60 solved GATE CS questions on Computer Networks, drawn from 8 exam years and grouped by year. Every question shows the official answer and a step-by-step solution.
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Determine which protocol layer a question addresses before applying its mechanisms. These selected foundations connect the physical, data link, network, transport, and application layers. Protocol behavior depends on the specific mechanism's assumptions, not on generic layering claims.
Our study notes and original examples support the PYQs below; they are not official exam questions or a replacement for the current syllabus.
Each layer adds its header (and sometimes trailer) to the payload from the layer above. The network layer handles host-to-host delivery; the transport layer handles process-to-process delivery. A frame encapsulates a packet, which encapsulates a segment.
Check yourself: At which layer does the question's mechanism operate?
CRC detects bit errors using polynomial division over GF(2). Ethernet uses CSMA/CD for shared media: sense, transmit, detect collisions. The minimum frame size constraint ensures collision detection within one round-trip time. Switches forward frames based on MAC address tables.
Check yourself: Is the channel shared (collision possible) or switched (dedicated)?
An IPv4 address is 32 bits. A subnet mask determines the network and host portions. A /n prefix means the first n bits identify the network. The number of host addresses is 2^(32−n) − 2 (excluding network and broadcast addresses in a standard subnet). CIDR replaces classful addressing.
Check yourself: Have you subtracted the network and broadcast addresses from the host count?
Forwarding uses the routing table to send a packet toward its destination by longest prefix match. Distance-vector protocols (e.g., RIP) share distance tables with neighbors; link-state protocols (e.g., OSPF) flood topology information. The count-to-infinity problem affects simple distance-vector protocols.
Check yourself: Which entry in the routing table provides the longest matching prefix?
TCP provides reliable, ordered delivery using sequence numbers, acknowledgments, and retransmission. Flow control uses a receiver-advertised window. Congestion control (slow start, congestion avoidance, fast retransmit) adjusts the sender's window. UDP provides no reliability, ordering, or congestion control.
Check yourself: Is the question about flow control (receiver capacity) or congestion control (network capacity)?
Original teaching example · not a PYQ
Original mini-example: a network is assigned the block 192.168.10.0/24. Subnet it into 4 equal subnets. Find the subnet addresses, broadcast addresses, and the number of usable host addresses per subnet.
Four /26 subnets with 62 usable hosts each. Subnets start at .0, .64, .128, .192.
A host sends a TCP segment with sequence number 100 and 50 bytes of data. What acknowledgment number does the receiver send for in-order delivery?
ACK number = 150.
TCP sequence numbers count bytes. The segment occupies bytes 100–149. The receiver acknowledges the next expected byte: 100 + 50 = 150.
Supplemental reading, not an official GATE reading list or an endorsement of these notes.
Free supplemental video lectures by the textbook authors covering all layers from application to physical, with Wireshark labs and interactive exercises.
This page shows 60 recent questions from the released archive, newest first. For older questions and complete papers, browse all GATE CS papers. Questions can carry more than one subject tag; counts are not marks weightage.
www.gate-2023.in URL. The browser cache is empty. The IP address for this URL is not cached in your local host, so…MSQ · +2 marks · Hardwww.gate.org.in by a DNS resolver. Assume that no resource records are cached anywhere across the DNS servers and…NAT · +1 marks · MediumContinue learning with Success Tracker
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