9. Compare and contrast link-state and distance-vector routing algorithms.
Link state algorithms (used in OSPF): Computes the least-cost path between source and destination using complete, global knowledge about the network. Distance-vector routing (used in RIP): The calculation of the least-cost path is carried out in an iterative, distributed manner. A node only knows the neighbor to which it should forward a packet in order to reach a given destination along the least-cost path, and the cost of that path from itself to the destination.
Link state algorithms (used in OSPF): Computes the least-cost path between source and destination using complete, global knowledge about the network. Distance-vector routing (used in RIP): The calculation of the least-cost path is carried out in an iterative, distributed manner. A node only knows the neighbor to which it should forward a packet in order to reach a given destination along the least-cost path, and the cost of that path from itself to the destination.
10. Discuss how a hierarchical organization of the Internet has made it possible to scale to millions of users.
Routers are aggregated into autonomous systems (ASs). Within an AS, all routers run the same intra-AS routing protocol. Special gateway routers in the various ASs run the inter-autonomous system routing protocol that determines the routing paths among the ASs. The problem of scale is solved since an intra-AS router need only know about routers within its AS and the gateway router(s) in its AS. It also allows prefix aggregation (per AS) to be able to represent a large number of routes
with one entry in the routing tables.
11. Is it necessary that every autonomous system use the same intra-AS routing algorithm? Why or why not?
No. Each AS has administrative autonomy for routing within an AS.