Path Mapping Approach for Network Function Virtualization Resource Allocation with Network Function Decomposition Support  
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1 Faculty of Engineering & Information Technology, University of Modern Sciences, 85 RC+6V Sana'a, Yemen; [EMAIL_ADDRESS]  
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2 Faculty of Computer science & Information System, Thamar University, H9 HG+H5 Thamar, Yemen; [EMAIL_ADDRESS]  
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3 Department of Information Technology, Faculty of Computer Science & IT, Sana'a University, 85 XR+C5 Sana'a, Yemen; [EMAIL_ADDRESS]  
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4 Department of Information Technology & Network, Faculty of Computer Science & IT, Universiti Putra Malaysia, Serdang 43400, Malaysia 4  
to its promising advantages such as flexible management, agile development of new services with faster time-to-market, potential cut down in Capital Expense (CAPEX) and Operational Expense (OpEx) [4; 5]. In the context of this new paradigm, Network Functions (NFs) were decoupled from their traditional physical equipment in order to implement them in general purpose high-volume servers. That decoupling has enforced a new re-implementation of NFs into their Virtual Network Functions (VNFs). In general, two methods were proposed in the literature for mapping traditional NFs into their VNFs. The first is decoupling of control plane from user plane which was introduced in SDN [6]. The 3 rd Generation Partnership Project (3 GPP) has proposed a functional separation of control plane from user plane for the re-implementation of the Evolved Packet Core (EPC) [7]. The second proposed method was mapping traditional NFs to a pool like sub-functions, which were called NF decompositions [8]. Authors of [9] claimed that EPC components as one to many VNFs would enhance scalability, flexibility and load balancing. The work in Reference [10] introduced a future-proof 5G mobile network architecture, which uses the function decomposition to locate mobile NFs based on the end-user requirements and infrastructure capabilities. They suggested a geographical perspective to locate control plane in the central office while user plane can be located in the edge near to the user equipment. The distributed characteristic of a mobile network usually increases the deployment and operational costs, especially for transmission. Function decomposition might generate large number of links between NF sub-functions as shown in Figure 1. In the literature, in works such as References [11; 12; 13; 14], only simple and forking paths were tested for developed algorithms. We believe that this paper presents the first effort to test the proposed algorithms on large multi-path services. Testing placement algorithms in a high number of physical nodes and a high number of virtual links is important for evaluating the possibility of using the algorithm for mobile NFVI networks, which is required to minimize costs and execution time. Figure 1: **(a)** Decomposition main types: decomposition into sub-functions or control/user planes. **(b)** Example of independent scaling of one sub-function in the decomposed user plane. **(c)** Example of path types, which might be generated after decomposing a single NF. However, the authors of Reference [15] claimed that the function placement on NFV Infrastructure (NFVI) is still a research opportunity, and the success of NFV is due to the fact that the full automation of NFV Management and Orchestration (MANO) during VNF life-cycle operations and fault management depends on developing rapid placement algorithms. The work in Reference [16] surveyed the placement on NFV as NFV Resource Allocation (NFV-RA) problem and the similarities and differences to/from Virtual Network Embedding (VNE) problem and Virtual Network Function problem (VNF-P). Unlike the VNE and/or VNF-P, the NVF-RA considers the placement of end-to-end Service Function Chains (SFCs) of the VNFs that works together to provide a service.