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Dynamic Routing Protocols Classification

In this tutorial, we will learn about the classification of dynamic routing protocols. By Mahima Rao Last updated : April 26, 2023

The following are the two major classes (classification) of dynamic routing protocols:

1. Distance Vector Routing Protocols

RIP and IGRP are the distance vector routing protocols. All the distance vector routing protocols have some features which are being given below.

• The periodic updates of the entire routing table are sent to all neighboring routers.
• Convergence is very slow in distance vector protocols and these are susceptible to protocols loops.
• The distance is used to calculate the metric of the routing.
• Bellman-Ford algorithm is used to find the shortest path.

Distance vector routing protocols send updates about all connected neighbors directly connected networks. This update is sent regularly. It is sent to RIP every 30 seconds and in IGRP, this update is sent every 90 seconds. With these updates, neighbors can add routes to their routing tables. After this, all the neighbors forward their entire routing table, sharing it with all the neighbors.

There are many disadvantages to this kind of process. Routing information goes from one neighbor to pass periodic updates of another, so convergence is very slow. Together, all the neighbors depend on each other, so the chances of looping are also very high.

Distance vector protocols use distance to calculate metric. RIP is calculated by metric hop counts. In IGRP the metric is calculated with bandwidth and delay.

2. Link State Routing Protocols

Link state protocols were developed to overcome looping and convergence problems in the distance vector protocols. Link state routing protocols build 3 kinds of routing tables. These are being given below.

1. Neighbor table
   This table contains a list of all the neighbors, and also, which of the neighbors is connected to which interface. Neighbor table is created by sending hello packets.
2. Topology table
   This is also called link state table. In this, all links of one area are stored in the map. Also, every link's status is also stored.
3. Shortest path table
   The best routes are stored for every destination in this table. The link states sending updates about the status of routers directly connected networks in routing protocols. All routers store this information in the topology table. The number of routers within an area is their topology table.

If any change occurs in a link, only related updates to this link are sent to all routers and all routers adjust their topology table accordingly. The only link that has changed has been updated, due to this, the bandwidth also does not have much effect. But due to the management of 3 tables, the CPU is highly utilized. The shortest path is calculated by the Dijkstra formula in the link state protocols.

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