VN-Tag and VEPA

One good article about VN-Tag and VEPA is here:
 Also found a couple of resources on the Internet: 

1. One blog article  is here
2. VNTAG 101 slides from IEEE 802
3. Another good link - IO Virtulization Overview

Both are network interface virtulization technologies,
which makes the switch be aware of VMs on the host,
so that traffic could be correctly forward.

VN-Tag is implemented on Cisco Nexus Series
Data Center Switches; while VEPA is implemented
by data center switching solutions from other vendors
like HP.