| Teletraffic Engineering In Broadband Networks |
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Firstly, the nature of broadband traffic is different from that of traditional voice networks. Many of the methodologies developed for traditional networks were based on the nature of voice calls, and are therefore not applicable to broadband networks. The nature of broadband traffic (broadband traffic characteristics) is discussed in the following sub-section. The inherent nature of broadband networks is also different from that of traditional voice networks. Broadband networks have:
These factors make teletraffic engineering in broadband networks more difficult than in traditional voice networks. A few more factors that further complicate teletraffic engineering in broadband networks are:
BROADBAND TRAFFIC CHARACTERISTICS In the traditional voice network, the study of traffic characteristics has matured over many years following the seminal work of Erlang in 1909. However, the teletraffic theory that has evolved relied heavily on the facts that
The diversity of broadband service connections (see Broadband Networks ) and the variety of holding times make the application of teletraffic theory in voice networks to broadband networks very difficult . Figure 1 and Figure 2 show some applications and the variation in holding time and Burstiness that may be expected for each one. To manage the traffic implications of all these types of connections, we must return to the basic principles of traffic statistics. This has been extensively studied in recent years, and there is a large volume of published work on the subject. A Poisson process with one parameter does accurately model telephony traffic. However, to account for the changes with broadband traffic, alternatives to the Erlang formula have been considered . Two methods of modelling the traffic are considered, namely the Bernoulli-Poisson-Pascal approximation and the Maximum Entropy method. These methods use two parameters for describing the traffic – one for the mean demand and another to characterize the variability of the traffic. (See also Long-tail Traffic ). MECHANISMS USED FOR TELETRAFFIC ENGINEERING IN BROADBAND NETWORKS There are two primary mechanisms that are used for teletraffic engineering in broadband networks, namely:
These two mechanisms are described in the following two sub-sections. Traffic control and Management '' Traffic control and management'' is defined as the set of actions performed by the network to:
The basic control problem is related to the efficient allocation of network resources so as to:
Traffic control and management provides the means by which:
Congestion Control ''Congestion control'' is defined as the set of actions performed by the network to prevent or reduce congestion. Congestion control is the most important part of the traffic management issue. A network that controls congestion must:
See Congestion Control for the full article. A SIMPLE EXAMPLE The process of how a broadband network provides different levels of service to different types of traffic while avoiding congestion will be described briefly by means of a simple example. Links are provided for the reader interested in a more detailed description of the various concepts involved. The concept of traffic control in broadband networks (particularly in (QoS) follows the following procedure :
THE ATM TRAFFIC MANAGEMENT FRAMEWORK The ITU-T has defined a collection of ATM control mechanisms that operate across a spectrum of timing intervals . These control mechanisms are summarised in table 1. SEE ALSO
<DIV ID="REF">REFERENCES</DIV> {Link without Title} Nguyen L. T., Fundamental of Online Traffic Engineering, http://216.239.59.104/search?q=cache:euaQfB_6w8AJ:www.zvolve.com/pdf/LucNguyenUSTA.PDF+fundamentals+of+online+TE&hl=en&client=firefox-a, Last accessed 25 February 2005. {Link without Title} Modern techniques of networking, Traffic and Congestion Control in ATM networks, http://scholar.google.com/scholar?hl=en&lr=&safe=off&q=cache:8j8I9JNI5WQJ:www.itm.hk-r.se/~adrian/courses/modern_techniques_networking/lectures/Lecture_8.ps+teletraffic+engineering+traffic+policing, last accessed 14 March 2005. {Link without Title} Sexton M., Reid A., “Broadband Networking: ATM, SDH and SONET”, Artech House Inc., Boston, London, 1997. ISBN 0-89006-578-0. {Link without Title} Molnar, S., Farago, A., Henk, T., and Blaabjerg, S., Towards precision tools for ATM network design, dimensioning and management, Technical University of Budapest, Hungary, 1995. {Link without Title} Saito, H., Teletraffic Technologies in ATM Networks, Artech House, 1993. ISBN 0-89006-622-1. {Link without Title} ATM Forum Traffic Management Specification, Version 4.0, 1996. |
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