network topologies

Topologies:  The term topology refers to the way in which the nodes of a network are linked together. It determines the data paths, which may be used between any pair of nodes in the network.

Main Types of Physical Topologies.

The following sections discuss the physical topologies used in networks and other related topics.

·                                 Linear Bus   

·                                 Star

·                                 Ring

·                                 Tree

Linear Bus

A linear bus topology consists of a main run of cable with a terminator at each end (See fig. 1). All nodes (file server, workstations, and peripherals) are connected to the linear cable. Ethernet and Local Talk networks use a linear bus topology.

Advantages of a Linear Bus Topology

·                                             Easy to connect a computer or peripheral to a linear bus.

·                                             Requires less cable length than a star topology.

Disadvantages of a Linear Bus Topology

·                                             Entire network shuts down if there is a break in the main cable.

·                                             Terminators are required at both ends of the backbone cable.

·                                             Difficult to identify the problem if the entire network shuts down.

·                                             Not meant to be used as a stand-alone solution in a large building.

Star

A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator.

Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.

Advantages of a Star Topology

·                     Easy to install and wire.

·                     No disruptions to the network then connecting or removing devices.

·                     Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

·                     Requires more cable length than a linear topology.

·                     If the hub or concentrator fails, nodes attached are disabled.

·                     More expensive than linear bus topologies because of the cost of the

            concentrators

Ring

Also known as a ring network, the ring topology is a type of computer network configuration where each network computer and device are connect to each other forming a large circle. Each packet is sent around the ring until it reaches its final destination. Today the ring topology is seldom used.

Advantages:

·                     Ring topology introduces less signal loss as data traveling along the path

·                     Ring-topology network is often used to cover a larger geographic location

where implementation of star topology is difficult.

Disadvantages.

·                     The problem with ring topology is that a break anywhere in the ring will

cause network communications to stop.

·                     Another drawback of ring topology is that users may access the data

circulating around the ring when it passes through his or her computer.

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 for the 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 the type of cabling used limits length of each segment.

·                     If the backbone line breaks, the entire segment goes down.

More difficult to configure and wire than other topologies.