[CLUG] Re: [ILUG] Re: Genesis

[tinet.ie]

Just add my two cents here,

To my mind, the wires betwixt exchange and house are for the most part
irrelevant, 44.whatever megabits of banwidth is a T3, give or take (if I am
not mistaken), and indeed exactly, I suspect. Now, excluding the engineering
feat of trying to squirt that down the twisted pair to your house from the
local exchange, which I'm prepared to believe is theoretically possible
(hell, I squirt 100mbit down damnably long twisted pair as it is, without
significant difficulty), we come to the problem of taking that data from the
local exchange to wherever it is required. Bear in mind that when you
telephone someone, you aren't getting a long wire between the pair of you
switched in mechanically, of even electronically. You are getting the data
packeted and transmitted along with everyone elses. Which means they are
ADCing the signal coming into the exchange, presumably at a fairly low
frequency (as in less than 20khz), mixing that in with all the other
conversations and squeezing the resultant hodge-podge down a comparatively
thin pipe to a bigger exchange, which in turn squirts it to a bigger
exchange. Now, again if I'm not mistaken, a T3 is about the bandwidth
required for 290 simultaneous telephone conversations. Which sounds somewhat
expensive to me, even if they are only doing it for short hops from your
local exchange to their own custom box in a big exchange. Indeed I'm
hazarding a guess that they wouldn't actually have that much free bandwidth
available in most exchanges, unless telecom are a lot more forward looking
than I give them credit for, assuming that a couple of people on each
exchange opt for the service.

However, if it is true anyway, cool, but I'm going to have to take a serious
look at my perception of reality, and the underlying physics thereof.

Dermot


----- Original Message -----
From: Kenn Humborg <kenn at linux.ie>
<snick>
> Note that _ethernet_ over coax is rated for 10Mbits.  It's a limitation
> of the _system_ (the cable propogation properties, the protocol design,
> the interface electronics, the signal levels) not just the cable.
>
> Ever used an oscilloscope?  The probe cables are 50ohm coax.  Wouldn't
> be much good if it was limited to 20MHz!  Not to mention all the other
> places coax is used...
>
> Later,
> Kenn
<snick>