another, and the Sequenced Packet Protocol (SPP), which was a modified form of IDP that was connection-based and reliable. The datagrams of an XNS network were individually addressed. The addressing scheme used a combination of a 4-byte IDP network address (which was uniquely assigned to each Ethernet LAN segment), and the 6-byte node address (the address of the NIC card). Routers were devices that switched datagrams between two or more separate IDP networks. IDP has no notion of subnetworks; any new collection of hosts requires another network address to be assigned. Network addresses are chosen such that they are unique on the internetwork in question. Sometimes administrators develop conventions by having each byte encode some other information, such as geographic location, so that network addresses are allocated in a systemic way; it isn't a protocol requirement, however.
The Novell Corporation chose to base their own networking suite on the XNS suite. Novell made small enhancements to IDP and SPP and renamed them IPX (Internet Packet eXchange) and SPX (Sequenced Packet eXchange). Novell added new protocols, such as the NetWare Core Protocol (NCP), which provided file and printer sharing features that ran over IPX, and the Service Advertisement Protocol (SAP), which enabled hosts on a Novell network to know which hosts provided which services.
Table 15.1 maps the relationship between the XNS, Novell, and TCP/IP suites in terms of function. The relationships are an approximation only, but should help you understand what is happening when we refer to these protocols later on.
Table 15.1: XNS, Novell, and TCP/IP Protocol Relationships
| XNS | Novell | TCP/IP | Features |
|---|---|---|---|
| IDP | IPX | UDP/IP | Connectionless, unreliable transport |
| SPP | SPX | TCP | Connection-based, reliable transport |
| NCP | NFS | File services | |
| RIP | RIP | Routing information exchange | |
| SAP | Service availability information exchange |
IPX and Linux
Alan Cox first developed IPX support for the Linux kernel in 1985.[83] Initially it was useful for little more than routing IPX datagrams. Since then, other people, notably Greg Page, have provided additional support.[84] Greg developed the IPX configuration utilities that we'll use in this chapter to configure our interfaces. Volker Lendecke developed support for the NCP filesystem to allow Linux to mount volumes on network-connected NetWare fileservers.[85] He also created tools that allow printing to and from Linux. Ales Dryak and Martin Stover each independently developed NCP fileserver daemons for Linux that allow network-connected NetWare clients to mount Linux directories exported as NCP volumes, just as the NFS daemon allows Linux to serve filesystems to clients using the NFS protocol.[86] Caldera Systems, Inc. offers a commercial and fully licensed NetWare client and server that supports the latest Novell standards, including support for the NetWare Directory Service (NDS).[87]
Today, therefore, Linux supports a wide range of services that allow systems to be integrated with existing Novell-based networks.
Caldera Support
Although we don't detail the Caldera NetWare support in this chapter, it is important that we talk about it. Caldera was founded by Ray Noorda, the former CEO of Novell. The Caldera NetWare support is a commercial product and fully supported by Caldera. Caldera provides the NetWare support as a component of their own Linux distribution called Caldera OpenLinux. The Caldera solution is an ideal way of introducing Linux into environments that demand both commercial support and the ability to integrate into existing or new Novell networks.
The Caldera NetWare support is fully licensed by Novell, providing a high degree of certainty that the two companies' products will be interoperable. The two exceptions to this certainty are 'pure IP' operation for the client, and NDS server, though neither of these were available at the time of writing. NetWare client and NetWare server are both available. A suite of management tools is also provided that can simplify management of not only your Linux-based NetWare machines, but your Novell NetWare machines, too, by bringing the power of Unix scripting languages to the task. More information on Caldera can be found at their web site.
More on NDS Support
Along with Version 4 of NetWare, Novell introduced a feature called the NetWare Directory Service (NDS). The NDS specifications are not available without a nondisclosure agreement, a restriction that hampers development of free support. Only Version 2.2.0 or later of the
