This file is a plain ASCII file, describing the various DARPA internet protocols that are available from the TCP/IP subsystem. It should be consulted instead of using the numbers in the ARPA include files, or, even worse, just guessing them. These numbers will occur in the protocol field of any ip header.
Keep this file untouched since changes would result in incorrect ip packages. Protocol numbers and names are specified by the DDN Network Information Center.
Each line is of the following format:
protocol number aliases ...
where the fields are delimited by spaces or tabs. Empty lines and lines starting with a hash mark (#) are ignored. Remainder of lines are also ignored from the occurrence of a hash mark.
The field descriptions are:
the native name for the protocol. For example ip, tcp or udp.
the official number for this protocol as it will appear within the ip header.
optional aliases for the protocol.
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