Computer Networks in GATE CSE is a mix of quick calculations and protocol facts. This GATE-style set covers subnetting, link efficiency, sliding window limits, the bandwidth-delay product, TCP congestion control, error detection and correction, MAC protocols and routing.
How to practise: read each question and tap the option you think is correct. You will see right away whether you got it, along with a short explanation, and your score is tracked at the bottom of the screen. This set has 15 questions.
Topics covered in this set
- Subnetting and CIDR
- Stop-and-wait efficiency and bandwidth-delay product
- Go-Back-N and Selective Repeat window sizes
- TCP congestion control
- CRC and Hamming distance
- ALOHA, Ethernet, ARP, DNS and routing
GATE CSE Computer Networks MCQs with answers and explanations
Q1. How many usable host addresses are there in a /26 IPv4 subnet?
a) 126
b) 62
c) 64
d) 30
Q2. What is the network address of the host 192.168.10.77/27?
a) 192.168.10.96
b) 192.168.10.0
c) 192.168.10.72
d) 192.168.10.64
Q3. A stop-and-wait link has a frame transmission time of 1 ms and a one-way propagation delay of 2 ms. What is the link efficiency (ignoring ACK time)?
a) 10%
b) 20%
c) 33%
d) 50%
Q4. With 3-bit sequence numbers, what is the maximum sender window size for Go-Back-N and for Selective Repeat?
a) 7 and 7
b) 4 and 4
c) 8 and 8
d) 7 and 4
Q5. A link has a bandwidth of 10 Mbps and a round-trip time of 20 ms. What is the bandwidth-delay product in bytes?
a) 200,000
b) 250,000
c) 25,000
d) 2,500
Q6. In TCP Reno, what happens to the congestion window when a timeout occurs?
a) ssthresh is set to half the current window and cwnd is reset to 1 MSS, followed by slow start
b) It is unchanged
c) It is set to ssthresh and grows linearly
d) It doubles
Q7. During TCP slow start (before reaching ssthresh), how does cwnd grow?
a) It halves every RTT
b) It stays constant
c) It doubles roughly every RTT
d) By 1 MSS per RTT
Q8. With a CRC generator polynomial of degree r, how many check bits are appended to the data?
a) r + 1
b) 2r
c) r
d) r − 1
Q9. What minimum Hamming distance does a code need to correct up to d bit errors?
a) 2d + 1
b) 2d
c) d
d) d + 1
Q10. Why does classic Ethernet (CSMA/CD) have a minimum frame size of 64 bytes?
a) To reduce overhead
b) So a sender is still transmitting when a collision from the far end of the network reaches it, allowing it to detect the collision
c) To fit the IP header
d) Because of the MTU
Q11. In the IPv4 header, the fragment offset field is measured in units of:
a) 8 bytes
b) 16 bytes
c) 1 byte
d) 4 bytes
Q12. What is the maximum throughput of pure ALOHA and slotted ALOHA?
a) 50% and 100%
b) 25% and 50%
c) 36.8% and 18.4%
d) 18.4% and 36.8%
Q13. Which protocol maps an IPv4 address to a MAC address on a local network?
a) ICMP
b) DHCP
c) DNS
d) ARP
Q14. Which problem is characteristic of distance vector routing?
a) Flooding of link-state packets
b) No support for metrics
c) Count-to-infinity
d) Too much memory per router
Q15. DNS queries normally use which transport protocol and port?
a) TCP port 25
b) UDP port 67
c) UDP port 53
d) TCP port 80
Quick revision notes
- Usable hosts = 2^(host bits) − 2.
- Stop-and-wait efficiency = 1/(1 + 2a), a = Tp/Tt.
- GBN window 2ⁿ − 1; SR window 2ⁿ⁻¹.
- Correct d errors: distance 2d + 1; detect d: d + 1.
- ALOHA: 18.4% pure, 36.8% slotted.
Frequently asked questions
Are these GATE previous year questions?
No, they are original GATE-style practice questions written to the syllabus.
How do I subnet quickly?
Find the block size as 256 minus the mask value in the interesting octet, then list multiples of the block size to find which range the address falls in.
Why is Selective Repeat's window limited to half the sequence space?
So that after a wrap-around, the receiver cannot mistake a retransmitted old frame for a new one.
Comments
Post a Comment