| 10.2 |  | Overview of Transport Layer Ports |
| 10.2.2 |  | Ports for services |

| Services running on hosts must have a port number assigned to them so communication can occur. A remote host attempting to connect to a service expects that service to use specific transport layer protocols and ports. Some ports, defined in RFC 1700 are known as the well-known ports, and reserved in both TCP and UDP. These well-known ports define applications that run above the transport layer protocols. For instance, a server running the FTP service will forward TCP connections using ports 20 and 21 from clients to its FTP application. In this way, the server can determine exactly what service a client is requesting. TCP and UDP use port numbers to determine the correct service to which requests are forwarded.
| Web Links Ports and Services http://www.spirit.com/Resources/ ports.html