Nowdays ethernet is a most common networking standard for LAN (local area network) communication, officially standardized by IEEE standard 802.3. Nowdays ethernet runs at 10Mb, 100Mb or 1Gb per second. It was originally developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus (old coaxial cable) or star topology (standard UTP cable). Most ethernet networks use unshielded twisted pair (UTP) cable. Category 5 (CAT5) cable widely used, but other variations are available. EIA/TIA specifies RJ-45 connectors - properly called 8P8C - (ISO 8877) for UTP (unshielded twisted pair) cable. (RJ45 refers to a set of connectors beyond the 8P8C standard but the former has replaced the latter in common usage).
1000BASE-T (also known as IEEE 802.3ab) is a standard for gigabit Ethernet over copper wiring. It requires, at least Category 5 cable (the same as 100BASE-TX), but Category 5e (Category 5 enhanced) or Category 6 cable may also be used and are often recommended. 1000BASE-T requires all four pairs to be present and is far less tolerant of poorly installed wiring than 100BASE-TX.
| Pin | Name | Description | EIA/TIA 568A cable colors | EIA/TIA 568B or AT&T 258A cable colors |
|---|---|---|---|---|
| 1 | TX+_D1 | Transmit Data+ | White with green strip  |
White with orange stripe |
| 2 | TX-_D1 | Transmit Data- | Green with white stripe or solid green  |
Orange with white stripe or solid orange |
| 3 | RX+_D2 | Receive Data+ | White with orange stripe |
White with green stripe |
| 4 | BI+_D3 | Bi-directional+ | Blue with white stripe or solid blue  |
Blue with white stripe or solid blue |
| 5 | BI-_D3 | Bi-directional- | White with blue stripe  |
White with blue stripe |
| 6 | RX-_D2 | Receive Data- | Orange with white stripe or solid orange |
Green with white stripe or solid |
| 7 | BI+_D4 | Bi-directional+ | White with brown strip |
White with brown strip |
| 8 | BI-_D4 | Bi-directional- | Brown with white stripe or solid brown  |
Brown with white stripe or solid brown |
Length:
Each network segment cable length may be up to 100 meters, although several chip manufacturers claim 150 meters. Autonegotiation is a requirement for using 1000BASE-T, according to the standard. Several device drivers will allow you to force 1000 Mbps full duplex to eliminate autonegotiation issues.
Note:
TX & RX are swapped on Hubs (see crossover cable). Also, please note that it is very important that a single pair be used for pins 1 and 2; 3 and 6. If not, performance will degrade.
The + side of each pair is called the tip and the - side is called the ring, a reference to old manual telephone switchboard plugs.
History:
Category 5 cable usually used in this cable, commonly known as Cat 5, is an unshielded twisted pair cable type designed for high signal integrity. With the 2001 introduction of the TIA/EIA-568-B standard, the category 5 cabling specification was obsoleted and superseded by the category 5e specification.
The original specification for category 5 cable was defined in ANSI/TIA/EIA-568-A, with clarification in TSB-95. These documents specified performance characteristics and test requirements for frequencies of up to 100 MHz. Category 5 cable included four twisted pairs in a single cable jacket. It was most commonly used for 100Mbit/s networks, such as 100BASE-TX Ethernet, although IEEE 802.3ab defined standards for 1000BASE-T - gigabit Ethernet over category 5 cable. Cat 5 cable typically had three twists per inch of each twisted pair of 24 gauge copper wires within the cable. The twisting of the cable reduces electrical interference and crosstalk. Another important characteristic is that the wires are insulated with a plastic (FEP). Special attention also has to be paid to minimizing impedance mismatches at connection points.
Cat 5e cable is an enhanced version of Cat 5 that adds specifications for far-end crosstalk, usually used for gigabit ethernet. Cat 5e cable does not enable longer cable distances for Ethernet networks: horizontal cables are still limited to a maximum of 90 m in length. Cat 5e cable performance characteristics and test methods are defined in TIA/EIA-568-B.2-2001.
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