VanLUG Email Archive
Tom Marinis (tmarinis99@netscape.com)
Mon, 21 Aug 2000 21:56:12 -0700
Greets G.Z.C.
"G.Z.C" wrote:
>
> Hi,
>
> I've been told, there are basically two different CAT5 UTP standards
> the 568A and 568B. They claim that new installations are to use the
> 568A standard, but people just seem to use whatever they like. It really
> makes no difference which standard you use, as long as you keep both ends
> of the cable consistent (assuming you are making a straight-thru cable.)
> With a 4pair UTP cable, you have the option of using the second set
> of wires to expand. Normally only pins 1,2,3,and 6 are used for 10BaseT.
> Add to this, you can cross the 1 & 3, and 2 & 6, to make a cross-over cable.
> Do you all agree with this? Which is preferred configuration for 100Mhz?
As a telephony person, I had to get certified in
UTP installations as well. I have at this time
7 years practical experience in the field, performing
both 568A, 568B, along with most of the RJ's, the
CATV, the 10Base2 (Coax), Fibre, etc....
Maybe I can help you out a little :-)
---First off, let me say I don't know what you are up to; setting up a network at home, or getting a quote for company. I'll cover both bases, so please do not singe me too bad, since I have little info to go on...
568A is supposedly the U.S.A. standard, but Canada decided to have their very own, and opted to create 568B. That's the difference, and a little piece of history :).
Parts are the same cost, either way. Hubs, Patch cords, Patch Panels, Jacks, etc, ad-infinitium. Trust me, I know.
( Think of Robertson and Philips screws, they both do the same job, both do the same thing, just one country has one standard, and the other country has the other.
In another sense, think of choosing between 2 colours you like. Ooh, say Green, and Blue. It merely comes down to a matter of preference really. ).
Answers to your questions are; ------------------------------
Preferred standards;
CAT5 UTP 568A and 568B are the more popular 100BaseT wire termination standard around ( see the term "cheaper").
The request I get from my customers the most is for 568A. This comes from web savy Accountants referring to U.S. web pages and quoting their standards to the contractor.
Advice: The choice is yours. Once you make it, you have to stick with it. Neither standard is going to be eliminated, so there are no worries about running out of a particular standards part or requirement.
Wiring; -------
CAT5 UTP Standards 568A and 568B are physically identical, as you can see what is used from the wiring diagram for the cable from here... http://wwwhost.ots.utexas.edu/ethernet/100quickref/ch10qr_4.html#HEADING3
This next link is the cross over cable.
http://wwwhost.ots.utexas.edu/ethernet/100quickref/ch10qr_6.html#HEADING5
What circumstances I have encountered under which a customer requires a cross-over cable for;
1/. A simple link between 2 computers, in-order to facilitate a small network, or a test for communication between 2 computers ( to confirm NIC card operation ).
2/. A cross over cable is also used to link HUBS together, chaining them together. Typically, every hub sold has a port for this, in order to expand the network with re-investing in new equipment and throwing away the old one.
This saves considerable expense for a company that wishes to exapnd it's current network without making two large and sizable investments in (A) wiring and the (B) hub/network expansion.
Splitting pairs; ----------------
I advice against this, don't even think about it. ( unless your doing something with 2 computers literally side by side. If your doing this at home, and trying to save a little money by creating your own little network, then go for it ).
Yes, I concede there is enough wire pairs to have 2 computers run off from a single cable, but the trade offs from doing this are;
1). Performance loss of the wire; ( say about 20% initially,more over distances of 25ft If your lucky. Therefore, since most NIC's today are 100/10 variety, guess what speed they'll drop down to in order to maintain a consistant connection to your server, network, hub. Again, if this is a home installation, keep the computers close, and you'll probably be fine.)
2). Applies to large installations; overall wiring management of the patch panel,jack terminators; ( The overall appearance will be horrible on the patch panel. there are occassions when there are bad wire pairs in a new box of wire.
There will be a considerable amount of time wasted to re-terminate cable pairs on an existing patch panel. It will be expensive, and costly, with the bulk being attributed to labour. )
Also, the wiring will be under some tension doing this, and could disconnect from the panel all by itself. This could render the network unusable until the fault is found and corrected ( talking hours of down-time here )
---Tom Marinis---
-- Registered Linux User; # 184093Chuggin' with Caldera Open Linux 2.3, Netscape 4.61
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