I think this is the file your af
#
# This file contains the Internet protocols as defined by RFC 1700
# (Assigned Numbers).
#
# Format:
#
# <protocol name> <assigned number> [aliases...] [#<comment>]
ip 0 IP # Internet protocol
icmp 1 ICMP # Internet control message protocol
ggp 3 GGP # Gateway-gateway protocol
tcp 6 TCP # Transmission control protocol
egp 8 EGP # Exterior gateway protocol
pup 12 PUP # PARC universal packet protocol
udp 17 UDP # User datagram protocol
hmp 20 HMP # Host monitoring protocol
xns-idp 22 XNS-IDP # Xerox NS IDP
rdp 27 RDP # "reliable datagram" protocol
rvd 66 RVD # MIT remote virtual disk