Abstract
Network Function Virtualization (NFV) is a paradigm that virtualizes traditional network functions and instantiates Virtual Network Functions (VNFs) as software instances separate from hardware appliances. Service Chaining (SC), seen as one of the major NFV use cases, provides customized services to users by concatenating VNFs. A VNF placement model for SC that relaxes the visit order constraints of requested VNFs has been considered. Relaxing the VNF visit order constraints reduces the number of VNFs which need to be placed in the network. However, since the model does not permit any loop within an SC path, the efficiency of utilization of computation resources deteriorates in some topologies. This paper proposes a VNF placement model for SC which minimizes the cost for placing VNFs and utilizing link capacity while allowing both relaxation of VNF visit order constraints and configuration of SC paths including loops. The proposed model determines routes of requested SC paths, which can have loops, by introducing a logical layered network generated from an original physical network. This model is formulated as an Integer Linear Programming (ILP) problem. A heuristic algorithm is introduced for the case that the ILP problem is not tractable. Simulation results show that the proposed model provides SC paths with smaller cost compared to the conventional model.
Highlights
Network functions such as firewalls and deep packet inspections are traditionally implemented as dedicated hardware devices, which achieve high reliability and performance
We introduce a Virtual Network Functions (VNFs) placement model called Visit order constraint Relaxation (Vo-R), which does not make any loop on an Service Chaining (SC) path and is more tractable than Visit order and Routing constraint Relaxation (VoR-R)
PERFORMANCE EVALUATION We evaluate the performance of VoR-R to show the effect of relaxing both VNF visit order and non-loop constraint at a time, in terms of the cost and the computation time
Summary
Network functions such as firewalls and deep packet inspections are traditionally implemented as dedicated hardware devices, which achieve high reliability and performance. We introduce a problem that considers the VNF placement in a logical layered network, which is generated by superposing topologies of an original physical network, to obtain SC paths with loops This problem is formulated as an Integer Linear Programming (ILP) problem which minimizes the cost for placing VNF instances and utilizing link capacity for providing service chains. M∈M ((v,t),(v ,t ))∈J v∈V t∈T where ψvLtvINtK and ψtVNF are the costs for utilizing logical link ((v, t), (v , t )) ∈ J and placing an instance of VNF t ∈ T , respectively, which should be set based on the actual situation by network operators. Uvmt represents the height of the node [27] for each SC path, which makes it possible to perform SC while satisfying the VNF visit order constraints imposed by SC request m.
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