Summary of light Exchange Technology and Its Comprehensive Characteristics

The optical switching technology is still quite common. So I have studied the optical switching technology and its comprehensive characteristics. I will share it with you here, hoping it will be useful to you. The application FDL cache can delay the burst package to the end of the competition. Compared with the cache in the electric domain, the FDL cache can only provide a fixed delay, and the data leaves the FDL cache in the order they enter the delay line, this limits the flexibility of competitive solutions.

In addition, there is also a major problem in the optical cache: power loss. In order to compensate for power loss, we have to introduce optical signal amplification or optical signal regeneration. The former will introduce noise, and the latter will be too costly. In general, the introduction of FDL will greatly increase the cost of optical switching technology.

Wavelength Conversion

With wavelength converter, burst packets can be sent at different wavelengths than the specified output line in the event of competition. This solution is optimal in terms of latency of competitive groups, suitable for circuit switching, and also suitable for Optical grouping/burst switching networks, but requires fast tunable converters. Recent research results show that wavelength switching is one of the most promising options in Packet Switched Optical Networks, which can effectively reduce packet loss rate in optical packets/bursts, it is especially used in the multi-wavelength DWDM system. Therefore, the fast adjustable wavelength converter is currently a hot topic.

Biased Routing

Biased routing is a method that uses idle links to resolve conflicts. When competition occurs, the Group/burst cannot be switched to the correct output port, and it is routed to another optional output port, it is possible to reach the target node through another path. When the link resources are sufficient, the redirection routing has better performance. However, this method has some potential problems in the re-sorting and fairness of the egress nodes. In addition, the performance may deteriorate when the load is heavy, so it is only suitable for networks with low network load.

OCBS (combined burst packet)/BS (burst packet segment)

OCBS and BS share the same idea. In the event of competition, they all divide burst packets into several parts, and forward as many parts as possible during the forwarding, to minimize data discarding.

Combination of multiple technologies

Since a single conflict resolution mechanism has limited performance improvement, and the above technologies do not affect or conflict with each other, the above technologies can be organically combined. The most effective combination scheme is to organically combine the cache with the full-wavelength conversion, and then cooperate with the spatial biased routing. The most economical solution is the smallest Light cache, which works with some wavelength transformations and then introduces a biased Routing Mechanism, which can greatly reduce costs, but slightly degrade performance.

Survivability

At present, the business capacity of a single optical fiber has reached the Tbit/s level. When a link fails, it will inevitably cause a large amount of data loss, therefore, appropriate protection measures should be taken to minimize data loss when a fault occurs. The survivability of the OBS network includes the protection and recovery of control channels and data channels. It is similar to the traditional optical network and can be used for reference to the protection and recovery mechanisms of the traditional optical network. However, the OBS network has its own characteristics. For example, the control channel must be processed by O/E/O, and data information is transmitted transparently in the optical domain. Therefore, the survivability of the OBS network needs to be further studied in many aspects.

Research Progress

With the continuous research on OBS technology, some researchers have proposed LOBS (LabeledOpticalBurstSwitching, label light Burst Switching) and WROBS (Wavelength Route Optical Burst Switching, wavelength Routing optical switching technology ).

LOBS Technology

The Optical Burst Switching Network is non-connection oriented, so it also has some inherent problems for non-connection networks, such as it is difficult to implement traffic engineering. MPLS technology can solve problems such as traffic engineering, QoS routing, and expansion of signaling and routing mechanisms. As the technology becomes increasingly mature, it is proposed to introduce MPLS, or LOBS, In the OBS network.

LOBS uses MPLS label technology to simplify some operations of optical switching technology and improve its shortcomings. Tag-carrying control groups are transmitted on pre-established LOBS channels. Burst data groups transmit and exchange data on the path determined by the control group. The extended explicit routing and restricted routing can be used for LOBS resource allocation and management, and the extended Internal Gateway Protocol (IGP) transmits network resources and topology information to reduce competition for different core node wavelength resources. Because the Tag Information (wavelength number, offset time, etc.) corresponding to each burst data is carried on the control group, therefore, LOBS can directly integrate multiple business groups into one burst group without O/E/O conversion, so that tags can be exchanged without all-optical switching.

WROBS Technology

The use of one-way Resource Reservation for optical burst switching will lead to competition of burst packages on core nodes. Among the many competitive solutions, the wavelength conversion technology has the most potential, but the wavelength conversion technology is not mature, and its performance is not ideal, it is not realistic to apply it in the optical burst switching network. As a result, MichaelDuser and so on proposed the use of two-way reserved mechanism of Optical Burst Switching-WROBS.

In WROBS, the edge router assembles the data to a certain algorithm and sends a request to the connected core router through a dedicated channel (or wavelength) at a specific time, request resources to send burst data. The request information mainly includes the burst packet length, source address, and destination address. Then, the core router forwards the request to the Central Control Node for processing, and allocate resources to corresponding links. If the allocation is successful, a "successful" message is returned, and a configuration message is sent to the path of the burst group to ensure that the configuration is completed before the arrival of the burst group; if the allocation fails, a "failed" message is returned, and the edge router will apply for it later. If the queue latency exceeds the maximum latency that the business can bear or the queue is full, some groups are discarded.

Conclusion

WROBS emerged when the fast wavelength conversion technology was not mature. It is currently a good transitional solution for large-scale man and small-sized Wan, such as provincial or national networks. LOBS has powerful control capabilities of the most advanced MPLS technology and combines the advantages of optical switching technology and optical packet switching. It is an ideal optical switching solution for the next generation optical Internet, it paves the way for the realization of optical group switching.

OBS combines the advantages of Optical Circuit Switching and optical group switching, and avoids their disadvantages. It is a promising optical switching technology. OBS features low latency (one-way reservation), high bandwidth utilization (Statistical Multiplexing), high efficiency, flexible switching, and large switching capacity (electronically controlled optical switching, it can achieve Tbit/s switching capacity, or even Pbit/s magnitude. Therefore, the OBS network is mainly used in the ever-growing large-scale man and WAN networks. It can support traditional services, as well as services with high burstable and diverse features in the future. The maturity of OBS requires constant efforts.