LVS IPVS负载均衡机制详解

IPVS的负载均衡机制有三种：

Virtual Server via NAT

Virtual Server via IP Tunneling

Virtual Server via Direct Routing

1、 NAT

http://www.linuxvirtualserver.org/VS-NAT.html

NAT(网络地址转换):直接篡改数据包的源/目的地址。

Packet rewriting works as follows.

The incoming packet for web service would has source and destination addresses as:

SOURCE 202.100.1.2:3456 DEST 202.103.106.5:80

The load balancer will choose a real server, e.g. 172.16.0.3:8000. The packet would be rewritten and forwarded to the server as:

SOURCE 202.100.1.2:3456 DEST 172.16.0.3:8000

Replies get back to the load balancer as:

SOURCE 172.16.0.3:8000 DEST 202.100.1.2:3456

The packets would be written back to the virtual server address and returned to the client as:

SOURCE 202.103.106.5:80 DEST 202.100.1.2:3456

2、 IP Tunneling

http://www.linuxvirtualserver.org/VS-IPTunneling.html

IP Tunneling(IP隧道):在原数据包上封装一层IP地址，让私有网络的数据可以在公网上传输。(v*n就是这么实现的)

3、 Direct Routing

http://www.linuxvirtualserver.org/VS-DRouting.html

Direct Route(直接路由):通过Mac地址广播。

LoadBalance服务器和所有后端服务器必须在同一网段，要能够进行Mac广播。