INTERNET PROTOCOL VERSION 4 (IPV4) (RFC791) has a field called Protocol that identifies the next level of protocol. This is an 8-bit field. In Internet Protocol Version 6 (IPv6) (RFC1883), this field is called Next Header. The following are currently assigned Internet protocol numbers (as of March 2001). Specifications of these protocols are defined in various RFCs and may be obtained from http://www.rfc-editor.org.
|0||HOPOPT||IPv6 Hop-by-Hop Option|
|1||ICMP||Internet Control Message Protocol|
|2||IGMP||Internet Group Management Protocol|
|3||GGP||Gateway-to-Gateway Protocol ...|