Ring topology is a network topology where each node is connected to two other nodes in a continuous path. Data flows either unidirectionally or bidirectionally around the ring. A token passing protocol allows only one node at a time to transmit data by passing a token between nodes. This work focuses on improving fault tolerance for lost tokens by assigning queues and timestamps to prioritize requests and using a special token format with indexes and counters. The proposed solution aims to recover from token loss, a major problem in token ring networks.

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2. Ring topology, also known as ring network, is a type of network topology where each
node is exactly connected to two other nodes, forward and backward, thus forming a
single continuous path for signal transmission.
There are two types of the ring topology based on the data flow:
• Unidirectional
• Bidirectional
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3. Token passing in a ring topology is often a term which is talked about.
So, a token contains a piece of information which is sent along with data
by the source computer. In easier terms, a token is like a permission
packet which allows a particular node the permission to release
information over the network.

5. In ring topology there are several problems such as: lack of scalability, low
speed of data …etc. In this work we will focus on the most important
problem which is the loss of token when it released from the latest node in
order to reach another nodes that have a high priority.
We tend to achieve fault tolerance by the following assumptions:
 Assigning a queue to each node to handle multiple requests.
 Using timeout (timestamp) as indicator of priority.
 Using special token format consists of indexes, queue information and a
counter

6. Fig.The proposed model of token ring topology
Format of token is:-

7. Fig. Sequence of steps with no failure

8. Fig.Sequence of steps with failure

9. Advantages of Ring topology:-
 Reduced chances of data collision as each node release a data packet after
receiving the token.
 Token passing makes ring topology perform better than bus topology under
heavy traffic
 No need of server to control connectivity among the nodes
 Equal access to the resources

10. Disadvantages of Ring topology:-
 In Unidirectional Ring, a data packet must pass through all the nodes.
 Single point of failure, that means if a node goes down entire network
goes down.

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CONCLUSIONS:-
The proposed solution gives improved performance to recover from
token-loss which is considered the main and critical problem in
token ring topology.

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Thank You