SNAP APPN provides a rich set of external interfaces for use during:
- OEM system integration (the N-BASE Interface)
- addition of different link connectivities (the DLC interface)
- application program development (APPC, CPI-C, MS, NOF, FM and LUA APIs).
The relationship between the different interfaces and the SNAP APPN components is shown in the diagram below.
Node Operator Facility
The Node Operator Facility (NOF) API is the primary configuration and management interface for SNAP APPN.
The NOF allows a node operator to control the operation of a SNAP APPN node, including:
- definition and deletion of resources (such as links or LUs)
- activation and deactivation of sessions and links
- querying the node for database, status and statistics information
- retrieval and safe-store of node information (such as the topology database)
- CNOS (Change Number of Sessions).
The information presented at the NOF interface is based on:
- signals described in IBM's SNA APPN Architecture Reference
- verbs and formats described in IBM Communications Manager/2 System Management Programming Reference (SC31-6173-02)
- the managed objects defined in the IBM 6611 APPN MIB and returned in response to SNMP GET requests.
APPC
The SNAP APPN APPC API is modelled on the IBM Extended Services APPC interface, as documented in IBM Communications Manager/2 APPC Programming Reference (SC31-6160-02).
CPI-C
The SNAP APPN CPI-C component provides a CPI-C Version 1.2 interface as defined in IBM's Common Programming Interface Communications Specification. The CPI-C component communicates with the SNAP APPN node by issuing verbs over the APPC API and the NOF API.
Management Services
The SNAP APPN Management Services (MS) API provides support for the three generations of management services defined by SNA.
- NMVT level
- Migration level
- Multiple Domain Support (MDS) level
The interface is modelled on the IBM Communication Manager/2 MS interface, as documented in IBM Communications Manager/2 System Management Programming Reference (SC31-6173-02).
LUs 0, 1, 2 and 3
The Function Management API (FM API) provides applications with direct access to the SNA data flows generated by LU Types 0, 1, 2 and 3. It also provides applications with information about SNA control flows by means of status signals, while shielding them from the full complexities of SNA protocol handling. It is particularly suited to the requirements of applications emulating 3270-type controllers.
SNAP APPN also provides a Transmission Control API (TC API), which allows conventional LU applications to access SNA data flows at the Transmission Control layer of the SNAP APPN conventional LU protocol stack. The interface can be used by applications emulating an SNA primary function. The SNAP APPN PU Concentration component is an example of such an application.
Conventional LU Applications
The SNAP APPN Conventional LU Application (LUA) Request-Unit Interface (RUI) closely models the RUI described in IBM's Conventional LU Application Programming Reference.
This interface allows applications to communicate with host applications that support LU Types 0, 1, 2 and 3.
Data Link Control
The SNAP APPN DLC Interface provides a standard, generic interface for use by one or more data link drivers. This interface is closely modelled on that described in the IBM Systems Network Architecture: APPN Architecture Reference (SC30-3422-03).