# US 8,571,029 B1 · Label switched path hierarchy for intra-area segments of inter-area point-to-multipoint label switched paths > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,571,029 B1 - Document ID: US8571029B1 - Status: Granted - Kind: B1 - Application number: 12/980,106 - Filed: 2010-12-28 - Granted: 2013-10-29 - Earliest claimed: 2010-11-12 - Assignees: Juniper Networks, Inc. - Applicants: Rahul Aggarwal; Yakov Rekhter - Inventors: Rahul Aggarwal; Yakov Rekhter - Web page: https://patentgrep.com/patent/US8571029B1 ## CPC - H04L 45/50: using label swapping, e.g. multi-protocol label switch [MPLS] - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract In general, techniques are described for providing multicast communication in a seamless MPLS architecture, in which thousands of PE routers within different routing areas of the same AS require P2MP connectivity to receive multicast communication. In particular, the techniques enable building inter-area P2MP segmented LSPs within an AS by stitching together intra-area segments of the inter-area P2MP segmented LSPs. The techniques provide LSP hierarchy with segmentation to enable aggregation of congruent intra-area segments within a routing area into an intra-area aggregate LSP. The AS may use the BGP as the inter-area label distribution protocol, and each routing area within the AS may independently select one of the multicast MPLS protocols as its intra-area label distribution protocol. The seamless MPLS architecture may be used by private network instances, such as multicast VPLS instances, MVPN instances, and IP multicast instances. ## Claims ### Claim 1 A method of establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within an autonomous system (AS) of a public network, the method comprising: advertising, with an egress network device in a first routing area, a first border gateway protocol (BGP) Leaf auto-discovery route identifying a leaf node for a first intra-area segment of a first inter-area P2MP segmented LSP in the first routing area; advertising, with the egress network device, a second BGP Leaf auto-discovery route identifying a leaf node for a second intra-area segment of a second inter-area P2MP segmented LSP in the first routing area, wherein the first and second BGP Leaf auto-discovery routes are used to establish an intra-area aggregate LSP within the first routing area that uses LSP hierarchy to carry the first intra-area segment of the first inter-area P2MP segmented LSP and the second intra-area segment of the second inter-area P2MP segmented LSP; establishing the first inter-area P2MP segmented LSP across two or more routing areas within the AS by stitching, with the egress network device, the first intra-area segment carried by the intra-area aggregate LSP in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP within a second routing area based on labels advertised in BGP; and establishing the second inter-area P2MP segmented LSP across two or more routing areas within the AS by stitching, with the egress network device, the second intra-area segment carried by the intra-area aggregate LSP in the first routing area to other intra-area segments of the second inter-area P2MP segmented LSP within the second routing area based on labels advertised in BGP. ### Claim 2 (depends on 1) The method of claim 1, wherein the intra-area aggregate LSP is established within the first routing area when the first and second intra-area segments are at least partially congruent within the first routing area, regardless of whether the first and second inter-area P2MP segmented LSPs are not even partially congruent within the AS. ### Claim 3 (depends on 1) The method of claim 1, the method further comprising binding the intra-area aggregate LSP to the first inter-area P2MP segmented LSP and the second inter-area P2MP segmented LSP within the first routing area. ### Claim 4 (depends on 3) The method of claim 3, wherein binding the intra-area aggregate LSP to the first inter-area P2MP segmented LSP comprises receiving a first BGP Provider Multicast Service Interface (PMSI) auto-discovery route for the first inter-area P2MP segmented LSP that includes an identity of the intra-area aggregate LSP and an upstream-assigned Multi-Protocol Label Switching (MPLS) label of the first intra-area segment, and wherein establishing the first inter-area P2MP segmented LSP comprises stitching the first intra-area segment in the first routing area to the other intra-area segments in the second routing area based on the first BGP PMSI auto-discovery route. ### Claim 5 (depends on 3) The method of claim 3, wherein binding the intra-area aggregate LSP to the second inter-area P2MP segmented LSP comprises receiving a second BGP Provider Multicast Service Interface (PMSI) auto-discovery route for the second inter-area P2MP segmented LSP that includes an identity of the intra-area aggregate LSP and an upstream-assigned Multi-Protocol Label Switching (MPLS) label of the second intra-area segment, and wherein establishing the second inter-area P2MP segmented LSP comprises stitching the second intra-area segment in the first routing area to the other intra-area segments in the second routing area based on the second BGP PMSI auto-discovery route. ### Claim 6 (depends on 1) The method of claim 1, wherein a multicast Multi-Protocol Label Switching (MPLS) protocol is independently selected as an intra-area label distribution protocol for the first routing area, and wherein the intra-area aggregate LSP is established within the first routing area based on the first and second BGP Leaf auto-discovery routes using the selected multicast MPLS protocol for the first routing area. ### Claim 7 (depends on 1) The method of claim 1, wherein the two or more routing areas comprise Interior Gateway Protocol (IGP) areas of the AS. ### Claim 8 A network system of an autonomous system (AS) of a public network for establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within the AS, the network system comprising: an egress network device within a first routing area that advertises a first border gateway protocol (BGP) Leaf auto-discovery route identifying a leaf node for a first intra-area segment of a first inter-area P2MP segmented LSP in the first routing area, and advertises a second BGP Leaf auto-discovery route identifying a leaf node for a second intra-area segment of a second inter-area P2MP segmented LSP in the first routing area; and an ingress network device within the first routing area that establishes an intra-area aggregate LSP within the first routing area based on the first and second BGP Leaf auto-discovery routes, wherein the intra-area aggregate LSP uses LSP hierarchy to carry the first intra-area segment of the first inter-area P2MP segmented LSP and the second intra-area segment of the second inter-area P2MP segmented LSP, and advertises binding of the intra-area aggregate LSP to the first and second inter-area P2MP segmented LSPs using BGP Provider Multicast Service Interface (PMSI) auto-discovery routes that include an identity of the intra-area aggregate LSP and Multi-Protocol Label Switching (MPLS) labels of the first and second intra-area segments, wherein the egress network device establishes the first inter-area P2MP segmented LSP across two or more routing areas of the AS by stitching the first intra-area segment in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP within a second routing area based on the BGP PMSI auto-discovery routes, and wherein the egress network device establishes the second inter-area P2MP segmented LSP across two or more routing areas of the AS by stitching the second intra-area segment in the first routing area to other intra-area segments of the second inter-area P2MP segmented LSP within the second routing area based on the BGP PMSI auto-discovery routes. ### Claim 9 (depends on 8) The network system of claim 8, wherein the ingress network device establishes the intra-area aggregate LSP within the first routing area when the first and second intra-area segments are at least partially congruent within the first routing area, regardless of whether the first and second inter-area P2MP segmented LSPs are not even partially congruent within the AS. ### Claim 10 (depends on 8) The network system of claim 8, wherein the ingress network device: receives the first BGP Leaf auto-discovery route identifying the leaf node for the first intra-area segment of the first inter-area P2MP segmented LSP within the first routing area; receives the second BGP Leaf auto-discovery route identifying the leaf node for the second intra-area segment of the second inter-area P2MP segmented LSP within the first routing area; and establishes the intra-area aggregate LSP within the first routing area based on the first and second BGP Leaf auto-discovery routes using a multicast MPLS protocol. ### Claim 11 (depends on 8) The network system of claim 8, wherein one or more provider devices within the first routing area use LSP hierarchy to maintain forwarding and routing information for the first and second intra-area segments carried within the intra-area aggregate LSP without maintaining forwarding and routing information for the first and second inter-area P2MP segmented LSPs. ### Claim 12 (depends on 8) The network system of claim 8, wherein a multicast MPLS protocol is independently selected as an intra-area label distribution protocol for the first routing area, and wherein the ingress network device establishes the intra-area aggregate LSP within the first routing area based on the first and second BGP Leaf auto-discovery routes using the selected multicast MPLS protocol for the first routing area. ### Claim 13 (depends on 8) The network system of claim 8, wherein the two or more routing areas comprise Interior Gateway Protocol (IGP) areas of the AS. ### Claim 14 An egress network device within a first routing area of an autonomous system (AS) of a public network for establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within the AS, the network device comprising: a control unit configured to: advertise a first border gateway protocol (BGP) Leaf auto-discovery route identifying a leaf node for a first intra-area segment of a first inter-area P2MP segmented LSP in the first routing area; advertise a second BGP Leaf auto-discovery route identifying a leaf node for a second intra-area segment of a second inter-area P2MP segmented LSP in the first routing area, wherein the first and second BGP Leaf auto-discovery routes are used to establish an intra-area aggregate LSP within the first routing area that uses LSP hierarchy to carry the first intra-area segment of the first inter-area P2MP segmented LSP within the AS and the second intra-area segment of the second inter-area P2MP segmented LSP within the AS; establish the first inter-area P2MP segmented LSP across two or more routing areas of the AS by stitching the first intra-area segment carried by the intra-area aggregate LSP in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP within a second routing area based on labels advertised in BGP; and establish the second inter-area P2MP segmented LSP across two or more routing areas of the AS by stitching the second intra-area segment carried by the intra-area aggregate LSP in the first routing area to other intra-area segments of the second inter-area P2MP segmented LSP within the second routing area based on labels advertised in BGP. ### Claim 15 An ingress network device within a first routing area of an autonomous system (AS) of a public network for establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within the AS, the network device comprising: a control unit configured to: establish an intra-area aggregate LSP within the first routing area that uses LSP hierarchy to carry a first intra-area segment of a first inter-area P2MP segmented LSP and a second intra-area segment of a second inter-area P2MP segmented LSP; advertise a binding of the intra-area aggregate LSP to the first inter-area P2MP segmented LSP using a first BGP Provider Multicast Service Interface (PMSI) auto-discovery route that includes an identity of the intra-area aggregate LSP and a first Multi-Protocol Label Switching (MPLS) label of the first intra-area segment, wherein the first inter-area P2MP segmented LSP is established by stitching the first intra-area segment in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP in a second routing area based on the advertised first BGP PMSI auto-discovery route; and advertise a binding of the intra-area aggregate LSP to the second inter-area P2MP segmented LSP using a second BGP PMSI auto-discovery route that includes the identity of the intra-area aggregate LSP and a second MPLS label of the second intra-area segment, wherein the second inter-area P2MP segmented LSP is established by stitching the second intra-area segment in the first routing area to other intra-area segments for the second inter-area P2MP segmented LSP in the second routing area based on the advertised second BGP PMSI auto-discovery route. ### Claim 16 (depends on 15) The network device of claim 15, wherein the control unit establishes the intra-area aggregate LSP within the first routing area when the first and second intra-area segments are at least partially congruent within the first routing area, regardless of whether the first and second inter-area P2MP segmented LSPs are not even partially congruent within the AS. ### Claim 17 (depends on 15) The network device of claim 15, wherein the control unit: receives a first BGP Leaf auto-discovery route identifying a leaf node for the first intra-area segment of the first inter-area P2MP segmented LSP within the first routing area; receives a second BGP Leaf auto-discovery route identifying a leaf node for the second intra-area segment of the second inter-area P2MP segmented LSP within the first routing area; and establishes the intra-area aggregate LSP within the first routing area based on the first and second BGP Leaf auto-discovery routes using a multicast MPLS protocol. ### Claim 18 A non-transitory computer-readable storage medium encoded with instructions for establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within an autonomous system (AS) of a public network, the instructions causing one or more programmable processors to: advertise a first border gateway protocol (BGP) Leaf auto-discovery route identifying a leaf node for a first intra-area segment of a first inter-area P2MP segmented LSP in a first routing area; advertise a second BGP Leaf auto-discovery route identifying a leaf node for a second intra-area segment of a second inter-area P2MP segmented LSP in the first routing area, wherein the first and second BGP Leaf auto-discovery routes are used to establish an intra-area aggregate LSP within the first routing area that uses LSP hierarchy to carry the first intra-area segment of the first inter-area P2MP segmented LSP and the second intra-area segment of the second inter-area P2MP segmented LSP; establish the first inter-area P2MP segmented LSP across two or more routing areas within the AS by stitching the first intra-area segment in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP within a second routing area based on labels advertised in BGP; establish the second inter-area P2MP segmented LSP across two or more routing areas within the AS by stitching the first intra-area segment in the first routing area to other intra-area segments of the second inter-area P2MP segmented LSP within the second routing area based on labels advertised in BGP. ### Claim 19 (depends on 18) The non-transitory computer-readable storage medium of claim 18, further comprising instructions for causing one or more programmable processors to bind the intra-area aggregate LSP to the first inter-area P2MP segmented LSP and the second inter-area P2MP segmented LSP within the first routing area. ### Claim 20 (depends on 19) The non-transitory computer-readable storage medium of claim 19, further comprising instructions for causing one or more programmable processors to receive the binding of the intra-area aggregate LSP to the first inter-area P2MP segmented LSP within a BGP Provider Multicast Service Interface (PMSI) auto-discovery route for the first inter-area P2MP segmented LSP that includes an identity of the intra-area aggregate LSP and an upstream-assigned Multi-Protocol Label Switching (MPLS) label of the first intra-area segment, and stitch the first intra-area segment in the first routing area to the other intra-area segments in the second routing area based on the first BGP PMSI auto-discovery route. ### Claim 21 (depends on 19) The non-transitory computer-readable storage medium of claim 19, further comprising instructions for causing one or more programmable processors to receive the binding of the intra-area aggregate LSP to the second inter-area P2MP segmented LSP within a BGP Provider Multicast Service Interface (PMSI) auto-discovery route for the second inter-area P2MP segmented LSP that includes an identity of the intra-area aggregate LSP and an upstream-assigned Multi-Protocol Label Switching (MPLS) label of the second intra-area segment, and stitch the second intra-area segment in the first routing area to the other intra-area segments in the second routing area based on the second BGP PMSI auto-discovery route. ### Claim 22 A method of establishing inter-area point-to-multipoint (P2MP) segmented label switched paths (LSPs) across two or more routing areas within an autonomous system (AS) of a public network, the method comprising: establishing, with an ingress network device in a first routing area, an intra-area aggregate LSP within the first routing area that uses LSP hierarchy to carry a first intra-area segment of a first inter-area P2MP segmented LSP and a second intra-area segment of a second inter-area P2MP segmented LSP; advertising, with the ingress network device, a binding of the intra-area aggregate LSP to the first inter-area P2MP segmented LSP using a first Border Gateway Protocol (BGP) Provider Multicast Service Interface (PMSI) auto-discovery route that includes an identity of the intra-area aggregate LSP and a first Multi-Protocol Label Switching (MPLS) label of the first intra-area segment, wherein the first inter-area P2MP segmented LSP is established by stitching the first intra-area segment in the first routing area to other intra-area segments of the first inter-area P2MP segmented LSP in a second routing area based on the advertised first BGP PMSI auto-discovery route; and advertising, with the ingress network device, a binding of the intra-area aggregate LSP to the second inter-area P2MP segmented LSP using a second BGP PMSI auto-discovery route that includes the identity of the intra-area aggregate LSP and a second MPLS label of the second intra-area segment, wherein the second inter-area P2MP segmented LSP is established by stitching the second intra-area segment in the first routing area to other intra-area segments for the second inter-area P2MP segmented LSP in the second routing area based on the advertised second BGP PMSI auto-discovery route. ### Claim 23 (depends on 22) The method of claim 22, further comprising establishing the intra-area aggregate LSP within the first routing area when the first and second intra-area segments are at least partially congruent within the first routing area, regardless of whether the first and second inter-area P2MP segmented LSPs are not even partially congruent within the AS. ### Claim 24 (depends on 22) The method of claim 22, wherein establishing the intra-area aggregate LSP comprises: receiving a first BGP Leaf auto-discovery route identifying a leaf node for the first intra-area segment of the first inter-area P2MP segmented LSP in the first routing area; receiving a second BGP Leaf auto-discovery route identifying a leaf node for the second intra-area segment of the second inter-area P2MP segmented LSP in the routing area; and establishing the intra-area aggregate LSP within the first routing area based on the first and second BGP Leaf auto-discovery routes using a multicast MPLS protocol. ### Claim 25 (depends on 22) The method of claim 22, further comprising advertising a first BGP Leaf auto-discovery route identifying a leaf node for a third intra-area segment of the first inter-area P2MP segmented LSP within an upstream routing area, and advertising a second BGP Leaf auto-discovery route identifying a leaf node for a fourth intra-area segment of the second inter-area P2MP segmented LSP within the upstream routing area. ### Claim 26 (depends on 22) The method of claim 22, further comprising independently selecting a multicast MPLS protocol as an intra-area label distribution protocol for the first routing area, and wherein establishing the intra-area aggregate LSP comprises establishing the intra-area aggregate LSP within the first routing area using the selected multicast MPLS protocol for the first routing area. ### Claim 27 (depends on 22) The method of claim 22, wherein the two or more routing areas comprise Interior Gateway Protocol (IGP) areas of the AS.