What is Traffic Engineering?
Ultimately, traffic engineering is about controlling the path packets take through a network, to optimize performance and the use of available capacity. Failure protection is also a common goal of traffic engineering.
Therefore, one of the most distinctive functions performed by Internet traffic engineering is the control and optimization of the routing function, to steer traffic through the network.IETF RFC 3272bis
Internet traffic engineering is defined as that aspect of Internet network engineering dealing with the issue of performance evaluation and performance optimization of operational IP networks. Traffic Engineering encompasses the application of technology and scientific principles to the measurement, characterization, modeling, and control of Internet traffic.IETF RFC 3272bis
Traffic oriented performance measures include delay, delay variation, packet loss, and throughput.IETF RFC 3272bis
Thus, the optimization aspects of traffic engineering can be viewed from a control perspective and can be pro-active and/or reactive. In the pro-active case, the traffic engineering control system takes preventive action to obviate predicted unfavorable future network states such as e.g. engineering a backup path. It may also take perfective action to induce a more desirable state in the future. In the reactive case, the control system responds correctively and perhaps adaptively to events that have already transpired in the network, such as routing after failure.IETF RFC 3272bis