# US 2019/0379596 A1 · Methods and Systems preventing Make Before Break failures during soft preemption in MPLS > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0379596 A1 - Document ID: US20190379596A1 - Status: Published application - Kind: A1 - Application number: 16/042,236 - Filed: 2018-07-23 - Published: 2019-12-12 - Earliest claimed: 2018-06-08 - Assignees: Ciena Corporation - Applicants: Ciena Corporation - Inventors: Piyush Sharma; Sudarshan Sodhani - Web page: https://patentgrep.com/patent/US20190379596A1 ## CPC - H04L 45/22: {Alternate routing} - H04L 45/28: using route fault recovery - H04L 45/50: using label swapping, e.g. multi-protocol label switch [MPLS] - H04L 43/0882: Utilisation of link capacity - H04L 67/56: Provisioning of proxy services (store-and-forward switching systems in data switching networks H04L12/54) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method implemented at an intermediate node in a Multiprotocol Label Switching (MPLS) network to prevent Make Before Break (MBB) failures during soft preemption of a lower priority Label Switched Path (LSP) includes, responsive to a determination the lower priority LSP needs preemption, determining a first route of a higher priority LSP which caused the preemption and bandwidth on the first route; determining a second route which is a current route of the lower priority LSP and bandwidth on the second route; analyzing the first route and the second route to determine one or more excluded interfaces which do not support the lower priority LSP due to the higher priority LSP; and transmitting a preemption message designating a soft preemption of the lower priority LSP including all of the excluded interfaces therein towards an ingress node along the second route. ## Claims ### Claim 1 A method implemented at an intermediate node in a Multiprotocol Label Switching (MPLS) network to prevent Make Before Break (MBB) failures during soft preemption of a lower priority Label Switched Path (LSP), the method comprising: responsive to a determination the lower priority LSP needs preemption, determining a first route of a higher priority LSP which caused the preemption and bandwidth on the first route; determining a second route which is a current route of the lower priority LSP and bandwidth on the second route; analyzing the first route and the second route to determine one or more excluded interfaces which do not support the lower priority LSP due to the higher priority LSP; and transmitting a preemption message designating a soft preemption of the lower priority LSP including all of the excluded interfaces therein towards an ingress node along the second route. ### Claim 2 (depends on 1) The method of claim 1, wherein the preemption message comprises a PATH ERROR message and the excluded interfaces are listed in an EXCLUDE_ROUTE object. ### Claim 3 (depends on 1) The method of claim 1, further comprising: receiving a second preemption message for a second lower priority LSP and a second higher priority LSP; determining any local interfaces listed in the excluded interfaces of the second preemption message; and preventing transmission of any preemption messages for the second lower priority LSP based on the local interfaces which are listed in the excluded interfaces of the second preemption message. ### Claim 4 (depends on 1) The method of claim 1, further comprising: receiving a second preemption message for a second lower priority LSP and a second higher priority LSP, wherein the intermediate node is an ingress node for the second lower priority LSP; determining any excluded interfaces listed in the excluded interfaces of the second preemption message; and determining and signaling a new path for the second lower priority LSP exclusive of the excluded interfaces. ### Claim 5 (depends on 1) The method of claim 1, wherein the excluded interfaces comprise an address of a local interface at the intermediate node and one or more addresses of remote interfaces of nodes that are in the first route of the higher priority LSP. ### Claim 6 (depends on 1) The method of claim 1, wherein the preemption message is transmitted to upstream towards an ingress node for the lower priority LSP and through one or more additional intermediate nodes. ### Claim 7 (depends on 6) The method of claim 6, wherein the one or more additional intermediate nodes analyze the preemption message for any of its local interfaces contained in the excluded interfaces and prevents sending another preemption for the lower priority LSP for any local interface in the excluded interfaces. ### Claim 8 (depends on 6) The method of claim 6, wherein the ingress node determines and signals a new path for the lower priority LSP exclusive of the excluded interfaces upon receipt of the preemption message. ### Claim 9 A node in a Multiprotocol Label Switching (MPLS) network configured to prevent Make Before Break (MBB) failures during soft preemption of a lower priority Label Switched Path (LSP), the node comprising: a plurality of ports; forwarding circuitry configured to forward data between the plurality of ports; and control circuitry communicatively coupled to the plurality of ports and the forwarding circuitry and configured to responsive to a determination the lower priority LSP needs preemption, determine a first route of a higher priority LSP which caused the preemption and bandwidth on the first route, determine a second route which is a current route of the lower priority LSP and bandwidth on the second route, analyze the first route and the second route to determine one or more excluded interfaces which do not support the lower priority LSP due to the higher priority LSP, and cause transmission of a preemption message designating a soft preemption of the lower priority LSP including all of the excluded interfaces therein towards an ingress node along the second route of the lower priority LSP. ### Claim 10 (depends on 9) The node of claim 9, wherein the preemption message comprises a PATH ERROR message and the excluded interfaces are listed in an EXCLUDE_ROUTE object. ### Claim 11 (depends on 9) The node of claim 9, wherein the control circuitry is further configured to responsive to reception of a second preemption message for a second lower priority LSP and a second higher priority LSP, determine any local interfaces listed in the excluded interfaces of the second preemption message, and prevent transmission of any preemption messages for the second lower priority LSP based on the local interfaces which are included in the excluded interfaces of the second preemption message. ### Claim 12 (depends on 9) The node of claim 9, wherein the control circuitry is further configured to responsive to reception of a second preemption message for a second lower priority LSP and a second higher priority LSP, wherein the node is an ingress node for the second lower priority LSP, determine any excluded interfaces listed in the excluded interfaces of the second preemption message, and determine and cause signaling of a new path for the second lower priority LSP exclusive of the excluded interfaces. ### Claim 13 (depends on 9) The node of claim 9, wherein the excluded interfaces comprise an address of a local interface at the node and one or more addresses of remote interfaces of nodes that are in a route of the higher priority LSP. ### Claim 14 (depends on 9) The node of claim 9, wherein the preemption message is transmitted to upstream an ingress node for the lower priority LSP and through one or more additional intermediate nodes. ### Claim 15 (depends on 14) The node of claim 14, wherein the one or more additional intermediate nodes analyze the preemption message for any local interface contained in the excluded interfaces and prevent sending another preemption for the lower priority LSP for the local interface in the excluded interfaces. ### Claim 16 (depends on 14) The node of claim 14, wherein the ingress node determines and signals a new path for the lower priority LSP exclusive of the excluded interfaces upon receipt of the preemption message. ### Claim 17 A Multiprotocol Label Switching (MPLS) network configured to prevent Make Before Break (MBB) failures during soft preemption of a lower priority Label Switched Path (LSP), the MPLS network comprising: a plurality of nodes interconnected by a plurality of links; wherein a lower priority LSP is configured over the plurality of links, and, responsive to a reservation for a higher priority LSP, an intermediate node of the plurality of nodes is configured to determine a requirement to preempt the lower priority LSP due to the higher priority LSP, determine a first route of the higher priority LSP and bandwidth on the first route, determine a second route which is a current route of the lower priority LSP and bandwidth on the second route, analyze the first route and the second route to determine one or more excluded interfaces which do not support the lower priority LSP due to the higher priority LSP, and transmit a preemption message designating a soft preemption of the lower priority LSP including all of the excluded interfaces therein towards an ingress node along the second route. ### Claim 18 (depends on 17) The MPLS network of claim 17, wherein the preemption message comprises a PATH ERROR message and the excluded interfaces are listed in an EXCLUDE_ROUTE object. ### Claim 19 (depends on 17) The MPLS network of claim 17, wherein another intermediate node is configured to responsive to reception of the preemption message, determine any local interfaces listed in the excluded interfaces of the preemption message, and prevent transmission of any preemption messages for the lower priority LSP based on the local interfaces which are included in the excluded interfaces of the second preemption message. ### Claim 20 (depends on 17) The MPLS network of claim 17, wherein an ingress node of the lower priority LSP is configured to responsive to reception of the preemption message, determine any excluded interfaces listed in the excluded interfaces of the preemption message, and determine and cause signaling of a new path for the lower priority LSP exclusive of the excluded interfaces.