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Hierarchical label switching across multiple OSPF areas

  • US 6,473,421 B1
  • Filed: 03/29/1999
  • Issued: 10/29/2002
  • Est. Priority Date: 03/29/1999
  • Status: Expired due to Term
First Claim
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1. An OSPF domain configured as a plurality of OSPF areas and comprising a plurality of OSPF-speaking label-switching routers, including at least one area border router and one autonomous-system border router, that maintain forwarding information bases containing forwarding entries, identified by respective forwarding labels, that contain information that the label-switching routers use for forwarding packets toward respective destinations, at least some of the label-switching routers responding to reception of an AS-External LSA by interpreting part of the AS-External LSA'"'"'s External Route Tag field as indicating whether the External Route Tag field contains a forwarding label and, if so, interpreting part of the External Route Tag field as a forwarding label and installing that forwarding label as a replacement label in any forwarding entry based on that LSA for the destination that the AS-External LSA'"'"'s Link-State ID field specifies.

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