/etc/protocols文件
定义了计算机主机使用的协议，以及每一个协议的协议号等相关信息
内容如下：
# /etc/protocols: # $Id: protocols,v 1.11 2011/05/03 14:45:40 ovasik Exp $ # # Internet (IP) protocols # # from: @(#)protocols 5.1 (Berkeley) 4/17/89 # # Updated for NetBSD based on RFC 1340, Assigned Numbers (July 1992). # Last IANA update included dated 2011-05-03 # # See also http://www.iana.org/assignments/protocol-numbers 协议名 协议号 协议全名 注释 ip 0 IP # internet protocol, pseudo protocol number hopopt 0 HOPOPT # hop-by-hop options for ipv6 icmp 1 ICMP # internet control message protocol igmp 2 IGMP # internet group management protocol ggp 3 GGP # gateway-gateway protocol ipv4 4 IPv4 # IPv4 encapsulation st 5 ST # ST datagram mode tcp 6 TCP # transmission control protocol cbt 7 CBT # CBT, Tony Ballardie <A.Ballardie@cs.ucl.ac.uk> egp 8 EGP # exterior gateway protocol igp 9 IGP # any private interior gateway (Cisco: for IGRP) bbn-rcc 10 BBN-RCC-MON # BBN RCC Monitoring nvp 11 NVP-II # Network Voice Protocol pup 12 PUP # PARC universal packet protocol argus 13 ARGUS # ARGUS emcon 14 EMCON # EMCON xnet 15 XNET # Cross Net Debugger chaos 16 CHAOS # Chaos udp 17 UDP # user datagram protocol mux 18 MUX # Multiplexing protocol dcn 19 DCN-MEAS # DCN Measurement Subsystems hmp 20 HMP # host monitoring protocol prm 21 PRM # packet radio measurement protocol xns-idp 22 XNS-IDP # Xerox NS IDP trunk-1 23 TRUNK-1 # Trunk-1 trunk-2 24 TRUNK-2 # Trunk-2 leaf-1 25 LEAF-1 # Leaf-1 leaf-2 26 LEAF-2 # Leaf-2 rdp 27 RDP # "reliable datagram" protocol irtp 28 IRTP # Internet Reliable Transaction Protocol iso-tp4 29 ISO-TP4 # ISO Transport Protocol Class 4 netblt 30 NETBLT # Bulk Data Transfer Protocol