physical topology of a network refers to the configuration of cables, computers

Written by Gianfranco Fracassi

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The protocols used with star configurations are usually Ethernet or LocalTalk. Token Ring uses a similar topology, calledrepparttar star-wired ring. Star-Wired Ring A star-wired ring topology may appear (externally) to berepparttar 146211 same as a star topology. Internally,repparttar 146212 MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring (See fig. 3). The Token Ring protocol uses a star-wired ring topology. Tree A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable (See fig. 4). Tree topologies allow forrepparttar 146213 expansion of an existing network, and enable schools to configure a network to meet their needs. Advantages of a Tree Topology •Point-to-point wiring for individual segments. •Supported by several hardware and software venders. Disadvantages of a Tree Topology •Overall length of each segment is limited byrepparttar 146214 type of cabling used. •Ifrepparttar 146215 backbone line breaks,repparttar 146216 entire segment goes down. •More difficult to configure and wire than other topologies. 5-4-3 Rule A consideration in setting up a tree topology using Ethernet protocol isrepparttar 146217 5-4-3 rule. One aspect ofrepparttar 146218 Ethernet protocol requires that a signal sent out onrepparttar 146219 network cable reach every part ofrepparttar 146220 network within a specified length of time. Each concentrator or repeater that a signal goes through adds a small amount of time. This leads torepparttar 146221 rule that between any two nodes onrepparttar 146222 network there can only be a maximum of 5 segments, connected through 4 repeaters/concentrators. In addition, only 3 ofrepparttar 146223 segments may be populated (trunk) segments if they are made of coaxial cable. A populated segment is one which has one or more nodes attached to it . In Figure 4,repparttar 146224 5-4-3 rule is adhered to. The furthest two nodes onrepparttar 146225 network have 4 segments and 3 repeaters/concentrators between them. This rule does not apply to other network protocols or Ethernet networks where all fiber optic cabling or a combination of a fiber backbone with UTP cabling is used. If there is a combination of fiber optic backbone and UTP cabling,repparttar 146226 rule is simply translated to 7-6-5 rule. Considerations When Choosing a Topology: •Money. A linear bus network may berepparttar 146227 least expensive way to install a network; you do not have to purchase concentrators. •Length of cable needed. The linear bus network uses shorter lengths of cable. •Future growth. With a star topology, expanding a network is easily done by adding another concentrator. •Cable type. The most common cable in schools is unshielded twisted pair, which is most often used with star topologi

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What is a Protocol? the communications between computers on a network

Written by Gianfranco Fracassi

Continued from page 1
Token Ring The Token Ring protocol was developed by IBM inrepparttar mid-1980s. The access method used involves token-passing. In Token Ring,repparttar 146210 computers are connected so thatrepparttar 146211 signal travels aroundrepparttar 146212 network from one computer to another in a logical ring. A single electronic token moves aroundrepparttar 146213 ring from one computer torepparttar 146214 next. If a computer does not have information to transmit, it simply passesrepparttar 146215 token on torepparttar 146216 next workstation. If a computer wishes to transmit and receives an empty token, it attaches data torepparttar 146217 token. The token then proceeds aroundrepparttar 146218 ring until it comes torepparttar 146219 computer for whichrepparttar 146220 data is meant. At this point,repparttar 146221 data is captured byrepparttar 146222 receiving computer. The Token Ring protocol requires a star-wired ring using twisted pair or fiber optic cable. It can operate at transmission speeds of 4 Mbps or 16 Mbps. Due torepparttar 146223 increasing popularity of Ethernet,repparttar 146224 use of Token Ring in school environments has decreased. FDDI Fiber Distributed Data Interface (FDDI) is a network protocol that is used primarily to interconnect two or more local area networks, often over large distances. The access method used by FDDI involves token-passing. FDDI uses a dual ring physical topology. Transmission normally occurs on one ofrepparttar 146225 rings; however, if a break occurs,repparttar 146226 system keeps information moving by automatically using portions ofrepparttar 146227 second ring to create a new complete ring. A major advantage of FDDI is speed. It operates over fiber optic cable at 100 Mbps. ATM Asynchronous Transfer Mode (ATM) is a network protocol that transmits data at a speed of 155 Mbps and higher. ATM works by transmitting all data in small packets of a fixed size; whereas, other protocols transfer variable length packets. ATM supports a variety of media such as video, CD-quality audio, and imaging. ATM employs a star topology, which can work with fiber optic as well as twisted pair cable. ATM is most often used to interconnect two or more local area networks. It is also frequently used by Internet Service Providers to utilize high-speed access torepparttar 146228 Internet for their clients. As ATM technology becomes more cost-effective, it will provide another solution for constructing faster local area networks. isJustFree

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