LSP Ping Service Mapping for Multicast VPN Connectivity
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Solution Overview
Problem
In computer networks, especially those using label switching protocols like MPLS, detecting connectivity loss in tunnels is challenging, particularly for multicast VPN services, as existing methods like BFD require separate sessions for each service and struggle to identify affected services due to label stripping and penultimate hop popping.
Innovation Solution
The proposed solution involves extending LSP ping messages with additional information to uniquely identify services and using a single OAM session associated with the underlying P2P tunnel, allowing the egress network device to map services and select new sources upon connectivity loss, thereby reducing the number of OAM sessions and enhancing failure detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate BFD sessions are established for each service, then service-specific connectivity detection is achieved, but device complexity and session management overhead increase significantly
Solution Approach 1:
The patent merges multiple service-specific OAM sessions into a single tunnel-level OAM session. By extending LSP ping messages to carry service identification information (such as service labels or VLAN tags), the system can monitor connectivity for multiple services simultaneously through one unified session, eliminating the need to establish separate BFD sessions for each service while maintaining service-specific detection capability
Solution Approach 2:
The LSP ping message is designed to serve multiple functions: it acts as both a tunnel connectivity probe and a service-specific connectivity detector. By incorporating service identification fields into the LSP ping message structure, the same message mechanism can identify which specific services are affected by tunnel failures, replacing the need for dedicated service-level OAM sessions
2Loss of information
If LSP ping messages are extended with service identification information, then service mapping capability is improved, but message complexity increases
Solution Approach 1:
The patent nests service identification information within existing LSP ping message structures by utilizing available fields such as the Label Stack or adding optional information elements. This nested approach allows service identification data to be carried within the standard LSP ping message framework without requiring completely new message types, thereby maintaining compatibility while adding functionality
Solution Approach 2:
The solution copies service identification mechanisms from other protocols (such as VLAN tags or MPLS labels) and integrates them into the LSP ping message structure. By reusing existing label formats and information elements from MPLS and VLAN standards, the message complexity is minimized while achieving comprehensive service identification capability
3Device complexity
If a single OAM session is used for the P2P tunnel, then session management is simplified, but the ability to identify affected services deteriorates
Solution Approach 1:
The system implements feedback by including service identification information in the LSP ping message that travels from ingress to egress. When the egress router detects tunnel failure through the OAM session, it can immediately identify which services are affected based on the service identifiers carried in the message, enabling precise service-level failure notification without requiring separate sessions for each service
Data Source
AI summary
An egress network device of a point-to-point (P2P) tunnel can receive an LSP Ping message via the P2P tunnel from an ingress network device of the P2P LSP, wherein the LSP Ping message specifies a label that the egress network device associates with a service provided to the egress network device via the P2P tunnel. In response to receiving the LSP Ping message, the egress network device can store an association between the label and the P2P tunnel. The egress network device also uses a fault detection network protocol session over the P2P tunnel to monitor a state of the P2P tunnel. In response to detecting based on the fault detection network protocol session that the state of the P2P tunnel is down, the egress network device determines the service is unavailable from the ingress network device via the P2P tunnel, and selects a new source to provide the service.