Re: Ethernet via existing phone wiring?

"Peter Robinson" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]

> I want to connect several computers (in different rooms) with ethernet
> in order to share a (potential) ADSL connection, and I hope I can avoid
> rewiring.  Near each computer there is a double phone socket, with the
> first port wired to a standard BT phone line.  The second phone ports
> are all wired up ready for a second line, but have never actually been
> used.
>
> Can I use the redundant phone wiring for ethernet?  I know the cabling
> is not ideal (presumably not cat-5), and it has the wrong topology
> (again, I assume), but will it work at all?  Perhaps as 10Base-T only?

The critical thing is the number of pairs. 10Base-T and 100Base-TX Ethernet
use two pairs. Telephone wires often have only 2 pairs. (This will vary from
contry to country and with age of the building. You will need a 3 pair wire
or you need to give up telephone service.

I have been trying to convert whole appartement blocks in Helsinki to
Ethernet using existing telephone wires. All the installations and tests so
far have worked. The idea has been to to use 10Base-T MDU (Multi-Dwelling
Unit) switches.

The quality of telephone cable varies from manufacturer to manufacturer and
with age. It is how ever very difficult to compare as no rating for signals
above 1MHz is usually given to telephone cable. (All new US cable is I
belive rated at Cat-3.)

In my experiments I have been astonished to find that almost all
instalations work also at the higher speed of 100Mbps (without any errors on
the switch statistics). Top results on finnish telephone cable: 100base-TX
90 meters, 10Base-T 150 meters.

The category or Cat-rating of the wiring is not only dependent on the type
of cable, but equally on the splices and terminations. For best results you
should connect the telephone wire straight (end-to-end) to Cat-5 jacks
without any splices in between.

If you need to provide telephone and Ethernet-service on only two pairs
there is an alternative: http://www.etherSPLIT.com
This US product uses a band-pass filter similar to ADSL and HomePNA
splitters to run both Ethernet and telephone on only two pairs.

****

As more and more people are giving up telephone service it will soon be
possible to take over the old wiring for Ethernet. One reasion for this
trend is mobile phones; "voice goes mobile". The other is the arrival of
cheap (65$) VoIP-phones and services.

An other alternative is to one additional Cat-5 cable in to the existing
conducts (16 mm plastic PVC piping) and change the legacy faceplate to a
RJ-11/RJ-45 combination. The cost of renovating a whole building (50 - 150
appartments) starts at 100 euros (66£, 119$) at finnish market prices.

In this new infrastucture we will have an IP-phone in every appartment, a
stack of Ethernet-switches in the wiring closet in the basement and
100Base-TX or 1000Base-SX multimode fiber connections connecting
neighbouring buildings.

****

A few words about the MDU broadband business.

There are two ways of providing LAN-based Internet access to appartment
blocks and condos, Ethernet and HomePNA. (For HomePNA-based MDU switches
see: http://homepna.org/products/index.asp#mdu )

This technology is often viewed only as a way for large property owners to
increase their revenue. (The owner should use his monopolistic control of
access to the infrastucture to squeeze every last penny from the tennants.)
I see the thing differently; we should try to utilize the "economies of
co-operation" and bring LAN-based Internet to *every* home.

For LAN-based delivery of Internet service to work two things are important:
 1) The LAN must be owner or controlled by the users
 2) It must be independent of any commersial ISP, an "open access" network.

In Finland appartment buildings are usually wholly owned by the residents.
(The co-operative is in fact arranged as a limited stock company.) All that
is needed to make investment decisions for in-house networking is to call an
extra shareholders meeting. With the present rate of activity we will have
all of Helsinki wired in a few years.


-- 
Petri Krohn
petri. krohn <[EMAIL PROTECTED]> iki. FI(nland)
_____________________________________________________________
Fiber-optic Community Networking: http://www.HelsinkiOpen.net