Which statement about MTU and TCP segment size is true?

Which statement about MTU and TCP segment size is true?

• A. The maximum TCP segment size is determined by the MTU of the network.
• B. MTU determines TCP's retransmission timeout.
• C. MTU has no effect on TCP segmentation.
• D. TCP segment size determines the MTU.

Answer: (A)

MTU defines the largest IP packet allowed on a network link, and a TCP segment is carried inside a single IP packet. Therefore, the maximum amount of data a TCP segment can carry is limited by the path MTU ( MTU minus the IP and TCP header overhead). This is why the maximum TCP segment size is determined by the MTU; hosts typically negotiate an MSS (Maximum Segment Size) based on the MTU so segments fit without fragmentation. For example, with a common Ethernet MTU of 1500 bytes, the typical maximum TCP payload is about 1460 bytes after headers. Retransmission timeouts depend on RTT and variance, not MTU; MTU does affect segmentation, since a larger MTU allows bigger segments but the limit is still enforced by the MTU; and the MTU is a network property that constrains TCP segment size rather than being determined by the TCP segment size.

MTU defines the largest IP packet allowed on a network link, and a TCP segment is carried inside a single IP packet. Therefore, the maximum amount of data a TCP segment can carry is limited by the path MTU ( MTU minus the IP and TCP header overhead). This is why the maximum TCP segment size is determined by the MTU; hosts typically negotiate an MSS (Maximum Segment Size) based on the MTU so segments fit without fragmentation. For example, with a common Ethernet MTU of 1500 bytes, the typical maximum TCP payload is about 1460 bytes after headers. Retransmission timeouts depend on RTT and variance, not MTU; MTU does affect segmentation, since a larger MTU allows bigger segments but the limit is still enforced by the MTU; and the MTU is a network property that constrains TCP segment size rather than being determined by the TCP segment size.