US Patent 7463597 Spanning tree protocol synchronization within virtual private networks

Loop detection information, such as information associated with the Spanning Tree Protocol (STP), is synchronized within virtual private networks. A routing protocol, such as the Border Gateway Protocol (BGP), is extended in a manner that allows STP information or other loop detection information to be opaquely communicated between routing devices across an intermediate network. These techniques may, for example, be useful in environments where Virtual Private LAN Service (VPLS) is run through one or more intermediate networks.