Holding-time-aware Routing And Spectrum Allocation Algorithm For Elastic Optical Network

With the diversification of traffic bandwidth requirements,a flexible transmission network is required to meet the different bandwidth requirements of the new traffic with a rapid growth;and elastic optical network(EON)came into being.In an EON,under a dynamic traffic scenario,connection establishment and release may lead to fragmentation throughout the network by separating the available frequency spectrum into small non-contiguous spectrum bands.Therefore,it is one of the key issues for EONs to reduce fragmentation and to improve the spectrum efficiency for routing and spectrum allocation algorithm(RSA).In this paper,the RSA algorithm of the elastic optical network is studied;and two improved RSA algorithms are proposed based on traffic holding-time.And the proposed algorithms are evaluated by extensive simulations.This paper first introduces the background and system structure of the EON and the constrains of RSA algorithm,analyzes the research status of EON,and discusses the fragmentation-aware RSA,holding-time-aware and multiple path RSA algorithms.Secondly,due to the shortage of several fragmentation-aware RSA algorithms,we propose a Holding-Time and Fragmentation Aware RSA(HTFA-RSA)algorithm.The proposed algorithm considers the fragmentations of spectral,spatial and time dimensions,that is,spectral fragmentation,the spatial fragmentation of the adjacent link and the time fragmentation due to the diversity of traffic holding-time,to reduce the production of three dimension fragments as much as possible for the connection establishment of a new arriving request.And then,based on the analysis of the multiple path algorithm,and with a consideration of traffic holding-time and the fragments of the frequency spectrum,we propose a Holding-time-aware Hybrid Single/Multiple-path Routing and Spectrum Allocation(HHSM-RSA)algorithm.The algorithm first tries to establish a traffic connection with a single path.When the connection is unsuccessful by a single path,the multiple path mechanism is used to set up the connection.For the multiple path mechanism,the limitations of bandwidth granularity and differential delay constraint are satisfied,and it selects the paths with minimum fragments of three dimension to establish the connection.Finally,based on VC++ 6.0 software,an EON simulation platform is developed to evaluate the performance of HTFA-RSA and HHSM-RSA.And we compare them with the existed algorithms proposed in the previous literatures.Simulation results verify the effectiveness of the proposed algorithm.