tgz downloads,
SSH tunnels/connections), and small transfers are constrained by TCP
slow-start (the acutal HTML of sensible size web pages).  I suppose
compression would help with those web pages which have stupid amounts of
javascript with long variable names and loads of whitespace.


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