Ring Topology and Bus Topology

                    Ring Topology

The diagram given below shows the circular a ring arrangement of a computer network.

Ring Topology

Ring Topology avoids dependence on Central Computer. Each node on ring can send a message to other terminal with a unique-address. A node receives data from one of its adjacent node. The only decision a node has to take is whether the data is for its use or not. If it is addressed to it utilises it. Otherwise it passes it on to the next node.

Addition of a new station involves breaking the ring and adding a Ring-interface Unit. (RIU)

Every Data Unit in ring contains source and destination address.

Merits:

It is a True Distributed Data processing system. More reliable than STAR because communication is not dependent on Hub. In ring topology, a shorter cable length is needed as compared to star topology. Ring topology delivers fast and efficient performance. It is suitable to setup high speed network using optical fibres.

Demerits:

Addition of New Node increases the communication delays. Complicated control Software. In the ring topology, the failure of a node causes failure in the network. As the single channel is shared by various nodes, it is difficult to diagnose the fault. It is difficult to add, remove or reconfigure the nodes in the network.

Something about bus Topology...

BUS Topology

In bus topology, a single cable acts as a backbone of the network and all the nodes or computers are attached to it by using T connectors as shown in figure below:

Bus Topology

Each computer on the network has a direct connection with the backbone cable. When one computer sends a signal up the cable; all the computers on the network receive the information, but the one with the address that matches the one encoded in the message accepts the information while all the others reject the message.

The speed of the bus topology is slow because only one computer can send a message at a time. A computer must wait until the bus is free before it can transmit.

The bus topology requires a proper termination at both ends of the cable. Therefore it has special devices called “terminators” which absorb the signal on both ends.

As with ring structure, Bus Network has also unique address. If geographic coverage needs to be expanded, repeaters which interconnect two buses are required.

In Bus topology, least length of physical Transmission medium is used. Coverage can be increased by extending the bus through use of repeaters.

The Bus Topology is one of most popular topology. One reason for popularity is that, its wiring requirements are comparatively simple and growth is obtained easily & quickly. With most bus-structured networks, workstations can be added without distributing the rest of network.

Merits

Less number of cables required. Easy to expand. Nodes can be added without distributing the rest of network. Easy to understand and install.

Demerits

If the communication line fails, the entire system breaks down. It is very difficult to repair the fault in this topology. Heavy network traffic slows down the bus speed. In bus topology, only one computer can transmit and other have to wait their turn comes and there is no co-ordination between computers for reservation of transmitting time slot.