Ports Continued
RFC 1700 defines Well-Known Port Numbers.
- TCP Port 20 – FTP data transfer
- TCP Port 21 – FTP control port
- TCP Port 23 – Telnet
- TCP Port 25 – SMTP
- TCP Port 53 –DNS (also known as name or domain server)
- TCP Port 80 – HTTP Web services
- UDP Port 53 –DNS server (also known as name or domain server)
- UDP Port 69 –TFTP
- UDP Port 161 –SNMP
The breakdown of port ranges typically follows this schema:
- Public applications, such as DNS, FTP, and HTTP, use ports below 256.
- Companies use ports from 256 to 1023 for their private applications
- Ports above 1023 are dynamically negotiated during a connection.