Project ForgeComputer Networks
Transport Protocols & IP Addressing
GATE 2016
Hard
An IP datagram of size 1000 bytes arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is 100 bytes. Assume that the size of the IP header is 20 bytes. The number of fragments that the IP datagram will be divided into for transmission is ____.
13
Explanation
Payload to fragment = 1000−20 = 980 bytes. Each fragment can carry at most 100−20=80 bytes of payload (already a multiple of 8, satisfying the fragmentation offset alignment rule). Number of fragments = ⌈980/80⌉ = ⌈12.25⌉ = 13.
Source: GATE CS 2016 (Session 1 / Set A) (2016)
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