User guide

14 DC 900-1303C

Freeway Client-Server Interface Control Document

The TSI and DLI provide a consistent, high-level, common interface across multiple

hosts, operating systems, and transport services. Note the following similarities and dif-

ferences between the DLI and TSI:

• The DLI provides session-oriented data services to your client application with a

subroutine library. This library contains functions that permit your application to

access, conﬁgure, establish and terminate sessions, and transfer data across multi-

ple data link protocols. The DLI uses the TSI for its transport services.

• The TSI provides connection-oriented data services to your client application with

a subroutine library. This library contains functions that permit your application

to access, conﬁgure, establish and terminate connections, and exchange data with

a TSI peer application (normally the Freeway server’s TSI).

1.1 Freeway Overview

Simpact’s Freeway communications servers enable client systems on a local-area net-

work (LAN) to access specialized wide-area networks (WANs). The Freeway server is

user programmable and communicates in real time. It provides multiple data links and

a variety of network services to LAN-based clients in ﬁnancial, defense, telecommuni-

cations, and process-control applications. Figure 1–1 shows a Freeway conﬁguration.

Note that all of the clients shown in the ﬁgure use the DLI, which is the usual case. This

document, however, focuses on clients that do not use the DLI. These types of clients

are shown later in Figure 1–2 on page 18.

To maintain high data throughput, Freeway uses a multi-processor architecture to sup-

port the LAN and WAN services. The LAN interface is managed by a single-board com-

puter, called the server processor. It uses the commercially available VxWorks operating

system to provide a full-featured base for the LAN interface and layered services needed

by Freeway.