Emulated Traffic types and scripts

NetSpec can produce many types of traffic flows the statistical properties of each according to user specifications. Thus NetSpec can generate different emulated types of traffic. In this section, we will present and explain scripts with all the emulated traffic supported by NetSpec. It is very important though, to read the paper below describing the traffic characterization of the models and its conjunction with NetSpec via the appropriate parameters.

All visitors are encouraged to read the following paper:


Emulated Traffic Models



 
 

FTP Traffic

Compared to TELNET traffic, FTP traffic doesn't have the duration and item interarrival time setups. This is because the duration of each FTP session is dependent upon the network capacity, such as link rate. The faster the link rate, the more items the network can transfer in the same amount of time.

The following three parameters are needed to characterize FTP traffic:

All of the above parameters have been implemented in Netspec to deliver FTP traffic. [Read the corresponding paper for more information]
 
 

Example Script

The bold words in red in the following example scripts denote key words. Bold blue letters denote key words again, but those can be changed by another NetSpec option. Table 1 explains all the key words used in the following scripts.
 
 

cluster {

test galaga {

type = burstq (blocksize=ftpItemSize(min=8) ,
                        repeats=ftpNOfItems(min=1),
                        period=ftpSessionInterarrival(lambda=0.00001, min=1000),
                        buffer=262144,
                      duration= 20);
protocol = tcp (window= 262144);
own = galaga.atm:45000;
peer = hopper.atm:45001;

}

test hopper {

type = sink (blocksize=262144, duration=10);
protocol = tcp (window=262144)
own = hopper.atm:45000;
peer = galaga.atm:45001;

}

}
 

All the key words are explained in Table 1. ftpItemSize and ftpNOfItems are the fixed models. In this script, the interarrival time of ftp sessions has a mean of 1/0.00001 = 100 milliseconds. The duration of the whole test is about 20seconds.



 
 

VBR Traffic

Broadband integrated networks are expected to carry substantial portions of the video services. Accurate source modeling of VBR services is essential to develop a network that achieves pre-defined quality of services and cost-efficiency.

Generally, there are two types of video traffic : (1) Teleconference video stream, and (2) MPEG video stream. Each of these video streams have difference characteristics based on its nature of object motions and use of compression algorithms. NetSpec is capable of producing both video traffic streams as specified.
 
 

Video Teleconference

Two basic parameters characterize Video teleconference traffic.
  1. Frame Interarrival Time(seconds); [1/frame rate].

  2. It's a constant value: In NTSC systems is 33 ms (30 frames/sec). In PAL systems is 40 ms (25 frames/sec).If using 25 to 30 frames/sec rates, it will produce high quality video stream that requires a large portion of network bandwidth. Typical conference calls with high compression technique that produce acceptable quality often only require 5 to 15 frames/sec rates. Generally, 12 frame/sec (83 milliseconds/frame) is commonly used.
  3. Number of Cells per frame; Modeled as a gamma distribution.
Both of the above parameters have been implemented in Netspec to deliver Video Teleconference traffic. [Read the corresponding paper for more information]
 
 

Example Script

The bold words in red in the following example scripts denote key words. Bold blue letters denote key words again, but those can be changed by another NetSpec option. Table 1 explains all the key words used in the following scripts.
 
 

cluster {

test galaga {

type = burstq (blocksize=videoTeleConferenceFrameSize(scale=42.50, shape=3),
                        period=83000,
                        duration= 6);
protocol = tcp (window= 262144);
own = galaga.atm:45000;
peer = hopper.atm:45000;

}

test hopper {

type = sink (buffer=131072, duration=900);
protocol = tcp (window=262144, rcvlowat=8);
own = hopper.atm:45000;
peer = galaga.atm:45000;

}

}
 

All the key words are explained in Table 1. The constant period is 83000 microseconds (83 ms); approximately 12 frames/sec [1/(83000*10^(-6))].
 
 

MPEG (Motion Picture Experts Group) Video stream

The basic parameters needed to characterize MPEG Video traffic are:
  1. Frame Interarrival Time (seconds); For high quality motion pictures, a high frame rate is often required. The typical constant interframe period is at least 33 ms (30 frames/sec) for NTSC standard systems and 40 ms (25 frames/sec) for PAL standard systems.
  2. Scene length; A video stream consists of several segments such that the sizes of I frames in each segment are close in value. The length of a scene (in I frames) is modeled as a geometric distribution.
  3. Number of Cell per frame; There are three types of coded frames : Intra-coded (I); Prediction (P), and Bidirectional (B) MPEG frames. The sizes of all three coded frames are modeled as log-normal distributions with different mean and standard deviation.
Both of the above parameters have been implemented in Netspec to deliver MPEG Video traffic. [Read the corresponding paper for more information]
 
 

Example Script

The bold words in red in the following example scripts denote key words. Bold blue letters denote key words again, but those can be changed by another NetSpec option. Table 1 explains all the key words used in the following scripts.
 
 

cluster {

test galaga {

type = burstq (blocksize=videoMPEGFrameSize(sceneLengthMean=10.5,
                                                                   Imean=5.1968, IstdDeviation=0.2016,
                                                                     Pmean=3.7380, PstdDeviation=0.5961,
                                                                     Bmean=2.8687, BstdDeviation=0.2675),
                        period=33000,
                        duration= 10);
protocol = tcp (window= 262144);
own = galaga.atm:45000;
peer = hopper.atm:45000;

}

test hopper {

type = sink (blocksize=131072, duration=10);
protocol = tcp (window=262144, rcvlowat=8);
own = hopper.atm:45000;
peer = galaga.atm:45000;

}

}
 

All the key words are explained in Table 1. The interarrival time of frames is 33000 microseconds; approximately 30 frames/sec.



 
 

CBR Traffic

The standard way for digitizing the voice signal is to bandlimit the signal to a band from 100Hz to 3400Hz and then to sample that at 8kHz. Each sample is given 8 bits. This produces the standard bit rate of 64kb/s for voice.

The following parameters are needed to characterize Voice traffic.

  1. Voice Session Interarrival Time (seconds); The connection arrivals can be modeled by a Poisson process with fix hourly rates within one-hour periods.
  2. Voice Session Duration (holding time); Modeled as an exponential distribution.
  3. CBR Voice Packet Interarrival Time; This type of traffic can be simply described by its peak rate. For a telephone speech, 64kbits/sec is a standard CBR rate. The shorter the packet interarrival time, the better quality of voice. An ATM cell has a 48-byte load. Based on common voice 8000 Hz sampling rate, it takes 6 milliseconds to transmit a ATM cell.
  4. Voice Packet Size; The packet size is determined by the data transfer rate. For a 64kbits/sec telephone voice stream, the packet size is 144 bytes with a 18 msec interarrival rate.
All of the above parameters have been implemented in Netspec to deliver CBR (Voice) traffic. [Read the corresponding paper for more information]
 
 

Example Script

The bold words in red in the following example scripts denote key words. Bold blue letters denote key words again, but those can be changed by another NetSpec option. Table 1 explains all the key words used in the following scripts.
 
 

cluster {

test galaga {

type =  burstq (blocksize=144,
            period=18000,
            duration=voiceSessionDuration(lambda=0.004167));
protocol = tcp (window= 65536);
own = galaga.atm:45000;
peer = hopper.atm:45000;
}

test hopper {

type = sink (blocksize=144, duration=180);
protocol = tcp (window=65536, rcvlowat=8);
own = hopper.atm:45000;
peer = galaga.atm:45000;

}

}
 

All the key words are explained in Table 1. The blocksize is 144 bytes and the constant period is 18 miliseconds. As a result, the rate is 144*8 bits/18 miliseconds = 64 kbits/sec. The mean of the voice session is about 1/0.004167 seconds = 3 minutes.



 
 

World Wide Web Traffic

The traffic of World Wide Web (WWW) has increased exponentially due to the explosion of the information superhighway and includes a significant portion of traffic that is generated by the WWW browsers.

The parameters needed to characterize WWW traffic are:

  1. Mean Inter-Request Time; Modeled as a Poisson process with a fixed rate.
  2. Document Transfer Size; Modeled as a Pareto Distribution.
The above parameters have been implemented in Netspec to deliver WWW traffic. [Read the corresponding paper for more information]
 
 

Example Script

The bold words in red in the following example scripts denote key words. Bold blue letters denote key words again, but those can be changed by another NetSpec option. Table 1 explains all the key words used in the following scripts.
 
 

cluster {

test galaga {

type = burstq (blocksize=WWWItemSize(min=8, max=10485760, shape=0.40),
                        period=WWWRequestInterarrival(lambda=0.000002, min=1000),
                        buffer=262144,
                      duration= 1200);
protocol = tcp (window= 262144);
own = galaga.atm:45000;
peer = hopper.atm:45000;

}

test hopper {

type = sink (buffer=262144, duration=1200);
protocol = tcp (window=262144, rcvlowat=8);
own = hopper.atm:45000;
peer = galaga.atm:45000;

}

}
 

All the key words are explained in Table 1. The Request Interarrival Time is set with a lambda = 0.000002. This corresponds to a mean of 1/0.000002 = 500 miliseconds.


|Table 1| |TOP|Introduction to NetSpec| User NetSpec scripts|



This page was last updated on 28th July 1999