1000BASE-T–a High-Performing Technology in Gigabit Ethernet
As Gigabit Ethernet leverages the organization’s existing investment in Ethernet and Fast Ethernet infrastructures, 1000BASE-T has become an attractive option by providing a simple, cost-effective performance boost while continuing to use the dominant horizontal/floor-cabling medium. It addresses the exploding bandwidth requirements on current networks that are the result of implementation of new applications and the increasing deployment of switching at the edges of the network.
1000BASE-T is specified to run over four pairs of Category 5 balanced cabling. The 1000BASE-T standard leverages the existing cable infrastructure as it is specified to operate up to 100 meters on Category 5 cabling. The other key specifications of 1000BASE-T make it a cost-effective, non-disruptive, and high-performing technology. First, it supports the Ethernet MAC, and is thus backward compatible with a 10/100 Mbps Ethernet. Second, many 1000BASE-T products will support 100/1000 auto-negotiation, and therefore 1000BASE-T can be incrementally deployed in a Fast Ethernet network. Third, 1000BASE-T is a high-performing technology with less than one erroneous bit in 10 billion transmitted bits. This bit error rate of less than 10 – 10 is the same error rate as that of 100BASE-T.
1000BASE-T is designed to run over Category 5 copper cabling. The transmission of 1 Gbps is possible thanks to the use of four twisted-pair links with 250 Mbps of throughput on each pair (250 Mbps x 4 = 1 Gbps). 1000BASE-T transmits at the same clock rate as 100BASE-T, 125 MHz, but uses a powerful signaling and coding/decoding scheme that enables the transmission of double the amount of data as 100BASE-T. Following is a comparison of the two specifications:
- 1000BASE-T: 125 MHz x 2 bits = 250 Mbps
- 100BASE-TX: 125 MHz x 1 bit-symbol = 125 Mbit-symbol/s
1000BASE-T cost-effectively leverages the design of proven existing Fast Ethernet and V.90/56K modem technologies. Signaling and coding/decoding methods already implemented in 802.3 Fast Ethernet transceivers and in V.90 or 56K modems using advanced DSPs are used to implement 1000BASE-T.
As an extension of standard Ethernet technologies to gigabit-level network speeds, 1000BASE-T is normally implemented using the commonly installed category 5 cabling or enhanced category 5 cabling version of UTP cabling (for example, category 5e). Unlike using only two pairs of wires in 10BASE-T and 100BASE-T networks, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of adaptive equalization and a five-level pulse amplitude modulation (PAM-5) technique.
In the process of transmitting a 1000 Mb/s data stream over four pairs of Category 5 twisted pair cables, there are certain associated problems caused by factors as attenuation, crosstalk, and echoes arising from full-duplex transmission over single wires. To solve these problems, special filters, the PAM-5, forward error correction techniques and pulse shaping technologies are specified to make 1000BASE-T a functional and reliable networking technology.
Fiberstore’s 1000BASE-T copper small form pluggable (SFP) transceivers are based on the SFP Multi Source Agreement (MSA). They are compatible with the Gigabit Ethernet and 1000BASE-T standards as specified in IEEE Std 802.3. For instance, Finisar FCLF-8521-3 compatible 1000BASE-T SFP copper RJ45 transceiver for 100m reach over Cat 5 UTP cable uses the SFP’s RX_LOS pin for link indication and supports 1000BASE-T operation on the host system. Another example is HP J8177C compatible 1000BASE-T SFP copper RJ45 transceiver which is supported on a wide range of HP equipment.
