|
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