Silent Failover for L2TP Network Tunnels
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Solution Overview
Problem
Existing network failover techniques often require explicit support from peer devices and can lead to termination of network tunnels and subscriber sessions, causing disruptions and inconsistencies during failover events.
Innovation Solution
The implementation of silent failover techniques within a network device, such as an L2TP Access Concentrator (LAC) or L2TP Network Server (LNS), allows for seamless failover without notifying the peer device, maintaining network tunnels and synchronizing sequence numbers and subscriber session databases to prevent termination and resolve inconsistencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If explicit failover notification is sent to peer device, then failover coordination is improved, but network tunnel termination and subscriber session disruption occur
Solution Approach 1:
The patent extracts the failover notification requirement from the failover process, implementing silent failover where the backup control unit takes over without notifying the peer device. This removes the coordination step that causes tunnel termination while maintaining reliability through local synchronization of sequence numbers and subscriber session databases.
Solution Approach 2:
The backup control unit performs self-synchronization by mirroring sequence numbers and subscriber session databases locally before failover. This self-service mechanism enables the backup unit to maintain network tunnels and handle packets independently without peer device knowledge or explicit coordination.
2Device complexity
If network tunnel is terminated during failover, then failover processing is simplified, but subscriber session disruption and data loss occur
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing sequence numbers and subscriber session databases in the backup control unit before the actual failover event. This preparation allows the backup unit to immediately assume functionality without terminating tunnels or losing data, as all necessary state information is already mirrored locally.
3Extent of automation
If silent failover is implemented without peer knowledge, then failover automation is improved, but sequence number and database synchronization complexity increases
Solution Approach 1:
The patent implements copying by creating a mirror image of sequence numbers and subscriber session databases in the backup control unit. This copy mechanism enables silent failover where the backup unit operates independently without peer device knowledge, automatically synchronizing state information locally to maintain network tunnel integrity.
Data Source
AI summary
A network device includes a primary control unit that establishes a network tunnel with another network device. The network device applies a silent failover technique to failover from the primary control unit to a backup control unit while maintaining the network tunnel. The network tunnel may be, for example, a Layer 2 Tunneling Protocol (L2TP) tunnel, and the network device may be an L2TP Access Concentrator (LAC) or an L2TP Network Server (LNS). The techniques may prevent abnormal termination of the network tunnel during the failover. Once the failover from the primary control unit to the backup control unit is complete, the backup control unit synchronizes sequence numbers associated with the network tunnel with sequence numbers of the non-failed network device, and resolves inconsistencies between subscriber session databases of the backup control unit and the non-failed network device.