Networking Assignment

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NET 351 Computer Network Technologies

Written Assignment #1-Part 2 (individual)

The goal of Assignment1-Part2 is to test your understanding of the concepts related to dynamic routing algorithms and to assess your problem-solving skills.

Note: Your answers must be typed (if not, you will get ZERO), and the late assignments policy will be applied .

Due Date: See the date on Blackboard

IMPORTANT: you must follow the instructions below. If not, you will lose marks

· Have all your answers typed

· Be clear in your answers

· Don’t copy-past content from Internet, slides, or any other source (write in your own words)

· Follow the instructions in answering the questions when given (e.g. each step in a new line)

· Include references (e.g. web site links, book chapters, course chapters, …)

Chapter 2: Review of dynamic routing (30 Marks)

I. Link state vs. distance vector routing (5 Marks)

Give two similarities and three differences between the Distance Vector and Link State routing algorithms. You must be clear enough in your answer using full sentences. The answers like “they are both routing algorithms” or “they are both used for dynamic routing” will not be accepted because this is what is stated in the question itself.

General example on how to express similarities and differences: Give one difference and one similarity between the two shapes in the figure:

Shape1 Shape2

Wrong answer

Correct answer

Similarity

Shape1 is green

Both shapes are green

Difference

Shape1 is a rectangle

Shape1 is a rectangle but shape2 is a circle

Difference

Shape 1 is a rectangle and shape 2 has a red outline

NOTE: you should compare both shapes on the same criteria

Link state vs. distance vector algorithms

Similarity 1

Similarity 2

Difference 1

Difference 2

Difference 3

NOTE: don’t copy-paste from internet or any other source; write in your own words.

II. Link state routing

Consider the following network. The objective is to fill the routing and forwarding tables of node X.

Figure 1: Network Topology

FA0/4

FA0/3

FA0/1

FA0/0

a) Use the Dijkstra’s algorithm to compute the shortest path from X to all the other routers. Show how the algorithm works by completing the table below (3.5 Marks)

NOTE: if at any step more than one node are illegible to be chosen, chose the first one from left side in the table (e.g. if Y and V are illegible, chose Y)

step

N’

D(w), P(w)

D(z), P(z)

D(y), P(y)

D(v), P(v)

D(t), P(t)

D(u), P(u)

0

1

2

3

4

5

6

b) Draw the resulting shortest-path tree from X (3 Marks)

c) Fill the routing table of router X (3.5 Marks)

Destination

Cost

Next hop

X

W

Z

Y

V

U

T

d) Fill the forwarding table of router X (1.75 Marks)

Destination

Exit interface

X

W

Z

Y

V

U

T

III. Distance vector routing

Consider the same network topology in Figure 1 and assume that the routers are now configured to use a distance vector routing protocol.

a) What is the initial distance vector of node Y? (1.75 Marks)

DV of node Y

X

W

Z

Y

V

U

T

b) Node Y has received the vectors below from its neighbors. It will then recalculate its distance vector and update its routing table. What will be the routing table of node Y? (7 Marks)

(Note: the numbers in the neighbors’ DVs here are not necessarily reflecting the ones shown in Figure 1)

From T

From V

From X

From Z

X

8

0

3

7

W

14

6

5

4

Z

0

3

20

15

Y

12

6

8

7

V

20

1

0

5

U

14

6

3

5

T

19

1

4

0

New Routing table of node Y

Destination

Cost

Next hop

X

W

Z

Y

V

U

T

c) What will node Y do after it completes calculating its new DV? Why? e.g. will it send something somewhere? Why? Explain your answer, don’t just say “yes, it will send something somewhere” or “no, it will not send anything” (3 Marks)

· NOTE: the new content of Y DV is what is represented in the first two columns of the routing table you just calculated in the previous question.

Answer: __________________________________________________________

IV. Routing table interpretation (3.25 Marks)

The table below shows the list of routes known by a router Rx. The router receives a packet with as destination IP: 172.32.50.25.

· Where will the router send the packet? Why?

Route number

Destination network

Next hop

Cost

1

172.32.0.0

R2

30

2

172.32.50.0

R3

50

3

172.32.48.0

R4

20

4

172.32.51.0

R5

10

5

172.32.50.20

R6

15

6

172.32.50.16

R7

12

7

172.32.50.16

R8

25

Answer: __________________________________________________________

A Note on Collaboration?

While students are encouraged to discuss ideas, copying another student’s answers is not allowed and a mark of zero will be assigned to all copied assignments.

What to Submit? You should type your answers in a Word document and submit that document via blackboard and submit a print-out of the document.

2

8

1

2

6

6

3

7

4

3

3

4

8

Z

Y

V

T

U

W

X