Explains flow-tag propagation concepts, including source and destination-based flow tag principles, to support advanced identification and handling of traffic flows across the network.
The flow-tag propagation is a routing feature that:
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establishes a correlation between route-policies and user-policies,
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enables you to steer traffic on the user side based on routing attributes such as AS number, prefix lists, community strings, and extended communities, and
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uses a logical numeric identifier (flow-tag) distributed through the RIB as a routing attribute in the FIB lookup table.
You instantiate a flow-tag using the 'set' operation in RPL, and reference it in a C3PL PBR policy, where it is associated with actions (policy-rules) based on the flow-tag value.
Applications of flow-tag propagation
You can use flow-tag propagation to:
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classify traffic based on destination IP addresses (using Community number) or based on prefixes (using Community number or AS number),
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select a TE-group that matches the cost of the path to reach a service edge, based on your site’s service level agreements (SLA),
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apply traffic policy (TE-group selection) for specific customers based on their SLA with clients, and
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divert traffic to an application or cache server.