se are the critical devices in the mobile broadband and cellular networks. Table 3.1 shows a taxonomy of different types of VNFs and their representative examples. These services range from traditional telecom devices to security appliances. In the trend of microservices, the VNFs will become small and modular. New services can be built by composing multiple microservices together in a flexible way. The objective of NFV is to separate software that defines the VNF from hardware and generic software that creates a generic hosting net- work functions virtualization infrastructure (NFVI), which executes the VNF. The VNFs and the NFVI are then separated from each other. Compared to the cloud architecture described in the previous chapter, the NFV architecture's mapping can be shown in Figure 3.1. The NFVI maps to both the hardware and infrastructure layer. The VNFs map to the software as a service layer. In the past 5 years, NFV has grown from research proposal to real deployment. There have been various industry activities to make it prosper. The ETSI consortium has published the NFV architecture documents and has formed various working groups to study the design Table 3.1 Types of VNFs and examples. Edge devices vCPE, IP Edge, BRAS Gateway functions IPsec, SSL, NAT NGN signaling IMS, VoIP, HSS Application optimization CDN, cache, video transcoder, HTTP header enrichment Performance improvements Load balancer Service assurance SLA monitoring, testing Mobile network equipments HLR, SBC, MME, SGSN, GGSN, RNC, eNodeB Security functions DPI, Anomaly detection, Firewall, IDS, IPS 3 Network Function Virtualization Software as a Service (SaaS) (applications) Platform as a Service (PaaS) (software frameworks, storage) Infrastructure as a Service (laaS) Hardware as a service (CPU, memory, disk, network) Figure 3.1 NFV architecture in cloud computing stacks. OSS/BSS management and orchestration Service, VNF, infrastructure description Orchestration VNF manager Virtual Virtual Virtual compute storage network Virtualization lay