GATE CS 2014 Set 3 — Question 35

MCQ+1 / -0.33EasyIPv4 Packet & FragmentationNetwork Layer: AddressingComputer Networks

Computer Networks → Network Layer: Addressing → IPv4 Packet & Fragmentation

Last updated 5 September 2026

Question

Host A (on TCP/IP v4 network A) sends an IP datagram D to host B (also on TCP/IP v4 network B). Assume that no error occurred during the transmission of D. When D reaches B, which of the following IP header field(s) may be different from that of the original datagram D? (i) TTL (ii) Checksum (iii) Fragment Offset

Correct answer (D) (i), (ii) and (iii) Solution 1. TTL (Time To Live): Decremented by at least 1 at each router (hop). Thus, it changes. 2. Checksum: Since the TTL field changes at each hop, the IP header checksum must be recomputed and updated at each router. Thus, it changes. 3. Fragment Offset: If the packet size exceeds the MTU of a link along the path, the router may fragment the packet. In this case, the Fragment Offset field will be modified in the fragments. The question asks what may be different. Since fragmentation is a possibility, this field may change. Therefore, (i), (ii), and (iii) may be different. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (D) (i), (ii) and (iii) Solution 1. TTL (Time To Live): Decremented by at least 1 at each router (hop). Thus, it changes. 2. Checksum: Since the TTL field changes at each hop, the IP header checksum must be recomputed and updated at each router. Thus, it changes. 3. Fragment Offset: If the packet size exceeds the MTU of a link along the path, the router may fragment the packet. In this case, the Fragment Offset field will be modified in the fragments. The question asks what may be different. Since fragmentation is a possibility, this field may change. Therefore, (i), (ii), and (iii) may be different.

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