Linux man pages : protocols (5)
PROTOCOLS(5) Linux Programmer's Manual PROTOCOLS(5)
protocols - the protocols definition file
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 proto-
col 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
Each line is of the following format:
protocol number aliases ...
where the fields are delimited by spaces or tabs. Empty lines are
ignored. If a line contains a hash mark (#), the hash mark and the
part of the line following it are ignored.
The field descriptions are:
the native name for the protocol. For example ip, tcp, or udp.
number the official number for this protocol as it will appear within
the ip header.
optional aliases for the protocol.
This file might be distributed over a network using a networkwide nam-
ing service like Yellow Pages/NIS or BIND/Hesiod.
The protocols definition file.
Guide to Yellow Pages Service
Guide to BIND/Hesiod Service
Linux 1995-10-18 PROTOCOLS(5)