Date: Sun, 26 May 1996 12:43:18 -0800 From: Sean Doran <smd@cesium.clock.org> To: dennis@etinc.com (Dennis) Cc: jkh@time.cdrom.com, hackers@freebsd.org, freebsd-isp@freebsd.org, smd@cesium.clock.org Subject: Re: The view from here (was Re: ISDN Compression Load on CPU) Message-ID: <96May26.124323pdt.119170-29765%2B19@cesium.clock.org> In-Reply-To: dennis@etinc.com's message of Fri, 24 May 1996 14:06:49 -0400 References: <199605241806.OAA01368@etinc.com>
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>>>>> "Dennis" == Dennis <dennis@etinc.com> writes:
Dennis> All of the routers on the market are just
Dennis> basically PCs, in one form or another. Cisco
Dennis> OS is just a hacked up unix os, so what your
Dennis> really saying is that the guys at cisco write
Dennis> better code than you do.
Well, your inaccuracies need correcting.
Firstly, "IOS" (a name I hate) is not like UNIX in just
about any respect you'd care to think about.
In particular, there is no preemptive scheduling,
processes are free to walk all over each other's memory,
there is a very weak distinction between user space and
kernel space (in particular, a crash in a process will
usually take the whole system out), and there is no
facility for adding in processes which are not linked
at compile time.
IOS is, pretty simply, a very specialized single program
controlling a hardware system. That it happens to
multitask internally doesn't really change this.
The easiest comparison between IOS and another OS would
probably have to do with TOPS-20, but that's largely
because of the interface that human users see.
The value of IOS is, IMO, essentially equal to the value
of the people coding. Dave Katz, Ravi Chandra, Paul
Traina (who plays with FreeBSD, I note), Greg Christy, the
late Tony Li and a number of others are certainly much
better at coding things having to do with such esoterica as
IS:IS, BGP4 and flinging IPv4 packets around too quickly
than anyone else I know anywhere. I'm not sure I'd trust
them to play with "a hacked up unix os", or certain other
guts in IOS, but that is not what they do. Conversely,
what they do is not what anyone else on this list does
unless he also works for Cisco or its competitors
including 3Com, Bad Notworks or the gated consortium (and
even then, gated people do not generally play with
anything more than the routing protocols and getting
routing information propagated into the kernel).
"All of the routers on the market are just basically PCs"
is, I hope, rhetorical licence, as it's pretty obviously
untrue. No high end router I can think of except perhaps
the current generation of Cisco 7500s (one RSP, no smart
interface cards) is very much like a PC at all.
On the low end, you're right, though, except you have to
get to the very low end before you get to "routers" that
_really_ are PCs, without more than a tiny amount of
specialized hardware goo. (I think of Netblazers here).
There are definite and obvious advantages to being able to
use a UNIX-using PC (or Sun SPARC) as a low-to-
moderate-end router. Making up stories about Cisco
products in particular is not necessary to prove that
point, and it doesn't really detract from the obvious
disadvantages of using a PC instead of a dedicated router,
both technical and non-technical.
Sean.
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