Hardware Versus Protocol Addresses

When communicating on the same network segment, a computer can communicate directly by sending directed datagrams to another computer and specifying the unique MAC address that's burned into the network card when it's manufactured. In TCP/IP networks, the Address Resolution Protocol (ARP) is used in a local broadcast domain to determine the hardware address of another computer by sending out a broadcast packet that contains the computer's IP address. When a computer recognizes an ARP packet that has its IP address, it responds to the ARP request with another packet that tells the original computer what the destination computer's MAC address is. For more information about hardware addresses and ARP, see Chapter 25, "Overview of the TCP/IP Protocol Suite."

The TCP/IP protocol is pretty much the standard today for local area networks. NetBIOS has been adapted to run over IP, and beginning with NetWare 5, IP is now the preferred protocol used in NetWare LANs. To begin, however, let's look at the older NetBIOS namespace and NetBEUI protocol that were used on Microsoft's first offerings in the LAN environment.