Download Model-Driven Development and Simulation of - Hu

3 Related Work
SDL Module
SDL System
SDL Environment Interface
SDL Kernel
named
pipe
ns-2 Simulator
Figure 3.9: ns+SDL components [86].
• Dispatching SDL transitions: the SDL Kernel triggers the transition scheduler and
dispatches scheduled transitions.
• Handling of messages between different SDL systems: message exchange between
different SDL systems is controlled by ns-2. The SDL Kernel provides encoding
and decoding functions for the messages.
• Handling of control messages: control messages are exchanged between ns-2 and
the SDL kernel to query the system time or to return control to ns-2 after all
pending transitions have been executed.
• Time synchronization between ns-2 and the SDL system: to support a global
time, the time of ns-2 is synchronized with the time of all SDL systems under
simulation.
Simulation runs can be made reproducible if concurrent behavior is avoided. This is
achieved by two measures. First, the tight synchronization between ns-2 and the SDL
kernel ensures that only one SDL system is executed at any point in time. Second, the
ns-2 scheduler ensures that transitions that are fireable at the same simulation instant
are executed sequentially.
SDL Environment Interface To implement open SDL systems (systems interacting
with their environment), an environment interface satisfying the semantics of the SDL
signaling mechanism is needed. The SDL Environment Interface allows SDL signals to
be exchanged between open SDL systems via a network configured from ns-2 components. It can be configured to interface either to ns-2 or to physical hardware. This has
the advantage that code for simulation and production purposes can be automatically
generated from the same SDL specification with the same code generator.
34