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

摘要

Policy-based traffic forwarding in a data network is implemented using polic y- based control over propagation of LSA messages through the data network. A route tag is asserted in respect of a link state advertisement (LSA) message advertising a network address. Propagation of the LSA through the data netwo rk is controlled using the asserted internal route tag. At each hop, a policy decision affecting the forwarding of the LSA is made. Exemplary policy decisions include, Pass and Discard. In addition, the forwarding table may b e updated using the route and address information contained in the LSA. In thi s case, routes entered in the forwarding table may be tagged as an inclusion route or an exclusion route. This may be based on the value of an exclusion route flag, such as a binary "0" or "1" inserted into an unused portion of t he options field of the LSA.