The benefits of implementing policy-based routing in networks include the following:
• Source-based transit provider selection—ISPs in particular use policy-based routing to make routing decisions based on the source address. This allows traffic belonging to different customers to be routed through different Internet connections, across the policy routers in accordance with whatever human policy needs to be adhered to.
• Quality of service (QoS)—By setting the precedence or TOS values in the IP packet headers in routers at the edge of the network, organizations can provide QoS. In this way, the traffic can be differentiated, and queuing mechanisms can be implemented to prioritize traffic based on the QoS in the core or backbone of the network. This improves network performance because the configuration is done only at the edge of the network.
• Cost savings—The bulk traffic generated by a specific activity can be diverted to use a higher-bandwidth, high-cost link for a short time. Meanwhile, interactive traffic is provided basic connectivity over a lower-bandwidth, low-cost link. For example, a dial-on-demand ISDN line might be raised in response to traffic to a finance server for file transfers selected by policy routing.
• Load sharing—This allows the implementation of policies to distribute traffic among multiple paths based on the traffic characteristics. This does not detract from the dynamic load-sharing capabilities offered by destination-based routing that the Cisco IOS software has always supported.
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