Network Technologies

Ethernet

Of all of the current Local Area Network (LAN) technologies available, Ethernet is the most popular industry standard. This networking standard is defined by the Institute for Electrical Engineers (IEEE) in a standard they created entitled IEEE Standard 802.3. The standard defines the rules for configuring Ethernet as well as the protocol that allow computers to communicate. A protocol is a standard that allows computers to communicate with each other by defining the following: how they identify each other, the form that the data should take in transit, how the information should be reconstructed once it reaches its final destination, and how damaged transmissions are handled. TCP/IP, IPX, AppleTalk, and NetBEUI are all examples of protocols that operate on the Ethernet standard.

Ethernet is typically deployed in two basic topologies called “bus” and “star”. A bus topology consists of nodes connected together by a single long cable. The bus topology connections are made by using one of two different types of coax cable. The first is called Thickwire, also known as 10BASE5 and the second is called Thin coax, also know as 10BASE2. An advantage of a bus topology is the easy, low cost expandability because you do not need a hub, but a major disadvantage is that any break in the line will disable the entire line. A star topology links two nodes together on the network. It consists of a central point that each of the nodes is connected to. The advantage here is each connection is independent, so that if a line breaks, only that particular node is affected. The disadvantage is the need for central point equipment. This central point is called a hub or switch. The connections from the hub or switch to the nodes are made using a type of wire called unshielded twisted pair (UTP), commonly known as 10BASE-T. An advantage of this kind of cable over 10BASE5 or 10BASE2 is cost. It is much cheaper as well as easier to work with and install. A major disadvantage to UTP is the maximum cable length of 100 meters. This cable is a 4 wire-pair structure that is very similar to telephone cable in appearance and comes in a variety of grades, with level 1 being the lowest quality and level 6 being the highest, and thus the best. The speed at which data is transmitted over these lines is 10Mbps or 10 mega-bits per second.

Token Ring

Token Ring is a LAN protocol first developed by IBM and later standardized as IEEE 802.5 that was published in 1985. Data access to the network is controlled by a token passing Media Access Control (MAC) protocol. The token is passed from one station to another according to rules. When each station gets the token, it has permission to transmit data. When the data is returned to the sender, the token removes the station