Ethernet was invented in 1979 at Xerox Corporation’s PARC by Bob Metcalfe. The original paper described communication over a single cable shared by all devices on the network. This idea was developed in the 1970s by Digital Equipment Corporation (DEC), Intel and Xerox. It was called DIX and later changed name to thick Ethernet. In 1980s, more functions were added to the Ethernet standards, and the new version of Ethernet was called Ethernet Version 2 (Ethernet II).
In 1985, the Institute of Electrical and Electronics Engineers (IEEE) formed many working groups, which produced a series of standards of Local Area Network (LANS), called the IEEE 802 standards, the predominant LAN standards in the world today. Two of the working groups did most of the work to produce the Ethernet standards. The Working Group 802.2 have developed standards for Logical Link Control (LLC); while the IEEE 802.3 Ethernet Working Group have specified the physical layer (Layer 1) and MAC portion of the data link layer (Layer 2). IEEE 802.3 Ethernet Working Group is the currently active working group that responsible for developing standards for Ethernet based LANs.
The most important Ethernet standards published so far include IEEE 802.2 standards and IEEE 802.3 standards.
IEEE 802.2 standards is the IEEE 802 standard defining Logical Link Control (LLC). The LLC sublayer is the upper portion of the data link layer of OSI Model, which presents a uniform interfae to the user of the data link service. A LLC header have a field indicating what network layer (Layer 3) protocol being carried in the Ethernet frame.
IEEE 802.3 standards is a collection of IEEE 802 standards defining the physical layer, and the media access control (MAC) sublayer of the data link layer, of wired Ethernet. The MAC sublayer is the lower portion of the data link layer of OSI Model, which controls transitions down to the physical layer. The IEEE 802.3 MAC specification defines MAC addresses, which uniquely identify multiple devices at the data link layer. The MAC sublayer maintains a MAC address (physical address) table of devices that attached to the Ethernet LAN.
Some notable IEEE 802.3 standards are listed in the following chart.
802.3 (1985) Base standard (10Base5)
802.3a (1992) 10Base2 Ethernet over thin coaxial cable
802.3u (1995) Definition of Fast Ethernet (100Base-TX, 100Base-T4, 100Base-FX)
802.3z Definition of Gigabit Ethernet (over Fiber)
802.3ab Definition of Gigabit Ethernet (over UTP CAT-5)
The first Ethernet networks, 10BASE5, used thick yellow cable with vampire taps as a shared medium (using CSMA/CD). Later, 10BASE2 Ethernet used thinner coaxial cable (withBNC connectors) as the shared CSMA/CD medium. The later StarLAN 1BASE5 and 10BASE-T used twisted pair connected to Ethernet hubs with 8P8C modular connectors (not to be confused with FCC’s RJ45).
Currently Ethernet has many varieties that vary both in speed and physical medium used. Perhaps the most common forms used are 10BASE-T, 100BASE-TX, and 1000BASE-T. All three utilize twisted pair cables and 8P8C modular connectors (often called RJ45). They run at 10 Mbit/s, 100 Mbit/s, and 1 Gbit/s, respectively. However each version has become steadily more selective about the cable it runs on and some installers have avoided 1000BASE-T for everything except short connections to servers.
- 10BASE5 (also known as thicknet): original standard uses a single coaxial cable into which you literally tap a connection by drilling into the cable to connect to the core and screen. Largely obsolete, though due to its widespread deployment in the early days, some systems may still be in use.
At the end-user level, provides connectivity between the end user and the user-level switch.
- 10BASE2 (also called ThinNet or Cheapernet): 50 Ω coaxial cable connects machines together, each machine using a T-adaptor to connect to its NIC. Requires terminators at each end. For many years this was the dominant Ethernet standard 10 Mbit/s.
- 10BASE-T: runs over four wires (two twisted pairs) on a Category 3 or Category 5 cable. A hub or switch sits in the middle and has a port for each node. This is also the configuration used for 100BASE-T and gigabit Ethernet. 10 Mbit/s.
- 10BASE-F: Ethernet over Fiber Media.
At the end-user level, gives high-performance, PC workstation 100-Mbps access to a server. At the workgroup level, provides high-performance connectivity to the enterprise server.
- 100BASE-T: A term for any of the three standard for 100 Mbit/s Ethernet over twisted pair cable. Includes 100BASE-TX, 100BASE-T4 and 100BASE-T2.
- 100BASE-FX: 100 Mbit/s Ethernet over fibre. This is the standard recommended by IEEE 802.3 standard for backbone installations.
Not typically used at the end-user level; at the workgroup level, provides connectivity between the end user and workgroups; at the backbone level, provides backbone and interswitch connectivity for low- to medium-volume applications.
- 1000BASE-T: 1 Gbit/s over Category 5e copper cabling.
- 1000BASE-SX: 1 Gbit/s over fiber.
- 1000BASE-LX: 1 Gbit/s over fiber. Optimized for longer distances over single-mode fiber.
- 10Base-T – specified by IEEE802.3. The “T” stands for twisted-pair. The “10″ stands for 10Mbit/s, the maximum cable length is 100 meters. The 10Base-T use baseband transmission, in which digital or analog data is ent over a single unmultiplexed channel. Baseband transmission use Time Division Multiplexing (TDM) to send simultaneous bits of data along the full bandwidth of the transmission channel.
- 10Base-F — Ethernet over Fiber Media.
- 10Base5 – specified by IEEE802.3. The “5″ stands for the maximum cable length is 500 meters. The “10″ stands for 10Mbit/s.
- 10Base2 — specified by IEEE802.3. The “2″ stands for the maximum cable lenght is 200 meters. The “10″ stands for 10Mbit/s.
- Fast Ethernet (e.g. 100BASE-T) – specified by IEEE802.3u, The “T” stands for twisted-pair. The “100″ stands for 100Mbit/s. the maximum cable length is 100 meters.
- Gigabit Ethernet (e.g. 1000BASE-T) – specified in 802.3z and 802.3ab. The “T” stands for twisted-pair. The “1000″ stands for 1000Mbit/s. the maximum cable length is 100 meters.
Using full-duplex Ethernet makes it possible for devices to transmit and receive at the same time which results in bandwidth optimization. Point-to-point connections are used between the device and switch. The IEEE802.x committee designed a standard for full duplex that covers 10BaseT, 100BaseX and 1000BaseX.
As a final note: as a network technician, you should know what is 5-4-3 rule to pass your CCENT and CCNA test. If you don’t already know it, here it is:
5-4-3 rule is implemented in Ethernet and IEEE 802.3 to minimize transmission times of the signals in LAN. 5-4-3 rule requires that between any nodes on the network, there can only be a maximum of five segments, connected through four repeaters, and only three of the five segments may contain user connections.