SNAX/APN Application Programming Manual

The SNALU Interface

SNAX/APN Application Programming Manual—420111-001

4-2

SNALU Message Format

To successfully implement an application using the SNALU interface, the programmer

must understand the conventions and rules associated with SNA LU-LU sessions.

SNALU Message Format

Figure 4-2 shows a SNALU application exchanging control information and data with

the SNALU interface using message units consisting of a 9-byte SNAX header and an

SNA request/response unit (RU). The SNAX header contains the SNA request/response

header (RH). The RH and RU are combined into a basic information unit (BIU). A link

header and trailer are added to the BIU to make a basic link unit (BLU).

For information on SNA message formats, see either the IBM Systems Network

Architecture: Technical Overview or the IBM Systems Network Architecture: Network

Product Formats manual.

Figure 4-1. SNA Layers Implemented by the SNALU Interface

Note. It is not within the scope of this manual to explain the various SNA conventions and

rules. Rather, the pages and sections that follow explore ways in which an application

implements SNA standards within a Tandem SNAX/APN environment.

401CDT .CDD

SNA Layers

Presentation Services (PS)

Data Flow Control (DFC)

User

Application

SNALU

Interface

Transmission Control (TC)

Path Control (PC)

Data Link Control (DLC)

Physical Control

Controller