Configuring Integrated Load Balancer

Certainly, Integrated Load Balancer (ILB) is one of the most attractive features of Oracle Solaris 11 because it provides network layer 3 and 4 with the load balance service. Basically, when a client requires a resource from an application (for example, a web server), the ILB framework decides which backend host (for example, web server A or B) will attend the request. Therefore, the main role of ILB is to decide to which backend server (for example, the Apache web server) the request will be forwarded. ILB supports two work methods in Oracle Solaris 11: Direct Server Return (DSR) and Network Address Translate (NAT). In both cases, the ILB framework uses one of four algorithms:

f Round robin: This tries to keep an equal statistic distribution over all backend servers

f Source IP hash: In this, the choice of the destination backend server is made by hashing the source IP address of the client

f Source IP port hash: In this, the choice of the destination backend server is made by hashing the source IP and port address of the client

f Source IP VIP hash: In this, the choice of the destination backend server is made by hashing the source and destination IP address of the client

The DSR method allows ILB to receive the request in order to decide which backend server (for example, Apache servers) the request will be forwarded to and to make the answer from the backend server return directly to the client. Nevertheless, if the ILB server is configured as a router, then all answers from backend servers can be routed to the client through ILB.

Networking

When ILB is configured to use the DSR method, its performance is better than NAT and it also shows better transparency because only the destination MAC address is changed and the answer returning to the client can bypass the ILB server, as we've mentioned previously.

Unfortunately, if we try to add a new backend server, the connection will be disrupted because the connection is stateless.

A scheme about what we've mentioned up to now can be viewed as follows:

f request: client | ILB server | backend servers (A or B)

f answer: backend server | client

f answer (ILB as router): backend server | ILB (router) | client

The following image (the IP addresses in the image are only an example) also describes the process:

The NAT method (half or full) allows ILB to rewrite all requests by changing the destination IP address and—when ILB is working in the NAT full method—by also changing the source address by masking the real IP client with the ILB IP address. Backend servers think that the request is coming from the ILB server instead of coming from the client.

Chapter 3

The following is a scheme that explains this process:

f request: client | ILB server (NAT) | backend server (A or B)

f answer: backend server (A or B) | ILB server (NAT) | client To make this easier, the following diagram explains the process:

Unlike DSR, the ILB NAT model requires the ILB server as a default gateway.