【 Weak current College 】 what is an optical burst switching technology

Introduction--current optical network switching technology there are three main: optical switching OCS (OpticalCircuitSwitching), optical packet switching OPS (OpticalPacketSwitching), OBS OBS (OpticalBurstSwitching).

Three optical switching technology

Current optical network switching technology there are three main: optical switching OCS (OpticalCircuitSwitching), optical packet switching OPS (OpticalPacketSwitching), OBS OBS (OpticalBurstSwitching).

One of the most mature of the light path switching OCS, network needs to establish a connection request from the source to the destination of the light path (each link will need to assign a professional wavelength). Exchange process is divided into three phases: ① link establishment phase is bi-directional bandwidth application process, you need to pass requests and responses confirmed that the two processes. ② link remains stage, the link is always communication both in use, do not allow the other communicating party sharing the link. ③ link demolition phase, any party disconnect signal, first issued in another party received disconnect signal after confirmation, resources are truly free.

In the long run, all-optical packet switching OPS is optical switching direction of development. OPS is a connection-oriented way, using a one-way exchange of booking mechanism for data transfer without need for routing and distribution of resources. Packet payload closely follow the group header in the same transmitting light path, a network node caching payload, waiting for the grouping with packet destination header processing to determine the routing. Compared to OCS, OPS has a very high level of resource utilization, and a strong ability to adapt to unexpected data. But also the existence of two near insurmountable obstacles: the optical buffer technology has not developed; the second is in OPS Exchange node, the more input the exact synchronization groups. So optical packet switch is difficult to achieve in a short period of time.

In 1997, by ChunmingQiao and J.STunnor respectively a new optical switching technology — — optical burst switching OBS as from circuit-switched to packet-switched technology transition technologies. OBS combines circuit-switched and packet-switched their benefits and overcome some shortcomings of both, has attracted more and more people's attention.

Burst

OBS in "burst" can be considered by the number of smaller with the same export edge node address and same QoS requirements of data grouping consisting of very long data is grouped, the data group can come from traditional IP network in the IP packet. Burst is optical burst switched networks in basic Exchange unit, it consists of a control group (BCP, BurstControlPacket, functions as a packet-switched in the group header) and burst BP (NET load) made up of two parts. Burst data and control groups on the physical channel is a separate group for each control corresponds to an unexpected data, this is also the core optical burst switching design concept. For example, in WDM systems, control group consumed one or several wavelength, burst then consume all other wavelengths.

The control group and burst data separation is control group can be the first to burst data transfer to compensate for the control group in the Exchange node in the processing of O/E/O converter and power processing delay. Then a burst in all-optical switching node in exchange for transparent transmission, thereby reducing on optical buffer needs, even reduced to zero, to avoid the current optical buffer the shortcomings of the technology was not ready. And, because of the control group size much less than the size, you need to burst O/E/O converter and electronic processing of data greatly decrease, reducing processing delays, greatly improving the exchange rate. This process is similar to an outbound tours, team before departure, carrying a staff members with relevant information, arrived one day earlier border clearance procedures and ticket, etc., before departure, then tours the visitors of the time also simplifies the process.

Edge and core node

Because optical fiber to the home network in the bottlenecks are now mainly used for backbone and metropolitan area networks, and user-end remains the traditional electric IP network. Optical burst switched network mainly by light core node and edge nodes of electricity. Edge nodes are mainly responsible for IP packet access, classification, packaging and dispatch, and reverse burst of receiving and remove frames. Entrance to the edge node data input through the line card, depending on the IP packet's destination address sorting after Assembly, forming burst data, and extract the corresponding group header generation control group, which breaking data cache to the burst queue waiting for scheduling. When a sudden burst of data in the send queue on the queue head, calculation of burst data with the appropriate control packet offset between time and feedback to control packet generator, and then issue the control group, the control group including time offset, burst length and specific route information. When the offset of the time expires, the issue of the burst. Export edge node simply burst apart, and which IP data extraction.

Core node functionality is to control the Group find, Exchange, burst monitor (such as blocking probability, delay, etc), it is assumed that each wavelength optic support for K + 1 (single wavelength used for transmission control block BCP, K a wavelength used for transmission burst). BCP for transmission wavelength in core nodes need to be O/E converter and power routing table lookups, light switching matrix control, last update BCP data for E/O converter. The rest of the k-wave transmission burst data in core node does not need O/E/O transform, the entire Exchange transmission in optical domain, ensuring the transparency of the data. Figure in optical switching matrix of fiber delay line is used to cache burst data (you can only cache a finiteLong time), wait for the control group, by setting the appropriate offset time offsettime can make sudden data does not need to be cached in the intermediate nodes, directly through the OBS networks, which in turn can cancel the optical delay lines. Besides optical delay lines can also be used to resolve competition issues, reducing conflict and achieve WDM layer of QoS (quality of service). When the burst into optical switching matrix, the control unit control of optical switching matrix to select the corresponding output wavelength.