The Internet and Its Protocols

578 Chapter12 Application Protocols

The scope of

well-known

as applied to the port on which the server listens

is an interesting point. For all application protocols defined by the IETF, there is

a well-known port for each transport protocol over which the application

protocol may be run. These port IDs are tracked by IANA and, in general, the

same port number is used by one application protocol over all transport protocols.

Although these standard port numbers serve as defaults in the Internet, some

system operators choose to vary them on their hosts. Of course, this works only

if ...