Patent ID: 6463061
Filing Date: 2002-10-08
Classification: H04L

Abstract:
A communications system comprising:A) a set of customer nodes so divided into at least first and second customer-node subsets that no node of any given subset is a routing adjacency of any other subset's node, the first customer-node subset including a target node associated with a target network address; B) a set of outside nodes separate from the set of customer nodes, at least one of the outside nodes being an outside edge router, and C) a service-provider network that associates internal and external VPN IDs with the set of customer nodes, forms a virtual private network with the set of customer nodes, and includes a plurality of provider nodes, including provider edge routers associated with the set of customer nodes, the provider edge routers associated with the set of customer nodes making routing decisions based on contents of reachability messages that they have received and together forming routing adjacencies with at least one node in every one of the customer-node subsets, each provider edge router associated with the set of customer nodes forming a routing adjacency with at least one customer node, denominated a customer edge router, to which the provider edge router is linked by at least one provider-customer channel, such that at least first and second ones of the provider-customer channels (i) are formed between the first customer-node subset and the service-provider network, (ii) provide access to the target node, and (iii) carry from at least one said customer edge router to at least one said provider edge router reachability messages that advertise a network-address range that includes the target network address, the provider nodes further including at least one provider edge router that is associated with the set of outside nodes, makes routing decisions based on the contents of reachability messages that it has received, and forms a provider-exterior channel with the outside edge router, wherein: i) when a said provider edge router receives through the first provider-customer channel a reachability message that advertises a network-address range that includes the target network address, the provider edge router sends a reachability message that advertises a combination of the internal VPN ID and the network-address range to each other provider edge router that forms a provider-customer channel with the set of customer communications nodes; ii) when a said provider edge router receives through the second provider-customer channel a reachability message that advertises a network-address range that includes the target network address, the provider edge router sends a reachability message that advertises a combination of the external VPN ID and the network-address range to at least one provider edge router associated with the set of outside nodes; iii) when a said provider edge router associated with the set of customer nodes receives from a provider router a reachability message that advertises a combination of a network-address range and the internal VPN ID associated with the set of customer nodes, the provider edge router sends to one said customer edge router with which it forms a provider-customer channel a reachability message that advertises the network-address range; and iv) when a said provider edge router associated with the set of outside nodes receives from a provider router a reachability message that advertises a combination of a network-address range and the external VPN ID associated with the set of customer nodes, it sends to at least one said customer edge, router with which it forms a provider-exterior channel a reachability message that advertises the network-address range.