Date: Mon, 24 May 1999 18:41:45 +0100 From: Brian Somers <brian@Awfulhak.org> To: Tom <tom@uniserve.com> Cc: Dag-Erling Smorgrav <des@flood.ping.uio.no>, isdn@FreeBSD.ORG, blitz@pdq.net, stable@FreeBSD.ORG Subject: Re: ISDN Terminal adapter no work Message-ID: <199905241741.SAA00585@keep.lan.Awfulhak.org> In-Reply-To: Your message of "Mon, 24 May 1999 09:41:42 PDT." <Pine.BSF.4.02A.9905240935480.29433-100000@shell.uniserve.ca>
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> On 24 May 1999, Dag-Erling Smorgrav wrote:
>
> > "Craig Harding" <crh@outpost.co.nz> writes:
> > > Most TA's act just like very fast modems.
> >
> > "very" is perhaps not the right word, since an single ISDN channel is
> > less than twice as fast as a 33k6 modem.
>
> Nope.
>
> First of all, most everyone gets 2B+D ISDN (2 x 64K) anyhow, in fact
> 1B+D (64k) isn't available in most areas of the world.
>
> Second, ISDN is sync, but modems are async. Now some people use various
> async emulation protocols over ISDN (like V.120), but that is a complete
> waste, especially if all you are doing is PPP.
>
> Here is what is looks like:
>
> 64k ISDN channel: 64000 / 8 = 8000 bytes/sec
> 2 x 33.6 modem: 67200 / 10 = 6720 bytes/sec
>
> So a 64k ISDN channel is fair amount faster (about 20%) than two 33.6k
> modems.
Recent tests with user-ppp show that running in sync mode (and
skipping all the hdlc and async packet reassembly stuff) will buy you
another 50% throughput wrt cpu load. This can make a big difference
if you're using a few ppp invocations.
> > DES
> > --
> > Dag-Erling Smorgrav - des@flood.ping.uio.no
>
>
> Tom
--
Brian <brian@Awfulhak.org> <brian@FreeBSD.org>
<http://www.Awfulhak.org>; <brian@OpenBSD.org>
Don't _EVER_ lose your sense of humour ! <brian@uk.FreeBSD.org>
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