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.This component manages theThe network size and resourcesnetwork s files and resources, commu-nicates with workstations, and dealsThe traffic load and patterns for thewith workstation requests.networkWorkstation software, which is a net-The configuration of the hardware onwork shell or redirector program.Thiswhich the NOS is runningcomponent provides the workstationSeveral core capabilities are availablewith access to the network and, there-with any NetWare version:fore, to the resources and files on theserver or on another workstation.Controlled file and directory access.NetWare provides access controls andServer Softwarefile and record locking.The NetWare program running on the serverShared access to printing resources.is an NOS.NetWare has its own partitionThe NOS (or a process controlled byon the hard disk, and it may replace thethe NOS) makes sure that print jobsnative operating system (for example, DOS)are added to the appropriate queueas the program with which applications andand are printed.other processes deal.In other cases, Net-Electronic mail (e-mail) capabilities.Ware may run as a process under the operat-In NetWare, this is provided throughing system, as does NetWare for UNIX.Novell s MHS (Message HandlingEven when it becomes the primary operatingService) protocol, which third-partysystem, NetWare may still rely on the nativee-mail packages can use.operating system.For example, NetWare forDOS uses some DOS services as well asSecurity controls.For example, Net-the DOS file system.Ware can require user log in andThe capabilities of the NOS running on aauthentication procedures and limitserver depend on several things, includinguser access rights.the following:Interprocess Communication (IPC),The version of NetWare runningwhich enables processes on the net-work to communicate with each other.For version 2.x, the combination ofValue-Added Processes (VAPs) loadedwith the NOS NetWare 651Workstation Software in versions preceding 4.x.In NetWare 4.x,athis software is known as the NetWare DOSThe software on the workstation in a Net-Requester.The DOS Requester softwarebWare network must be able to communicateruns as a DOS process, but takes consider-with the network and also with the work-cable control by intercepting certain key DOSstation s operating system.interrupts.This is done so that network-dThe workstation software determinesrelated requests go on to the network.whether a request from a program or user isThe workstation software consists ofeintended for the workstation (that is, forseveral utilities, each responsible for oneDOS) or for the network.If the request is forfof the shell s tasks.These utilities includethe workstation, the software passes it on toNETx.COM, SPX.COM, and IPX.COM.gDOS.If it is a network request, the softwareNETx does the intercepting, redirecting,does the following:and the first round of processing (into NCP hform); SPX and IPX create packets designedConverts the request into the appropri-ifor their counterpart programs at theate format.destination.jPacks the request into a packet,The DOS Requester (NetWare 4.x) con-together with routing and otherksists of a collection of Virtual Loadableadministrative information.NetWareModules (VLMs), which are modules run-luses the NCP (NetWare Core Protocol)ning on a workstation.The VLMs accom-to formulate (and respond to) theplish generally the same kinds of tasks as the mrequests and the IPX (Internetworkshell utilities, but do so in different ways.Packet Exchange) protocol to create nthe packet to be transmitted.NetWare ProtocolsoPasses this packet on to a networkThe NetWare NOS software correspondspinterface card (NIC) for packaging in aroughly to the layers defined in the OSI Ref-format suitable for the actual networkerence Model.The protocols supportedqarchitecture.within this framework are listed in the tabler NetWare Protocol Suite. Verifies that the packet was receivedBy default, NetWare uses the protocolcorrectly, and requests a retransmis-sstack shown in the figure Default NetWaresion if an error occurred.protocol stack. In addition to these proto-tOnce the packet is passed to the NIC, thecols, NetWare supports frame formats foruworkstation component of the NOS is fin-different network architectures (Ethernet,ished with its task.The software running theToken Ring, ARCnet, and so on).Add-onvNIC does further processing and makes suremodules also provide support for other pro-the packet gets onto the network.wtocol suites, such as the TCP/IP (used inFor DOS workstations, the program thatUNIX systems) and AppleTalk protocolxdoes these things is called the NetWare shellfamilies
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