Protecting Critical Applications with SLAs
Another use case that drives changes in the WAN is the capability to provide an SLA for critical applications. This is accomplished by being able to route traffic based on the application requirements, as mentioned briefly earlier. This also provides statistics on how the applications are performing. Based on the policy that can be created, an SLA determines if the application is adhering to that policy, and performing properly, or if it is experiencing some sort of detriment such as jitter, loss, or delay. If this is the case, the application can be routed to another transport that will ensure the application is within policy and able to perform to the SLA that is expected of it. Figure 1-9 illustrates this particular scenario. A good example of this in a hybrid WAN environment would be an MPLS link and an Internet link. If the MPLS link is experiencing 5% packet loss and the Internet link is not, it might be appropriate to route the application over the Internet link to ensure that the application is functioning properly and users are having the best experience interacting with the application.
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FIGURE 1.9 Routing Based on Application Performance