IPX/SPX (which stands for Internetwork Packet Exchange/Sequenced Packet Exchange ) is a network protocol stack developed by Novell for use on networks running the Novell NetWare network operating system. Novell NetWare is a popular network operating system (NOS) that has provided file and print server functionality to LANs since the early 1980s (we will discuss Novell NetWare in Chapter 6, "Configuring Peer-to-Peer Networks").
IPX/SPX, like TCP/IP, is actually a stack of protocols that perform different functions in the overall network communication process. Also like TCP/IP, IPX/SPX does not map directly on a layer-per-layer basis to the OSI conceptual model. IPX/SPX actually requires fewer resources (both from a computer and a network) than TCP/IP and therefore gained a strong foothold (as did Novell NetWare) in the early decades of the PC revolution, because computers with limited capabilities (limited in terms of the amount of memory and hard drive space, if any, on the computers) running the DOS operating system could be networked. IPX/SPX is suitable for small and large networks and is a routable network protocol suite (like TCP/IP).
The IPX/SPX protocol stack is made up of a number of protocols that handle the various duties required for network communication on both a sending and a receiving node. Figure 5.4 shows a mapping of IPX/SPX stack protocols to the OSI conceptual model. Table 5.4 provides definitions of some of the more important protocols in the IPX/SPX stack.
As you can see from Figure 5.4, IPX/SPX has protocols that handle the functionality of the Application, Presentation, Session, Transport, and Network layers . These protocols basically plug into the standards that operate at the Data Link layer of the OSI model and are defined by the IEEE standard discussed in Chapter 3, "Networking Hardware." Novell NetWare can be used as the NOS on both Ethernet and Token Ring networks.
Table 5.4. IPX/SPX Protocol Stack Members
IPX/SPX also uses a logical addressing system to identify the nodes on the network. The IPX protocol is in charge of this addressing system. The IPX address is similar in theory to an IP address in that it provides both the network location and the actual node address of a computer.
Here's how it works: When you install the first NetWare server on the network, the server generates a network number. This hexadecimal number becomes the network number for the LAN, no matter how many additional NetWare servers (additional file and print servers) are added to the LAN. Therefore, all client machines (and additional servers) on the LAN will be assigned the same network number.
The clever part of IPX addressing is how the node address portion of the IPX address is determined. As you already know from Chapter 3, each computer has a MAC address, which is burned into a ROM chip on the NIC. The node portion of the IPX address is the MAC address of the computer (or other device).
Figure 5.5 shows an IPX address that was taken from a node on a NetWare network. The first portion of the address, as shown in the figure, is the network address, and the remainder of the address is the MAC hardware address for the device.
Figure 5.5. An IPX address is made up of a network address and a node address.
Novell NetWare is a good example of a client/server network operating system; a computer on the network either functions as a client or a server. Therefore, this means servers (such as the logon server and file and print servers) have to be configured and then clients configured so that they can access the resources provided by the various NetWare servers.
We will discuss some of the issues related to setting up and configuring NetWare servers in Chapter 8, "Networking with Novell NetWare 6.5." For now, I will say that actually installing the NetWare software on a server is very straightforward (as almost all network operating systems are now). However, even Novell now uses TCP/IP as the default network protocol, so during the installation, the IPX/SPX protocol stack must be enabled.
Configuring clients for NetWare is very straightforward because client software is included with the Novell network operating system that helps a network administrator in configuring the NetWare clients. NetWare can support DOS, Windows, Macintosh, and Unix clients. This add-on software for the client operating system sets up the computer with a NetWare logon so that users with user accounts on the NetWare server can log on to the network using their usernames and passwords.
Windows 9x, Windows 2000, and Windows XP computers can all be configured as NetWare clients. You can use the WIN32 client setup software included with the Novell NetWare NOS, or you can configure Windows clients for a NetWare network using your Windows software. You'll learn more about configuring Windows clients for NetWare in Chapter 8.