Koydo
CDLNCLEXIELTSOpen Koydo

GATE · 10% of test plan

Computer Networks for the GATE Exam

Computer Networks is the most calculation-heavy GATE CS topic after Computer Organization. Subnetting, sliding-window throughput calculations, and routing-table lookups are numerically tested every year. The topic also includes conceptual questions on TCP state machines and protocol mechanisms.

GATE 2024 CS Syllabus — Computer Networks (OSI/TCP-IP Layers, LAN Protocols, IP Addressing, Routing, Transport Layer, Application Layer).

Locale-specific study guides

Pass-rate data, regulatory context, and study tips for Computer Networks all change by candidate locale. Pick your context:

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

  • !Subnetting errors — off-by-one in the number of usable hosts (subtract 2 for network and broadcast addresses)
  • !Confusing the window size in bytes vs in segments when calculating TCP throughput
  • !Applying CSMA/CD to wireless networks (CSMA/CA is used in 802.11, not CSMA/CD)
  • !Misidentifying which layer a protocol belongs to: ARP is Layer 2/3 boundary, ICMP is Layer 3, DNS is Layer 7
  • !Calculating distance-vector routing loops instead of counting-to-infinity scenarios correctly

Study tips

  • 1Drill IPv4 subnetting until it is mechanical: given an IP address and prefix length, identify the network address, broadcast address, first host, last host, and number of usable hosts.
  • 2For TCP throughput, use: throughput = window_size / RTT. Know how to adjust for slow-start and packet loss.
  • 3Memorise the OSI layer and which protocols live where. GATE asks "at which layer does X protocol operate?" in 1-mark questions.
  • 4Practice sliding-window protocol problems: given window size W and propagation delay, find channel utilisation.
  • 5Trace distance-vector and link-state routing convergence on small topologies (4–5 nodes).

Sample GATE Computer Networks questions

These sample items mirror the format and difficulty of real GATE questions. Practice with thousands more on the free Koydo question bank.

  1. 1

    A subnet mask of 255.255.255.192 (i.e., /26) gives how many usable host addresses per subnet?

    • A62Correct
    • B64
    • C126
    • D30
    Why this answer?

    (GATE CS style) /26 means 6 host bits. Total addresses = 2⁶ = 64. Usable hosts = 64 − 2 = 62 (subtract network and broadcast addresses).

  2. 2

    Which protocol resolves an IP address to a MAC address on a local network?

    • ADNS
    • BDHCP
    • CARPCorrect
    • DICMP
    Why this answer?

    (GATE CS style) ARP (Address Resolution Protocol) broadcasts a request with a target IP address; the host with that IP replies with its MAC address. DNS resolves hostnames to IP addresses; DHCP assigns IP addresses dynamically; ICMP handles error messages.

  3. 3

    In a sliding-window protocol, if the window size is W and the link propagation delay is T_p and transmission time is T_t, maximum utilisation is:

    • AW / (1 + 2T_p/T_t)Correct
    • BT_t / (T_t + T_p)
    • CW × T_t / T_p
    • DT_p / (W × T_t)
    Why this answer?

    (GATE CS style) For stop-and-wait, efficiency = 1/(1 + 2a) where a = T_p/T_t. For a window of W frames, efficiency = W/(1 + 2a) provided W ≤ 1 + 2a; otherwise efficiency approaches 1.

Practice GATE branch-specific questions free with Koydo.

CS, EE, ME, CE, ECE — full GATE syllabus with PYQs.

Start free GATE practice →