Study Of Routing And Spectrum Assignment Algorithm With Low Delay In Software Defined Optical Networks

High bandwidth,high reliability and low delay have become the development object of future optical network driven by the various representative requests,such as HD video,remote medical and financial data,etc.However,the traditional wavelength division multiplexing(WDM)optical networks adopt the fixed channel spacing,leading to inefficient spectrum resource utilization,and the physical impairments are still to be the critical factor for the establishment of the end-to-end connection.With the continuous augment of service of data center,cloud computing and large data,it is imperative to provide variable services of quality of service(QoS)to requests.The flexible gird technology is adopted in elastic optical networks,which employs finer grained frequency gap spacing and implements the elastic bandwidth allocation.The utilization rate of bandwidth resource is improved.The new network architecture of SDN(Software Defined Network)provides a control manner of flexible,efficient and intelligent.It is SDON(Software Defined Optical Networks)when combined SDN with optical networks,which can provide variable services of QoS,such as avoiding physical impairments,low delay and considering the tolerant latency of establishment of optical paths,to various requests in application layer.In this paper,the routing and spectrum assignment(RSA)strategy with considering the constraints of physical impairments,delay and tolerant latency of establishment of optical paths is studied by using the technology of reconfiguration of virtual topology,rescheduling of requests queues and multi-threads in SDON to effectively guarantee the quality of transmission(QoT)of service and improve the comprehensive performance of network.The main research results are as follows:(1)In order to avoid the influence caused by cross phase modulation(XPM)to quality of transmission and reduce the delay of optical link establishment,the paper provides an impairment aware and low delay routing and spectrum assignment algorithm.By using the strategy of avoiding the XPM effect and the control model of reducing the delay,the algorithm decreases the delay of optical path establishment and blocking probability of requests,and the throughput capacity and spectrum efficiency in the fibers are consequently improved.The validity of the proposed algorithm is verified by experiment simulations.(2)Requests grooming and service resilience in multi-layer architecture are realized by the joint optimization of IP and optical networks in optical interconnections of data center.Due to the burst character of requests in intra-data center and the transport of high bandwidth request among inter-data center,burst requests are groomed to optical network that leads to the longer delay of queuing and establishment of light paths of requests.In order to reduce the establishment delay of optical paths,the paper proposed a RSA algorithm with low delay,which separates the spectrum resource of fibers into spectrum layers,and multi threads can parallel set up optical paths among or in spectrum layers.The algorithm sets up colored virtual topology with the points and edges of establishing optical paths in every spectrum layer,and the topology is used as constraints of resource utilization in current spectrum layer.The colored and usable virtual topologies in spectrum layers are reconfigured according to transformations of requests of establishing,unestablished and new arrived,which can adapt bursts of requests and promptly groom the requests flocked in optical network.The simulation results demonstrate that the proposed algorithm can efficiently reduce the average delay and delay variance of establishment of optical paths and blocking probability of requests,and improve the rate of spectrum utilization and quality of experience(QoE).(3)The fast and diversified developments of Internet services lead to numerous service requests flocked in the optical network,consequently the establishment delay of optical paths is increased and the QoE is declined.To resolve this problem,a low delay RSA algorithm constrained by tolerant latency of optical path establishment is proposed.The algorithm can reasonably discern the various service requests with different requirements of delay on QoS and queue a request into the service queue according to its priority,tolerant latency of establishment of optical paths and waiting time;Threads running in the SDN controller with multi-threads technology select requests to parallel serve from the service window of queue waiting service.The sharing utilization of resource by multi-threads is accurately realized by the resource utilization model with mutual exclusion constraint constructed by technology of virtual topology reconfiguration.The colored virtual topology is reconfigured according to the transforming of serving requests,and the usable virtual topology is reconfigured to adapt to the waiting and new arrival requests.The simulation results demonstrate that the real-time services are timely served and the requests with low priority is fairly served according to the augment of waiting time,and the average establishment delay of optical paths of various requests is obviously reduced.