Knowledge Checks

What’s a “good” path?

What is the definition of a “good” path for a routing protocol? Chose the best single answer.

Routing algorithms typically work with abstract link weights that could represent any of, or combinations of, all of the other answers.

A high bandwidth path.

A path that has little or no congestion.

A path that has a minimum number of hops.

A low delay path.

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1/5

Dijkstra’s link-state routing algorithm.

Consider Dijkstra’s link-state routing algorithm that is computing a least-cost path from node a to other nodes b, c, d, e, f. Which of the following statements is true. (Refer to Section 5.2 in the text for notation.)

The values computed in the vector D(v), the currently known least cost of a path from a to any node v, will always decrease following an iteration.

In the initialization step, the initial cost from a to each of these destinations is initialized to either the cost of a link directly connecting a to a direct neighbor, or infinity otherwise.

Following the initialization step, if nodes b and c are directly connected to a, then the least cost path to b and c will never change from this initial cost.

The values computed in the vector D(v), the currently known least cost of a path from a to any node v, will never increase following an iteration.

Suppose nodes b, c, and d are in the set N’. These nodes will remain in N’ for the rest of the algorithm, since the least-cost paths from a to b, c, and d are known.

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2/5

What type of routing?

Match the name of a general approach to routing with characteristics of that approach.

Question List:

Centralized, global routing.

Decentralized routing.

Static routing.

Dynamic routing.

Answer List:

An iterative process of computation, exchange of informatoin with neighbors. Routers may initially only know link costs to directly-attached neighbors.
Routes change slowly over time.
Routing changes quickly over time.
All routers have complete topology, and link cost information.

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3/5

Dijkstra’s link-state routing algorithm (Part 1).

Consider the graph shown below and the use of Dijkstra’s algorithm to compute a least cost path from a to all destinations. Suppose that nodes b and d have already been added to N’. What is the next node to be added to N' (refer to the text for an explanation of notation).

[Note: You can find more examples of problems similar to this here.]

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4/5

Dijkstra’s link-state routing algorithm (Part 2).

Consider the graph shown below and the use of Dijkstra’s algorithm to compute a least cost path from a to all destinations. Suppose that nodes b and d have already been added to N’. What is the path cost to the next node to be added to N' (refer to the text for an explanation of notation).

[Note: You can find more examples of problems similar to this here.]

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5/5

Knowledge checks

What’s a “good” path?

Dijkstra’s link-state routing algorithm.

What type of routing?

Question List:

Answer List:

Dijkstra’s link-state routing algorithm (Part 1).

Dijkstra’s link-state routing algorithm (Part 2).