Distance-vector routing

Definition

Distance-vector routing is a type of routing protocol used in computer networks where routers periodically share information about the distance and direction (vector) to reach various destinations. This method relies on each router sharing its knowledge of the entire network with its immediate neighbors, allowing for the establishment of a routing table that informs packet forwarding decisions. It emphasizes simplicity and ease of implementation, making it suitable for smaller networks.

5 Must Know Facts For Your Next Test

1. Distance-vector routing protocols, like RIP (Routing Information Protocol), update their routing tables based on the distance to reach a destination, typically measured in hops.
2. Each router sends its entire routing table to its neighbors at regular intervals or when changes occur, making it simple but potentially inefficient in larger networks.
3. This approach can lead to routing loops if not managed properly, which is why mechanisms like split horizon and hold-down timers are used to stabilize the network.
4. Distance-vector protocols converge more slowly than link-state protocols due to their periodic updates, which can cause temporary inconsistencies in routing information.
5. The simplicity of distance-vector routing makes it easy to configure and manage, but it lacks the scalability and speed of more advanced protocols like OSPF (Open Shortest Path First).

Review Questions

• How does distance-vector routing differ from link-state routing in terms of information sharing and convergence time?
  • Distance-vector routing relies on routers sharing their entire routing tables with immediate neighbors, resulting in simpler but slower convergence compared to link-state routing, where routers maintain a complete view of the network. This method of information sharing can lead to slower updates and potential inconsistencies, especially in larger networks. In contrast, link-state protocols allow routers to quickly adapt to changes by flooding updated information throughout the network, leading to faster convergence.
• Discuss the advantages and disadvantages of using distance-vector routing protocols in network design.
  • The advantages of distance-vector routing protocols include their simplicity and ease of configuration, making them suitable for smaller networks with less complex topology. However, they also have notable disadvantages, such as slower convergence times and susceptibility to routing loops without additional mechanisms. As networks grow in size and complexity, these drawbacks can become significant, leading many network designers to favor more advanced protocols like link-state routing.
• Evaluate the impact of distance-vector routing's periodic updates on network performance and reliability over time.
  • The periodic updates characteristic of distance-vector routing can create delays in propagating changes across the network, which may temporarily lead to suboptimal routing paths and increased latency. This delay in convergence can be problematic during network topology changes, as outdated information may still influence packet forwarding decisions. Over time, these performance issues can undermine network reliability, especially as the number of routers and paths increases. Consequently, while distance-vector routing is adequate for smaller setups, larger networks may experience significant challenges that necessitate the adoption of more sophisticated protocols.

Related terms

Link-state routing: A routing protocol where routers maintain a complete map of the network topology and independently calculate the shortest path to each destination.

Routing table: A data structure maintained by routers that contains information about network paths, including the best next hop for reaching each destination.

Bellman-Ford algorithm: An algorithm used in distance-vector routing to calculate the shortest paths from a source node to all other nodes in a weighted graph.