L2TP Tunnel State Keeping via Active-Standby Message Synchronization
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Solution Overview
Problem
Existing methods fail to maintain real-time synchronization of L2TP tunnel serial numbers during active-standby device switching, leading to chaotic working states and potential user disconnections.
Innovation Solution
An active device sends interactive L2TP control messages to a standby device, which stores and responds before the active device processes them, ensuring that control messages are synchronized and processed correctly during switching, maintaining normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backup messages are sent via direct connection link or up and down layer network link, then device redundancy is achieved, but real-time synchronization of tunnel serial numbers cannot be realized
Solution Approach 1:
The active device sends the interactive L2TP control message to the standby device in advance, before the standby device needs to take over. This preliminary action ensures that the standby device has the latest control message and serial number information ready before switching occurs, eliminating synchronization delays and information loss during failover.
2Loss of information
If the standby device waits for control message or hello message of the active device, then message synchronization is attempted, but normal user on and off line operations are influenced
Solution Approach 1:
Instead of the standby device waiting passively for messages from the active device, the active device proactively sends the interactive L2TP control message to the standby device in advance. This eliminates the waiting period and ensures the standby device is immediately ready to take over without affecting user operations.
3Reliability
If the active device sends tunnel message serial number to backup device, then backup is implemented, but serial number desynchronization occurs during active-standby switching
Solution Approach 1:
The interactive L2TP control message mechanism establishes a feedback loop where the active device sends control messages to the standby device, which stores them and sends acknowledgments back. This ensures both devices maintain synchronized serial number information, preventing desynchronization during active-standby switching while preserving backup functionality.
Data Source
AI summary
A method and apparatus for keeping alive an L2TP tunnel state are provided, wherein the method includes: an active device and an opposite-end device establish an L2TP tunnel, the active device transmits to a standby device an interactive L2TP control message between the active device and the opposite-end device, and the active device performs corresponding processing on the L2TP control message only after having received a response about having stored the L2TP control message sent by the standby device; and when active-standby switching occurs between the active device and the standby device, the standby device connects to the opposite-end device via the L2TP tunnel, and performs corresponding processing according to the L2TP control message which has already been stored. Control messages of an active and standby device and an opposite-end device of the present invention always keep synchronous, ensuring that when the active device has failed, after switching between the active and standby device, the standby device and the opposite-end device can work normally, which will not cause discarding of the message, and ensuring the normal working state.