POLICY-BASED FORWARDING IN OPEN SHORTEST PATH FIRST (OSPF) NETWORKS

摘要

Policy-based traffic forwarding in a data network is implemented using policy-based control over propagation of LSA messages through the data network. Aroute tag is asserted in respect of a link state advertisement (LSA) messageadvertising a network address. Propagation of the LSA through the data networkis controlled using the asserted internal route tag. At each hop, a policydecision affecting the forwarding of the LSA is made. Exemplary policydecisions include, Pass and Discard. In addition, the forwarding table may beupdated using the route and address information contained in the LSA. In thiscase, routes entered in the forwarding table may be tagged as an inclusionroute or an exclusion route. This may be based on the value of an exclusionroute flag, such as a binary "0" or "1" inserted into an unused portion of theoptions field of the LSA.