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NETWORKING TOPOLOGIES

What is a Topology?

The physical topology of a network refers to the configuration of cables, computers, and other peripherals.

The logical topology of a network refers to the method used to pass information between workstations.

Main Types of Physical Topologies

Star
Ring
Bus
Mesh

Considerations when choosing a topology

Star Topology

Star Topology

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

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 the data flow.

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 Topology

Ring Topology

A star-wired ring topology may appear (externally) to be the same as a star topology. Internally, the 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. The Token Ring environment uses a star-wired ring topology.

Ring-All computers or network devices are attached directly to each other in a ring fashion. An example is an FDDI (fiber distributed data interface) network, where all the hubs connect to each other in a ring or a token ring network.

Advantages of a Ring Topology

• Easy to install and wire.
• Equal Access to devices no one computer will use all the bandwidth
• Easy to detect faults and to remove parts.

Disadvantages of a Ring Topology

• Slow since signals goes in sequential order
• If the MAU or concentrator fails, nodes attached are disabled.
• Single break in cable can disrupt the flow of network

Bus Topology

Bus Topology

A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable. 10Base is an example of a network that would use a 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.
• Cheaper compared to start topology

Disadvantages of a 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.

 

Mesh Topology

Mesh Topology

A mesh topology combines characteristics of bus, ring and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable and ring networks . Mesh topologies allow for the expansion of an existing network, and enable companies to configure a network to meet their needs.

Internet is the most famous example of a mesh topology

Advantages of a Mesh Topology

• Point-to-point wiring for individual segments. (redundant)
• Supported by several hardware and software venders.

Disadvantages of a Mesh Topology
• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.

Considerations When Choosing a Topology:

• Money. A bus network may be the least expensive way to install a network; you do not have to purchase concentrators.
• Length of cable needed. The 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 topologies.

Summary