IANA (Internet Assigned Numbers Authority)
IANA is the overall authority for:
- IP addresses;
- top-level-domains;
- Autonomous Systems number;
- other parameters (protocol numbers, port numbers, etc.)
See the file /etc/protocols on a UNIX machine
0 IP pseudo protocol number
1 ICMP
6 TCP
17 UDP
Well known TCP ports (see the file /etc/services on a UNIX machine):
21 - FTP server
23 - telnet server
25 - SMTP mail server
53 - domain nameserver