WINDOWS 1002000 PROFESSIONAL RESOURCE KIT [Electronic resources] نسخه متنی

Overview of Interoperability with IBM Host Systems

IBM host systems use a different network architecture, Systems Network Architecture (SNA), than does Windows 2000 Professional. Therefore, in order for Windows 2000 Professional-based computers to communicate with IBM host systems, either a gateway device to interpret the two different network protocols or a common network protocol is required.

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For a general description of SNA, see "IBM Systems Network Architecture" later in this chapter.

To connect to IBM hosts by using a gateway device, you must have a local area network (LAN) protocol on Windows 2000 Professional and a gateway that provides the translation between the LAN protocol and the IBM host protocol or data stream. SNA Server is a gateway that provides this translation service. Figure 26.1 illustrates how SNA Server acts as the gateway between IBM hosts and Windows 2000 Professional.

Figure 26.1 Host Connectivity Through SNA Server

Table 26.1 lists the LAN protocols that are supported for access to an IBM host system through an SNA Server.

Table 26.1 SNA Server LAN-to-Host Protocols

To connect to an IBM host without SNA Server providing the gateway services, you must ensure that both Windows 2000 Professional and the IBM host have the same protocol installed and configured. Figure 26.2 presents an example of direct connectivity between Windows 2000 Professional and the IBM host.

Figure 26.2 Direct Connectivity to an IBM Host

Common network protocols that can be implemented on IBM host systems and Windows 2000 Professional-based computers for direct communication, without using a gateway, are listed in Table 26.2.

Table 26.2 Common Network Protocols

SNA Server

SNA Server provides administrators with a range of solutions for integrating heterogeneous networks and intranets with IBM mainframe, midrange, and AS/400 host systems. (See Figure 26.3.) SNA Server is a Microsoft® BackOffice® application that runs on the Microsoft® Windows® 2000 Server operating system and which provides advanced network-to-host and Web-to-host integration services.

SNA Server provides interoperability between host systems that run SNA or TCP/IP protocols. If your IBM host system runs SNA protocols, SNA Server provides network connectivity by acting as a secure, high-performance gateway between heterogeneous clients and IBM host systems. Because SNA Server runs on Windows 2000, heterogeneous clients can connect to SNA Server by using standard networking protocols such as TCP/IP, IPX/SPX, NetBIOS Enhanced User Interface (NetBEUI), Banyan VINES IP, AppleTalk, and Windows 2000 routing and remote access services. SNA Server then completes the network connection to the mainframe or AS/400 system using standard IBM SNA protocols.

After SNA or TCP/IP-based network connectivity is established, clients can use the advanced host integration features of SNA Server to gain secure access to IBM host data, applications, and network services without leaving their familiar desktop or Web browser interface.

Figure 26.3 Heterogeneous Networks Integrated with IBM Host Systems Through SNA Server

SNA Server's power lies in its ability to provide a wide range of host integration services. These host integration services and how they apply to each layer of the Windows 2000 interoperability model are described in the following list.

Network Integration Network integration provides cross-platform network connectivity and protocols, security integration, and single sign-on. (Single sign-on allows users to log on once for access to multiple servers, systems, or applications.)

Data Access Data access provides transparent file transfer services, universal data access technologies such as OLE DB and open database connectivity (ODBC), and host data replication.

Application Interoperability Application interoperability provides terminal access, integrated transaction services, and Web-to-host integration.

Network Management Integration Network management integration provides integration between Windows 2000 network management services and IBM NetView-based management services.

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For detailed information about SNA Server interoperability at each layer of the Windows 2000 interoperability model, see the Microsoft® Windows® 2000 Server Resource Kit Internetworking Guide.

IBM Systems Network Architecture

SNA is a computer networking architecture that was developed by IBM to provide a network structure for IBM mainframe, midrange, and personal computer systems. SNA defines a set of proprietary communication protocols and message formats for the exchange and management of data on IBM host networks.

SNA can be used for the following types of tasks:

Terminal access to mainframe and midrange computer applications.

File transfer of data between computer systems.

Printing of mainframe and midrange data on SNA printers.

Program-to-program communications that allow applications to exchange data over the network.

SNA can be implemented in a networking infrastructure that uses either a hierarchical or peer-to-peer model.

Hierarchical Networking

In the hierarchical SNA networking model, also called subarea networking, geographically disparate users have access to centralized mainframe systems. In a hierarchical network, centralized host-based communication systems (mainframes) must provide the networking services for all users on the network, as illustrated in Figure 26.4.

Figure 26.4 Hierarchical SNA Network

This model uses the SNA protocol for IBM mainframe computers known as 3270. This protocol facilitates conversations between the mainframe and devices such as terminals, printers, and controllers.

Peer-to-Peer Networking

The more recently developed Advanced Peer-to-Peer Networking (APPN) model makes use of LAN and WAN resources and client/server computing. APPN networking enables a form of distributed processing by allowing any computer on the network to use SNA protocols to gain access to resources on any other computer on the network. Computers on an APPN network do not have to depend on mainframe-based communication services.

Advanced Program-to-Program Communication (APPC) is generally used in an AS/400 environment; however, mainframe systems also can use APPC-based networking. APPC is used for a variety of applications, including 5250 access and file transfers. IBM SNA uses the 5250 protocol to facilitate conversations between an AS/400 and devices such as terminals and printers.

A typical APPN network is composed of several different devices, such as IBM host computers or personal computers connected to one or more LANs, as illustrated in Figure 26.5.

Figure 26.5 APPN Network Components

The peer-oriented model can be employed in many different environments. The AS/400 midrange computer, because of its popularity and primary use of APPN, is the host that is most often associated with APPN and the peer-oriented networking model. Mainframe systems are beginning to support APPN as well.

Because of the large installed base of legacy applications that run on IBM mainframe and midrange systems, both of these SNA networking models continue to be widely used in enterprise networks.

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SNA is gradually evolving into more of a peer-to-peer networking structure, where APPN networking is often combined with hierarchical SNA networking. For more detailed information about APPN see the appendix "IBM SNA Interoperability Concepts" in the Windows 2000 Server Resource Kit Internetworking Guide.

Both hierarchical and peer-to-peer SNA networking include several classes of components that support communication between different systems -mainframe, midrange, and personal computer systems. These components, as shown in Table 26.3, are the core components of IBM SNA.

Table 26.3 SNA Core Components