Patent ID: 8102775
Filing Date: 2012-01-24
Classification: H04L

Abstract:
1. A method comprising: attaching by a first router to an attachment router based on detecting a first router advertisement message from the attachment router, the first router advertisement message specifying an attachment prefix owned by the attachment router and a first tree information option, the attachment prefix distinct from a first address prefix owned by the first router, the first tree information option specifying a depth of the attachment router within a first tree topology and a first IP host address, the first IP host address of a first border router of a first autonomous system and serving as a first clusterhead having established the first tree topology in the first autonomous system, the attaching including attaching to the first tree topology based on selecting a default attachment address within the attachment prefix owned by the attachment router, and identifying the depth of the first router relative to the first clusterhead based on the incrementing the depth specified for the attachment router; receiving, by the first router, a second advertisement from a second router and specifying a second address prefix and a second tree information option, the second address prefix distinct from the attachment prefix and the first address prefix, the second tree information option specifying a second IP host address, the second IP host address of a second border router of the first autonomous system and serving as a second clusterhead distinct from the first clusterhead and having established a second tree topology in the first autonomous system and distinct from the first tree topology, the second tree information option further specifying the corresponding depth of the second router relative to the second clusterhead; and selectively sharing routing information, by the first router, with the second router based on the first router determining that the corresponding depth of the first router relative to the first clusterhead equals the corresponding depth of the second router relative to the second clusterhead, the routing information including specifying that the first address prefix is reachable via the first router, the routing information further including a host route for reaching the first IP host address via the first router, enabling the first border router and the second border router to share routing information for reaching a second autonomous system distinct from the first autonomous system.