Question

can somebody please help me with the following two questions:

List and explain three differences between distance vector routing and link state

routing. Explain some problems encountered with distance vector and link state

routing.

2. In case a change occurs in the network (for example: a node/communication link

comes up or goes down), which routing approach converges faster and why?

Answer 1

Solution 1---

A] Distance Vector Routing:-

• It contains 2 factors-

1) Vector or Direction to reach destination.

2) Distance or Metric of destonation.

• The directly connected neighbours exchange Routing information between themselves.
• A router knows to which neighnour router to route with but the router is unawared from where the neighbour has learned the route.
• The beyond neighbours can't be seen by the router.
• The Distance Vector Routing uses Bellman Ford algorithm.
• It is sometimes called as "Routing by Rumor".
• The Distance Vector Routing uses methods like Poison Reverse and Split Horizon to avoid routing loops.

B] Link State Routing:-

• This routing requires information about all the routers, reachable paths to all other routers in the network.
• All the routers posses a synchronized copy of area's link state database Link State information is flooded throughout the Link state domain(an area in IS-IS or OSPF).
• For all known routes, each router with itself as a root, constructs its own relative Shortest-Path tree from this common database.
• The Link State routing uses Djikstra's algorithm.

Distance Vector Routing	Link State Routing
1) Less Bandwidth required.	1) More Bandwidth required.
2) Implemented using Bellman Ford algorithm.	2) Implemented using Djikstra's algorithm.
3) Less Traffic.	3) More Traffic.
4) Slow in Convergence.	4) Fatser in Convergence.
5) Problem of Persistent Looping.	5) No Problem of Persistence Looping.
6) Hop Count is been used as a Metric.	6) Shortest Path is used here.
7) Less processing power and memory of routers required.	7) More processing power and memory of routers required.

The problems encountered with Distance Vector Routing are as follows:-

• It is highly risky from count-to-infinity problem.
• It is much slower to converge than Link state.
• As a hop count change is propagated and processed to all routers this routing creates more traffic than Link state.
• Bandwidth Wasting broadcasts occurs because hop count updates takes place periodically, even if there is no chnages in network topology.
• In Distance Vector Routing there are larger routing tables for larger networks because each router must know about all other routers.This can lead to WAN Link congestion.

The problems encountered with Link State Routing are as follows:-

• Due to flooding of packets there is heavy traffic.
• Flooding caused Infinite Looping which is resolved by Time-To-Leave field.
• Link State Routing is more CPU and memory intensive.
• To reduce the size of the table it requires hierarchical network design
• The network's total bandwidth is wasted.
• The maximum load on the network increases beacuse a message has to be sent to every router inspite of having only one destination.
• Duplication of message is also possible.

Solution 2:-

• In case a change occurs in the network then Link State Routing converges faster.
• This is because each router knows about its own directly connected networks and learns about its own link.
• In Link State Routing each router manages all the responsibilty automatically if any problem or changes occur in the network.
• The routers also search the shortest path.
• All the routers floods the Link State Packets(LSP) to all its neighbours, which are then saved in the database.