Ethernet Protocols

Ethernet protocol is one method for computers to communicate over a local area network. Since its beginning in the 1970s, Ethernet protocol has gone through three development stages from transmitting data at ten megabits per second to the present ten gigabits per second. In development is the next generation---terabit speed. The latter requires fiber optic cabling.

History

The Ethernet protocol was developed in the mid-1970s by Robert Metcalfe, David Boggs, Chuck Thacker and Butler Lampson while working for Xerox. The initial type of Ethernet protocol permitted data transmission speeds up to ten megabits per second (Mbps). Fast Ethernet followed this original protocol to support up to 100 Mbps transmission. The faster speeds required different network devices and interface cards as well as improved cables called Category Five. A later improvement was Gigabit Ethernet, allowing transmission speeds up to one Gigabit per second (Gbps). There is also ten-Gigabit transmission available. Gigabit travels over fiber optic cables or copper.

Types

Ethernet protocols are defined in terms of the Institute of Electrical and Electronics Engineers (IEEE) standards. Available standards are 802.3 for basic Ethernet ten Mbps speeds over cable with twisted pair wire called 10Base-T. Fast Ethernet rated at 100 Mbps uses the IEEE 802.3u standard. This still uses twisted pair copper wire labeled 100Base-T. These standards used wire described as Category Five, which describes the quality of the cabling. A later cabling improvement is Category 5e, which improves transmission efficiency for Gigabit Ethernet. The standard for Gigabit Ethernet is 802.3z and uses 1000Base-T cable. As noted, this can use Category 5e cabling but greater efficiency comes with Category Six. The IEEE standard for 10-Gigabit networks is 802.3ae.

Function

Ethernet protocol, as with other computer protocols such as LocalTalk, Token Ring, Fiber Distributed Data Interface and the Asynchronous Transfer mode system, controls how computers on a network communicate. They are rules that regulate certain network characteristics. The characteristics are how the computers access the network, how individual computers can be configured in the network (topology), what kind of cables can be used, and how fast data can be transferred. Without adherence to these standards, local area networks could not exist.

Features

Two modes of transmission of data connections using Ethernet protocols exist. The first is half-duplex. This method uses Carrier-Sense Multiple Access/Collision Detection. During network connections each computer listens for a clear channel before transmitting data. If the line is not clear, that is, more than one computer is sending the data may collide. In this case, the particular computers wait a very short time to try again. However, this introduces communication inefficiencies. Full duplex eliminates the problem.

Potential

As with every other computer development, speeds constantly increase. Local area networks, particularly in business applications, require ever increasing transmission efficiency and speed. To move into the next generation of Ethernet protocols will require replacement of twisted cable wiring with fiber optic cable. Optical devices already exist in laboratories for terabit speeds (one million Mbps). Once this becomes cost-effective in general use and appropriate standards are developed, with corresponding routers and switches that will handle the speeds, multiple terabit data transmission will become a reality.