Orchestrating Multicast-based VNFs In Elastic Optical Networks

It is known that by incorporating network function virtualization(NFV)in inter-datacenter(inter-DC)networks,service providers(SPs)can use their network resources more efficiently and adaptively and expedite the deployment of new services.This dis-sertation studies the provisioning algorithms to realize tree-type virtual network func-tion forwarding graphs(VNF-FGs),i.e.,multicast NFV trees(M-NFV-Ts),in inter-DC elastic optical networks(IDC-EONs)cost-effectively.Specifically,we try to optimize the virtual network function(VNF)placement and multicast routing and spectrum as-signment(RSA)jointly for orchestrating M-NFV-Ts in an IDC-EON with the lowest cost.Firstly,we study the problem of the formulation of the multicast sessions in the IDC-EONs.Due to the traffic dynamics in inter-DC networks,we might have to con-sider the case that the multicast members can join or leave a multicast session dynami-cally.The continuous changing of multicast group members can degrade the optimality of a multicast-tree.Hence,we propose to rearrange the multicast-trees adaptively to re-duce their spectrum usage.Meanwhile,we try to minimize the frequency of rearrange-ments to avoid unnecessary operation complexity.Based on these considerations,we propose several multicast-tree rearrangement algorithms for updating multicast sessions dynamically with lightpath reroutings in IDC-EONs.Both partial and full multicast-tree rearrangements are studied.Simulation results indicate that the proposed algorithms can rearrange the multicast-trees intelligently such that the blocking probability can be re-duced effectively with the least lightpath reroutings.Next,based on these theoretical investigations,we consider how to implement the proposed algorithms in the control plane of an software defined network(SDN).We extend the OpenFlow(OF)protocol to support the dynamic formulation of multicast sessions and also design the functional models in the control plane elements to realize multicast-tree rearrangements.Experi-ment results verify the effectiveness of our proposed algorithms and system design.Secondly,we study how to optimize the VNF placement and multicast RSA jointly for orchestrating M-NFV-Ts in an IDC-EON with the lowest cost.Our study addresses both static network planning and dynamic network provisioning.For network planning,we first formulate a mixed integer linear programming(MILP)model to solve the prob-lem exactly,and then propose three heuristic algorithms,namely,AFM-MILP,AFM-GS,and RB.Extensive simulations show that AFM-MILP and AFM-GS can approx-imate the MILP's performance on low-cost M-NFV-T provisioning with much shorter running time.For network provisioning,we design four additional online algorithms based on AFM-GS and RB to serve M-NFV-Ts in a dynamic IDC-EON,with the con-sideration of spectrum fragmentation.Simulation results indicate that taking care of spectrum fragmentation can reduce the network blocking probability.When adopting the same RSA schemes,algorithms based on AFM-GS perform better than those based on RB.