Consider the data transfer using TCP over a 1 Gbps link. Assuming that the…
2022
Consider the data transfer using TCP over a 1 Gbps link. Assuming that the maximum segment lifetime (MSL) is set to 60 seconds, the minimum number of bits required for the sequence number field of the TCP header, to prevent the sequence number space from wrapping around during the MSL is____________.
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Correct answer: 33
Key insight: TCP sequence numbers count bytes, so the sequence number space must be at least the number of bytes that can be sent during the maximum segment lifetime (MSL).
Step 1: Convert link speed to bytes per second: 1 Gbps = 1,000,000,000 bits/s = 125,000,000 bytes/s.
Step 2: Bytes sent during the MSL of 60 s: 125,000,000 bytes/s × 60 s = 7,500,000,000 bytes.
Step 3: Find the smallest integer n with 2^n ≥ 7,500,000,000. Since 2^32 = 4,294,967,296 < 7,500,000,000 and 2^33 = 8,589,934,592 ≥ 7,500,000,000, n = 33.
Answer: The minimum number of bits required for the TCP sequence number field is 33.
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