quick network engineering review question

[Gerald Combs]

Jonathan Hutchins wrote:

> It's arguable whether the variants are actually ethernet or not.  You can get 
> ethernet range extenders, and if you're using thin-net you can usually get 
> across an urban street or rural campus with them.

Did you look at the first link?  1000BASE-ZX is an IEEE standard
(802.3z, I think).  The only "name brand" is the one the IEEE placed on
it.  We have several clients using 100BASE-FX, 1000BASE-ZX and the like
to span distances of 1 - 60 km by simply plugging fiber into a port on a
switch.  No range extenders or extra equipment involved.

The other two examples replace Ethernet's physical layer with other
network technologies (I think GigaMAN uses SONet, and LRE uses DSL).
This is irrelevant from the client perspective -- they get a 10, 100, or
1000BASE-T RJ-45 jack, which they just plug into their network...

> None of these protocols, however, will work if you plug it into a standard 
> 10/100bT hub.  For distance, you need a "modem" or an interface device that 
> efectively does the same thing as a modem; one at each end in fact.

...and the same is true for cable and DSL "modems" (which are more
accurately called bridges).  They simply forward Ethernet frames over
long distances.  If you want to capture traffic on your cable, DSL, LRE,
or GigaMAN connection you only have to worry about the LAN side.

> (You're quite right that subsets of the ethernet standard are prevelant in 
> other transport protocols - why re-invent the wheel - but that doesn't make 
> them ethernet.)

You're not making a distinction between Ethernet's physical layer
specifications (100BASE-T, 10BASE2, 1000BASE-LH, etc) and its data link
layer spec.  I am.