IPVS (IP Virtual Server) implements transport-layer load balancing inside the Linux kernel, so called Layer-4 LAN switching. IPVS is incorporated into Linux Virtual Server, where it runs on a host and acts as a load balancer at the front of a cluster of real servers, it can direct requests for TCP and UDP based services to the real servers, and makes services of the real servers appear as a virtual service on a single IP address. It is built on top of Netfilter.
