Introduction to Networking for NonStop S-Series Servers

Communications Product Concepts and
Components
Introduction to Networking for HP NonStop S-Series Servers—520670-005
2-7
Processes
Figure 2-3 illustrates how calls are passed from a user process to an IOP and then to
communications lines:
1. The user process obtains access to subsystem resources by issuing Guardian
procedure calls to the file system, identifying the resource and the action to be
performed. (Some user processes that are part of communications subsystems
use the message system directly, but all applications use the file system.)
2. The file system determines the location of the resource and passes the request to
the message system, which in turn passes it to the appropriate IOP.
3. The IOP manipulates the data communications resource on behalf of the user
process, using a ServerNet adapter or SWAN concentrator.
Other Communications Processes
Many communications products include processes other than IOPs. Such processes
typically perform higher-level protocol functions or resource-management functions for
the subsystem. Examples of higher-level communications processes are the NonStop
TCP/IP and the SNAX Extended Facility (SNAX/XF) service manager.
Figure 2-3. User Process Communicates With IOP Through the File System
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