Routing Information Protocol (RIP) is one of the oldest and simplest dynamic routing protocols used in computer networks. It was designed for small to medium-sized networks and operates based on the distance-vector algorithm. RIP exchanges routing information with neighboring routers to dynamically update routing tables and calculate optimal paths for forwarding data packets. Here's an overview of RIP and its characteristics:
1. Distance-Vector Algorithm:
- RIP uses the distance-vector algorithm to calculate routes based on the number of hops (router-to-router connections) to reach destination networks.
- Each router maintains a routing table containing information about directly connected networks and their associated hop counts.
- Periodically, routers broadcast routing updates to neighboring routers, sharing their routing tables and updating hop counts for destination networks.
2. Routing Updates:
- RIP routers exchange routing updates every 30 seconds by broadcasting RIP messages (RIP version 1) or multicast updates (RIP version 2).
- Routing updates contain information about network topology changes, including new routes, route deletions, and updated hop counts.
- RIP version 1 broadcasts updates using User Datagram Protocol (UDP) port 520 and sends updates as broadcast packets, limiting its scalability and efficiency.
- RIP version 2 supports features such as classless routing, authentication, and route summarization. It uses multicast updates and supports Variable Length Subnet Mask (VLSM) and Classless Inter-Domain Routing (CIDR).
3. Hop Count Limit:
- RIP has a maximum hop count limit of 15, meaning it cannot support networks with more than 15 hops between routers.
- If a destination network is unreachable within 15 hops, RIP considers it unreachable and marks it as inaccessible in the routing table.
4. Route Selection:
- RIP routers maintain routing tables containing routes to destination networks and their associated hop counts.
- Routers select routes based on the shortest hop count to the destination network, preferring routes with lower hop counts.
- If multiple routes have the same hop count, RIP selects the route with the lowest IP address as the successor route.
5. Convergence:
- RIP routers converge relatively slowly compared to more advanced routing protocols due to the periodic nature of routing updates and the simplicity of the distance-vector algorithm.
- Convergence time can be prolonged in large networks or in the presence of network topology changes, leading to potential routing loops or suboptimal routing decisions.
6. Limitations:
- RIP has several limitations, including its limited scalability, slow convergence, and susceptibility to routing loops and routing table instability.
- The maximum hop count limit of 15 restricts RIP's applicability in larger networks with more complex topologies.
In summary, RIP is a simple and easy-to-implement dynamic routing protocol that operates based on the distance-vector algorithm. While RIP is suitable for small to medium-sized networks, its limitations in scalability and convergence make it less ideal for larger and more complex networks. However, RIP remains relevant in certain environments and can still be found in legacy networks or in scenarios where simplicity and ease of configuration are prioritized over advanced features and performance.