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).



Novell NetWare was based on the XNS (Xerox Network Systems) network operating system that was created at the Xerox Palo Alto Research Center in the 1970s.

IPX/SPX Protocols

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




The NetWare Core Protocol handles network functions at the Application, Presentation, and Session layers. It is responsible for providing the connection between clients and servers. It also handles packet creation when the sending of data is initiated by a computer on the network.


The Service Advertising Protocol is used by NetWare servers to announce the addresses of file and print servers on the network. This is how NetWare clients know how to find network resources.


The Sequenced Packet Exchange protocol is a connection-oriented protocol that operates at the Transport layer of the OSI model.


The Internetwork Packet Exchange protocol is a connectionless transport protocol that handles the addressing of nodes on an IPX/SPX network.


The Routing Information Protocol (the Novell flavor) is responsible for the routing of IPX/SPX packets on the network.



As we discuss network protocols and networking in general, two terms that keep popping up are resources and bandwidth . A resource can be memory or hard drive space on a computer. The processor on a computer is also a resource in that it can only process so much information at any one time. On the network itself, bandwidth is probably the most important resource. I'm speaking of bandwidth in terms of the amount of data that can be pushed along the network media (the term bandwidth means something else entirely when you are discussing analog signals and their different amplitudes). Network administrators do everything they can to preserve the bandwidth on their networks. TCP/IP is generally considered more of a bandwidth hog when compared to IPX/SPX and therefore is one of the reasons why IPX/SPX was embraced early on for PC networking.

IPX/SPX Addressing

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.


Configuring IPX/SPX

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.



Windows NetWare clients actually use a Microsoft clone of the IPX/SPX network protocol called NWLink , which stands for NetWare link clever, huh?

Absolute Beginner's Guide to Networking
Absolute Beginners Guide to Networking (4th Edition)
ISBN: 0789729113
EAN: 2147483647
Year: 2002
Pages: 188
Authors: Joe Habraken

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net