EC310 Lesson 28: Routing Part II objectives
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- Navigate this page:
- Link State Routing
- Problems Problem 1.
- Problem 2. Consider the network shown below which uses distance vector routing. You are router C
finite number = . If we set, for example,  , then after seven distance vector exchanges in the example above, both Router A and Router B would have concluded that Router X was unreachable.
Most distance vector routing uses a hop-count metric, which means that the weight on each edge is equal to one. To avoid the count-to-infinity problem, many algorithms set  .
3. Routing Protocol Summary Distance Vector Routing: Is easy to implement In a static environment, the algorithm will correctly compute shortest paths to all destinations. But... In a dynamic environment route computations might not stabilize and/or might be incorrect The algorithm does not scale well Link State Routing: Each router does its own calculations (Dijkstra) independent of other routers. Convergence is better because calculations are local Better scalability But... Uses flooding. Example 4 In the event that router G experienced a fatal power supply failure, which protocol would be best suited to recovering from this failure and sharing correct routing information? (a) Link State Routing (b) Distance Vector Routing (c) Both protocols are robust and would be unaffected by this anomaly.
Assistant Professor Patrick Vincent Help us improve these notes! Send comments, corrections and clarifications to vincent@usna.edu Problems Problem 1. (a) Compare how well link-state algorithms and distance vector algorithms respond in the event of a router failure. (b) Suppose a network uses distance vector routing. What would happen if a router sent a distance vector with all zeros? (c) Describe the “count-to-infinity” problem. (Use a picture is you find it helpful.) (d) In distance vector routing, each router receives distance vectors from (choose one): (i) Every router in the network (ii) Its one-hop neighbors (iii) DHCP (iv) The table set up by the network administrator (v) Messages exchanged using ARP Problem 2. Consider the network shown below which uses distance vector routing. You are router C. You have just received the following distance vectors: from B: (4, 0, 8, 13, 7, 2) from D: (17, 11, 6, 0, 8, 10) from E: (8, 6, 2, 10, 0, 4). Your distances to B, D and E are 7, 4 and 6, respectively. What is your new routing table (include the distance and next hop for each destination)? 
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