Research On Dimensioning Of ROADM Node And The Fragmentation-aware Virtual Optical Network Embedding In Elastic Optical Network

In recent years,with the emergency of the new telecom business such as cloud computing,IPTV,blockchain and IoT,telecom operators meet the inherent challenge in the development of optical network.Compared with traditional telecommunication services,these new telecommunication services have higher dynamic characteristics and unpredictability.Therefore,optical network needs to provide higher flexibility and intelligent functions,so that it can respond quickly when the connection request and network distribution change,and provision the connection request flexibly.To overcome these problems,flexible-grid elastic optical networks(EONs)are introduced in [1],which greatly improve the spectrum resource utilization and the flexibility of the network.Compared with the traditional wavelength division multiplexing(WDM)fixed-grid networks,which divides the optical spectrum of a fiber into separate channels with spectrum spacing of 50 GHz or 100 GHz,as specified by ITU-T standards,the EONs allow to allocate on-demand the just-enough spectral resources at the granularity of a few gigahertzes.Therefore,the EONs have been considered as a promising supporting technology for the future infrastructure of the next generation Internet [1].The ROADM is one of the key technology for this EON,which enable network operators to deliver lower CAPEX and OPEX,since they can quickly and flexibly respond to network status changes,such as fiber cut,establishing new lightpaths or releasing existing lightpaths [2].Next-generation ROADMs generally requires three key features: colorlessness,directionlessness,and contentionlessness [3]-[5].A set of TP-banks and TPs should be arranged in ROADM to realize the contentionless feature.In order to achieve pure contentionless feature in CD-ROADM,the number of TP-bank in each ROADM node should be equal to the node degrees,and the number of TPs in each TP-bank should be equal to the number of spectrum channels in the fiber link.However,these requirements bring about some shortages,such as higher TP bank hardware cost,massive scale of ports in WSSs,as well as higher power budget [6].Therefore in the internal-node contention-aware EON,the impact of different TP resources on network performance is studied,in order to reduce redundant hardware.Thus,the optimized ROADM node can obtain contentionless feature,as well as achieve the best network performance in practical.The concept of network virtualization was proposed as a future solution,to improve the flexibility and scalability in EON [7]-[8].And,the network virtualization can significantly improve the resource utilization and reduce the energy consumption by allowing multiple virtual optical networks(VONs)to exist on a shared SON.Typically,a VON can be constructed for each application,and multiple VON requests share these resources in the same physical SON [9].A VON consists of several virtual nodes(VNs)and several virtual optical links(VOLs),and these VNs are connected by the VOLs.Specially,each VN is mapped to a physical node,while each VOL is mapped to one lightpath in the physical network.The process is called to be virtual optical network embedding(VONE),which allocates the physical network's resources to the VON requests.Thus,the VONE is considered as a major way to implement the optical network virtualization,but its complexity becomes an inevitable challenge [10].The fragmentation problem is widely concerned in EON [11],but the fragmentation problem is more complex in VON.Therefore,this paper studies different fragmentation-aware VONE algorithms in EON to improve the spectrum utilization and network performance in practical.In this thesis,we dimensioned the internal-node contention factors of CD-ROADM in EON.We also proposed a traffic grooming policy which is based on the spectrum reserved scheme and lightpath grafting approach.This paper evaluated the network performance under different provision of CD-ROADM.We gave out the provisioning of CD-ROADM while achieving the pure internal-node contentionless feature.This reduce the cost of the hardware cost and power consumption in elastic ROADM node.Moreover,this paper also designed a VONE algorithm which is based on weight value.We first formulate an integer linear programming(ILP)model for multiple static virtual optical network(VON)requests.And,we also proposed the fragmentation-aware VONE heuristic algorithm.Simulation results show that the fragmentation-aware VONE algorithm can greatly improve the spectrum utilization and network performance.