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(12) United States Patent ao) Patent No.: us 6,339,595 Bi
Rekhter et al. (45) Date of Patent: Jan. 15,2002
(54) PEER-MODEL SUPPORT FOR VIRTUAL
PRIVATE NETWORKS WITH POTENTIALLY
(75) Inventors: Yakov Rekhter, New Rochelle, NY (US); Eric C. Rosen, Arlington, MA (US)
(73) Assignee: Cisco Technology, Inc.
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 08/997,343
(22) Filed: Dec. 23, 1997
(51) Int. CI.7 H04L 12/28
(52) U.S. CI 370/392; 370/400; 370/401
(58) Field of Search 370/351-360,
370/389, 392, 393, 400, 401, 474, 404,
(56) References Cited
U.S. PATENT DOCUMENTS
A service provider's routers (PE1, PI, P2, PE2) provide connections between and share routine information with routers (CE1, CE2) of a customer virtual private network (VPN) as well as routers of other customers' VPNs, which may have overlapping address spaces. A service provider's edge router (PE1) informed by the customer's router (CE1) that it will forward packets to a given prefix notifies the other edge router (PE2) that PE1 can forward packets to that address prefix if the destination is in the VPN to which CE1 belongs. PE1 also tells PE2 to tag any thus-destined packets with a particular tag T3. PE2 stores this information in a forwarding information base that it separately keeps for that VPN so that when PE2 receives from a router CE2 in the same VPN a packet whose destination address has that prefix, it tags the packet as requested. But PE2 also tags it with a tag T2 that the router P2 to which PE2 first sends it has asked PE2 to apply to packets to be sent to PEL P2 routes the packet in accordance with T2, sending it to PI after replacing T2 with a tag Tl that PI has similarly asked P2 to use. PI removes Tl from the packet and forwards it in accordance with Tl to PE1, which in turn removes T3 from the packet and forwards it in accordance with T3 to CE1. In this manner, only the edge routers need to maintain separate routing information for separate VPNs.
21 Claims, 24 Drawing Sheets
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