Expand Configuration and Management Manual (G06.24+)

Subsystem Description
Expand Configuration and Management Manual—523347-008
18-4
Expand Line-Handler Processes
Although the satellite-connect line-handler process is provided for use with satellite
connections, it can also be used to manage terrestrial lines. This type of configuration
can enhance the reliability of terrestrial lines that carry small messages at high speeds.
Expand-Over-NAM Line-Handler Processes
Expand-over-NAM line-handler processes use the NETNAM protocol to access the
network access method (NAM) interface provided by an X25AM or a SNAX/APN
line-handler process.
Expand-Over-NAM With X25AM
The X25AM subsystem provides access to X.25 packet-switched data networks
(PSDNs). The X25AM subsystem consists of a layered set of protocols that
corresponds to the lower three layers of the International Standards Organization (ISO)
Open Systems Interconnection (OSI) Reference Model.
Each X25AM line-handler process controls a single data communications line and
supports both permanent virtual circuits (PVCs) and switched virtual circuits (SVCs).
Up to 254 circuits can be configured for each X25AM line-handler process. One
X25AM line-handler process can service multiple Expand-over-NAM line-handler
processes.
When it interfaces to an X25AM line-handler process, the Expand-over-X.25 line-
handler process sends data over one virtual circuit running in the X25AM line-handler
process; the X25AM line-handler process manages the physical communications line.
The Expand-over-X.25 line-handler process is also responsible for
•
Establishing the connection between itself and the X25AM line-handler process
•
Reestablishing communications with the remote server when an unavailable
network service becomes available again
•
Error recovery
Expand-Over-NAM With SNAX/APN
The SNAX/APN subsystem provides access to IBM Systems Network Architecture
(SNA) networks. The SNA network can be a traditional network of host mainframes
and front end processors, an advanced peer-to-peer network of IBM AS400 systems,
or a mix of these two types of networks. SNAX access methods support a wide range
of physical connections to IBM systems and networks, including
•
Synchronous Data Link Control (SDLC) connections, using RS-232, RS-449, X.21,
and V.35 electrical interfaces
•
X.25 packet-switched networks
•
Token Ring networks
Note. For more information about the Expand-to-NAM interface, refer to Expand-to-NAM
Interface on page 18-49.