Client is connected to firewall via link with MTU 1500 bytes, server is connected to...

The TCP MSS (Maximum Segment Size) defines the maximum TCP payload size, excluding headers. When the firewall sets MSS to 1450 bytes, the TCP segment size is limited to this value. For IP packets, the total size includes the TCP header (20 bytes) and IP header (20 bytes), so 1450 (MSS) + 20 (TCP) + 20 (IP) = 1490 bytes, which fits within both link MTUs (1500 and 1496 bytes). Thus, the maximum IP packet size is not limited by the link MTUs but by the MSS, adjusted for headers. Options C and F (bits) are incorrect units; A and B exceed the MSS limit. Exact extract: "The TCP MSS is adjusted to prevent fragmentation... FortiGate can rewrite the MSS in TCP SYN packets to ensure the total IP packet size (including IP and TCP headers) does not exceed the configured value."