Traffic generation
Encyclopedia
A traffic generation model is a stochastic model of the traffic flow
s or data sources in a communication network, for example a cellular network or a computer network. A packet generation model is a traffic generation model of the packet flows or data sources in a packet-switched network. For example, a web traffic
model is a model of the data that is sent or received by a user's web-browser
. These models are useful during the development of telecommunication technologies, in view to analyse the performance and capacity of various protocols, algorithms and network topologies.
in a testbed
network, using a network traffic generator such as iperf
, bwping
and Mausezahn
. The traffic generator sends dummy packets, often with a unique packet identifier, making it possible to keep track of the packet delivery in the network.
Numerical analysis using network simulation
is often a less expensive approach.
An analytical approach using queueing theory
may be possible for simplified traffic model, but is often too complicated if a realistic traffic model is used.
model. It may be useful in analyzing the maximum throughput for best-effort traffic (without any quality-of-service guarantees). Many traffic generators are greedy sources.
, where the number of incoming packets or calls per time unit follows the Poisson distribution
. The length of each phone call is typically modelled as en exponential distribution
. The number of simultaneously ongoing phone calls follows the Erlang distribution.
. For a more realistic model, a self-similar process
such as the Pareto distribution can be used as a long-tail traffic
model.
is often assumed, i.e. a random sequence of independent binary numbers. In this case a channel model reflects channel impairments such as noise, interference and distortion.
model and the 802.16 model. The 3GPP2
model is much more complex to implement but it is supposed to give more precise results. The 802.16 model is much simpler in realization.
model is described in . This document describes the following types of traffic generators:
The main idea is to partly implement HTTP, FTP and TCP protocol
s. For example, an HTTP traffic generator simulates the download of a web-page, consisting of a number of small objects (like images). A TCP stream (that's why TCP generator is a must in this model) is used to download these objects according to HTTP1.0 or HTTP1.1 specifications. These models take into account the details of these protocols' work. The Voice, WAP and Mobile Network Gaming are modelled in a less complicated way.
and mix them together in order to simulate different kinds of web-traffic. Every interrupted process may be either in ON or OFF state. The packets are generated only in ON state. The lengths of ON and OFF periods, sizes of the packets and intervals between them are defined separately in each model, so these models differ in the way their parameters are defined. These models may be mixed together, for example: 4IPP means a mix of four IPP flows with different parameters.
HTTP and FTP is simulated as 4IPP; VoIP is simulated as IDP, 2IDP, 4IDP; Video is simulated as 2IRP.
Traffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...
s or data sources in a communication network, for example a cellular network or a computer network. A packet generation model is a traffic generation model of the packet flows or data sources in a packet-switched network. For example, a web traffic
Web traffic
Web traffic is the amount of data sent and received by visitors to a web site. It is a large portion of Internet traffic. This is determined by the number of visitors and the number of pages they visit...
model is a model of the data that is sent or received by a user's web-browser
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
. These models are useful during the development of telecommunication technologies, in view to analyse the performance and capacity of various protocols, algorithms and network topologies.
Application
The network performance can be analysed by network traffic measurementNetwork traffic measurement
In computer networks, network traffic measurement is the process of measuring the amount and type of traffic on a particular network. This is especially important with regard to effective bandwidth management.- Tools :...
in a testbed
Testbed
A testbed is a platform for experimentation of large development projects. Testbeds allow for rigorous, transparent, and replicable testing of scientific theories, computational tools, and new technologies.The term is used across many disciplines to describe a development environment that is...
network, using a network traffic generator such as iperf
Iperf
Iperf is a commonly used network testing tool that can create TCP and UDP data streams and measure the throughput of a network that is carrying them. Iperf is a modern tool for network performance measurement written in C++....
, bwping
Bwping
bwping is a tool to measure bandwidth and response times between two hosts using Internet Control Message Protocol echo request/echo reply mechanism. It does not require any special software on the remote host...
and Mausezahn
Mausezahn
' is a fast network traffic generator written in C which allows the user to craft nearly every possible and "impossible" packet. Since version 0.31 Mausezahn is open source in terms of the GPLv2...
. The traffic generator sends dummy packets, often with a unique packet identifier, making it possible to keep track of the packet delivery in the network.
Numerical analysis using network simulation
Network simulation
In communication and computer network research, network simulation is a technique where a program models the behavior of a network either by calculating the interaction between the different network entities using mathematical formulas, or actually capturing and playing back observations from a...
is often a less expensive approach.
An analytical approach using queueing theory
Queueing theory
Queueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...
may be possible for simplified traffic model, but is often too complicated if a realistic traffic model is used.
The greedy source model
A simplified packet data model is the greedy sourceGreedy source
A greedy source is a traffic generator that generates data at the maximum rate possible and at the earliest opportunity possible. Each source always has data to transmit, and is never in idle state due to congestion avoidance or other local host traffic shaping...
model. It may be useful in analyzing the maximum throughput for best-effort traffic (without any quality-of-service guarantees). Many traffic generators are greedy sources.
Poisson traffic model
Another simplified traditional traffic generation model for circuit-switched data as well as packet data, is the Poisson processPoisson process
A Poisson process, named after the French mathematician Siméon-Denis Poisson , is a stochastic process in which events occur continuously and independently of one another...
, where the number of incoming packets or calls per time unit follows the Poisson distribution
Poisson distribution
In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time and/or space if these events occur with a known average rate and independently of the time since...
. The length of each phone call is typically modelled as en exponential distribution
Exponential distribution
In probability theory and statistics, the exponential distribution is a family of continuous probability distributions. It describes the time between events in a Poisson process, i.e...
. The number of simultaneously ongoing phone calls follows the Erlang distribution.
Long-tail traffic models
However, the Poisson traffic model is memoryless, which means that is does not reflect the bursty nature of packet data, also known as the long-range dependencyLong-range dependency
Long-range dependency is a phenomenon that may arise in the analysis of spatial or time series data. It relates to the rate of decay of statistical dependence, with the implication that this decays more slowly than an exponential decay, typically a power-like decay...
. For a more realistic model, a self-similar process
Self-similar process
Self-similar processes are types of stochastic processes that exhibit the phenomenon of self-similarity. A self-similar phenomenon behaves the same when viewed at different degrees of magnification, or different scales on a dimension . Self-similar processes can sometimes be described using...
such as the Pareto distribution can be used as a long-tail traffic
Long-tail traffic
This article covers a range of tools from different disciplines that may be used in the important science of determining the probability of rare events....
model.
Payload data model
The actual content of the payload data is typically not modelled, but replaced by dummy packets. However, if the payload data is to be analyzed on the receiver side, for example regarding bit-error rate, a Bernoulli processBernoulli process
In probability and statistics, a Bernoulli process is a finite or infinite sequence of binary random variables, so it is a discrete-time stochastic process that takes only two values, canonically 0 and 1. The component Bernoulli variables Xi are identical and independent...
is often assumed, i.e. a random sequence of independent binary numbers. In this case a channel model reflects channel impairments such as noise, interference and distortion.
Standardized Internet traffic models
There are at least two standardized traffic generation models for packet-switched wireless networks: the 3GPP23rd Generation Partnership Project 2
The 3rd Generation Partnership Project 2 is a collaboration between telecommunications associations to make a globally applicable third generation mobile phone system specification within the scope of the ITU's IMT-2000 project...
model and the 802.16 model. The 3GPP2
3rd Generation Partnership Project 2
The 3rd Generation Partnership Project 2 is a collaboration between telecommunications associations to make a globally applicable third generation mobile phone system specification within the scope of the ITU's IMT-2000 project...
model is much more complex to implement but it is supposed to give more precise results. The 802.16 model is much simpler in realization.
3GPP2 model
The 3GPP23rd Generation Partnership Project 2
The 3rd Generation Partnership Project 2 is a collaboration between telecommunications associations to make a globally applicable third generation mobile phone system specification within the scope of the ITU's IMT-2000 project...
model is described in . This document describes the following types of traffic generators:
- Downlink:
- HTTP/TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
- FTPFile Transfer ProtocolFile Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
/TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP... - Wireless Application ProtocolWireless Application ProtocolWireless Application Protocol is a technical standard for accessing information over a mobile wireless network.A WAP browser is a web browser for mobile devices such as mobile phones that uses the protocol.Before the introduction of WAP, mobile service providers had limited opportunities to offer...
- near real-time VideoVideoVideo is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
- VoiceVoice messageVoice message refers to a message that could be sent to a destination using voice media. Voice itself could be 'packaged' and sent through the IP backbone so that it reaches its marked 'address'. In a technical sense, the process of sending 'voice packets' is a semi passive way of communication...
- HTTP/TCP
- UplinkUplinkA telecommunications link is generally one of several types of information transmission paths such as those provided by communication satellites to connect two points on earth.-Uplink:...
:- HTTP/TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
- FTPFile Transfer ProtocolFile Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
/TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP... - Wireless Application ProtocolWireless Application ProtocolWireless Application Protocol is a technical standard for accessing information over a mobile wireless network.A WAP browser is a web browser for mobile devices such as mobile phones that uses the protocol.Before the introduction of WAP, mobile service providers had limited opportunities to offer...
- VoiceVoice messageVoice message refers to a message that could be sent to a destination using voice media. Voice itself could be 'packaged' and sent through the IP backbone so that it reaches its marked 'address'. In a technical sense, the process of sending 'voice packets' is a semi passive way of communication...
- Mobile Network Gaming
- HTTP/TCP
The main idea is to partly implement HTTP, FTP and TCP protocol
Communications protocol
A communications protocol is a system of digital message formats and rules for exchanging those messages in or between computing systems and in telecommunications...
s. For example, an HTTP traffic generator simulates the download of a web-page, consisting of a number of small objects (like images). A TCP stream (that's why TCP generator is a must in this model) is used to download these objects according to HTTP1.0 or HTTP1.1 specifications. These models take into account the details of these protocols' work. The Voice, WAP and Mobile Network Gaming are modelled in a less complicated way.
802.16 model
The 802.16 model is much simpler. It was proposed in several 802.16 TG3 contributions. The idea is to define three basic models:- Interrupted Poisson Process (IPP)
- Interrupted Discreet Process (IDP)
- Interrupted Renewal Process (IRP)
- Virtual Private Network (vps)
and mix them together in order to simulate different kinds of web-traffic. Every interrupted process may be either in ON or OFF state. The packets are generated only in ON state. The lengths of ON and OFF periods, sizes of the packets and intervals between them are defined separately in each model, so these models differ in the way their parameters are defined. These models may be mixed together, for example: 4IPP means a mix of four IPP flows with different parameters.
HTTP and FTP is simulated as 4IPP; VoIP is simulated as IDP, 2IDP, 4IDP; Video is simulated as 2IRP.
See also
- Channel model
- Measuring network throughputMeasuring network throughputThroughput of a network can be measured using various tools available on different platforms. This page explains the theory behind what these tools set out to measure and the issues regarding these measurements.-Reasons for measuring throughput in networks:...
- Mobility modelMobility modelMobility models represent the movement of mobile users, and how their location, velocity and acceleration change over time. Such models are frequently used for simulation purposes when new communication or navigation techniques are investigated...
- Network emulationNetwork emulationNetwork emulation is a technique where the properties of an existing, planned and/or non-ideal network are simulated in order to assess performance, predict the impact of change, or otherwise optimize technology decision-making.-Methods of emulation:...
- Network traffic simulationNetwork traffic simulationNetwork traffic simulation is a process used in telecommunications engineering to measure the efficiency of a communications network.-Overview:...
- Network simulatorNetwork simulatorA network simulator is a piece of software or hardware that predicts the behavior of a network, without an actual network being present.-Uses of network simulators:Network simulators serve a variety of needs...
- Packet erasure channelPacket erasure channelThe packet erasure channel is a communication channel model where sequential packets are either received or lost . This channel model is closely related to the binary erasure channel....
- Radio propagation modelRadio propagation modelA radio propagation model, also known as the Radio Wave Propagation Model or the Radio Frequency Propagation Model, is an empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions...
- Queueing theoryQueueing theoryQueueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...
- Packet generatorPacket generatorA packet generator or packet builder is a type of software that generates random packets or allows the user to construct detailed custom packets. Packet generators utilize raw sockets....
- Packet snifferPacket snifferA packet analyzer is a computer program or a piece of computer hardware that can intercept and log traffic passing over a digital network or part of a network...