Backup Egress Path Computation for P2MP LSPs
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Solution Overview
Problem
In modern network communications, computing a backup egress path for point-to-multi-point (P2MP) Label Switched Paths (LSPs) that span multiple autonomous systems (AS domains) is challenging due to the lack of centralized topology information and the burden of disseminating and storing topological data across multiple domains, making centralized computation impractical.
Innovation Solution
A method and architecture for computing a backup egress path by establishing a backup egress LSP between a previous-hop node of a primary egress node and a backup egress node, utilizing proprietary extensions to the Path Computation Element Protocol (PCEP) and PCE discovery protocol to advertise and compute backup egress path capabilities, providing localized protection against faults in the primary egress path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If centralized computation is used to compute P2MP LSP across multiple AS domains, then path computation can be performed with complete topology information, but the complexity of storing and updating topological information for multiple domains becomes burdensome
Solution Approach 1:
The patent divides the centralized computation task into distributed segments by deploying PCEs in each AS domain. Each PCE computes paths within its local domain using locally available topology information, eliminating the need for a single central database to store and manage all domain topologies while maintaining computation accuracy.
Solution Approach 2:
The patent introduces PCEP (Path Computation Element Protocol) as an intermediary mechanism that enables coordination between distributed PCEs. The protocol allows PCEs to exchange path computation requests and results across domain boundaries, facilitating collaborative path computation without requiring direct access to remote domain topologies.
2Productivity
If multiple P2P LSPs are used to achieve multicast, then content can be delivered to multiple destinations, but managing multiple individual LSPs becomes cumbersome and inefficient
Solution Approach 1:
The patent merges multiple P2P LSPs into a single P2MP (point-to-multipoint) LSP structure that efficiently delivers content from one source to multiple destinations. The P2MP LSP creates a shared distribution tree where common path segments are consolidated, reducing the number of individual LSPs that need to be managed while maintaining full multicast capability.
Solution Approach 2:
The P2MP LSP structure provides multi-functionality by serving as a universal framework that can deliver content to any number of destinations simultaneously. A single P2MP LSP can dynamically serve multiple endpoints, replacing the need for separate P2P LSPs for each destination while maintaining flexible content delivery options.
3Reliability
If backup egress path computation is performed centrally, then complete path options can be evaluated, but the burden of disseminating and storing topological data across multiple domains makes centralized computation impractical
Solution Approach 1:
The patent segments the backup path computation into distributed components, with each PCE computing backup egress paths within its local domain. This eliminates the need for centralized storage and dissemination of complete multi-domain topology information, as each PCE only needs local topology data to perform its computation task.
Solution Approach 2:
The patent performs preliminary backup path computation at each PCE before faults occur, using locally available topology information. This preliminary action enables fast fault recovery because backup paths are pre-computed and ready for immediate activation, eliminating the need for real-time centralized computation when faults occur.
Data Source
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AI summary
An apparatus for requesting computation of a backup egress path comprising a processor configured to send a path computation element (PCE) protocol (PCEP) request (PCReq) message requesting computation of the backup egress path to protect against a fault in a primary egress path of a Point to Multi-Point (P2MP) or Point-to-Point (P2P) label switched path (LSP), wherein the backup egress path extends from a previous-hop internal node of the primary egress node of the P2MP or P2P LSP to a backup egress node. A method for advertising or discovering a backup egress path computation capability comprising exchanging a message that indicates that a PCE comprises a backup egress path computation capability.