Lesson 3: Intradomain Routing

Question 1

Lesson 3 Quiz 1:
In this lecture, we discuss intradomain routing, where all the nodes and subnets are owned and managed by the same organization. (In contrast, interdomain routing is about routing between different organizations – such as between two ISPs.) Before we begin talking about intradomain routing algorithms, what could weights on the graph edges represent in these diagrams, when we are seeking the least-cost path between two nodes?

A: Length of the cable
B: Time Delay to traverse the link
C: Monetary cost
D: Business relationships
E: Link Capacity
F: Current load on the link

Answer 1

All are correct except:

D: Business relationships

Question 2

Lesson 3 Quiz 2:
In the previous example, node u was the source node, and distances were calculated from u to each other node. Consider the same example, but let x be the source node. Notice that node x has more direct neighbors than u does. Suppose x is executing the linkstate algorithm as discussed, and has just finished the initialization step. Which of the following statements are true?

A: Node x will execute fewer iterations than node u did, as there were fewer “infinity distance nodes” after initialization

B: Node x will execute the same number of iterations that node u did, as the number of immediate neighbors has no impact on the number of iterations the algorithm requires.

C: Node x will execute more iterations than node u did, as there are more immediate neighbors to consider.

Answer 2

Answer is B

Question 3

What are the two major classes of intradomain routing algorithms?

Answer 3

Link-state and Distance-vector

Question 4

What is the computational complexity of the link-state routing algorithm?

Answer 4

O(n^2)

Question 5

What is the basic premise of link-state routing?

Answer 5

The algorithm identifies a source node and then iterates through all the nodes in the network, calculating least cost paths and then comparing them.

Example: Open Shortest Path First (OSPF)

Question 6

What is the basic premise of distance vector routing?

Answer 6

Iterative, synchronous, and relies on a distributed process. Using the Bellman Ford Algorithm, each node maintains a table of all the nodes and their costs to reach every other node in the network. Once a cost update occurs, each nodes sends updated distance vectors to each other to propagate the change.

Example: RIP

Limitations: The “count to infinity” problem is when a lot of iterations occur as a result of a large cost increase. The only solution is the Poison Reverse technique but it only works on 2 nodes.

Question 7

What is hot potato routing?

Answer 7

The technique/practice of choosing a path within a network, by choosing the closest egress point based on intra-domain (IGP) path costs.