High Availability for Applications

Downtime Is Not an Option

Application downtime costs businesses of all sizes thousands to millions of dollars each year, from the inability to process transactions, opportunity loss and brand perception damage. In the Internet age alternatives are just a click away, so to mitigate loss a comprehensive High Availability strategy is needed.

In the event any network device such as Layer 2 or 3 switches, routers, servers or active Layer 4/7 devices have an outage, the standby Layer 4/7 device must provide immediate detection and failover. 

The AX Series meets this challenge, through internal redundant components and by ensuring the Layer 4/7 devices can fail over efficiently. To enable 100 percent uptime for critical business applications, features such as sub-second Layer 2 failover and session synchronization are essential to ensure user sessions are not lost. Examples of failures that require seamless traffic failover include:

• Layer 3 switch failover due to link down/up or Layer 3 switch failure
• Active power off or any unexpected stop and restart
• Loss of connectivity to the Layer 2 switch due to link down/up or Layer 2 switch failure
• 10Gb uplink down/up

Failover modes that can be used to recover include:

• Active-Passive
• Active-Active

Active-Active allows both boxes to handle traffic continuously, while each box also serves as a standby for the other box. Active-Standby uses one of the boxes for traffic and uses the other box as a hot standby. Due to the need for High Availability, capacity has to be carefully analyzed to ensure Active-Active configurations are not over 50 percent utilization. This ensures that a single load balancer can accommodate the load in the event of any issue.

AX Series for Layer 2 Hot Standby

Another unique AX Series feature is failover for Layer 2 traffic, in addition to Layer 4/7 traffic. This feature offers enterprises and service providers with redundant data center networks the confidence that their key business applications will be available to their customers, employees and anyone who needs to access their information (see diagram below).