RIP vs OSPF: A Comparison of Routing Protocols

This article outlines the key differences between RIP (Routing Information Protocol) and OSPF (Open Shortest Path First), two important routing protocols used in computer networks. Both protocols play a crucial role in building routing tables, which are essential for routers to forward data packets efficiently.

Understanding Routers and Routing Tables

A router is a network device that filters traffic based on logical addresses (IP addresses) and routes IP packets accordingly. Routers operate at the OSI layer-3 (network layer) and are fundamental to the internet. Without routers, the internet as we know it would not exist.

Routing tables are used by routers to determine the best path for forwarding data packets. These tables can be populated in two ways:

• Statically: A network administrator manually configures the routing table entries.
• Dynamically: Routing protocols automatically learn and update the routing table entries.

A typical routing table entry includes the destination IP address, the next hop router, and the router’s port interface. Different types of routers, such as core routers, exterior routers, and interior routers, employ different protocols and algorithms to build their routing tables. Interior routers specifically utilize Interior Gateway Protocols (IGPs), and both RIP and OSPF fall under this category.

RIP: Routing Information Protocol

RIP is a distance-vector routing protocol. It determines the optimal route for a packet to reach its destination based on the hop count – the number of routers a packet must pass through.

Here’s how RIP works:

• Routers participating in RIP are classified as either active or passive.
• Active routers: Send their routing tables to other routers and listen for updates from them.
• Passive routers: Listen for updates from other routers but do not broadcast their own routing entries.
• RIP routers broadcast update messages approximately every 30 seconds.

RIP operates most effectively when the network is stable and in equilibrium. However, as the network grows, RIP’s performance can degrade due to the time it takes to build and update routing tables. To mitigate this, RIP imposes a limit on the maximum number of router hops allowed between the source and destination, which is 15 hops.

Due to its limitations, RIP is gradually being replaced by more advanced routing protocols like OSPF.

OSPF: Open Shortest Path First

OSPF, which stands for Open Shortest Path First, is a link-state routing protocol. The initial version of OSPF was defined in RFC 1131 in 1989. The updated version, OSPF version 2, is described in RFC 2328.

In OSPF, each router is assigned a unique router ID. Link-state routers build an internal map of the entire network topology. Each router then calculates the shortest path to every other router in the network by constructing a shortest-path tree, with itself as the root. This “shortest path tree” represents the optimal routes based on various metrics, such as bandwidth and delay.

RIP vs. OSPF: Key Differences

The following table summarizes the key differences between RIP and OSPF: