Teletraffic engineering
Encyclopedia
Telecommunications traffic engineering, teletraffic engineering, or traffic engineering is the application of traffic engineering theory to telecommunications. Teletraffic engineers use their basic knowledge of statistics
including queuing theory, the nature of traffic, their practical models, their measurements and simulations
to make predictions and to plan telecommunication networks such as a telephone network
or the Internet
. These tools and basic knowledge help provide reliable service at lower cost.
The field was created by the work of A. K. Erlang
for circuit-switched
networks but is applicable to packet-switched
networks. The most notable difference between these sub-fields is that packet-switched data traffic is self-similar. This is a consequence of the calls being between computers, and not people.
The crucial observation in traffic engineering is that in large systems the law of large numbers
can be used to make the aggregate properties of a system over a long period of time much more predictable than the behaviour of individual parts of the system.
of traffic in a public switched telephone network
(PSTN) allows network operators to determine and maintain the quality of service
(QoS) and in particular the grade of service
(GoS) that they promise their subscribers. The performance of a network
depends on whether all origin-destination pairs are receiving a satisfactory service.
Networks are handled as:
Congestion is defined as the situation when exchanges or circuit groups are inundated with calls and are unable to serve all the subscribers. Special attention must be given to ensure that such high loss situations do not arise. To help determine the probability of congestion occurring, operators should use the Erlang formulas or the Engset calculation.
Exchanges in the PSTN make use of trunking
concepts to help minimize the cost of the equipment to the operator. Modern switches generally have full availability and do not make use of grading concepts.
Overflow systems make use of alternative routing circuit groups or paths to transfer excess traffic and thereby reduce the possibility of congestion.
A very important component in PSTNs is the SS7 network
used to route signalling traffic. As a supporting network, it carries all the signalling messages necessary to set up, break down or provide extra services. The signalling enables the PSTN control the manner in which traffic is routed from one location to another..
Transmission and switching of calls is performed using the principle of time-division multiplexing
(TDM). TDM allows multiple calls to be transmitted along the same physical path, reducing the cost of infrastructure.
Queueing systems used in call centers have been studied as a science. For example completed calls are put on hold and queued until they can be served by an operator. If callers are made to wait too long, they may lose patience and default from the queue (hang up), resulting in no service being provided.
, the teletraffic engineering methodologies used for voice networks are inappropriate. Various aspects relating to teletraffic engineering in broadband networks are discussed in this article.
. In some designs, the network might be required to withstand the unanticipated traffic.
. Forecasting allows network operators to calculate the potential cost of a new network / service for a given GoS during the planning and design stage, thereby ensuring that costs are kept to a minimum.
An important method used in forecasting is simulation
, which is described as the most common quantitative modelling technique in use today. An important reason for this is that computing power has become far more accessible, making simulation the preferred analytical method for problems that are not easily solved mathematically.
As in any business environment, network operators must charge tariffs for their services. These charges must be balanced with the supplied QoS. When operators supply services internationally, this is described as trade in services
and is governed by the General Agreement on Trade in Services
(GATS).
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
including queuing theory, the nature of traffic, their practical models, their measurements and simulations
Network traffic simulation
Network traffic simulation is a process used in telecommunications engineering to measure the efficiency of a communications network.-Overview:...
to make predictions and to plan telecommunication networks such as a telephone network
Telephone network
A telephone network is a telecommunications network used for telephone calls between two or more parties.There are a number of different types of telephone network:...
or the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
. These tools and basic knowledge help provide reliable service at lower cost.
The field was created by the work of A. K. Erlang
Agner Krarup Erlang
Agner Krarup Erlang was a Danish mathematician, statistician and engineer, who invented the fields of traffic engineering and queueing theory....
for circuit-switched
Circuit switching
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...
networks but is applicable to packet-switched
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
networks. The most notable difference between these sub-fields is that packet-switched data traffic is self-similar. This is a consequence of the calls being between computers, and not people.
The crucial observation in traffic engineering is that in large systems the law of large numbers
Law of large numbers
In probability theory, the law of large numbers is a theorem that describes the result of performing the same experiment a large number of times...
can be used to make the aggregate properties of a system over a long period of time much more predictable than the behaviour of individual parts of the system.
Teletraffic in PSTN architectures
The measurementTraffic measurement (telecommunications)
Measurement of traffic within a network allows network managers and analysts to both make day-to-day decisions about operations and to plan for long-term developments...
of traffic in a public switched telephone network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
(PSTN) allows network operators to determine and maintain the quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS) and in particular the grade of service
Grade of service
In telecommunication engineering, and in particular teletraffic engineering, the quality of voice service is specified by two measures: the grade of service and the quality of service ....
(GoS) that they promise their subscribers. The performance of a network
Network performance
Network performance refers to the service quality of a telecommunications product as seen by the customer. It should not be seen merely as an attempt to get "more through" the network....
depends on whether all origin-destination pairs are receiving a satisfactory service.
Networks are handled as:
- loss systems where calls that cannot be handled are given equipment busy tone or
- queuing systems where calls that cannot be handled immediately are queued.
Congestion is defined as the situation when exchanges or circuit groups are inundated with calls and are unable to serve all the subscribers. Special attention must be given to ensure that such high loss situations do not arise. To help determine the probability of congestion occurring, operators should use the Erlang formulas or the Engset calculation.
Exchanges in the PSTN make use of trunking
Trunking
In modern communications, trunking is a concept by which a communications system can provide network access to many clients by sharing a set of lines or frequencies instead of providing them individually. This is analogous to the structure of a tree with one trunk and many branches. Examples of...
concepts to help minimize the cost of the equipment to the operator. Modern switches generally have full availability and do not make use of grading concepts.
Overflow systems make use of alternative routing circuit groups or paths to transfer excess traffic and thereby reduce the possibility of congestion.
A very important component in PSTNs is the SS7 network
SS7
SS-7 can stand for:* Signaling System #7, a set of telephone signaling protocols.* The R-16 missile, with NATO reporting name SS-7 Saddler.* China Railways SS7, an electric locomotive model in China.* Super Socket 7, a chip socket introduced by AMD...
used to route signalling traffic. As a supporting network, it carries all the signalling messages necessary to set up, break down or provide extra services. The signalling enables the PSTN control the manner in which traffic is routed from one location to another..
Transmission and switching of calls is performed using the principle of time-division multiplexing
Time-division multiplexing
Time-division multiplexing is a type of digital multiplexing in which two or more bit streams or signals are transferred apparently simultaneously as sub-channels in one communication channel, but are physically taking turns on the channel. The time domain is divided into several recurrent...
(TDM). TDM allows multiple calls to be transmitted along the same physical path, reducing the cost of infrastructure.
Teletraffic engineering in call centers
A good example of the use of teletraffic theory in practice is in the design and management of a call center. Call centers use teletraffic theory to increase the efficiency of their services and overall profitability through calculating how many operators are really needed at each time of the day.Queueing systems used in call centers have been studied as a science. For example completed calls are put on hold and queued until they can be served by an operator. If callers are made to wait too long, they may lose patience and default from the queue (hang up), resulting in no service being provided.
Teletraffic engineering in broadband networks
Teletraffic Engineering is a well-understood discipline in the traditional voice network, where traffic patterns are established, growth rates can be predicted, and vast amounts of detailed historical data are available for analysis. However, in modern broadband networksBroadband Networks
The ideal telecommunication network has the following characteristics: broadband, multi-media, multi-point, multi-rate and economical implementation for a diversity of services [1][2]. The Broadband Integrated Services Digital Network provides these characteristics in today's networks...
, the teletraffic engineering methodologies used for voice networks are inappropriate. Various aspects relating to teletraffic engineering in broadband networks are discussed in this article.
Long-tail traffic
Of great importance is the possibility that extremely infrequent occurrences are more likely than anticipated. This situation is known as long-tail trafficLong-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....
. In some designs, the network might be required to withstand the unanticipated traffic.
Teletraffic economics and forecasting
As mentioned in the introduction, the purpose of teletraffic theory is to reduce cost in telecommunications networks. An important tool in achieving this goal is forecastingTelecommunications forecasting
All telecommunications service providers perform forecasting calculations to assist them in planning their networks. Accurate forecasting helps operators to make key investment decisions relating to product development and introduction, advertising, pricing etc., well in advance of product launch,...
. Forecasting allows network operators to calculate the potential cost of a new network / service for a given GoS during the planning and design stage, thereby ensuring that costs are kept to a minimum.
An important method used in forecasting is simulation
Network traffic simulation
Network traffic simulation is a process used in telecommunications engineering to measure the efficiency of a communications network.-Overview:...
, which is described as the most common quantitative modelling technique in use today. An important reason for this is that computing power has become far more accessible, making simulation the preferred analytical method for problems that are not easily solved mathematically.
As in any business environment, network operators must charge tariffs for their services. These charges must be balanced with the supplied QoS. When operators supply services internationally, this is described as trade in services
Trade in services
Trade in Services refers to the sale and delivery of an intangible product, called a service, between a producer and consumer. Trade in services takes place between a producer and consumer that are, in legal terms, based in different countries, or economies, this is called International Trade in...
and is governed by the General Agreement on Trade in Services
General Agreement on Trade in Services
The General Agreement on Trade in Services is a treaty of the World Trade Organization that entered into force in January 1995 as a result of the Uruguay Round negotiations...
(GATS).
See also
- Asynchronous Transfer ModeAsynchronous Transfer ModeAsynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
- Busy hour call attempts
- Cellular trafficCellular trafficThis article discusses the mobile cellular network aspect of teletraffic measurements. Mobile radio networks have traffic issues that do not arise in connection with the fixed line PSTN...
- Erlang unitErlang unitThe erlang is a dimensionless unit that is used in telephony as a statistical measure of offered load or carried load on service-providing elements such as telephone circuits or telephone switching equipment. It is named after the Danish telephone engineer A. K...
- Clos networkClos networkIn the field of telecommunications, a Clos network is a kind of multistage circuit switching network, first formalized by Charles Clos in 1953, which represents a theoretical idealization of practical multi-stage telephone switching systems. Clos networks are required when the physical circuit...
- Multi-protocol label switching
- Mobile QoSMobile QoSQuality of service mechanism controls the performance, reliability and usability of a telecommunications service. Mobile cellular service providers may offer mobile QoS to customers just as the fixed line PSTN services providers and Internet Service Provides may offer QoS...
- Predictive dialerPredictive dialerA predictive dialer dials a list of telephone numbers and connects answered dials to people making calls, often referred to as agents. Predictive dialers use statistical algorithms to minimize the time that agents spend waiting between conversations, while minimizing the occurrence of someone...
- RoutingRoutingRouting is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
- RSVP – traffic engineeringRSVP-TEResource Reservation Protocol - Traffic Engineering is an extension of the resource reservation protocol for traffic engineering. It supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature of the packet...
- Traffic mixTraffic MixTraffic mix is a traffic model in telecommunication engineering and teletraffic theory.-Definitions:A traffic mix is a modelisation of user behaviour. In telecommunications, user behaviour activities may be described by a number of systems, ranging from simple to complex...
- Traffic generation model