Introduction to Networking for NonStop S-Series Servers

Communications Product Concepts and
Components
Introduction to Networking for HP NonStop S-Series Servers—520670-005
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Levels of Protocol Support
Higher-level communications processes usually run as fault-tolerant process pairs, and
most are accessible to applications through the file system, as in the case of IOPs.
Some, however, have a different style of interface, as described in Using Standards-
Based Interfaces on page 3-18.
Management Processes
A management process provides an interface through which applications, including
subsystem command interpreters, can control and monitor system resources. (A
command interpreter is a command-oriented operator interface for controlling and
monitoring one or more subsystems.)
Communications products share a management process called the Subsystem
Control Point (SCP). SCP provides a management interface through which
applications can control any number of communications subsystems. The Subsystem
Control Facility (SCF)—the utility that operators use to control communications
subsystems—uses SCP. Management processes and interfaces are described in detail
in Section 4, Managing Communications Subsystems.
Levels of Protocol Support
Communications subsystems differ in the levels of protocol support they provide. Many
of them provide full protocol support, often for a very specific kind of device. For
example, AM3270 supports communications with IBM 3270 terminals that use byte-
synchronous protocols. HP provides subsystems that implement a large number of
standard and popular protocols.
Other subsystems implement basic features common to a set of related protocols,
relying on the application to implement other features as required by the target device.
Such subsystems allow you a greater degree of flexibility and control over specialized
protocols than do the full protocol implementations; however, they require your
application to do more work, and they require that you be much more familiar with the
communications protocol. In general, you use such subsystems only if you need to
connect a device for which HP does not offer a full protocol implementation. Examples
of subsystems in this group are EnvoyACP/XF and CP6100, described in Section 6,
Device-Specific Connections.
Many subsystems offer interfaces at several levels of function and complexity. For
example, SNAX/XF provides a high-level interface for 3270 devices and a low-level
interface for custom device support, in addition to other interfaces.