Methods Of Optimizing Anycast Strategy And Resource Allocation For Elastic Optical Inter-datacenter Networks

In recent years,with the rapid development of applications in inter-datacenter elastic optical networks,such as cloud computing,video streaming,mobile applications and content delivery networks(CDNs),the datacenter networks have a successive increasing scale.Meanwhile,the spectrum requirements are increasing exponentially in the datacenter networks,which leads to a number of challenges for the limited bandwidth resources.However,the traditional fixed-grid wavelength division multiplexing(WDM)networks strictly use the fixed rigid granularity level,resulting in underutilization of spectrum resources and granularity severe mismatch.And it does not meet the needs of the datacenter networks.Owing to their major advantages,such as ultra-large capacity,high bandwidth,high flexibility and so on,elastic optical networks(EONs)have become a powerful physical layer technology,which effectively support the development of the datacenter networks.While EONs must allocate spectrum block that is made up of a series of contiguous subcarrier frequency slots(FSs),dynamically setting up and tearing down connections can generate bandwidth fragmentation.Generally,spectrum fragmentation,i.e.,the existing of non-aligned,isolated,and small-sized unused spectrum blocks,can hardly be utilized for new requests and will have great influence on the routing and spectrum allocation of the following requests.The spectrum fragmentation leads to a number of challenges for improving the network performance,e.g.,spectrum utilization and bandwidth blocking probability,significantly.How to reduce the spectrum fragmentation and bandwidth blocking probability,and to improve the spectrum utilization,makes a great significance on the development of the datacenter networks.This paper has deeply analyzed and summarized the anycast and manycast service provisioning strategy in inter-datacenter elastic optical networks from the aspects of the routing and spectrum allocation,and several methods of resources allocation are proposed.The specific research content and innovative work of this paper is mainly in the following:Firstly,a traffic splitting algorithm based on fragmentation avoided and multi-path delay-constrained for anycast in inter-datacenter elastic optical networks is creatively proposed in this paper.In order to reduce the spectrum fragmentation,during thespectrum allocation phase,a new scheme of fragmentation avoided,a spectrum block allocation scheme of exact-fit or fragmented-minimal is put forward.Moreover,this paper designs a modified scheme of traffic splitting and it tries the best to transmit sub-requests in a single-path with minimal spectrum fragmentation when the resources are insufficient.If it fails,the sub-requests are transmitted over multi-path with minimum delay.Finally,when the enough spectrum block is found for the split anycast request,merging split sub-requests to a single-path is activated to minimize the additional guard-bands and improve spectrum efficiency.Comparing with other two anycast algorithms,simulation results show that the proposed algorithm can obtain minimal time delay between split multi-path,bandwidth blocking probability and the higher spectrum utilization.Secondly,an algorithm of optimizing bandwidth blocking probability for manycast basing on tree-splitting and share lightpath-merged in inter-datacenter elastic optical networks is creatively proposed in this paper.At the routing phase of manycast,a model of spectrum consumption cost is designed to minimize the cost of spanning light tree.In consideration of trying to adopt low modulation level,the proposed algorithm selects the new inserted branch having minimum influence on the light-tree’s maximal length with lowest spectrum consumption cost.At the phase of spectrum allocation,the light tree may be split into several sub-light trees when the spectrum resources are insufficient to the manycast using a light tree transmission.In order to further reduce the spectrum consumption,this paper designs a novel sub-light trees reconfiguration scheme based on link-sharing degree.When an expired request releases and there has adequate spectrum resources on a light tree of manycast,the split sub-light tree is rerouted to transmit on a light tree.Compared with other algorithms,simulation results show the proposed algorithm can obtain the lowest bandwidth blocking probability and highest spectrum utilization.