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From: torben@FORALIE.ICS.HAWAII.EDU (Torben Nielsen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Talking to cisco routers with Unix machines
Message-ID: <90Aug18.204052hst.2201@foralie.ics.Hawaii.Edu>
Date: 19 Aug 90 06:40:48 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 29

>    >Has anyone had any experience using SLIP and/or PPP from a Sun
>    >(a 3/50 or SPARCstation) at 56 or 64Kbits/sec?  I'm interested
>    >in using one of the serial ports to do this.
>
>You really do NOT want to do this.  The zippy CPU in a sparcstation
>is much better off doing user stuff, rather than trying to service
>13000 interupts/second.  Servicing interrupts is not something that
>most risc processors are good at.  I've heard people complain about
>the impact of much slower SLIP connections.

I disagree. We did this on a Sun-3/50 and sure, you could feel it. On an
SS-1, the impact isn't what I'd call major. We use the on-board serial ports
at 56Kbps in a couple of cases and we don't see a really noticeable impact
from it. We've actually gone a good bit higher than this on an SS-1 :-)
It all depends on what you're after. If you happen to have an SS-1 handy
and you're willing to give up a little chunk of the CPU, go for it. Under
normal circumstances, you won't notice it. My feeling is that the load is
about the same as you get if you add a reasonably active process to your
SS-1.

>You would be better off getting a sync serial interface, which only
>interrupts the CPU per frame, or a stand alone router box.

We're actually playing with this. We have hardware that allows us to run
serial lines out of an SS-1 at a full 2.048Mbps. Neat. And the SS-1 is fast.
Hopefully, we'll manage to get a hold of a Cisco pretty soon so we can test
interoperability.

					Torben