Installation guide

84 DC 900-1564A
Synchronous Link Control (SLC) Programmer’s Guide
Since the SLC protocol software supports multiple access modes simultaneously, the
design of an application can be simplified by dividing its responsibilities among several
independent processes. For example, a process under operator control could use
SLC_CONTROL_MODE access to manage link configuration and operations. A second pro-
cess could use
SLC_READER_MODE access to gather and record statistics automatically.
Finally, a third process could use
SLC_MASTER_MODE access to handle all SLC message
traffic for the SLC network connection. Together, the three processes implement an
application that manages one SLC network connection and all of its associated physical
channels.
6.3 Layered Applications
A layered application solves multiple problems by coordinating independent solutions
to each. For example, a layered application might handle Data Link Operation and Net-
work Routing by coordinating the interactions between other applications that handle
these tasks independently.
When more than one SLC network connection is needed, each SLC network connection
and its associated SLC channels could be managed independently by an application
such as the three-process application described in Section 6.2 Using interprocess com-
munications on the client computer, a layered application can coordinate traffic
between low-level SLC network connections and high-level SLC network connections
to implement entry/exit center operations. By adding another application to support
network routing, a layered application could also implement transit center operations.
6.4 Data Content Dependencies
The SLC protocol service provided is sensitive to the content of selected portions of the
message header. The client application is responsible for conforming to the message
header format constraints for the configured level of network service. Each section that
follows identifies specific message header requirements for each level of SLC network
service provided. For more complete information on SLC protocol message formats,