1000BASE-T (Gigabit Ethernet)

What is 1000BASE-T (Gigabit Ethernet)?

1000BASE-T is Gigabit Ethernet -- 1 gigabit is 1,000 megabits per second (Mbps) on copper cables, using four pairs of Category 5 (Cat5) unshielded twisted pair (UTP) to achieve the gigabit data rate. 1000BASE-T can be used in data centers for server interconnects or network switch uplinks or be used directly with the desktop. A big advantage of 1000BASE-T is that existing copper cabling can be used instead of having to rewire with optical fiber or newer-generation cables.

1000BASE-T can also be referred to as Gigabit Ethernet, 1000BaseT, GbE, 1 GigE or just Gigabit. It is on Layer 1 of the Open Systems Interconnection model, the physical layer.

1000BASE-T is the most common networking standard. Gigabit Ethernet quickly replaced older Ethernet standards -- such as Ethernet (10BASE-T, 10 Mbps) and Fast Ethernet (100BASE-T, 100 Mbps) -- as the de facto standard for network equipment.

It is supported by almost all modern equipment, offering good enough performance for most common applications. 1000BASE-T is used for general server interconnects and for endpoint client connections. Almost all networking equipment supports it on the access layer, although some backbone applications will require a faster standard. Most home equipment produced in the last decade will have Gigabit Ethernet.

Institute of Electrical and Electronics Engineers (IEEE) standard 802.3ab defines 1000BASE-T, establishing it in 1999:

• 1000 sets the transmission speed of 1,000 Mbps.
• BASE sets the standard as Ethernet baseband signaling.
• T sets the cable media type as twisted pair.

What are the 1000BASE-T specifications?

1000BASE-T uses cheap and readily available cables that preexisted for many applications. It uses four twisted pairs for full-duplex communication -- simultaneous transmit and receive. The minimum standard is Cat5 cable, but it is readily compatible with all newer standards, such as Cat5e, Cat6, Cat6e and Cat8.

1000BASE-T maximum cable length is 100 meters (m), or about 330 feet. It uses the RJ45 connector and jack. 1000BASE-T operates at 1,000 Mbps, or 1 gigabit per second (Gbps).

Automatic medium-dependent interface crossover is a standard feature for Gigabit Ethernet. This means that Gigabit ports can auto negotiate the transmit and receive twisted pairs in the cable. It, therefore, does not need crossover cables, and dedicated upload ports on switches are largely redundant. The physical medium attachment sublayer can potentially correct for nonstandard or reversed cabling.

1000BASE-T cabling is also compatible with some faster standards. 2.5GBASE-T (2.5 Gbps) and 5GBASE-T (5 Gbps) Ethernet can use the same Cat5e and Cat6 cables as Gigabit Ethernet. Extremely fast 10GBASE-T (10 Gbps) is capable over Cat6e cables. These standards are interoperable and auto-negotiated, enabling simple upgrade paths. This enables business and users to continue to use their existing wiring and increase available bandwidth with only relatively minor upgrades.

What are other Gigabit Ethernet standards?

There are other standards for Gigabit Ethernet. These use different types of cables than 1000BASE-T. They can be broadly divided into ones using copper cable and ones using fiber optics.

Copper wire Gigabit Ethernet

• 1000BASE-T uses four pairs of Cat5 UTP cable for a maximum length of 100 m.
• 1000BASE-TX uses two pairs of shielded twisted pair (STP) using Cat6 or Cat7 cable for a maximum length of 100 m. It uses more expensive cables but less expensive electronics; it is no longer widely used.
• 1000BASE-CX uses two pairs of balanced 150 ohm STP cable for a maximum length of 25 m. It uses a different connector than 1000BASE-T. It is still used in some specific data center applications.

Fiber optic Gigabit Ethernet

• 1000BASE-SX is a short laser wavelength on multimode fiber optic cable for a maximum length of 550 m.
• 1000BASE-LX/LH/LX10 is a long wavelength for a long-haul fiber optic cable for a maximum length of 10 kilometers (km).
• 1000BASE-ZX is an extended wavelength single-mode optical fiber for up to 100 km. It is not an IEEE standard, but is supported by many vendors.