Maximum legal size of ICMP echo packet

Question

Can someone please explain why maximum legal size of ICMP echo packet is calculated as follows:

65535 - 20 - 8 = 65507

Thanks.

Answer 1

65535字节是IPv4网络数据包的最大允许大小，而20和8是IP和ICMP标头的大小，最多为ICMP数据留下65507个字节。