Installation guide

DC 900-1564A 83
Chapter
6
Programming
Considerations
This chapter describes recommended strategies for programming applications to access
SLC network connections using the SLC protocol software.
6.1 SLC Envelope Service versus SLC Protocol Service
The SLC envelope service gives the application direct control over most ICP link oper-
ations, but requires the application to take complete responsibility for the results. The
SLC protocol service is provided to make the SLC protocol software easier to use, but
reduces application control over and visibility into ICP link operations.
When the SLC protocol service is used, the message blocking operations on the ICP
prevent the forwarding of a message to the client until all message blocks have been
received. Therefore, network transit centers cannot forward a message until all message
blocks have been received by the ICP and the message sent to the application. In a net-
work that has several transit centers between entry and exit centers, accumulated mes-
sage transit delay could become noticeable. At the cost of increased application
complexity, SLC envelope service can used to reduce such delays by allowing the appli-
cation to forward message blocks immediately when appropriate.
6.2 Application Simplification Using Access Modes
The architecture of an application has a significant influence on design complexity, and
hence on implementation and maintenance costs over the life-time of the software
project. By dividing a large problem domain into smaller well-defined tasks, the soft-
ware developer can usually reduce the effort needed to achieve a successful solution.