LSP Ping Mechanism for Tunneled MPLS Failure Detection
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Solution Overview
Problem
Existing MPLS LSPs face challenges in detecting and diagnosing data plane failures, particularly when LSPs are tunneled through or stitched across other LSPs, leading to mis-routing and black-holing of data due to corrupted forwarding information, which existing technologies fail to effectively address.
Innovation Solution
The LSP ping mechanism is extended to include modes for testing end-to-end connectivity and fault isolation, allowing label-switching routers to respond with additional information for modifying FEC stacks, enabling detection of failures even in complex tunneling scenarios, and ensuring synchronization between control and data planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If label-switching is used to establish fixed paths and improve forwarding efficiency, then data transmission speed is improved, but forwarding information may become corrupted causing mis-routing and black-holing
Solution Approach 1:
The patent implements preliminary failure detection by sending LSP ping packets along the label-switched path before normal data transmission begins. This allows the system to proactively identify potential forwarding issues in the LSP path, including corrupted forwarding information, before they cause actual data mis-routing or black-holing. The LSP ping mechanism performs advance verification of path integrity.
Solution Approach 2:
The patent establishes a feedback mechanism where LSRs along the LSP path respond to LSP ping packets with status information about their forwarding tables and path integrity. This feedback allows the source LSR to detect corrupted forwarding information and take corrective actions such as refreshing LSP paths or notifying network management systems, thereby maintaining forwarding accuracy.
2Ease of operation
If control plane uses IP addresses to route messages while data plane uses labels, then control plane remains active for management, but control plane cannot recognize data plane failures
Solution Approach 1:
The patent introduces LSP ping packets as an intermediary mechanism that bridges the control plane and data plane. These special packets traverse the data plane using label-switching but generate control plane events when they reach destination LSRs or encounter failures. This allows the control plane to become aware of data plane conditions without compromising its IP-based routing and manageability.
Solution Approach 2:
The LSP ping mechanism serves multiple functions simultaneously: it tests data plane connectivity, verifies forwarding information accuracy, detects path failures, and provides feedback to the control plane. This multi-functionality allows a single mechanism to address both control plane manageability and data plane failure detection needs.
3Adaptability or versatility
If LSPs are tunneled through other LSPs to create complex network paths, then network flexibility and routing options are improved, but failure detection becomes more difficult
Solution Approach 1:
The patent segments the failure detection process by having each LSR along the tunneled LSP path independently process and respond to LSP ping packets. Instead of requiring end-to-end detection that would be complex in nested tunnels, each LSR performs local verification and generates appropriate responses, simplifying the overall detection mechanism while maintaining support for complex tunneled paths.
Solution Approach 2:
The patent handles nested LSP tunnels by allowing LSP ping packets to traverse through multiple levels of encapsulation, with each LSR peeling off its corresponding tunnel layer and processing the packet appropriately. This nested processing approach maintains the flexibility of complex tunneled paths while enabling systematic failure detection at each tunnel level.
Data Source
AI summary
In general, principles of the invention relate to techniques for detecting data plane failures in Multi-Protocol Label Switching (MPLS) Label-Switched Paths (LSPs) that may be tunneled over one or more other LSPs. More specifically, the techniques described herein allow for testing connectivity of an LSP that is tunneled through at least one other LSP, and testing connectivity of an inter-autonomous system LSP. For example, a method comprises providing, with an intermediate label-switching router (LSR) of an LSP, instructions to an ingress LSR of the LSP to modify a forwarding equivalence class (FEC) stack of MPLS echo request packets. The intermediate LSR may provide the instructions within an MPLS echo reply packet.