Network Toploigies

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Network Topologies

What is a Topology?

A Local Area Networks’ physical layout of its resources is called a topology. The connection of a topology always involves two or more computers. A network's topology affects its capabilities. The type of topology used will determine the network growth, the capabilities of the equipment, the type of equipment needed and the network management.

Physical Topology

A physical topology is the physical layout of devices on a network. Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other. The way that the workstations are connected to the network and the physical structure of the network is called the physical topology.

A network's logical topology is not necessarily the same as its physical topology. For example, twisted pair Ethernet is a logical bus topology in a physical star topology layout.

Logical Topology

The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.

Logical topologies are bound to the network protocols that direct how the data moves across a network. For example, IBM's Token Ring is a logical ring topology, but it is physically set up in a star topology.

Standard Topologies

In the Bus Topology, all devices are connected to a central cable called the backbone. These networks are inexpensive and east to install on small networks. When a sending machine transmits its data, it is transmitted to all devices on that segment. Due to the nature of transmission on a bus network, both ends of the cable or segment must be terminated. Terminators absorb all signals that reach the segment ends. Only one computer at a time can send information on the bus topology. “Because of this limitation, the number of computers attached to a bus network can affect network performance” (p. 51 Tomsho). If a break in the connection occurs, both ends of the network must be sealed with a terminator in order to avoid signal bounce. If cable failure occurs, then the computers can still act as standalones, but “no network communications are possible” (p. 51 Tomsho). Ethernet systems use the bus topology.

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