Introducing the Link Controller
What is the BIG-IP Link Controller?
The BIG-IP Link Controller is a dedicated IP Application Switch that manages bi-directional traffic to a site across multiple links, regardless of connection type or provider. The Link Controller provides granular traffic control for Internet gateways, so that users can define how traffic is distributed across their links in a way that meets their business priorities. The Link Controller transparently monitors the availability and health of links to optimally direct traffic across the best available link.
The Link Controller includes the following features:
- Dynamic load balancing, based on the following link attributes:
- Total available bandwidth of the link
- The costs of purchased incremental bandwidth segments
- Inbound link capacity and resource limits
- Outbound link capacity and resource limits
- Router monitoring, to ensure high availability and continuous uptime
- Internet Link Evaluator, to view current Internet connectivity metrics
Understanding link load balancing
Link load balancing is defined as managing traffic across multiple Internet or WAN gateways. Link load balancing ensures high availability in the network, and enhances the performance of a web site or data center. Link load balancing provides a method by which an organization can reliably manage a multi-homed network. A multi-homed network is composed of one or more data centers that have more than one gateway, or link, to the Internet.
As enterprises increase their reliance on the Internet for delivering mission-critical applications and services, using only one link and ISP provider to access the public network represents a single point of failure. Link Load balancing, with the BIG-IP Link Controller, removes the risk of this single point of failure by enabling enterprises to control and monitor multiple links for their Internet connectivity.
The BIG-IP Link Controller:
- Guarantees reliable network connections and eliminates downtime by detecting any type of connection outage and transparently directing traffic away from malfunctioning or unavailable links.
- Distributes traffic to optimize the capacity of each connection by monitoring line throughput so that links do not become over-saturated.
- Increases user and site performance. The BIG-IP Link Controller measures and directs users over the best performing link to increase end user and site response times.
- Directs traffic over the least expensive link. Administrators can define the price of links and tiered pricing schemes. The BIG-IP Link Controller can direct traffic to the least expensive connection, lowering bandwidth costs.
- Traffic control to match business priorities. Organizations can define traffic policies to direct traffic over specified connections.
- Provides the Internet Link Evaluator, so that you can evaluate link performance, over time, to help you choose the Internet service providers that can best serve your customers.
- Provides integrated firewall load balancing, and enables customers to double their firewall performance through intelligent traffic management to redundant firewall configurations.
With the Link Controller, you can manage both inbound and outbound traffic over multiple links. You can distribute traffic based on performance, bandwidth cost, and bandwidth availability. The metrics you can specify are the limits on bandwidth usage and the pricing structure of your purchased bandwidth. When you specify the limits and pricing metrics for your links, the Link Controller then load balances the links based on those metrics.
Figure 1.1 shows the Modify Link screen, in the Configuration utility, where you define the metrics for a link.
Figure 1.1 The Modify Link screen in the Configuration utility
You can monitor several aspects of your managed links using the following tools:
- Link Statistics
The Link Statistics screen, in the Configuration utility, displays information about the status, bandwidth usage, bandwidth limits, and bandwidth costs for each of the links managed by the Link Controller.
For more information on link statistics, review the online help for the Link Statistics screen, in the Configuration utility.
- Internet Link Evaluator
The Internet Link Evaluator shows the average round trip times, completion rates, and router hops over the links managed by the Link Controller for any of the seven continents. You can use the Internet Link Evaluator to determine which links best serve a particular global region. You can also use the Internet Link Evaluator to compare link performance to a particular global region.
For more information on the Link Evaluator, review the online help for the Link Statistics screen, in the Configuration utility.
- Transparent monitoring
Transparent monitoring provides the health status of the routers for the managed links.