Using a Bus Topology


The bus topology was used in the Ethernet networks. It is simply a series of workstations or devices connected to a single cable (see Figure 14.1). Connecting workstations along a single cable is commonly referred to as daisy-chaining . This is the topology used for networks that are composed of 10BASE-2 or 10BASE-5 coaxial cabling.

Figure 14.1. The bus topology consists of multiple devices connected to a single cable segment.

graphics/14fig01.gif

The bus topology, although simple to implement, has a few problems, including the following:

  • The cable itself is a single point of failure for the LAN. Each end of the bus must be terminated . One broken or loose terminator can disrupt the entire LAN.

  • Because all workstations or devices share a common cable, tracking down a node that is causing problems on the network can be very time-consuming . For example, a loose terminator or connector on a single workstation can disrupt the entire LAN, and you might spend hours going from one node to the next checking connections.

  • Bus topologies for Ethernet are usually built using coaxial cable (10BASE-2 and 10BASE-5). Although less cable is used than in a star topology, these cables are more expensive than simple twisted-pair cables. In the case of 10BASE-5, the cable is not very flexible and can be difficult to route through wall or ceiling structures.

In spite of its limitations when used to connect individual workstations into a LAN, the bus is a method that has often been used to join smaller groups that are connected in star formation. For example, before Fast Ethernet and Gigabit Ethernet using fiber- optic cables were developed, connections between hubs or switches in a LAN were often done using coaxial cable.



Upgrading and Repairing Networks
Upgrading and Repairing Networks (5th Edition)
ISBN: 078973530X
EAN: 2147483647
Year: 2003
Pages: 434

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