Network topology

By which one computer is connected to another or more computer is called network topology. Network topology is the layout pattern of interconnections of the various elements of a computer. In communication networks, a topology is a usually schematic description of the arrangement of a network, including its nodes and connecting lines.

Some topology’s are: - Star topology, Ring topology, completely connected network, Multi-access Bus topology, etc. 

Star topology: - In the star network topology, there is a central computer or server to which all the workstations are directly connected. Every workstation is indirectly connected to every other through the central computer.

The following types of networks are examples of star topologies:

• ARC net

• 10Base-T, 100Base-TX

• Star LAN

Most modern cabling systems are designed in a star physical topology. The

Advantages of the star topology are many, including the following:

1. Easy to implement and extend, even in large networks
2. Well suited for temporary networks (quick setup)
3. The failure of a non central node will not have major effects on the functionality of the network.

However, the big advantage of the star network is that it is fast. This is because each

Computer terminal is attached directly to the central computer.

Star topology has the following disadvantages:

1. Hub failures can disable large segments of the network.
2. Limited cable length and number of stations.
3. Very expensive due to use of a lot of cable.
4. Maintenance costs may be higher in the long run.
5. Failure of the node can disable the entire network.
6. One virus in the network will affect them all.

Ring topology: - The ring topology is a physical, closed loop configuration consisting of point-to-point links. It is a topology of computer networks where each user is connected to two other users, so as to create a ring. A failure in any cable breaks the loop and can take down the entire network. All messages travel through a ring in the same direction effectively either "clockwise" each node passing on the data to the next node till it reaches its destination.

The following are examples of ring topologies:

• IBM Token Ring (although wired as a star)
• Fiber Distributed Data Interface (FDDI)

Advantages of Ring topology

• Growth of the system has minimal impact on performance
• All stations have equal access
• Each node on the ring acts as a repeater, allowing ring networks to span greater distances than other physical topologies.
• Because data travels in one direction high speeds of transmission of data are possible.
• When using a coaxial cable to create a ring network the service becomes much faster.

Disadvantages of Ring topology

• Often the most expensive topology
• Failure of one computer may impact others

Completely connected network: - The mesh topology connects all computers to each other. It is a way to route data, voice and instructions between nodes. A mesh network effectively extends a network by sharing access to higher cost network infrastructure. The cable requirements are high, but there are redundant paths built in.

Mesh topology has the following advantage:

• A mesh network is reliable and offers high speed.
• If one node can no longer operate, all the rest can still communicate with each other, directly or through one or more intermediate nodes.
• Mesh networks work well when the nodes are located at scattered points that do not lie near a common line.
• Easy to solve problems.

Disadvantages of mesh topology are as follows:

• The chief drawback of the mesh topology is expense, because of the large number of cables and connections required.
• Instillation and configuration system is very complex.

Bus topology: - In the bus network topology, every workstation is connected to a main cable called the bus. Therefore, in effect, each workstation is directly connected to every other workstation in the network. A single cable, the backbone functions as a shared communication medium, attaches or taps into with an interface connector with the devices.

Bus topology has the following advantage:

• Cabling costs are minimized because of the common trunk.
• Easy to implement.
• A relatively cheap and reliable topology.

Disadvantages of Bus topology

• Difficult to trouble shoot because no central distribution points exist.
• Limits on cable length and Workstation numbers.