Defines the Internet protocols used on the local host.
The /etc/protocols file contains information about the known protocols used in the DARPA Internet. Each protocol is represented by a single line in the protocols file. Each entry corresponds to the form:
Name Number Aliases
The fields contain the following information:
| Item | Description |
|---|---|
| Name | Specifies an official Internet Protocol name. |
| Number | Specifies a protocol number. |
| Aliases | Specifies any unofficial names used for the protocol. |
Items on a line are separated by one or more spaces or tab characters. Comments begin with the # (pound sign), and routines that search the protocols file do not interpret characters from the beginning of a comment to the end of the line. A protocol name can contain any printable character except a field delimiter, new line character, or comment character.
The lines appear as follows:
ip 0 #dummy for IP
icmp 1 #control message protocol
#ggp 2 #gateway^2 (not normally used)
tcp 6 #tcp
#egp 8 #exterior gateway protocol
#pup 12 #pup
udp 17 #user datagram protocol