Network Techs help: Whats the difference between a bus network and a Token-Ring one?

Discussion in 'Archived Threads 2001-2004' started by NickSo, Nov 18, 2001.

  1. NickSo

    NickSo Producer

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    I gotta answer this for infotech, but i cant find one thats un-technical enough for me to paraphrase into normal english...
    So whats the diff between a bus network and a token-ring network?
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  2. Colin Dunn

    Colin Dunn Supporting Actor

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    The differences are in how the network is connected, and how media access is controlled.
    All local area networks have some mechanism to prevent multiple stations from "talking" simultaneously on the network. Token Ring works by a "token-passing" system. Only the system that possesses the "token" may place a signal on the network. In fact, if a system talks out of turn on Token Ring, it usually gets physically shut down by the multi-station access units (MAUs).
    A "bus" topology is used on an Ethernet network. Ethernet uses CSMA/CD (carrier-sense multiple access / collision detection). Basically, any system may place a signal on the Ethernet network without mediation. However, if two systems do so simultaneously, they both detect the "interruption," stop immediately, and each wait a random amount of time before retrying. (By randomizing the wait time, the systems are not likely to collide again.)
    As for wiring - Token Ring is one big loop. If a workstation drops off the network, it is up to the multistation access unit (MAU) to "repair" the break and restore the loop.
    A "bus" topology Ethernet network has a single backbone with branches coming off it; every station is connected to one of those branches, or the backbone itself. If a system drops off the network, it does not physically cut the network.
    Token Ring is in theory better, as it allows realistic utilization of about 90% of the rated bandwidth. CSMA/CD is a kludgy approach that realistically lets you use about 30-35% of the rated bandwidth. But Token Ring was an expensive, proprietary solution from IBM, so it didn't catch on outside of Big Blue shops. Ethernet, being cheaper and an "industry standard," caught on instead despite being technically inferior (shades of Beta vs. VHS).
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  3. NickSo

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