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Date:      Fri, 26 Oct 2001 20:19:40 +0200 (CEST)
From:      hm@kts.org (Hellmuth Michaelis)
To:        Andrew Gordon <arg-bsd@arg1.demon.co.uk>
Cc:        Martin Husemann <martin@duskware.de>, freebsd-isdn@FreeBSD.ORG
Subject:   Re: RFC1974 (STAC)
Message-ID:  <20011026181940.1EA51F9C4@bert.kts.org>
In-Reply-To: <20011026132510.N36971-100000@server.arg.sj.co.uk>

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> > 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.

Dito.

> 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/

A year or so ago i had a look at it, it looked not bad but it is _VERY_ 
Linux kernel specific so i just gave up after some time ....

The code seems to be documented good, there are masses of comments
in it IIRC.

The author was very responsive, i asked a few questions about the code
and if he had any difficulties re. the patented status (he had not at
that time).

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

I consider it not only questionable but highly questionable. 

On the other side it would be a good thing to have it for the kernel
sppp interfaces and i always think that if i have some more spare time
when i'm old and grey, i will look at it again :-)

hellmuth
-- 
Hellmuth Michaelis                hm@kts.org                   Hamburg, Europe
 We all live in a yellow subroutine, yellow subroutine, yellow subroutine ...

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