VanLUG Email Archive
Simon A. de Weerdt (deweerdt@radiant.net)
Fri, 13 Aug 1999 18:54:15 -0700
Shane Wegner wrote:
>
> On Thu, Aug 12, 1999 at 01:07:05PM -0700, Brian Edmonds wrote:
> >
> > This is a fundemental difference between a hub and a switch. You can
> > get 10/100 autosensing hubs, but the whole hub must run at one speed or
> > the other. If you want different ports running at different speeds you
> > must upgrade to a switch. Hubs are cheap because they're simple.
> Hi,
>
> Thanks for the note. I think I might have to scrap the Linux router idea
> unless I setup two of them. I have a bunch of 386 and 486 machines on the
> network as well which have to be 10mbps only because I can't find 100mbps
> isa nics? Do they exist?
>
There is no reason you couldn't have a 100mbps isa nic but it seems a little
silly. If I recall correctly the ISA bus is limited to about 500kbps or
0.5mbps. As long as the nic has a buffer which can hold all or most of an
ethernet frame this doesn't really matter. The effective bandwidth of an
ethernet is 15-30% of the bit rate anyway for multi host networks. If the nic
gets to much traffic it will just drop frames.
> So I'm thinking about this switch thing. Can you give me an example of a
> switch? Is it like a hub except that it can do both 10 and 100mbps. Is
> that the sort of thing a sisco router would do or is that completely
> different?
A hub doesn't buffer things. It just maintains the signal strength along
multiple cables. A signal coming in is repeated without loss of voltage and
current into multiple cables, this wouldn't happen if the cables were just
connected in a multi-way Y. One would expect the hub to be rate specific as the
different signals likely have different voltage rise times and other
charactaristics.
A switch performs a bit of simple routing. It only echos signals to the cable
with the correct destination address. Each line from a switch only sees traffic
intended for that line. I'm not sure how much routing a switch can do but it
basically gives each host a private line instead of the party line from the
hub. The switch requires greater smarts than the hub since it reads addresses
and buffers ethernet frames to some degree.
So both hubs and switches can be just 10 or 100mbps or they could detect which
is being used and switch between 10 and 100mbps (10/100mbps) however your
network connected to the switch or hub will most likely have to be all 10 or all
100mbps. I think that running both 10 and 100mpbs in one box would be router
territory.
-- Simon deWeerdt \(o)/ deweerdt@radiant.net //T\\ http://www.namous.com/simon |O^O|
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