Local area network cabling

First of all, there are many ways to interconnect devices on a LAN. But the most popular for indoor cabling is by far the UTP cable.

As you can see in the picture bellow, this kind of cable got it's name from the twisted pairs inside. UTP stands for Unshielded Twisted Pairs.

Here are the facts you should know about this widespread type of cable:

1. Conductors

UTP cable has 8 cooper conductors, isolated by a thin plastic cover. In fact not all of these conductors are used for sending and receiving data. Part of them (4) are used to diminish the "cross-talk" effect; basically cross-talk refers to a noise generated by a metal conductor that will interfere with one next to it. The 4 twisted pairs work like this: 4 conductors carry data, 4 carry the noise away from them.

2. Color coding

There are some cabling standards involved in implementing UTP-based networks. All these are based on a color coding of the wires inside. The colors are (no order here): Orange, Orange-White, Blue, Blue-White, Green, Green-White, Brown and Brown-White.

3. Problems with UTP

UTP cable is highly susceptible to electromagnetic interferences (EMI). This means that high voltage cables or electric motors can jam even block a transmission.

If electromagnetic waves can get it, they can get out too. This means that UTP cables offer only a maximum distance of 100 meters per cable of guaranteed delivery due to signal attenuation. If you want to go more than 100 meters, you need to amplify the signal with something (switch, hub, etc). This is why UTP suites better on indoor.
Use UTP cable outdoor only in safe places (no winds, heavy rain or snowing) because it can break easily.

4. Cabling standards

There are two major cabling standards that you should be aware of:

a) TIA/EIA 568B, using this order:
PIN1: Orange - White
PIN2: Orange
PIN3: Green - White
PIN4: Blue
PIN5: Blue - White
PIN6: Green
PIN7: Brown - White
PIN8: Brown

b) TIA/EIA 568A, using this order:
PIN1: Green - White
PIN2: Green
PIN3: Orange - White
PIN4: Blue
PIN5: Blue - White
PIN6: Orange
PIN7: Brown - White
PIN8: Brown

You can see an example bellow:

These connectors are called RJ-45. They are similar to RJ-11 (telephone connectors), but have 8 pins instead of 4.




5. Types of cables and their usage

Connections are standardized like this:

A. Straight-through cable (TIA/EIA 568B both ends of the cable)
- switch to PC
- switch to router
- between any other different devices

B. Crossover cable (TIA/EIA 568B at one end, TIA/EIA 568A at the other)
- switch to switch
- PC to PC
- router to router
- between any devices of the same type

C. Rollover cable (TIA/EIA 568B at one end, exactly the opposite of TIA/EIA 568B at the other end)
- used to connect DB-9 to RJ-45 connectors to management consoles.

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written by David Wall , September 22, 2007

Good info on the basics of LAN cabling.

I also recommend a white paper "De-Mystifying Cabling Specifications From 5e to 7A" written by a TIA committee chair, Val Rybinski.

The paper goes over the categories/classes of ISO and TIA cabling standards from cat 5e to 7A at:
http://www.siemon.com/us/white_papers/07-03-01-demystifying.asp

written by Mihai Dobos , September 22, 2007

Hello

It's a pretty good white paper giving many details about network cabling technolgies. Kind of advanced though, i tried to keep it simple in this article.


Mihai D.

written by amarkant , September 26, 2007

i want more details about cabling

written by k.Arun , October 19, 2007

Different Between Managable & unManagable Switchs

written by Mihai Dobos , October 22, 2007

Hello


A switch that support management functions has an administrative interface (web interface, console, etc). It support configurations, changing general purpose and security options.

A switch that has only basic functions (usually destined for home user networks) doesn't support such things.


Mihai D.

written by Akbar khan , November 14, 2007

i want see network patch paneles taging in server room see the pic

written by padam sindhra , November 23, 2007

thankx very much sir i salute you from true heart i want to be hacker plz suggest me This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

written by Ahamed Bazullah , January 10, 2008

Best site.

written by Paul , March 07, 2008

I request you help on this matter. We have 6 computers, there is no server. My query is our computers are connected through the router, there is no one administrator so is there a possibility that if one computer is infected with virus, the possibility of other computer getting the same virus

written by Plasmo , April 27, 2008

nice explanation
I would add that Straight-through cable is TIA/EIA 568B or A both ends of the cable

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