Are we virtualizing everything in the cloud be it computing resources, CPU, memory, storage, applications and what about the network? Few years back could ever think that mighty firewalls, switches, and routers can be virtualized and become the most powerful segment across the cloud. Convergence of physical network to virtual is a phenomenal leap in the technology which had given organizations absolute power over management of diverse resources spread in disparate locations geographically 

In today’s article we would look more in detail about terminology network virtualization, how it works, use cases, its advantages etc. 

What is Network Virtualization? 

The history of network virtualization goes back to the 1980s when Bill Yeager developed a multi-protocol router at Stanford while DEC was building ‘Fuzzballs’ or routers supporting the Internet with software developed by David Mills. Virtual private networks (VPNs) were implemented using frame relay and ATM networks in the 1990s and virtual LANs (VLANs) became part of the Ethernet standards in late 1990s. 

Network virtualization is a combination of hardware appliances and specific software for the creation and management of virtual networks. Network virtualization is an aggregation of multiple physical networks into a single logical network or provide network-like functionality to an operating system partition (also known as internal virtualization). 

Network virtualization software allows network administrators to mobilize virtual machines across different domains without the need for reconfiguring the network. The software creates a network overlay which can run a separate virtual network layer on top of same physical fabric.

How does Network Virtualization work?

Network virtualization decouples network services from the underlying hardware and allows virtual provisioning of the whole network. It makes programmatically to create, provision, and manage networks all in software, and continue to leverage underlying physical networks as packet forwarding backplane.

Physical network resources such as switches, routers, firewalls, load balancers, virtual private networks (VPNs) are pooled, delivered in software, and require only Internet protocol (IP) packet forwarding from the underlying physical network. 

Network and security services are distributed to virtual layers (or hypervisors in data centers) and attached to individual workloads e.g., virtual machines or containers (Kubernetes). 

As per the network and security policy definitions for each connected application when workload moves from one host to another host network services, security policies move along. And when a new workload is created to scale an application, required policies are dynamically applied to new workloads.

Since VMs need to move around the data center, their IP addresses need to be decoupled from physical network topology as we do not want a particular VM to be restricted to its location by subnet addressing of the underlying physical network. 

Network virtualization makes use of overlay encapsulation such as VXLAN or NVGRE. Encapsulation is a low level mechanism to solve an important problem: decoupling the address space of virtual network from physical network. 

Architecture of Network Virtualization 

The three planes of network virtualization are data, control and management plane as depicted in figure below.

At the bottom is the data plane; it is a set of virtual switches which run inside hypervisors or container hosts. The data plane is where virtual networks are implemented. Data plane has information about the current state of the system such as VM locations which are indicated by the discovered state.

Control plane is centrally located and it sits between desired state and actual state of the system. As the control plane receives the discovered state from the data plane it compares it against the desired state. If the desired state does not match the actual state the control plan calculates necessary changes and pushes to the data plane as indicated by the ‘controls directive’ arrow. 

At the top most is the management plane which serves API requests, and understands the abstraction of virtual networks. 

Advantages of Network Virtualization

• Reduction in network provisioning time from weeks to minutes
• Greater operational efficiency by automation of manual process
• Place and movement of workloads independently of underlying physical topology
• Improving network security within data center

Some of the common examples of network virtualization are virtual LAN or VLANs, network overlays such as virtual extensible local area network (VXLANs), Generic network virtualization encapsulation (GENEVE) 

Quick facts!

Network virtualization market is projected to reach $180.67 billion by 2031.