traffic engineering

The theory of traffic engineering was originally conceived by A.K. Erlang, a Danish mathematician who developed methods of signal traffic measurement in the early 1900s. Traffic engineering makes use of a statistical concept known as the law of large numbers (LLN), which states that as an experiment is repeated, the observed frequency of a specific outcome approaches the theoretical frequency of that outcome over an entire population. In telecommunications terms, the LLN says that the overall behavior of a large network can be predicted with reasonable certainty even if the behavior of any single packet cannot be predicted.

When the level of network traffic nears, reaches or exceeds the design maximum, the network is said to be congested. In a telephone network, traffic is measured in call seconds (CCS) or erlangs. One CCS is equal to 100 seconds of telephone time. One erlang is equal to one hour or 36 CCS of telephone time. In a congested network, one of three things can happen when a subscriber attempts to send a message or place a call:

• The user receives a busy signal or other indication that the network cannot carry out a call at that time.
• A message is placed in a queue and is eventually delivered according to specified parameters.
• A message is rejected, returned or lost.

When message queues become unacceptably long or the frequency of busy signals becomes unacceptably high, the network is said to be in a high-loss condition. A major objective of traffic engineering is to minimize or eliminate high-loss situations. In particular, the number of rejected messages or failed call attempts should be as close to zero as possible. Another goal of traffic engineering is to balance the QoS (Quality of Service) against the cost of operating and maintaining the network.

Getting started with traffic engineering

To explore how traffic engineering is used in the enterprise, here is an additional resource:

Traffic engineering the service provider network: Learn about the evolution of traffic engineering, including its role in networks transitioning from Layer 2 to IP technology and MPLS traffic engineering.

Read more about traffic engineering: - Rick Gallagher describes the principles of traffic engineering in simplified terms. - Richard Parkinson discusses the technical aspects of traffic engineering. - Intel offers a traffic engineering model for LAN videoconferencing.

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