Properties of Routing Algorithm
Every router on the internet runs an algorithm inside it. The purpose of Routing Algorithms is to decide to which output line an incoming packet should be transmitted to reach the power destination. This decision steers the incoming packet to the proper outgoing line. It is a part of the network layer software. There are two types of routing:
1. Datagram Routing
2. Virtual Circuit Switching Routing
In this case, the decision for the next route is done for every packet of a message separately at each router. According to this instantaneous decision the datagram is delivered to the next hop.
Virtual Circuit Switching Routing:
In this case decision for the next route for all the packets is made at the time of establishing the virtual path between the source and the destination. Once the path is established all the packets follow the same path to reach the destination till the connection is closed. Sometimes it is also called as Session Routing.
Properties of Routing Algorithm:
1. Correctness: The routing algorithm should be correct enough to deliver the right packet to the right destination.
2. Simplicity: It should be simple enough to implement and also to manipulate.
3. Robustness: It should be robust enough to adapt to the situation in which the desired path is congested or a router in the path is under maintenance or they may be topological changes in the network.
4. Stability: The routing algorithm should come to equilibrium after running a certain amount of time and after accommodating the changes in the network.
5. Fairness: The routing algorithm should be fair to all the hosts in delivering the data sent by them. Although some situations may require non-fairness to implement optimality.
6. Optimality: To achieve efficient routing one or more of the metrics should be optimized. The metric may be the number of hops, delay bandwidth etc.
Classes of Routing Algorithm:
1. Non-Adaptive Algorithm: In the case of the non-adaptive algorithm, the choice for the route is calculated in advance offline by the administrator and is downloaded to the router at the time of booking. This decision is independent of the current traffic condition and topology. This method is also known as Static Routing.
2. Adaptive Algorithm: In the case of an Adaptive Algorithm, the routing decision is changed according to the current topology and traffic condition and the choice of the route is dynamically calculated at regular intervals of time by taking information from the adjacent router or all the routers and optimizing the metric. This method is also known as Dynamic Routing.