TCP and UDP Port Assignments

Port Assignments and Protocol Numbers

In TCP/IP networking, a port is a mechanism that allows a computer to simultaneously support multiple communication sessions with computers and programs on the network. A port directs the request to a particular service that can be found at that IP address. The destination of a packet can be further defined by using a unique port number. The port number is determined when the connection is established.

The Internet Assigned Numbers Authority (IANA) defines the unique parameters and protocol values necessary for operation of the Internet and its future development. In the past, these numbers were documented through the RFC document series. Since that time, the assignments have been listed on the IANA Web site, constantly updated and revised when new information is available and new assignments are made. The description of the ports and protocols in this chapter is from the IANA. The Internet Engineering Task Force (IETF) is the protocol engineering and developmental arm of the Internet. Also, the Internet Society (ISOC), a professional organization of Internet experts, comments on policies and practices and oversees a number of other boards and task forces dealing with network policy issues. For more information about port assignments, see the Port Assignments link on the web resources page at http://windows.microsoft.com/windows2000/reskit/webresources.

This appendix describes Microsoft® Windows® 2000 Server and Microsoft® Windows® 2000 Professional default port assignments and IP Protocol Numbers. Protocol Numbers direct a packet to the appropriate protocol, such as UDP or TCP, that is one layer higher in the protocol stack. This appendix contains three tables:

Table C.1 lists Well-Known Ports.
Table C.2 lists the Registered Ports.
Table C.3 lists TCP and UDP ports that support commonly-used Windows 2000 services.
Table C.4 lists IP Protocol Numbers and the functions they support.
By definition, Dynamic Ports are randomly assigned and therefore cannot be known until they are assigned. Private Ports are not registered with the IANA but are used by software applications.