Mailinglist Archive: opensuse (2271 mails)

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Re: [SLE] HowTos for a home LAN
  • From: Vince Littler <suse@xxxxxxxxxxxxxxxxxxxxxxxxx>
  • Date: Sun, 18 Apr 2004 07:44:32 +0100
  • Message-id: <200404180744.32124.suse@xxxxxxxxxxxxxxxxxxxxxxxxx>
On Sunday 18 April 2004 5:21 am, Jim Cunning wrote:
> On Apr 18 at 3:43am, Let_Me_Be wrote:
> > >What hardware do I need to buy? Would prefer to set
> > >up a wireless - but if it is not practical I can go
> > >the hardwire route. (My house is wired for telephone
> > >in every room and there are four pairs of wires in
> > >each box, but only one pair is being used for
> > >telephone service, do if worse comes to worst could I
> > >use some of those extra 6 wires?)
> >
> > You need only 2 pairs for 100Mbit, I don't see any problems with using
> > the same cable for both telephone and network. (I'm using 1 cable for
> > 2 computers on each sides). Sure telephone does use other voltage, but
> > it will simply run on other cable, and i'm sure that it won't
> > interfere with the network much.
>
> You CAN use one cable for both ethernet and telephone, but the cable must
> be Category 5 or more for 100 Mbit. You cannot use the ordinary telephone
> wiring in your house for ethernet, unless it is at least Cat5. Cat5 cable
> is usually wired using one of two standards called EIA/TIA 568A or EIA/TIA
> 568B. A Google search for either one will return lots of pages about them.
> Here is one: http://www.pera.net/Category_5_Document.htm
>
> An ordinary Cat5 ethernet connector has 8 contacts (4 pair), but only
> contacts 1, 2, 3, and 6 are used for ethernet. Contacts 4, 5, 7, and 8
> could be used for telephone. An interesting set of slides on UTP
> (unshielded twisted pair) wire can be found at:
>
> http://boulder.noaa.gov/noc/Training/noframes/sectionIII/sld001.htm
>
> Many other resources are available. Google can help....
>
> Jim

Even then, some issues remain for the LAN at home. The context in which all
you have brought applies is wiring of an office. In this case, the telephone
system is a star layout and it has its own switch which effectively isolates
the internal telephone network from the outside.

So firstly, the domestic telephone system is a bus topology, because all
phones pick up directly on the outside line. There is no place on such a
network which can serve as a location for a hub for more than 2 wallplates.

So secondly, being connected directly to many km of outside line, you need to
think about lightning strike transfer potentials from strikes near either end
of the route [even if the incoming route is entirely underground], and all of
the other interference a long line can bring. Let_Me_Be says the telephone
runs in another cable, but it is actually a different pair of wires in the
same cable we are talking about. and CAT5 insulation is quite thin.

I suppose it is cost benefit. If you think that the cost of replacing fried
network hardware [ignoring the possible interference] is outweighed by the
cost of not using the existing wiring, then that's the way to do it. While I
might share CAT5 cable in an office, this is because the phone lines are not
natively external. I wouldn't at home, because this does not apply.


Vince


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