About the Integrated Load Balancer

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Load balancers distribute network traffic across a number of servers. The distribution of a network's workload optimizes resource sharing and increases throughput and availability.

In Oracle Solaris, ILB provides Layer 3 and Layer 4 load-balancing capabilities. ILB operates at the network (IP) and transport (TCP/UDP) layers. ILB can be used to improve reliability and scalability, and to minimize the response time of network services.

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.
Assists traffic and load distribution and server selection by using a set of algorithms for the two modes of operation.
Enables ILB administration through the ilbadm command.
Provides server monitoring capabilities through health checks.

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

Table 4 ILB Features

Features	Description	Mode of Operation
Client systems can ping virtual IP (VIP) addresses	ILB responds to ICMP echo requests from client systems to VIP addresses.	DSR and NAT
Add or remove servers from group without interrupting service	ILB dynamically adds or removes servers.	NAT
Configure session persistence ("stickiness")	Through ILB rules, applications can send the connections or packets from a client system to the same back-end server.	DSR and NAT
Perform connection draining	Servers can be shut down without disrupting active connections or sessions.	NAT
Load balance TCP and UDP ports	ILB balances the load on all ports on a given IP address across different sets of servers without requiring explicit rules for each port.	DSR and NAT
Specify independent ports for virtual services	ILB enables you to specify different destination ports across multiple servers in the same server group.	NAT
Load balance a simple port range	ILB balances loads on a range of ports on the VIP to a given server group.	DSR and NAT
Port range shifting and collapsing	Port range shifting and collapsing depend on the port range of a server in a load-balancing rule.	NAT

ILB Components

ILB is managed by the Service Management Facility (SMF) service svc:/network/loadbalancer/ilb:default. ILB has three major components:

ilbadm command-line interface (CLI) – Enables you to configure load-balancing rules, perform optional health checks, and view statistics.
libilb configuration library – Contains functionalities that ilbadm and third-party applications can use for ILB administration.
ilbd daemon – Performs the following tasks:
- Manages persistent configuration across reboots and package updates
- Provides serial access to the ILB kernel module by processing the configuration information and sending it to the ILB kernel module for execution
- Performs health checks and sends the results to the ILB kernel module so that the load distribution is properly adjusted