33.5 Commands at a glance

Following is a list of commands used to simulate dynamic scenarios in ns:

$ns_ rtmodel model model-params args
This command defines the dynamic model (currently implemented models are: Deterministic, Exponential, Manual or Trace) to be applied to nodes and links in the topology. The first two arguments consists of the rtmodel and the parameter to configure the model. <args> stands for different type of arguments expected with different dynamic model types. This returns a handle to a model object corresponding to the specified model.

• In the Deterministic model <model-params> is <start-time>, <up-interval>, <down-interval>, <finish-time>. Starting from start-time the link is made up for up-interval and down for down-interval till finish-time is reached. The default values for start-time, up-interval, downinterval are 0.5s, 2.0s, 1.0s respectively. finishtime defaults to the end of the simulation. The start-time defaults to 0.5s in order to let the routing protocol computation quiesce.

• If the Exponential model is used model-params is of the form <up-interval>, <down-interval> where the link up-time is an exponential distribution around the mean upinterval and the link down-time is an exponential distribution around the mean down-interval. Default values for up-interval and down-interval are 10s and 1s respectively.

• If the Manual distribution is used model-params is <at> <op> where at specifies the time at which the operation op should occur. op is one of up, down. The Manual distribution could be specified alternately using the rtmodel-at method described later in the section.

• If Trace is specified as the model the link/node dynamics is read from a Tracefile. The model-params argument would in this case be the file-handle of the Tracefile that has the dynamics information. The tracefile format is identical to the trace output generated by the trace-dynamics link method (see TRACE AND MONITORING METHODS SECTION).

$ns_ rtmodel-delete model
This command takes the handle of the routemodel <model> as an argument, removes it from the list of rtmodels maintained by simulator and deletes the model.

$ns_ rtmodel-at at op args
This command is a special interface to the Manual model of network dynamics. It takes the time <at>, type of operation <op> and node or link on which to apply the operation <args> as the arguments. At time <at>, the operation <op> which maybe up or down is applied to a node or link.

$rtmodel trace ns f optional:op
This enables tracing of dynamics effected by this model in the links. <ns> is an instance of the simulator, <f> the output file to write the traces to and <op> is an optional argument that may be used to define a type of operation (like nam). This is a wrapper for the class Link procedure trace-dynamics.

$link trace-dynamics ns f optional:op
This is a class link instance procedure that is used to setup tracing of dynamics in that particular link. The arguments are same as that of class rtModel's procedure trace described above.

$link dynamic
This command inserts a DynamicLink object at the head of the queue and signals to all connectors in the link that the link is now dynamic.

Internal procedures:

$ns_ rtmodel-configure
This is an internal procedure that configures all dynamic models that are present in the list of models maintained by the simulator.