TCP does not cause IP fragmentation, while UDP and ICMP will cause IP fragmentation.

TCP will not cause IP sharding, while UDP and ICMP will cause IP sharding. Why does TCP not cause IP sharding? The reason is that TCP itself supports segmentation: when TCP needs to transmit data with a length greater than the MSS (Maxitum Segment Size), it first segments the data. Normally, the MSS is smaller than the MTU. Therefore, TCP generally does not cause IP fragmentation. UDP and ICMP do not support this segmentation function. UDP and ICMP believe that the network layer can transmit data with an infinite length (in fact there is a 65535 limit). When the two Protocols send data, regardless of the Data Length, they only add UDP or ICMP headers to their headers, and then directly deliver them to the network layer. Then, the IP protocol at the network layer splits the data with long headers and short headers. Do not expect the IP address to intelligently identify where the data is sent to it, and where the load is, it will directly cut the entire data into N parts. The result is that only the first part has the UDP or ICMP header, while other parts do not. For details, see: