Archived from groups: comp.dcom.lans.ethernet (
More info?)
Michelot wrote:
> Bonjour Glen,
>
>> Does that help any?
>
> Yes, it's wonderful! As I always say, I have some difficulties talking
> about telecom technicals with my dear wife, or with my neighbours, on
> Sundays during aperitif! Thanks for that interesting synthesis.
>
>> AUI cables up to 50m long reach from
>> the host to the nearest tap on the cable.
>
> We always talk about AUI in 10Base-T, and MII or GMII. Are these
> interfaces really used? Perhaps it is used in specific applications as
> banking terminal... But, nowadays, I don't see the advantages.
>
>> Electrically
>> such hubs were ethernet repeaters, as the term had been used
>> since the coaxial ethernet days, but, as all twisted pair
>> hubs were repeaters, the term hub became commonly used.
>
> Yes, it's commonly used by the users, not by the Standard. In the IEEE, I
> note that the term hub is used 2 times in the sections relative to twisted
> pair or optical 10 Mbit/s and, on the contrary, the term repeater is used
> more than 300 times.
>
>> So, technically there are repeating hubs and bridging,
>> or switching, hubs. The word hub alone is often taken
>> to mean repeating hub, and the word switch to mean
>> switching hub. Hub is the topology, repeater is
>> the function.
>
> Great! I just trying to look for a generic word for naming hubs (in the
> sense of repeatind hubs) and bridges (either a full equipment, either
> embeded in routers, domestic modems, industrial modems as LMDS CPE,
> stations...). So, as you say, we can define the generic hub word which can
> be qualified of repeating or switching feature. In France, hubs is opposed
> to switches (or bridges), but I can all the same to be clear on a generic
> word for gathering both device concepts.
In marketing-speak generally if it says "hub" on the label one may assume a
repeater and if it says "switch" one may assume a bridge, but this has
become complicated as multiport bridge ICs have become cheaper, the ability
to support multiple speeds has become necessary, and as routing features
have been added to switching hubs.
For the rest of this when I use "hub" and "switch" assume I mean a device
labelled as such, regardless of its actual function.
The result is that multiple-speed "hubs" are often several multiport
repeaters connected by two-port bridges to allow multiple speeds to be
handled, sometimes inexpensive "hubs" are implemented as bridges because it
was cheaper to implement using bridge chips (a 5-port gigabit bridge which
also supports 100baseTX and 10baseT is a single not terribly expensive chip
for example, and in a few more years they'll be 50 cent parts) than as a
conventional repeater, and a "switch" may in fine print say "layer 3" which
makes it a router. Unfortunately spec sheets these days seldom contain
enough detail for one to be able to determine how the particular device is
actually implemented--you have to take one apart and refer to chip vendors'
data sheets in many cases, _if_ the identifying information hasn't been
sanded off of the chip or covered with a blob of epoxy.
I suggested a while back that the Committee look into finding some means of
beating the marketroids into submission with regard to nomenclature but I
think I worded my suggestion poorly as it was taken as criticism of the
terminology used in the spec and not a request to recognize that the
marketroids are creating chaos by making up their own nomenclature and by
redefining standard nomeclature to suit themselves.
> Regards,
> Michelot
--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net)
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