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Dijkstra Algorithm and Link-State Routing
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Dijkstra Algorithm and Link-State Routing
Dijkstra Algorithm and Link-State Routing
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1
Question
What nodes are labeled in the network diagram?
Answer
A, B, C, D, E, F, G, and H.
2
Question
What does the highlighted source tree for node E indicate?
Answer
The shortest paths from node E to other nodes.
3
Question
What is the shortest path from node E to node F and its weight?
Answer
E to F with weight 2.
4
Question
What is the shortest path from node E to node G and its weight?
Answer
E to G with weight 4.
5
Question
What is the shortest path from node G to node B and its weight?
Answer
G to B with weight 3.
6
Question
What is the shortest path from node B to node A and its weight?
Answer
B to A with weight 4.
7
Question
What is the shortest path from node E to node D and its weight?
Answer
E to D with weight 2.
8
Question
What is the shortest path from node D to node C and its weight?
Answer
D to C with weight 2.
9
Question
What is the shortest path from node C to node H and its weight?
Answer
C to H with weight 3.
10
Question
Who was Edsger W. Dijkstra?
Answer
A famous computer scientist known for programming languages, distributed algorithms, and program verification.
11
Question
What year was Dijkstra's algorithm introduced?
Answer
1959.
12
Question
What problem does Dijkstra's algorithm solve?
Answer
Single-source shortest paths in a network with non-negative link costs.
13
Question
What does the set N represent in Dijkstra's algorithm?
Answer
The set of all nodes.
14
Question
What does the set M represent in Dijkstra's algorithm?
Answer
The set of nodes for which we think we have a shortest path.
15
Question
What does the variable s represent in Dijkstra's algorithm?
Answer
The node executing the algorithm.
16
Question
What does Li,j represent in Dijkstra's algorithm?
Answer
The cost of edge i,j if no edge connects.
17
Question
What does Ci represent in Dijkstra's algorithm?
Answer
The cost of the path from s to i.
18
Question
What are the two phases of Dijkstra's algorithm?
Answer
1. Initialize Cn according to s's neighbors. 2. Compute the shortest path to all nodes from s.
19
Question
What initial step is described for Dijkstra's algorithm?
Answer
M is the set of all nodes considered so far. For each n in N - s, Cn is initialized to Ls,n.
20
Question
What happens if there are unconsidered nodes in Dijkstra's algorithm?
Answer
If unconsidered, break otherwise, choose node w such that Cw is the smallest in unconsidered.
21
Question
What does Cn represent in the context of Dijkstra's algorithm?
Answer
The cost to reach node n.
22
Question
What does the algorithm do with nodes that are unconsidered?
Answer
For each n in unconsidered, update Cn to be the minimum of its current value and the cost from w.
23
Question
What does the term 'Considered' indicate in the Dijkstra example?
Answer
Nodes that have been decided to be part of the shortest path tree.
24
Question
In the Dijkstra example, what does a red circle represent?
Answer
The Considered node.
25
Question
In the Dijkstra example, what does a plain circle represent?
Answer
The Unconsidered node.
26
Question
What is the runtime complexity of Dijkstra's algorithm using Fibonacci heaps?
Answer
OE log V, where E is the number of edges and V is the number of vertices.
27
Question
What is the primary characteristic of Link-State Routing?
Answer
Each router knows only the addresscost of its neighbors.
28
Question
What are the two main steps in the Link-State Routing process?
Answer
1. Nodes flood topology in the form of link state packets LSPs. 2. Each node computes its own
29
Question
How is a forwarding table determined in Link-State Routing?
Answer
By running Dijkstra's algorithm.
30
Question
What does the term 'Flooding' refer to in the Link-State approach?
Answer
The process where nodes share their view of the network topology with other nodes.