Practical TCP/IP and Ethernet Networking for Industry

Appendix B

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As discussed earlier, there are three levels of addressing:

• The hardware address which resides on the network interface card

• The software or IP address which is broken down into a host and net portion

and is set by the network administrator

• A host-to-host address (TCP) level of address known as the port address

Each PC or host is assumed to have numerous applications or processes running. An

identifier known as the port number specifies the process the user wishes to access. These

port numbers are 16 bits long and are standardized according to their use.

Port numbers 0–255 are assigned by the Internet ...