How IPX/SPX works

SCO IPX/SPX provides interoperability between DOS Workstation NetWare clients and SCO OpenServer systems over the NetWare network. It also provides the transport protocols used by SCO Gateway for NetWare to communicate with NetWare file and print servers. It eliminates the need for multiple protocol stacks in a Novell network, providing greater efficiency and lower administrative overhead. SCO IPX/SPX consists of the three components: kernel, user, and DOS.

Kernel component

This component is comprised of the following drivers:

A STREAMS driver supporting the Novell Internetwork Packet Exchange (IPX) protocol. Depending on the capabilities of the underlying network driver, the IPX driver uses either the SCO Data Link Provider Interface (DLPI) or Link Level Interface (LLI) lower interface. In addition, IPX exposes a Transport Layer Interface (TLI) user interface with connectionless services.

A STREAMS driver supporting the Novell Sequenced Packet Exchange (SPX) protocol. The SPX protocol provides connection-oriented transport services and exposes a Transport Layer Interface (TLI) user interface. SPX depends on an IPX service provider; to run SPX, you must be running IPX.

A STREAMS driver supporting the Novell Virtual Terminal (NVT) protocol. NVT depends on the IPX service provider; to run NVT, you must be running IPX.

User component

This component includes the following protocols by which the SCO OpenServer system can advertise itself to NetWare clients:

The NetWare Protocol Stack (NPS) daemon. NPSD is responsible for initializing and assembling the stack from various kernel components.

The Novell Virtual Terminal daemon (NVTD). NVTD establishes the connection between the client and host NVT drivers and mediates the communication between them.

The Service Advertising Protocol daemon (SAPD). SAPD advertises the services offered by a SCO IPX/SPX server. SAPD also responds to remote queries, for example, "give me the address of the nearest NVT server." Multiple SCO servers may respond to this query; it is up to the requester to pick from a set.

Administrative commands and utilities.

DOS component

This component consists of an executable that allows a DOS client to establish a connection to the UNIX server. The NVT.EXE executable is a terminate-and-stay-resident program (TSR) and acts as a network redirector, allowing a DOS end user to establish a connection with an NVT server. For more information about installing the DOS component and using NVT.EXE, see ``Installing and using the DOS component''.

In addition to NVT.EXE, the DOS client must be running a NetWare protocol support module to provide the IPX protocol support and the device driver for the LAN card used in the DOS client machine. Currently, there are two prevalent IPX protocol modules and a terminal emulator provided by Novell:

IPX.COM, which is generally used with NetWare 2.x and 3.x systems. There are a number of known problems with IPX.COM; its use should be avoided where possible.

IPXODI.COM, which is generally used with NetWare 3.x and 4.x systems. IPXODI.COM is compatible with SCO IPX/SPX .

A terminal emulator supporting the INT14 or INT6B/UB-NETCI interfaces.

NetWare protocols, including packet structures and broadcast operations.

Packet delivery, including a discussion of routers, bridges, and routing broadcasting and administration.

Service advertising, used to advertise IPX addresses and services using the Service Advertising Protocol (SAP).

Client-server interaction, including the files needed by a DOS workstation to access data from a server running IPX/SPX.

The configuration files used by IPX/SPX, including those that tune IPX, SPX, and NVT.

Network Access Protection Design Guide

Updated: October 6, 2008

Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista

Network Access Protection (NAP) is one of the most anticipated features of the Windows Server� 2008 operating system. NAP is a new platform that allows network administrators to define specific levels of network access based on a client�s identity, the groups to which the client belongs, and the degree to which the client complies with corporate governance policy. If a client is not compliant, NAP provides a mechanism for automatically bringing the client into compliance (a process known as remediation) and then dynamically increasing its level of network access. NAP is supported by Windows Server 2008 R2, Windows Server 2008, Windows 7, Windows Vista�, and Windows� XP with Service Pack 3 (SP3). NAP includes an application programming interface that developers and vendors can use to integrate their products and leverage this health state validation, access enforcement, and ongoing compliance evaluation. For more information about the NAP API, see Network Access Protection (http://go.microsoft.com/fwlink/?LinkId=128423).

The following are key NAP concepts:

NAP Agent. A service included with Windows Server 2008, Windows Vista, and Windows XP with SP3 that collects and manages health information for NAP client computers.
NAP client computer. A computer that has the NAP Agent service installed and running, and is providing its health status to NAP server computers.
NAP-capable computer. A computer that has the NAP Agent service installed and running and is capable of providing its health status to NAP server computers. NAP-capable computers include computers running Windows Server 2008, Windows Vista, and Windows XP with SP3.
Non-NAP-capable computer. A computer that cannot provide its health status to NAP server components. A computer that has NAP agent installed but not running is also considered non-NAP-capable.
Compliant computer. A computer that meets the NAP health requirements that you have defined for your network. Only NAP client computers can be compliant.
Noncompliant computer. A computer that does not meet the NAP health requirements that you have defined for your network. Only NAP client computers can be noncompliant.
Health status. Information about a NAP client computer that NAP uses to allow or restrict access to a network. Health is defined by a client computer's configuration state. Some common measurements of health include the operational status of Windows Firewall, the update status of antivirus signatures, and the installation status of security updates. A NAP client computer provides health status by sending a message called a statement of health (SoH).
NAP health policy server. A NAP health policy server is a computer running Windows Server 2008 with the Network Policy Server (NPS) role service installed and configured for NAP. The NAP health policy server uses NPS policies and settings to evaluate the health of NAP client computers when they request access to the network, or when their health state changes. Based on the results of this evaluation, the NAP health policy server instructs whether NAP client computers will be granted full or restricted access to the network.