A.2.2 NetWare's Networking Services and the OSI Reference Model

Using the OSI Reference Model, we are able to see and better understand how NetWare implements network services such as file and print sharing, and how it also implements other protocols such as TCP/IP, AppleTalk, and others. Figure A.3 below illustrates how the native networking services and Novell's TCP/IP stack compare to the OSI Reference Model.

Figure A.3 Comparing NetWare to the OSI Reference Model.

At the bottom is the physical layer, which consists of the network cabling such as Ethernet, Token Ring, ISDN, or any other medium used to transmit information. This layer is consistent across all of the NetWare protocol implementations. IPX, TCP/IP, AppleTalk and other protocols all use the same network interfaces when used on a NetWare server.

Novell provides a set of specifications called the Open Data-Link Interface (ODI) which are designed to allow network adapter vendors and protocol developers to use a standardized method of communicating with each other. The ODI specifications include Media Link Interface Driver (MLID) services that allow hardware vendors to write network drivers for many common media types (such as Ethernet, Token Ring and others) without having to re- invent the technology themselves. ODI also includes the Link Support Layer (LSL), which provides a consistent set of interfaces to the higher-level protocols, allowing developers to write new protocols without having to deal with the intrinsic differences between Ethernet, Token Ring, and all of the other media types.

Because of these services, ODI addresses some of the attributes of the physical layer, and most of the attributes of the data-link layer. However, adapter vendors still have to deal with many physical layer issues, and protocols still have to deal with some data-link layer issues directly, so ODI does not cover each layer completely.

The various protocols are above ODI, and provide the network layer services such as address management, delivery, and the routing of packets between different networks.

From here on out, the two protocol families begin to take divergent paths. For more information on the IPX protocol suite, refer to section A.3 More About IPX and Related Protocols. For more information on the TCP/IP protocol family, refer to section A.4 More About the TCP/IP Protocol Suite.

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