Mixed practice set 2

Twelve more mixed questions. Time yourself: aim for under 30 minutes.

1. NAT · 1 mark

   G(x) = x⁵ + x² + 1. How many CRC bits are appended?

   Write your answer before opening the key.

2. NAT · 1 mark

   Check bits of a single-error-correcting Hamming code for 10 data bits?

   Write your answer before opening the key.

3. NAT · 2 marks

   CSMA/CD: minimum frame 512 bits, 10 Mbps, v = 2 × 10⁸ m/s. Maximum length (m)?

   Write your answer before opening the key.

4. NAT · 1 mark

   Token ring, early release, N = 4, a = 2. Efficiency (3 decimals)?

   Write your answer before opening the key.

5. MCQ · 2 marks

   Forwarding table: 172.16.0.0/12 → A, 172.16.64.0/18 → B, 172.16.64.0/20 → C, 0.0.0.0/0 → D. Destination 172.16.70.9 goes to:

   1. A
   2. B
   3. C
   4. D
6. NAT · 1 mark

   How many /26 subnets fit in a /22 block?

   Write your answer before opening the key.

7. NAT · 2 marks

   A first fragment carries 1480 data bytes (offset 0, MF = 1) and meets an MTU of 532. Offset of the third sub-fragment?

   Write your answer before opening the key.

8. NAT · 1 mark

   Maximum Selective Repeat window with 5-bit sequence numbers?

   Write your answer before opening the key.

9. NAT · 1 mark

   Window of 7 frames, a = 5. Utilisation (3 decimals)?

   Write your answer before opening the key.

10. NAT · 2 marks

    TCP Reno: cwnd starts at 1 MSS, ssthresh 8. Three duplicate ACKs are seen during RTT 6. cwnd (in MSS) during RTT 8?

    Write your answer before opening the key.

11. MCQ · 1 mark

    Which socket call blocks a server until a client connects?

    1. bind()
    2. listen()
    3. accept()
    4. socket()
12. NAT · 1 mark

    Iterative DNS, cold cache: RTTs 4 (host-local), 30 (root), 20 (TLD), 10 (authoritative) ms. Lookup ms?

    Write your answer before opening the key.