Probability Engine · CSC258

Computer Networks (BSc CSIT, CSC258): the questions likely to come

31 analyzed questions from 7 past papers (2074-2081), grouped by syllabus unit — each with its probability, how often it's been asked, and where to study the answer.

Papers analyzed

2074-2081

Analyzed questions

across 6 syllabus units

Very likely units

high-probability topics

Units = 80% of marks

study these first

Model answers for this subject are being written. Every question links to its original paper so you can study from the source meanwhile.

Pick a unit

U4 · Q1/9 · 208110 marks

Network Layer

Assume a Class B network. Divide it into four subnets. Write the subnet ID and broadcast address of each subnet and determine the new subnet mask.

33%

Possible to appearAppeared in 2 of the last 2 board papers

Seen in

How well do you know this?rating moves you on

MODEL ANSWERU4 · 10 marks

Subnetting a Class B Network into 4 Subnets

Given: A Class B network. Take the example network 172.16.0.0 with the default mask 255.255.0.0 (/16).

Step 1: Number of subnet bits

To create 4 subnets we need $n$ borrowed bits such that $2^n \ge 4$ .

2^2 = 4 \Rightarrow n = 2 \text{ borrowed bits}

Step 2: New subnet mask

Class B default is /16. Borrowing 2 bits gives /18.

The third octet borrows the top 2 bits: $11000000_2 = 192$ .

\text{New mask} = 255.255.192.0 \;(/18)

Step 3: Block size

\text{Block size} = 256 - 192 = 64 \text{ (in the 3rd octet)}

So subnets increment by 64 in the third octet.

Step 4: Subnet ID and Broadcast addresses

Subnet	Subnet ID (Network)	Valid Host Range	Broadcast Address
1	172.16.0.0	172.16.0.1 – 172.16.63.254	172.16.63.255
2	172.16.64.0	172.16.64.1 – 172.16.127.254	172.16.127.255
3	172.16.128.0	172.16.128.1 – 172.16.191.254	172.16.191.255
4	172.16.192.0	172.16.192.1 – 172.16.255.254	172.16.255.255

Step 5: Hosts per subnet

Host bits = $32 - 18 = 14$ .

\text{Usable hosts} = 2^{14} - 2 = 16382 \text{ per subnet}

Result: New subnet mask = 255.255.192.0 (/18), with the four subnets, subnet IDs and broadcast addresses listed above.

AI-generated answer · unverifiedView in 2081 paper →

U4 · Question 1 of 9

Question Priority · U4ranked by appearance likelihood — study top-down

Network Layer

Analyzed next58%

★ TOP PICK

Assume a Class B network. Divide it into four subnets. Write the subnet ID and broadcast address of each subnet and determine the new subnet mask.

10 marksSEEN IN

33%

Explain the distance vector routing algorithm. Discuss the count-to-infinity problem and the methods used to solve it.

10 marksSEEN IN

31%

What is routing? Explain the Link State routing algorithm (Dijkstra's) in detail with a suitable example.

10 marksSEEN IN

30%

Explain CIDR (Classless Inter-Domain Routing) with an example.

5 marksSEEN IN

58%

What is the purpose of ICMP? List some common ICMP message types.

5 marksSEEN IN

58%

What is ARP? Explain how ARP resolves a logical address to a physical address.

5 marksSEEN IN

53%

What is NAT? Explain its types and uses.

5 marksSEEN IN

52%

Explain the IPv4 datagram header format in detail. Differentiate between IPv4 and IPv6 addressing.

10 marksSEEN IN

22%

Discuss congestion control in the transport layer. Explain the leaky bucket and token bucket algorithms for traffic shaping.

10 marksSEEN IN

22%

03The mock

Sit a probable paper

A full mock exam built from the most likely questions, mirroring the real paper's structure. Every slot is a real past question.

Most Probable Paper

Mirrors the real structure · 60 marks · based on 7 past papers

Section A: Long Answer QuestionsAttempt any TWO questions.

1.
What is TCP? Explain the TCP segment structure and the three-way handshake mechanism for connection establishment and termination.
[10 marks]
Transport LayerVery likelyfrom 2081 paper →
This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Transport Layer) appears in 100% of years.
2.
Assume a Class B network. Divide it into four subnets. Write the subnet ID and broadcast address of each subnet and determine the new subnet mask.
[10 marks]
Network LayerVery likelyfrom 2081 paper →
This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.
3.
Explain the distance vector routing algorithm. Discuss the count-to-infinity problem and the methods used to solve it.
[10 marks]
Network LayerVery likelyfrom 2080 paper →
This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.

Section B: Short Answer QuestionsAttempt any EIGHT questions.

1.
Explain CIDR (Classless Inter-Domain Routing) with an example.
[5 marks]
Network LayerVery likelyfrom 2081 paper →
This question has recurred in 5 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.
2.
What is the purpose of ICMP? List some common ICMP message types.
[5 marks]
Network LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.
3.
What is ARP? Explain how ARP resolves a logical address to a physical address.
[5 marks]
Network LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.
4.
What is NAT? Explain its types and uses.
[5 marks]
Network LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Network Layer) appears in 100% of years.
5.
Differentiate between a hub, a switch, and a router.
[5 marks]
Data Link LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Data Link Layer) appears in 100% of years.
6.
What is framing? Explain bit stuffing and byte stuffing.
[5 marks]
Data Link LayerVery likelyfrom 2080 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Data Link Layer) appears in 100% of years.
7.
Explain the difference between connection-oriented and connectionless services.
[5 marks]
Transport LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Transport Layer) appears in 100% of years.
8.
What is UDP? Explain the UDP header format.
[5 marks]
Transport LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Transport Layer) appears in 100% of years.
9.
Explain the working of the HTTP protocol.
[5 marks]
Application LayerVery likelyfrom 2081 paper →
This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Application Layer) appears in 86% of years.

04The receipts

Behind the numbers

The raw evidence the predictions are computed from: marks per unit per year, syllabus weights, trends, and coverage.

Show the heatmap, topic table and coverage analysis

The receipt: marks per unit, per year

Each row is a syllabus unit, each column an exam year, each cell the marks that unit earned that year. Click any cell to see the actual questions behind it.

Marks:nonefew → many

2074

2075

2077

2078

2079

2080

2081

Total

U4Network Layer

165

U3Data Link Layer

U5Transport Layer

U6Application Layer

U1Introduction to Computer Networks

U2Physical Layer

#	Syllabus unit	Probability	Appeared	Avg marks	Syllabus weight	Exam vs syllabus	Trend	Questions
1	U4Network Layer	Very likely100%	2074 2075 2077 2078 2079 2080 2081	23.6	22%10 lecture hrs	Over-examinedexam 31% · syllabus 22%	Steady	7 recurring9 total
2	U3Data Link Layer	Very likely100%	2074 2075 2077 2078 2079 2080 2081	13.6	18%8 lecture hrs	Balancedexam 18% · syllabus 18%	Steady	5 recurring5 total
3	U5Transport Layer	Very likely100%	2074 2075 2077 2078 2079 2080 2081	13.6	16%7 lecture hrs	Balancedexam 18% · syllabus 16%	Steady	4 recurring5 total
4	U6Application Layer	Very likely86%	2075 2077 2078 2079 2080 2081	10	13%6 lecture hrs	Balancedexam 11% · syllabus 13%	Rising	3 recurring4 total
5	U1Introduction to Computer Networks	Likely57%	2074 2078 2079 2080	15	13%6 lecture hrs	Balancedexam 11% · syllabus 13%	Steady	3 recurring4 total
6	U2Physical Layer	Likely57%	2074 2078 2079 2080	12.5	18%8 lecture hrs	Under-examinedexam 10% · syllabus 18%	Steady	3 recurring4 total

Study smart, not hard

Drag the slider: studying the top 5 units in priority order covers ~90% of all observed marks.

Units to study5/6

~80% line

Lecture time vs exam marks

Where the exam pays more than the curriculum spends: ● lectures vs ● exam marks, as a share of the whole course. A long teal-leading bar = high-yield unit.

U4Network Layer

22% of lectures → 31% of markshigh yield

U3Data Link Layer

18% of lectures → 18% of marks

U5Transport Layer

16% of lectures → 18% of marks

U6Application Layer

13% of lectures → 11% of marks

U1Introduction to Computer Networks

13% of lectures → 11% of marks

U2Physical Layer

18% of lectures → 10% of markslow yield

Computer Networks (BSc CSIT, CSC258): the questions likely to come

Subnetting a Class B Network into 4 Subnets

Step 1: Number of subnet bits

Step 2: New subnet mask

Step 3: Block size

Step 4: Subnet ID and Broadcast addresses

Step 5: Hosts per subnet

Network Layer

Sit a probable paper

Most Probable Paper

Behind the numbers

The receipt: marks per unit, per year

Study smart, not hard

Lecture time vs exam marks

2081 B.S.

Computer Networks (BSc CSIT, CSC258)

2080 B.S.

Computer Networks (BSc CSIT, CSC258)

2079 B.S.

Computer Networks (BSc CSIT, CSC258)

2078 B.S.

Computer Networks (BSc CSIT, CSC258)

2077 B.S.

Computer Networks (BSc CSIT, CSC258)

2075 B.S.

Computer Networks (BSc CSIT, CSC258)

2074 B.S.

Computer Networks (BSc CSIT, CSC258)