Lösungen > xBalancer™ On Link-State Awareness

Few weeks ago we wrote about xBalancer link-state awareness and hash parameters. It looks like this feature continues to generate a lot of interest from our customers and prospects.

Link State Awareness, when enabled, means that load balancing will react to the link status of a sensor port. Below is the explanation from the user guide. Please let us know if this is not clear enough:

For high-availability in inline load balancing applications, xBalancer constantly monitors the links attached to the tools. If any links go down, xBalancer reallocates traffic away from the down tools and distributes it among the remaining up tools. When a down tool comes back online, traffic resumes being allocated to it. When traffic reallocation happens, flows that are not being switched are not affected.
For example, if tool #1 goes down, flows going through tool #1 are temporarily broken (a) because packets are dropped between the time the tool fails and traffic reallocation takes place, about a few seconds, and (b) because the flows are switched to other tools. But flows going through the other tools are not broken.
However, you should plan for the risk of tool oversubscription due to the increased load on the remaining tools; for example, if you are load balancing to two tools and one tool goes down, the other tool gets the entire traffic load which may oversubscribe it. (Link-state awareness can be enabled or disabled on a global basis.)
The lb_link_aware argument controls whether the load balancer is link-state aware: When lb_link_aware=on, load balancers distribute all traffic among all ports in the load balance group that have link up; if a link goes down, no traffic is lost. When lb_link_aware=off, load balancers distribute all traffic among all ports in the load balance group regardless of link state; if a link goes down, the traffic that would be sent to that link is lost.




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