OSI/AS Configuration and Management Manual

OSI/AS Subsystem Description
OSI/AS Configuration and Management Manual—424119-001
7-2
OSI Layer Information Flow
OSI Layer Information Flow
In the OSI Reference Model, requests (in the general sense) are sent from the top layer
down, until the request is sent as data over a physical communications medium to a
remote peer. Responses (in the general sense) are received at the bottom, physical layer
and forwarded up to the local user. A generalized view of the data flow is shown in
Figure 7-1
.
Since the Compaq OSI processes do not map one-to-one onto the OSI Reference Model
layers, this subsystem description is divided into five major subsections:
•
The application program interface (API)
•
The TAPS process (Layer 7 ACSE, Layer 6, and Layer 5)
•
The TSP process (Layer 4 and OSI IP in Layer 3)
•
The NSP process (Layer 3 for subsystems using X25AM)
•
The NSP process (Layer 2 for subsystems using TLAM for D-series releases and
PAM for G06 and above releases)
Figure 7-1. Information Flow in OSI Reference Model
071CDT .CDD
Request and
Response
Primitives
Confirm and
Indication
Primitives
I/O Completions
(Errors & Error 0)
Layer n+1
Layer n
Layer n-1
(Exceptions)
Downward
Information
Flow
Upward
Information
Flow
(Exceptions)
(Exceptions)