Port Address

In a node, many processes will be running. Data which are sent/received must reach the right process. Every process in a node is uniquely identified using port numbers.

Ranges from $0-65535$.

Port = communication endpoint Putting it all together, IP vs. MAC vs. Port Address

• Reaching the network $\to$ IP Address
• Reaching the host $\to$ MAC Address
• Reaching the right process $\to$ Port Adress

Some ports are reserved for certain applications:

• Port 80: HTTP
• Port 21: FTP
• Port 25: SMTP server (mail)

Well-Known Port Numbers

Port numbers rangers from 0 to 1023 are called well-known port numbers since they are reserved for use by well known application protocols. The list of well-known port numbers is given in RFC 1700 and is updated at http://www.iana.org.