# US 2018/0324090 A1 · Multicast systems and methods for Segment Routing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0324090 A1 - Document ID: US20180324090A1 - Status: Published application - Kind: A1 - Application number: 16/034,495 - Filed: 2018-07-13 - Published: 2018-11-08 - Earliest claimed: 2015-07-28 - Assignees: Ciena Corporation - Applicants: Ciena Corporation - Inventors: Ian H. Duncan; Nigel L. Bragg - Web page: https://patentgrep.com/patent/US20180324090A1 ## CPC - H04L 45/50: using label swapping, e.g. multi-protocol label switch [MPLS] - H04L 12/18: for broadcast or conference {, e.g. multicast} - H04L 12/1854: {with non-centralised forwarding system, e.g. chaincast} - H04L 12/4625: {Single bridge functionality, e.g. connection of two networks over a single bridge} - H04L 12/4641: {Virtual LANs, VLANs, e.g. virtual private networks [VPN] (LAN interconnection over a bridge based backbone H04L12/462; encapsulation techniques H04L12/4633; routing of packets H04L45/00; packet switches H04L49/00; virtual private networks for security H04L63/0272)} - H04L 12/66: Arrangements for connecting between networks having differing types of switching systems, e.g. gateways - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A multicast method for Segment Routing includes, in a Segment Routing network with a plurality of nodes, wherein Segment Routing utilizes globally significant labels as node identifiers such that path state installation is only required at an ingress node of a Segment Routing domain, advertising a multicast flow by a source node; determining roles in the multicast flow for the plurality of nodes; and installing appropriate forwarding behavior for the multicast flow at the plurality of nodes based on the determined roles. The advertising can utilize Interior Gateway Protocol (IGP). For the multicast flow, source node segments are used to construct source routed trees rather than destination-based paths, wherein the source routed trees define broadcast paths, versus destination-based paths which are used in Segment Routing to define a node segment. ## Claims ### Claim 1 A multicast method for Segment Routing comprising: in a Segment Routing network comprising a plurality of nodes, wherein Segment Routing utilizes globally significant labels as node identifiers such that path state installation is only required at an ingress node of a Segment Routing domain, advertising a multicast flow by a source node; determining roles in the multicast flow for the plurality of nodes; and installing appropriate forwarding behavior for the multicast flow at the plurality of nodes based on the determined roles. ### Claim 2 (depends on 1) The multicast method of claim 1, wherein the advertising utilizes Interior Gateway Protocol (IGP). ### Claim 3 (depends on 1) The multicast method of claim 1, wherein, for the multicast flow, source node segments are used to construct source routed trees, wherein the source routed trees define broadcast paths. ### Claim 4 (depends on 1) The multicast method of claim 1, wherein the multicast flow is assigned a Segment Identifier (SID). ### Claim 5 (depends on 1) The multicast method of claim 1, wherein the determined roles are one of a branch point for replication, a root, and a leaf. ### Claim 6 (depends on 5) The multicast method of claim 5, wherein, at the branch point, the appropriate forwarding behavior comprises installation of labels for multiple egress ports associated with the multicast flow. ### Claim 7 (depends on 1) The multicast method of claim 1, wherein the multicast flow is a tree with a root at the source node, and further comprising: pruning the tree to deliver a flow-specific multicast tree. ### Claim 8 A Segment Routing network comprising: a plurality of nodes interconnected to one another, wherein Segment Routing utilizes globally significant labels as node identifiers such that path state installation is only required at an ingress node of a Segment Routing domain; wherein a multicast flow is advertised by a source node, and wherein each of the plurality of nodes is configured to determine its role in the multicast based on the advertisement and to install appropriate forwarding behavior for the multicast flow based on a determined role. ### Claim 9 (depends on 8) The Segment Routing network of claim 8, wherein the advertisement utilizes Interior Gateway Protocol (IGP). ### Claim 10 (depends on 8) The Segment Routing network of claim 8, wherein, for the multicast flow, source node segments are used to construct source routed trees, wherein the source routed trees define broadcast paths. ### Claim 11 (depends on 8) The Segment Routing network of claim 8, wherein the multicast flow is assigned a Segment Identifier (SID). ### Claim 12 (depends on 8) The Segment Routing network of claim 8, wherein the determined roles are one of a branch point for replication, a root, and a leaf. ### Claim 13 (depends on 12) The Segment Routing network of claim 12, wherein, at the branch point, the appropriate forwarding behavior comprises installation of labels for multiple egress ports associated with the multicast flow. ### Claim 14 (depends on 8) The Segment Routing network of claim 8, wherein the multicast flow is a tree with a root at the source node, and wherein the tree is pruned to deliver a flow-specific multicast tree. ### Claim 15 A node in Segment Routing network comprising: one or more ports; forwarding circuitry communicatively coupled to the one or more ports; and control circuitry communicatively coupled to the one or more ports and the forwarding circuitry, wherein Segment Routing utilizes globally significant labels as node identifiers such that path state installation is only required at an ingress node of a Segment Routing domain; wherein a multicast flow is advertised by a source node, and wherein the control circuitry is configured to determine the node's role in the multicast based on the advertisement and to install appropriate forwarding behavior for the multicast flow based on a determined role. ### Claim 16 (depends on 15) The node of claim 15, wherein the advertisement utilizes Interior Gateway Protocol (IGP). ### Claim 17 (depends on 15) The node of claim 15, wherein, for the multicast flow, source node segments are used to construct source routed trees, wherein the source routed trees define broadcast paths. ### Claim 18 (depends on 15) The node of claim 15, wherein the multicast flow is assigned a Segment Identifier (SID). ### Claim 19 (depends on 15) The node of claim 15, wherein the determined roles are one of a branch point for replication, a root, and a leaf. ### Claim 20 (depends on 15) The node of claim 15, wherein the multicast flow is a tree with a root at the source node, and wherein the tree is pruned to deliver a flow-specific multicast tree.