Introduction to OPST
Optical Packet Switch and Transport is a new idea at the cutting edge of telecommunications technology and lies at the heart of the Exemplar Network. It uses ultra high-speed tunable laser technology to deliver an optical layer that can respond at the same rate as packets arrive into the system. This achieves one of the holy grails of networking: a true collapsing of the traditional network layers. This is because the tunable lasers effectively perform two traditional functions in one device. These functions are the transmission of light and the switching of layer 2 logical packet flows. OPST collapses the optical transmission of layer 1 into the logical packet flows of layer 2. Both functions are controlled by a single system.
Another way of viewing OPST is to consider it as a single layer 2 switch that has been expanded out to the size of a typical fibre optic ring (100-300km). The fibre now acts as both the transmission medium and the switching fabric of a massive distributed switch. The diagrams below illustrate what OPST has achieved compared to traditional architectures. On the left-hand side is a picture of today’s architectures with separate optical transport and electronic switching. It is worth noting that this is a collection of individual switches connected together with an optical transport system. On the right-hand side is the OPST architecture. This architecture is a single large switch and the transport system is effectively embedded within it.
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Optical Burst Switching
OPST has been created by utilising Optical Burst Switching (OBS) at the optical layer. OBS has been used in a large variety of research networks over the past 20 years as a transport system, but OPST is the first time that OBS has been used to build a distributed switch. As the name suggests, the lasers are used in bursts, turning them on and off and switching them to different wavelengths. The wavelength or colour of the laser beams are used to direct the transmitted burst to its destination. Effectively, optical filters at the destination node “pick off” the optical bursts that are addressed for them. This is called wavelength routing. Therefore the Exemplar will be the world’s first example of a multi-wavelength OBS-based system that forms the switching fabric of a distributed switch.
Intune Scheduling Theory
The mathematical theory behind the world’s first distributed switch has been derived by the scientists at Intune and used to support the computer models and proofs of the Exemplar Network. The Intune Scheduling Theory sets out to prove how the system can guarantee network performance in terms of fairness, bandwidth delivery, packet delays and packet jitter. Exemplar partners can test this theory on the testbed to verify that it can guarantee network fairness for all users in an engineered and controlled manner. The theory can also be tested and benchmarked against the state of the art switching efficiencies achievable in existing networks.