LVS/TUN
From LVSKB
It stands for Linux Virtual Server via IP Tunneling, an IP load balancing technology implemented in LVS.
IP tunneling (IP encapsulation) is a technique to encapsulate IP datagram within IP datagram, which allows datagrams destined for one IP address to be wrapped and redirected to another IP address. This technique can be used to build a virtual server that the load balancer tunnels the request packets to the different servers, and the servers process the requests and return the results to the clients directly, thus the service can still appear as a virtual service on a single IP address.
See more information about Linux Virtual Server via IP Tunneling at http://www.linuxvirtualserver.org/VS-IPTunneling.html
