The Evolution of Ethernet Nomenclature

To address new reaches, new media, and new speeds on links, Ethernet is continuously expanding into new applications and has become the dominant data communication channel in the world. From the basic twisted pair technology of BASE-T, Ethernet nomenclature has mirrored the evolution of the copper physical layer to include other copper cabling and backplane connections. This article will introduce the industry nomenclature of the most common types of Ethernet ports.

Ethernet (10 Mbps)

The first standard version of Ethernet used coaxial cable and operated at 10 Mbps. The main type of 10 Mbps Ethernet deployed today is 10BASE-T. 10BASE-T operates over two Twisted-pairs of telephone wire (26 to 22 AWG), or better, terminated with RJ-45 connectors. The two twisted-pairs are used as two simplex links: one twisted-pair to transmit in one direction and one twisted-pair to transmit in the other direction. While many switches support 10BASE-T for backward compatibility, most ports auto-negotiate to the higher speeds of either 100BASE-T or 1000BASE-T.

Since the majority of Ethernet ports sold have an RJ-45 connector and support 10BASE-T, 100BASE-T and 1000BASE-T, these ports are often referred to as 10/100/1000 or 10/100/1000BASE-T ports. The RJ-45 is found on almost every personal computer and Ethernet switch.

Fast Ethernet (100 Mbps)

Fast Ethernet operates at 100 Mbps and has the largest installed base of links. The main types of Fast Ethernet links are 100BASE-TX, 100BASE-FX and 100BASE-LX. 100BASE-X links use 4B/5B coding to encode and decode the data and is specified eXternal to the IEEE 802.3 standard by referencing to the FDDI standard. 100BASE-TX, which is almost universally known by the vernacular of 100BASE-T, operates over two Twisted-pairs of Cat5 cable or Cat6 cable terminated with RJ-45 connectors. 100BASE-T increases the speed of 10BASE-T by an order of magnitude and uses the same two twisted-pairs of wires as 10BASE-T.

Cat6 cable

100BASE-FX was the first 100Mbps Fiber link to be defined and used “F” as the “additional distinction” field of the port name. 100BASE-FX links use two 62.5μm “FDDI grade” multimode fibers to support up to at least 2 kilometers. Since 100BASE-LX10 uses Long wavelength lasers at 1310 nm, eXternal coding and supports at least 10kilometers over single-mode fibers, “LX10” was used as the “additional distinction” field of the port name. In both cases the fibers use two simplex links. Over 90% of Fast Ethernet links are 100BASE-T links.

Gigabit Ethernet (GbE)

Gigabit Ethernet (GbE) ports have been the workhorse of the data center for several years now and began shipping more ports than Fast Ethernet for the first time in 2010. Over 90% of GbE links are 1000BASE-T links that operate over four Twisted-pairs of Category 5 cabling, or better, terminated with RJ-45 connectors. The four twisted-pairs are used as four duplex links where all four twisted-pairs are used to transmit in both directions at the same time while 10 and 100 Mbps Ethernet use only two simplex pairs.

All other GbE links are in the 1000BASE-X family and use eXternal 8B/10B coding to encode and decode the data. The eXternal source for the coding in the IEEE 802.3 standard is the Fiber Channel standard. For shorter distances up to 25 meters where structured cabling is not required, 1000BASE-CX uses copper cables and eXternal source coding. 1000BASE-CX uses a jumper cable assembly that contains two pairs of twin axial cable terminated with D-sub connectors.


Ethernet has grown and evolved over the years. Apart from the three original types of Ethernet ports mentioned above, 10 Gigabit Ethernet, 40 Gigabit Ethernet, 100 Gigabit Ethernet and even above have already been put into wide use. Nowadays, Ethernet is the most ubiquitous networking technology. It has grown from its roots in enterprise networks, and now addresses other markets such as data centers, storage, metro, wide area, and carrier networks.


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