ABSTRACT

How do things change when a physical server is converted into a Virtual Machine (VM), run on top of a Hypervisor (like KVM, VirtualBox, XEN, vSphere, Hyper-V, etc.) and connected to a virtual network? With more and more servers being virtualized (occupying the majority of all servers in the world now), we need to understand virtual network connections and virtual infrastructures.

In this chapter, we provide a review of virtual network solutions. Compared to a physical network, which is a network of physical machines that are connected; a virtual network is a technical approach that provides mapping functions to represent various logical views or isolations of underlying physical networks at the network layer of the TCP/IP protocol stack to better serve its supported applications for easier management and stronger security protection.

In this chapter, we first provide a few definitions to clarify the differences among physical networks, virtual networks, overlay networks, and logical networks in Section 2.1. Next, we focus on layer-2 virtual networking techniques and realizations in Section 2.2. Then, in Section 2.3, we describe a closely related concept – Virtual Private Network (VPN)-at different layers of the protocol stack. Finally, we briefly discuss virtual networking and forwarding concepts in Section 2.4.