2.3 Ring Topology

Ring Topology

                                   

Ring Topology

A ring network is a local area network (LAN) in which the nodes (workstations or other devices) are connected in a closed loop configuration. Adjacent pairs of nodes are directly connected. Other pairs of nodes are indirectly connected, the data passing through one or more intermediate nodes.

The illustration shows a ring network with five nodes. Each node is shown as a sphere, and connections are shown as straight lines. The connections can consist of wired or wireless links.

The ring topology may prove optimum when system requirements are modest and workstations are at scattered points. 

If the workstations are reasonably close to the vertices of a convex polygon (such as the pentagon shown in the illustration), the cost can be lower than that of any other topology when cable routes are chosen to minimize the total length of cable needed.

A break in the cable of a ring network may result in degraded data speed between pairs of workstations for which the data path is increased as a result of the break. If two breaks occur and they are not both in the same section of cable, some workstations will be cut off from some of the others. When system reliability is a critical concern, a bus network or star network may prove superior to a ring network. If redundancy is required, the mesh network topology may be preferable.

A token ring is a widely-implemented kind of ring network.

Advantages

1. Very orderly network where every device has access to the token and the opportunity to transmit.
2. Performs better than a star topology under heavy network load.
3. Can create much larger network using Token Ring.
4. Does not require network server to manage the connectivity between the computers.
5. Data is quickly transferred without a "bottle neck". (very fast, all data traffic is in the same direction).
6. The transmission of data is relatively simple as packets travel in one direction only.
7. It prevents network collisions because of the media access method or architecture required.
8. Adding additional nodes has very little impact on bandwidth.
9. This type of network topology is very organized. Each node gets to send the data when it receives an   empty token. 
10. This helps to reduces chances of collision. Also in ring topology all the traffic flows in only one  direction at very high speed.
11. Even when the load on the network increases, its performance is better than that of Bus topology.
12. There is no need for network server to control the connectivity between workstations.
13. Additional components do not affect the performance of network.
14. Each computer has equal access to resources.

Disadvantages

1. One malfunctioning workstation or bad port in the MAU can create problems for the entire network.
2. Data packets must pass through every computer between the sender and recipient therefore this makes it slower.
3. Moves, adds and changes of devices can affect the network.
4. Network adapter cards and MAU's are much more expensive than Ethernet cards and hubs.
5. Much slower than an Ethernet network under normal load.
6. A physical ring topology uses a single length of cable interconnecting all computers and forming a loop. If there is a break in the cable, all systems on the network will be unable to access the network. Total dependence upon the one cable.
7. All Network Interface Cards (NICs) on the ring network must operate at the same speed.
8. The MSAU on a logical ring topology represents a single point of failure. If all devices are unable to access the network and there is no cable break, it might be that the MSAU is faulty.
9. Because all stations are wired together, to add a station you must shut down the network temporarily.
10. Difficult to troubleshoot a ring network.
11. In order for all computers to communicate with each other, all computers must be turned on.
12. Each packet of data must pass through all the computers between source and destination. This makes it slower than Star topology.
13. If one workstation or port goes down, the entire network gets affected.
14. Network is highly dependent on the wire which connects different components. 
15. MAU’s and network cards are expensive as compared to Ethernet cards and hubs.