White Paper Abstract:
With the advent of server virtualization, two basic assumptions of data center network design have changed: multiple OS images (or virtual machines) are now allowed to transparently share the same physical server and I/O devices, and the relationship between an OS image and the network is now dynamic. The access layer of the network extends further to support local switching between different virtual machines within the same server, thus invalidating the traditional assumption that each network access port corresponds to a single physical server running a single image. Further complicating the picture, each virtual machine can be moved from one physical server to another within the data center or even across data centers.
One option for network virtualization is to implement a software switch as part of the hypervisor. Another option is to enable the switching function to be performed by an external switch. Both approaches offer advantages and should be looked at as complementary options for different workload profiles and data center designs.
This document describes the two main standards for virtual networking and briefly discusses existing Cisco® solutions.