load balancing, usually called Layer 4 LAN switching, as part of Linux kernel. • IPVS is incorporated into the LVS (Linux Virtual Server), where it runs on a host and acts as a load balancer in front of a cluster of real servers. • Same to IPTables, IPVS is built on top of Netfilter. • Support 3 load balancing mode: DNAT, DR(or DSR) and IP tunnel.