4.1cBSD/etc/protocols

#
# Internet (IP) protocols
#
ip	0	IP	# internet protocol, pseudo protocol number
icmp	1	ICMP	# internet control message protocol
ggp	2	GGP	# gateway-gateway protocol
tcp	6	TCP	# transmission control protocol
pup	12	PUP	# PARC universal packet protocol
udp	17	UDP	# user datagram protocol