Structure of SNA IMF

Figure 1-2 SNA IMF Components and the IBM Host

SNA IMF Product

SNA IMF is a software product that implements the upper three layers of SNA: the Data Flow Control, Presentation Services, and Application layers. In other documents you may see SNA IMF referred to as an SNA Service. An SNA Service is an HP data communications software product, like SNA IMF, SNA NRJE, or LU 6.2 API, which runs on top of the SNA link product.

SNA IMF stores data in the form of an internal screen image. The internal screen image contains the location and attributes of all the fields on the screen. It also contains any information that has been entered into the fields. Whenever an application or end user on the HP 3000 enters data to be transmitted to the IBM host, or whenever the IBM host sends data to the HP 3000, SNA IMF modifies the internal screen image.

SNA Link Products

Hewlett-Packard offers three SNA link products: SNA Link/V, SNA/SDLC Link/XL, and SNA/X.25 Link/XL. SNA link products are bundled software and hardware products that permit a logical and physical connection from an HP 3000 into an SNA network. An SNA link product has two parts:

SNA Link/V has a third component: Node Management Services (software). On MPE XL, Node Management Services is part of the Fundamental Operating System (FOS) and is not bundled with SNA/SDLC Link/XL or SNA/X.25 Link/XL. The FOS is a collection of MPE programs, utilities, and subsystems bundled together for one price and supplied on a Master Installation Tape (MIT).

	NOTE: In this manual, the term SNA link product is used when the information being given is true for all three SNA link products. The terms SNA Link/V, SNA/SDLC Link/XL, and SNA/X.25 Link/XL are used when a distinction between the SNA link products is necessary.

SNA Transport emulates an SNA Type 2 node. Through the Path Control and Transmission Control layers, it coordinates the communication sessions within the SNA network.

The hardware portion of the SNA link product is the INP (Intelligent Network Processor) card on MPE V, or the PSI (Programmable Serial Interface) card on MPE XL. The INP or PSI card implements the Physical Control and Data Link Control layers of SNA. It uses the SDLC protocol to control transmission over the communications line.

Node Management Services (NMS) is used by all the SNA Services (like SNA IMF and SNA NRJE) installed on the HP 3000. NMS handles configuration, link and node level startup and shutdown, logging, tracing, and diagnostic functions.

In both Pass Thru mode and programmatic mode, SNA IMF intrinsics call SNA link intrinsics whenever data is sent to or received from the host. SNA IMF and the SNA link product together implement all architectural layers of SNA.

A separate INP or PSI card is required for each communications line from the HP 3000 to an IBM host. With multiple INP or PSI cards, you can connect the HP 3000 to multiple IBM hosts, or you can run multiple communications lines to a single IBM host.

The same INP or PSI can be used by multiple SNA Services.

The PSI card can also be used to run Network Services (NS). The same PSI card can be used for both NS and SNA communications, but NS and SNA cannot be run concurrently on the same PSI card.

	NOTE: The SNA link products are not supported as separate products independent of the SNA Services. Therefore, you must order and use SNA link products only with SNA Services.