[NTLUG:Discuss] RE: Switch Question

[Bryan J. Smith]

On Sun, 2004-11-14 at 13:10, Paul Ingendorf wrote:
> Connecting from one switch to another switch your fine.  The real problems
> are usually experience using hubs which for 100Mb ethernet I would never use
> any more because supposedly you can't from one hub to another without a
> switch, never actually tried this to see how it breaks.

It has to do with frame timing, typically repeat through discrete
semiconductors and the speed of light.  You may be able to get away with
more, but the 4 for 10, 1 for 100 hop rule is a safe standard.

Also note that a "transceiver" is considered a hop.

> Electrical isolation only prevents ground loop problems that were common
> with things like 10 base 2.  Going from one building to another can
> offer other electrical issues that will traverse the cable however. 
> This is why it is still recommended you use fiber for ethernet from
> one building to another.

Exactly.  With 1000Base-T[4], it gets mighty noisy in the closet too.

> Also as far as I have ever known the limit to standard copper ethernet has
> always been 100m or about 330ft.

Typically it is considered 85m per segment (x2 for node-to-node).  I
don't know if that is a safe buffer or if the repeat has something to do
with it.

-- 
Bryan J. Smith                                    b.j.smith at ieee.org 
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