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In the evolution of IP routing, Cisco performance routing (PfR) is a more advanced routing mechanism. Compared to traditional IP routing protocols like Static routing, RIP, OSPF, EIGRP or BGP that use static metrics to provide reachability information to the higher layers, PfR enhances traditional IP routing by selecting the best path based on live measurements and configured policies.

As we move from applications hitherto satisfied with simple reachability to applications whose performance is directly tied to network performance, traditional IP routing protocols fall short. They cannot guarantee complex application SLA requirements as these parameters are not included in the decision making process. This void can be filled by a routing mechanism that takes applications’ requirements while making routing decisions. PfR makes adaptive routing decisions based on criteria like latency, packet loss, jitter, traffic load and configured cost policies. This ability to configure flexibility into the routing decision process makes PfR closer to applications.

Expectations of applications from the underlying network infrastructure are ever increasing. Video applications for example are not just interested in reachability. Video applications have to satisfy delay, loss and jitter requirements to be of use to the end user. Even with reachability established, there can be pockets inside a network where video packets can be delayed or dropped. Reasons for this behaviour can range from over-subscription to badly configured QoS policies to link flapping. To mitigate such soft errors or brown-outs, a routing mechanism will have to continuously monitor the state of a path and might have to choose a different path upon breaching a set threshold.

Cisco PfR is typically deployed at an enterprise WAN edge where there are at least two egress network interfaces to the service provider network. Cisco PfR has several novel advantages. Apart from working around soft errors and best path selection based on advanced criteria, PfR provides intelligent load balancing at an application level. PfR can also be used for better utilization of links and increased availability when redundant network links are available. PfR cannot only be used to improve applications’ performance but also to minimize bandwidth usage costs by diverting the non-critical applications over cheaper links.

Upgrading from a traditional IP based routing mechanism to PfR is an inexpensive affair and relatively straight forward. Since PfR is inbuilt in IOS router images customers can upgrade easily with the addition of a single router acting as a master controller. To learn more about PfR, please visit the following website.

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