ip	0	IP	# internet protocol, pseudo protocol number
icmp	1	ICMP	# internet control message protocol
igmp	2	IGMP	# internet group multicast 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
idp	22	IDP	# WhatsThis?
raw	255	RAW	# RAW IP interface