
361Data Link and Physical Layers
However, not all of the TR features have been implemented in OPNET because
the model was primarily designed for simulation and performance estimation only.
Specically, OPNET does not explicitly model ring initialization and recovery pro-
cesses. The interface between the network management (NMT) and MAC is not
implemented as well. There is no support for error detection and error reporting
to NMT. To improve simulation performance, the TR model implements the token
acceleration feature, which blocks token passing during the time periods when there
is no data transmission. When data transmission restarts, the token ...