Introduction to Data Communications
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The Open Datalink Interface (ODI) is a software standard developed by Novell and Apple Corporation to provide a layered approach to comply with the ISO Open System Interconnect (OSI) model for the Physical, Datalink and Network layers.

The Open Datalink Interface was developed to overcome several limitations on the previous network interface card driver software. Previous to the ODI standard, each workstation was required to "compile" its own workstation's IPX.COM shell using Novell's "WSGEN" program (workstation generation program). This resulted in a single program, that contained the network card driver, Datalink interface and Network layer protocol (IPX/SPX), commonly called the "workstation shell".

This approach limited the workstation to 1 network card and only 1 Network layer protocol. Multiple network cards and Network layer protocols were not allowed under "WSGEN".

The ODI standard broke the "workstation shell" into manageable parts that permits multiple network cards and protocols. For example: This means that 1 workstation/client can have an Ethernet 10BaseT card running IPX/SPX protocols (Novell) and a Farallon Localtalk card in it for running Appletalk (Macintosh).

The ODI standard compared to the OSI Model:

OSI	= Open System Interconnect		ODI	= Open Datalink Interface

SPX 	= Sequenced Packet Exchange		IPX	= Internetwork Packet Exhange

LSL 	= Link Suppport Layer			VLM 	= Virtual Loadable Modules

MLID 	= Multiple Link Interface Driver	MSM 	= Media Support Module

HSM 	= Hardware Support Module

Novell Lite (very old - defunct) is Novell's Peer to Peer Network Operating system. Peer to Peer Networks use DOS's File Allocation Table (FAT) and Novell Lite is no exception (Novell Netware has its own high performance disk operating system). Novell Lite follows Novell's Netware structure for the Network, Datalink and Physical layers and it is an excellent example of an ODI compliant NOS (Network Operating System). At the Transport layer it uses Peer to Peer Client and Server software instead of Novell's Netware Transport layer software - SPX (VLM).

A typical Novell client is loaded from the DOS prompt or from a STARTNET.BAT file:

	SET NWLANGUAGE= ENGLISH

	LSL.COM				Link Support Layer Software

	3C509.COM			3C509 Network Interface Card Driver (MLID) ODI Compliant

	IPXODI				IPX Network layer protocol driver

	VLM				Loads client software

NET.CFG is the network configuration file used by the above files. It is a text file and contains the following basic section:

	Link Driver 3C5X9		(NIC drivername)

		INT 10			(IRQ #)

		PORT 300		(Base memory address in hexadecimal)

		FRAME Ethernet_802.2	(Frame type on Netware 3.12 & newer)

		FRAME Ethernet_802.3	(Frame type on Netware 3.11 and older)

		FRAME Ethernet_II		(Frame type used by UNIX)

		FRAME Ethernet_SNAP 	(Frame type used by Appletalk)

		NetWare DOS Requester

  		FIRST NETWORK DRIVE = F

   		USE DEFAULTS = OFF

  		VLM = CONN.VLM

   		VLM = IPXNCP.VLM

   		VLM = TRAN.VLM

  		VLM = SECURITY.VLM

		;  VLM = NDS.VLM	(used for Netware 4.11 NDS services)

   		VLM = BIND.VLM

   		VLM = NWP.VLM

  		VLM = FIO.VLM

   		VLM = GENERAL.VLM

		VLM = REDIR.VLM

   		VLM = PRINT.VLM

   		VLM = NETX.VLM

Introduction to Data Communications
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