Fixed and Flooding Routing algorithms

Routing is the process of moving the data across a network from a source to a destination. Routing algorithms are used to decide the route or the output line a packet should be transmitted on. Routing algorithms determine the optimal path to reach a destination.

A good routing algorithm should process properties such as correctness, simplicity, robustness, stability, fairness, and optimality.

Fixed Routing

Fixed routing is used to find a single permanent route for each source-to-destination pair. It determines the routes using a least-cost algorithm and the routes are fixed at least until a change occurs in the network topology.

Fixed Routing − Example

Central Routing Directory and Bridge Routing Table

The above central routing directory and bridge-routing table are created by using the least-cost path that is stored in the network control center.
The matrix shows the route from each source to the destination and the identity of the next node on the route.

Routing table with different nodes of the network

The following routing table is created for all six nodes. The routing table can be created using the least-min path or the min-hop reach method.

Node 1

Destination	Next Code
2	2
3	4
4	4
5	4
6	4

Node 2

Destination	Next Code
1	1
3	3
4	4
5	4
6	4

Node 3

Destination	Next Code
1	5
2	5
4	5
5	5
6	5

Node 4

Destination	Next Code
1	2
3	2
4	5
5	5
6	5

Node 5

Destination	Next Code
1	4
3	4
4	3
5	4
6	6

Node 6

Destination	Next Code
1	5
2	5
4	5
5	5
6	5

Flooding Routing Algorithm

In a flooding algorithm, network information is not required. It sends the packet by a node to every neighbor.

Incoming packets are retransmitted on every link except the incoming link. Several copies arrive at their destination.
Each packet is uniquely numbered so that duplicates can be discarded.
Nodes can remember the packets already forwarded, to keep network load in bounds.
It can include a hop count in packets.
It uses all the possible paths.

Flooding Routing Algorithm Diagram −

This diagram uses all the possible paths −

Flooding Routing Algorithm Properties

Robustness − All the possible routes between a source and a destination are tried. A packet will always get through as long as at least one path between a source and a destination exists.
Optimality − All the routes are tried; at least one copy of the packet to arrive at the destination will have used a minimum-hop route.