Ethernet network
Twisted pair
As any bad design this RJ45 connector and twisted pair will live for ever. So lets take a closer look at it:Cabling
Twisted pair cables are nowadays so cheap, that you better buy ready cables and not try to make them yourselves. Only in special cases you got to.If you have only two computers you need only one special crossower cable between the computers. If possible try to get a red one so you know afterwards that it is a crossover.
If you have more devices, you will need a hub. The computers will be connected to the hub with normal straight cables. If you are going to buy a hub, remember to buy one with at least 50% more connectors than you have PC's. PC's have a tendency to accumulate.
The cable used is special. The lines inside the cable are twisted in special algorithm to make sure your signal doesn't get distorted. This is where the name "twisted" comes from.
Pinout for the RJ45 connector (suggested wire colors)
| 8 7 6 5 4 3 2 1 | brown ( or brown/white ) -white/brown - green ( or green/white ) blue ( or blue white ) - white/blue white/green - orange ( or orange/white ) white/orange |
( I got this colour table from some producers catalog and I dont understand why there was this "or" part so I closed it to parentheses )
Normal straight cable
This is used between a PC and a hub.
1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 7-7, 8-8
Of course you can leave four of the lines out: 4-4, 5-5, 7-7 and 8-8
Special crossower cable
This can be used between two PCs.
It's a good practice to use either red cable or red patches in both ends of the
cable
1-3, 2-6, 3-1, 4-4, 5-5, 6-2, 7-7, 8-8
Of course you can leave four of the lines out: 4-4, 5-5, 7-7 and 8-8
If you hace a female-female connector, you can open it and change from the
other female lines 1, 3, 2, 6 so that
old 1 goes to 3, old 3 goes to 1,
old 2 goes to 6, old 6 goes to 2
Here the same thing is told in a picture
As you see there is only four lines. This is an absolute minimum.
The remaining 4 lines can be used either for a phone or for another computer.
What you need
is two Y-connectors, one long cable and four short cables.
Remember: you need two connectors in the hub !
One cable, four ends
Here is an example how you can save half of the cables, if you don't want to use lines 4,5,7 and 8 for for example telephone (btw. normal old fashioned phone needs only two lines = one pair) I made a Y-Y -cable for my network home because I have 12 devices to be connected to 6 wall connector boxes. Each box has two connectors. In the other end I have one 16+1-port HUB and one 4+1-port WLAN box. HUB and WLAN are connected with a short cable. In the wall box I connected the lines like this:| A nonstandard Y-Y-connection | Professional Y-module | |
Connector 1
| Connector 2
|  A professional Y-adapter seems to be like my nonstandard ! You need these in both ends of the 8-line cable. |
1: White/orange + orange and white/green + green
2: White/blue + blue and white/brown + brown
I drew over the groups pieces of hot shrinkable tube leaving abt. 1.5 cm out
and shrinked it. Over that I drew a 2 cm long piece of the original cover of
the cable. Over the original cable i drew another shrinkable piece and shrinked
it where the original cable cover ends.
I cat the heads of the lines and inserted the connectors so that the original
cover went in the connectors to make the fit tight.
Here is a kinda picture of the HUB end of the cable
In the PC end you will of course use a double wall connector:
Remember that you must keep the twisted pairs tight. Do not open them for more than 1 cm. I made here an error and the line didn't work. I cat the connector out and made a new try -now it worked OK.
A good reference about cabling in the net.
Remember
If you use poor cabling, you get poor results. Use CAT6 or CAT5e cabling if possible. You can use home the cheap connection described above, but do not use it at work. If you have some tens or hundreds of computers, you better get the professionals make the work. It costs you some $$ but they do know how to make it right.Gigabit ethernet
Internet speed is rising all the time. The last achievement so far is the gigabit ethernet. There is many technologies in use. One of the 'most bromising' is gigabit over copper. IEEE 802.3ab Recent gigabit over copper standards have been adopted that make gigabit Ethernet as easy to use as 100Mbps Ethernet. Gigabit ethernet can now utilize Cat5 or better twisted pair cabling and the same RJ-45 connectors that are used in 10/100Mbps networks. To achieve gigabit speeds, you must use ethernet cable with all 8 wires (four pairs) present. Many inexpensive cat5 Ethernet cables have only 4 wires and can not reach gigabit speeds.| GIGABIT ETHERNET (1000BASE-T) CROSSOVER (sorry, I have not found straight cable table yet) | |||||
| Plug A | Plug B | ||||
| Pin # | Signal | Conductor Color Code | Pin # | Signal | Conductor Color Code |
| 1 | BI_DA+ | white/green | 1 | BI_DA+ | white/orange |
| 2 | BI_DA- | green | 2 | BI_DA- | orange |
| 3 | BI_DB+ | white/orange | 3 | BI_DB+ | white/green |
| 4 | BI_DC+ | blue | 4 | BI_DC+ | white/brown |
| 5 | BI_DC- | white/blue | 5 | BI_DC- | brown |
| 6 | BI_DB- | orange | 6 | BI_DB- | green |
| 7 | BI_DD+ | white/brown | 7 | BI_DD+ | blue |
| 8 | BI_DD- | brown | 8 | BI_DD- | white/blue |
Own opinion
Twisted pair is intended to replace older coaxial cabling. Coaxial cable RG-58 and the BNC connectors had their negative sides:- The coaxial cable was rather expensive
- Cable was of dull colour
- Security: any PC in the line could spy the others
- Connectors were bulky
- The stress release of the connectors was bad
- The first argument that was used for the twisted pair, the price of the cabling was the worst mistake. The cable might be cheaper per meter, but it is easily forgotten, that you need to draw a cable for every client from the repeater. In Coaxial net you had only one cable running from client to client.
- You can have coaxial gray and black ;)
- The security is now obsolete. In the network the vulnerable data is moved crypted.
- Where the BNC connectors where bulky, the RJ45 connector is from deep under. It seems that nobody has designed it, it has only been been made. If only the hook in the connector would be on the female side, it would be MUCH better.
- There is a kind of stress release in RJ45 but on the real life it doesn't work.
- Twisted pair cabling is originally built so that lines 1,2,3 and 6 would carry
Ethernet traffic and 4,5,7 and 8 would carry telephone connection. Thats why
every cable has now 8 lines where only 4 is used. Only some BIG
organisations use telephones connected to the RJ45.
The remaining 4 lines could of course carry ethernet traffic, if only there were connectors for that. As any bad design this RJ45 connector and twisted pair will live for ever
As a device you either use your PC as a phone or have a special VOIP phone.
Think about coming to your site early in the evening. You notice there is a fire or your neighbourhood has had an heart attack. You calmly start your PC, waiting for Windows to get up. this might take some 5 minutes plus what it takes if you misswrite your password. Here you will get an error message or the Windows might start some of it's mysterious clean up routines. After some 10 minutes you might get the Windows up and running only to see that the network is down.
Next time you want a special VOIP phone on your table. As any computer it does need power. It draws it either from the RJ45 connection or from an external power supply. In the first case the whole network have been re-wired to carry the supply power. If the power is taken from the wall, you got to have one power connector tied to the phone.
Expences
If you are going to make a network to your home or to a small office with up to 10 computers, I'll recommend having WLAN. Lets have a comparition where one PC is connected to a HUB that is 10 meters away. (based in prices in Suomi 08d12m04).| Twisted | WLAN 802.11b | |
| Card | 10 E | 29 E |
| cable | 3 E | - |
| wall connector | 22 E | - |
| fixed line | 5 E | - |
| wall connector | 22 E | - |
| cable | 3 E | - |
| SUM | 65 E | 29 E |
I left the expences of the work and the HUB out in purpose. The cabling and the wall connectors will take about 1 hour using twisted pair. The twisted pair HUB is abt 30 E and WLAN repeater abt 50 - 100 Eur, and falling.
Some words about the connectors
There is many connectors that look like the same. In this picture you can see the difference between RJ-11 which is used in the telephones and RJ-45 which is used in twisted pair ethernet lines. RJ-12 is for some special uses, not in ethernet.
Twisted pair female connector RJ-45