这是用于识别独特的操作系统的特点,因为rfc - 1122预期行为写道:“每一个ICMP错误消息包括互联网头和至少的前8个数据字节的数据报,引发了错误;超过8个八位字节可能发送[…]”。This contrasts with RFC-792 expected behavior, which limited the quoted text to 64 bits (8 octets). Given the latitude in the specification the resulting RFC-1122 stack implementations often respond with a high degree of variability in the amount of data quoted in the error message because "older" or "legacy" stacks may comply with the RFC-792 specification, while other stacks may choose a longer format in accordance with RFC-1122. As a general rule most operating systems or firmware will quote the first 8 bytes of the datagram triggering the error, but some IP stacks will quote more than the first 8 bytes of data.