Network Virtualization (NV) refers to the conceptual network resources traditionally delivered in hardware to software. Virtual Network (slice) provides a setting for examining novel networking paradigms independent of the constraints imposed by the presently dominant Internet structures and protocols.

The NV abstraction decouples the control plane from hardware, making it easier to modify, upgrade and manage. It allows multiple service providers to offer new and innovative services over an existing underlying physical network infrastructure. Virtualization is the context of wireless and mobile networks in an emerging area that has been contemplated.

NV technologies have effectively deployed cloud, Internet of Things (IoT), big data and 5G networks. The main issue in network virtualization is mapping virtual networks to substrate the network. NV authorizes the emulation of connections among applications, dependencies, services and end users for software testing. Network virtualization separates traditional Internet service providers (ISPs) into two new roles:

 •  infrastructure network providers (InPs)
 •  service providers (SPs).

Network virtualization has been widely used in many aspects of networking, which achieves,

 •  Higher resources utilization
 •  Lower cost
 •  Flexible management
 •  Higher energy efficiency in data centers and cloud computing.

Many reasons why users can need virtualize resources:

 •  Resource Sharing
 •  User Isolation
 •  Resources Aggregation
 •  Dynamic Management and Control
 •  Ease/ Simplify management

Network Virtualization also provides various benefits over SDN :

 •  Cost-effective
 •  Increase application performance
 •  Efficient utilization of resources
 •  Fast accessibility
 •  Higher server availability

Some of the challenges faced by Network Virtualization in SDN

 •  Making virtual network appliances to achieve high performance and portability among different hardware vendors.
 •  Ensuring an appropriate level of resilience in both software and hardware failures.
 •  Achieving compatibility and co-existence with the special equipment in the network platform.
 •  Guaranteeing the security and reliability of the entire network system.
 •  Achieving all the NF automated to guarantee the scalability of NFV.
 •  Enabling to choose network servers and virtual appliances from numerous vendors and to integrate without excessive integration costs.