Consider a long-lived TCP session with an end-to-end bandwidth of 1 Gbps (=…
2018
Consider a long-lived TCP session with an end-to-end bandwidth of 1 Gbps (= 109 bits-persecond). The session starts with a sequence number of 1234. The minimum time (in seconds, rounded to the closest integer) before this sequence number can be used again is _______.
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Correct answer: 34
Key idea: TCP sequence numbers are 32-bit and count bytes, so the sequence space is 2^32 = 4,294,967,296 bytes.
Convert bandwidth to bytes per second: 1 Gbps = 10^9 bits/s = 10^9 / 8 = 125,000,000 bytes/s.
Time to reuse a sequence number (wraparound time) = 2^32 bytes ÷ 125,000,000 bytes/s ≈ 34.3597 s.
Round to the nearest integer: 34 seconds.
Note: The given starting sequence number (1234) does not affect the wraparound time.
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