MPLS-TP OAM Connectivity Verification via Context Descriptor
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Solution Overview
Problem
The standard MPLS data forwarding mechanism in MPLS-TP networks does not adequately address Maintenance EndPoints (MEPs) for Operations, Administration, and Maintenance (OAM) functions, particularly in LSP Tunnel and Section layers, leading to insufficient connectivity verification due to the loss of tunnel labels and inability to identify incoming connections with multiple parallel paths.
Innovation Solution
Extending the MPLS frame forwarding procedure by defining a context descriptor for each frame, which includes key attributes characterizing the terminated connection, allowing the original context to be retained and used for de-multiplexing to the corresponding MEP, and checking both the first and second labels to prevent dropping the tunnel label when the second label is a Generic Association Channel Label (GAL).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the standard MPLS data forwarding mechanism is used to terminate LSP tunnels and process GAL labels, then the forwarding process is simplified, but the tunnel label is dropped and connectivity verification capability is lost
Solution Approach 1:
The patent applies preliminary action by performing the tunnel label pop operation before processing the GAL label. This ensures that the tunnel label is removed from the stack in advance, allowing the GAL to be processed as the new top label while maintaining awareness of the original tunnel context through the popped label information, thus preserving connectivity verification capability.
Solution Approach 2:
The patent segments the label processing into distinct phases: first processing the tunnel label (popping it), then processing the GAL label separately. This segmentation allows each label to be handled according to its specific requirements, with the tunnel label providing context for connectivity verification while the GAL label directing traffic to the control function.
2Productivity
If only the first label is checked for termination, then processing speed is improved, but the ability to verify connectivity and identify incoming connections is reduced
Solution Approach 1:
The patent performs the tunnel label pop operation as a preliminary action before connectivity verification. This allows the system to quickly identify termination points while preserving the ability to verify connectivity through the GAL label processing that follows, thus maintaining both speed and accuracy.
Solution Approach 2:
The patent uses the GAL label as an intermediary that bridges the simplified fast forwarding process and the detailed connectivity verification process. The GAL label allows the system to quickly forward traffic while simultaneously enabling comprehensive connectivity verification through its association with the OAM payload and tunnel context.
3Device complexity
If the tunnel label is popped immediately upon GAL label detection, then label stack management is simplified, but the original packet context is lost and MEP addressing becomes impossible
Solution Approach 1:
The patent performs the tunnel label pop operation as a preliminary action before processing the GAL label. This ensures that the tunnel label is removed from the stack in advance, allowing the GAL to be processed as the new top label while maintaining awareness of the original tunnel context through the popped label information, thus preserving connectivity verification capability.
Solution Approach 2:
The patent discards the tunnel label from the active stack but recovers its information for use in connectivity verification. The popped tunnel label information is retained in the context descriptor, allowing the system to verify connectivity and address MEPs accurately while maintaining a simplified label stack for ongoing traffic forwarding.
4Adaptability or versatility
If OAM frames are multiplexed into data flows using existing MPLS mechanisms, then backward compatibility is maintained, but sufficient addressing methods for MEPs from the data plane are not provided
Solution Approach 1:
The patent makes the GAL label and OAM payload processing mechanism universal by applying it to both LSP tunnel and section layer OAM frames. The same processing logic handles different types of OAM frames, providing unified MEP addressing capability while maintaining backward compatibility with existing MPLS mechanisms.
Solution Approach 2:
The patent uses the GAL label as an intermediary that enables MEP addressing in the data plane. The GAL label acts as a mediator between the existing MPLS forwarding mechanism and the new requirement for MEP addressing, allowing OAM frames to be correctly routed to their destination MEPs while maintaining compatibility with standard MPLS processing.
Data Source
AI summary
Extensions to a Multi-Protocol Label Switching (MPLS) frame forwarding procedure in an MPLS node are described. A context descriptor is defined for each frame received on a connection terminated at that node, and where this context descriptor is provided together with the frame to a corresponding function (e.g. Operations, Administration and Maintenance, OAM) if needed. The context descriptor is constructed based on key attributes characterizing the terminated connection, over which the frame is received, and addresses a particular function endpoint (Maintenance Endpoints (MEPs), Selector Bridge of a protection instance etc.) of a corresponding function (OAM, protection, etc.). In one embodiment, a Multi-Protocol Label Switching (MPLS) node is directed to check not only the first but also the second label, and not to drop the first label (and the label space if relevant) when the second label is the Generic Association Channel Label (GAL). In this way, the original context of the packet is kept (i.e. the information relating to the connection over which the packet was received), and can be used for de-multiplexing to the corresponding MEP. Then the identifiers within the OAM payload can be used for verification of the connectivity. Other embodiments describe alternative solutions.