For each protocol a single line should be present with the following information:
official-protocol-name protocol-number aliases
Items are separated by any number of blanks and/or tab characters. A ``#'' indicates the beginning of a comment; characters appearing after the ``#'' are ignored.
Protocol names may contain any printable character other than a field delimiter, newline, or comment character.
When the Network Information Service (NIS) is in use, it references the NIS maps protocols.byname or protocols.bynumber on the NIS server instead of /etc/protocols.
# # Internet (IP) protocols # ip 0 IP # internet protocol, pseudo protocol number icmp 1 ICMP # internet control message protocol ggp 3 GGP # gateway-gateway protocol tcp 6 TCP # transmission control protocol pup 12 PUP # PARC universal packet protocol udp 17 UDP # user datagram protocol