RFC 综合指南（RFC Sourcebook）

The RFC Sourcebook is a comprehensive guide to the Request for Comments (RFCs) series of documents published by the IETF.

http://www.networksorcery.com/enp/default.htm

互联网协议族的全面详尽指南，各种网络协议格式详解

如ICMPv6:

这里查看各字段值的含义： https://www.iana.org/protocols