GATE 2014 CS (CS3) – Question 37
Every IPv4 host has a battery-backed, one-second-resolution real-time clock and a globally unique IPv4 address. Each must generate up to 1000 unique identifiers per second. A globally unique identifier is 50 bits. After how many seconds will a host’s identifiers wrap around?
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Correct answer: 256 to 256
Explanation
Globally unique IPv4address needs32bits. Up to1000IDspersecond needs10counter bits. That leaves8timestamp bits at1secondresolution, wrapping after2⁸=**256seconds**. Counter bits distinguish IDswithin a second; address bits distinguish hosts.