Integrated Load Balancer Overview

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In Oracle Solaris, Integrated Load Balancer (ILB) provides Layer 3 and Layer 4 load-balancing capabilities. ILB operates at the network (IP) and transport (TCP/UDP) layers for the Oracle Solaris operating system installed on SPARC-based and x86-based systems. ILB can be used to improve reliability and scalability, and to minimize the response time of network services.

How Integrated Load Balancer Works

ILB intercepts incoming requests from clients, decides which back-end server should handle the requests based on load-balancing rules, and then forwards the requests to the selected server. ILB can also be used as a router for the back-end server. ILB performs optional health checks and provides the data for the load-balancing algorithms to verify whether the selected server can handle the incoming requests.

Features of ILB

The key features of ILB include the following:

Supports stateless Direct Server Return (DSR) and Network Address Translation (NAT) modes of operation for IPv4 and IPv6.

For information about DSR and NAT modes of operation, see ILB Operation Modes.
Assists traffic and load distribution and server selection by using a set of algorithms for the two modes of operation.
Enables ILB administration through a command-line interface (CLI).

For information about configuring ILB by using CLI, see Configuring ILB by Using the Command-Line Interface.
Provides server monitoring capabilities through health checks.

For information about server monitoring capabilities, see Monitoring Health Checks in ILB.

The following table lists and describes the features of ILB that are available for different modes of operation.

Table 3 ILB Features

Features	Description	Mode of Operation
Enables clients to ping virtual IP (VIP) addresses	ILB responds to ICMP echo requests from clients to VIP addresses.	Both DSR and NAT modes
Enables you to add and remove servers from a server group without interrupting service	ILB dynamically adds or removes servers from server group.	NAT mode
Enables you to configure session persistence ("stickiness")	ILB enables you to configure session persistence to your applications to send the connections or packets from a client to the same back-end server. ILB enables you to configure session persistence (that is, source address persistence) for a virtual service by using the `-p` option and specifying the `pmask` option in the `ilbadm create-rule` command. For more information, see Creating an ILB Rule.	Both DSR and NAT modes
Enables you to perform connection draining	ILB prevents new connections from being sent to a server that is disabled. This feature is useful for shutting down a server without disrupting the active connections or sessions. The existing connections to the server continue to function. After all the connections to that server are terminated, the server can be shut down for maintenance. After the server is ready to handle requests, it is enabled so that the load balancer can forward new connections to it.	NAT mode
Enables load-balancing of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ports	ILB balances the load on all ports on a given IP address across different sets of servers without requiring you to set up explicit rules for each port.	Both DSR and NAT modes
Enables you to specify independent ports for virtual services within the same server group	ILB enables you to specify different destination ports for different servers in the same server group.	NAT mode
Enables you to load-balance a simple port range	ILB balances loads on a range of ports on the VIP to a given server group. For convenience, you can conserve IP addresses by load-balancing different port ranges on the same VIP to different sets of back-end servers. Also, when session persistence is enabled for NAT mode, ILB sends requests from the same client IP address for different ports in the range to the same back-end server.	Both DSR an NAT modes
Enables port range shifting and collapsing	Port range shifting and collapsing depend on the port range of a server in a load-balancing rule. If the port range of a server is different from the VIP port range, port shifting is automatically implemented. If the server port range is a single port, then port collapsing is implemented.	NAT mode

For information about the ILB components, operating modes, algorithms, and how ILB works, see Overview of an Integrated Load Balancer. For more information about configuring and managing ILB, see Configuring and Managing the Integrated Load Balancer and Configuring ILB for High Availability.