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Routing is the process of establishing the routes that data packets must follow to reach their destination. In this process, a routing table is created which contains information regarding routes that data packets follow. Various routing algorithms are used for the purpose of deciding which route an incoming data packet needs to be transmitted on to reach the destination efficiently. |
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Simple
Works well in reliable network with stable load in a reliable network
Lack of flexibility
Doesn’t react to failure or network congestion
Flooding Algorithms
Requires no network information like topology, load condition, cost of diff. paths
Every incoming packet to a node is sent out on every outgoing like except the one it arrived on.
All possible routes between Source and Destination are tried. A packet will always get through if the path exists
As all routes are tried, there will be at least one route which that is the shortest
All nodes directly or indirectly connected are visited
Flooding generates a vast number of duplicate packets
Suitable damping A suitable dampening mechanism must be used to ensure the network is not overwhelmed
A hop counter may be contained in the packet header which is decremented at each hop.
with , the packet being is discarded when the counter becomes zeroThe sender initializes the hop counter. If no estimate is known, it is set to the full diameter of the subnet.
Keep track of the packets which are responsible for flooding using a sequence number. Avoid sending them out a second time.
Highly Robust, Are highly robust, emergency or immediate messages can be sent (eg military applications)Set up the route in virtual circuit
Flooding always chooses the shortest path
Broadcast messages to all the nodes
Adaptive Algorithms (dynamic routing)
These are the algorithms that change their routing decisions whenever network topology or traffic load changes. The changes in routing decisions are reflected in the topology as well as the traffic of the network. Also known as dynamic routing, these These algorithms make use of dynamic information such as current topology, load, delay, etc. to select routes. Optimization parameters are distance, number of hops, and estimated transit time.
Routing tables algorithms may be
Isolated
Centralized
Distributed
Non-Adaptive Algorithms (status routing)
These are the algorithms that do not change their routing decisions once they have been selected. This is also known as static routing as a The route to be taken is computed in advance and downloaded to routers when a router is booted.
Routing tables algorithms may be
Flooded
Random Walk