31.5 Applications objects

An application object may be of two types, a traffic generator or a simulated application. Traffic generator objects generate traffic and can be of four types, namely, exponential, pareto, CBR and traffic trace.

Application/Traffic/Exponential objects

Exponential traffic objects generate On/Off traffic. During "on" periods, packets are generated at a constant burst rate. During "off" periods, no traffic is generated. Burst times and idle times are taken from exponential distributions. Configuration parameters are:

PacketSize_

constant size of packets generated.

burst_time_

average on time for generator.

idle_time_

average off time for generator.

rate_

sending rate during on time.

Application/Traffic/Pareto

Application/Traffic/Pareto objects generate On/Off traffic with burst times and idle times taken from pareto distributions. Configuration parameters are:

PacketSize_

constant size of packets generated.

burst_time_

average on time for generator.

idle_time_

average off time for generator.

rate_

sending rate during on time.

shape_

the shape parameter used by pareto distribution.

Application/Traffic/CBR

CBR objects generate packets at a constant bit rate.

$cbr start
Causes the source to start generating packets.

$cbr stop
Causes the source to stop generating packets.

Configuration parameters are:

PacketSize_

constant size of packets generated.

rate_

sending rate.

interval_

(optional) interval between packets.

random_

whether or not to introduce random noise in the scheduled departure times. defualt is off.

maxpkts_

maximum number of packets to send.

Application/Traffic/Trace

Application/Traffic/Trace objects are used to generate traffic from a trace file. $trace attach-tracefile tfile
Attach the Tracefile object tfile to this trace. The Tracefile object specifies the trace file from which the traffic data is to be read. Multiple Application/Traffic/Trace objects can be attached to the same Tracefile object. A random starting place within the Tracefile is chosen for each Application/Traffic/Trace object.

There are no configuration parameters for this object.

A simulated application object can be of two types, Telnet and FTP.

Application/Telnet

TELNET objects produce individual packets with inter-arrival times as follows. If interval_ is non-zero, then inter-arrival times are chosen from an exponential distribution with average interval_. If interval_ is zero, then inter-arrival times are chosen using the "tcplib" telnet distribution.

$telnet start
Causes the Application/Telnet object to start producing packets.

$telnet stop
Causes the Application/Telnet object to stop producing packets.

$telnet attach agent
Attaches a Telnet object to agent.

Configuration Parameters are:

interval_

The average inter-arrival time in seconds for packets generated by the Telnet object.

Application FTP

FTP objects produce bulk data for a TCP object to send.

$ftp start
Causes the source to produce maxpkts_ packets.

$ftp produce n
Causes the FTP object to produce n packets instantaneously.

$ftp stop
Causes the attached TCP object to stop sending data.

$ftp attach agent
Attaches a Application/FTP object to agent.

$ftp producemore count
Causes the Application/FTP object to produce count more packets.

Configuration Parameters are:

maxpkts

The maximum number of packets generated by the source.

TRACEFILE OBJECTS Tracefile objects are used to specify the trace file that is to be used for generating traffic (see Application/Traffic/Trace objects described earlier in this section). $tracefile is an instance of the Tracefile Object. $tracefile filename trace-input
Set the filename from which the traffic trace data is to be read to trace-input.

There are no configuration parameters for this object. A trace file consists of any number of fixed length records. Each record consists of 2 32 bit fields. The first indicates the interval until the next packet is generated in microseconds. The second indicates the length of the next packet in bytes.