Introduction
Fifteen questions on the whole of Phase 0. Time yourself; GATE-style marking applies.
Practice questions
- MCQ · 1 mark
Which is a host?
- A hub
- A fibre link
- A web server
- A switch
- NAT · 1 mark
Links in a full mesh of 15 nodes?
Write your answer before opening the key.
- MSQ · 1 mark
Which are true?
- A router joins different networks.
- A hub sends each signal only to the intended host.
- A star fails completely if its centre fails.
- Full-duplex allows simultaneous two-way flow.
- NAT · 1 mark
Bits in 2.5 KB (KB = 1024 B)?
Write your answer before opening the key.
- NAT · 2 marks
A 4 KB file (KB = 1024 B) is pushed out at 64 kbps. Time in ms?
Write your answer before opening the key.
- MCQ · 1 mark
If the question states 1 KB = 1000 B, a 5 KB file at 2 kbps takes:
- 20 s
- 20.48 s
- 2.5 s
- 160 s
- MCQ · 1 mark
0b11011010 in hex is:
- 0xDA
- 0xAD
- 0xD5
- 0xBA
- NAT · 1 mark
Minimum bits to represent every integer from 0 to 2000?
Write your answer before opening the key.
- MCQ · 1 mark
10110 ⊕ 01111 = ?
- 11001
- 00110
- 11111
- 10001
- NAT · 2 marks
16-bit 1's-complement sum of 0x8000 and 0x9000, in decimal?
Write your answer before opening the key.
- MCQ · 2 marks
Remainder of 1011011 ÷ 1011 in modulo-2 division?
- 000
- 011
- 110
- 101
- NAT · 2 marks
6 stations each send with p = 1/6. P(exactly one)? (3 decimals)
Write your answer before opening the key.
- MSQ · 1 mark
Which are correct?
- (1 − 1/n)ⁿ → 1/e
- 1/e ≈ 0.368
- 1/(2e) ≈ 0.184
- e ≈ 3.14
- NAT · 1 mark
1 + 2 + 4 + … + 2¹¹ = ?
Write your answer before opening the key.
- MCQ · 1 mark
Two hosts exchange the bits correctly but cannot understand each other. Why?
- Their encodings differ.
- Bits were lost.
- The link is simplex.
- A router is missing.
Answer key
Try the questions first. Open when you are ready to check.
- C — Servers start and end messages.
- A: A hub only repeats signals.
- B: A link, not a device.
- D: A switch passes data along inside a LAN.
- 105 — 15 × 14 / 2 = 105.
- ACD — Router between networks, star centre is a single point of failure, full-duplex = both at once.
- B: A hub repeats to every cable — sending only to the intended host is a switch's job.
- 20480 — 2.5 × 1024 × 8 = 20,480.
- 512 — 32,768 bits ÷ 64,000 bit/s = 0.512 s = 512 ms.
- A — 40,000 bits ÷ 2000 = 20 s.
- B: Uses 1024 although the question fixed 1000.
- C: Forgot × 8.
- D: Multiplied instead of dividing correctly.
- A — 1101 = D, 1010 = A.
- B: Nibbles swapped.
- C: 0101 is 5, but the low nibble is 1010.
- D: 1011 is B, but the high nibble is 1101.
- 11 — 2001 values; 2¹⁰ = 1024 < 2001 ≤ 2048 = 2¹¹ → 11.
- A — Bitwise differences: 11001.
- B: That is AND.
- C: That is OR.
- D: Differs from the correct 11001 in the second bit (0 ⊕ 1 = 1).
- 4097 — 0x8000 + 0x9000 = 0x11000 → 0x1000 + 1 = 0x1001 = 4097.
- B — XOR long division leaves 011 (keep the leading zero: the remainder has 3 bits).
- A: The divisor does not divide it exactly.
- C: Arithmetic slip in the XOR steps.
- D: Arithmetic slip in the XOR steps.
- 0.401..0.403 — (5/6)⁵ ≈ 0.4019.
- ABC — Standard values.
- D: That is π; e ≈ 2.718.
- 4095 — Sum of 2⁰ to 2¹¹ = 2¹² − 1 = 4095.
- A — Meaning comes from agreed encoding only.
- B: The question says the bits arrived correctly.
- C: A simplex link still delivers bits one way.
- D: Bits arrived, so the path worked.