# 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.

Updated on: 23-Nov-2021

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