10.2 Overview of Transport Layer Ports  
  10.2.4 Port numbering and well-known port numbers  

Port numbers are represented by 2 bytes in the header of a TCP or UDP segment. This 16-bit value can result in port numbers ranging from 0 to 65535. These port numbers are divided into three different categories: well-known ports, registered ports, and dynamic or private ports. The first 1023 ports are well-known ports. As the name implies, these ports are used for well-known network services, such as FTP, Telnet, or DNS. Registered ports range from 1024 to 49151. Ports between 49152 and 65535 are defined as dynamic or private ports.

 

 Interactive Media Activity

Drag and Drop: Port Numbers

After completing this activity, the student will be able to understand port numbers.

 
 

Web Links

Port Knowledgebase

http://www.iss.net/security_center/ advice/Exploits/Ports/