EVPN Multihoming Backup Path Pre-computation for Link Failure
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Solution Overview
Problem
In Ethernet Virtual Private Network (EVPN) environments, multihoming configurations face prolonged network outages and traffic disruptions when a link between redundant network devices is interrupted, as existing systems require extensive route withdrawals and updates across the network.
Innovation Solution
Redundant network devices are configured to store backup paths in forwarding tables and quickly switch to these paths when an Ethernet segment link is interrupted, minimizing the need for reconfiguration and resource usage by updating next hop identifiers and maintaining route consistency across devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant network devices use standard EVPN route advertisement and withdrawal mechanisms for failover, then network reliability is maintained through proper routing updates, but network outage duration increases due to prolonged route withdrawals and updates across the network
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing backup paths in forwarding tables before link failures occur. When a link failure is detected, the system immediately switches to the pre-computed backup path without needing to perform route withdrawals and updates, thus reducing outage duration while maintaining reliability
Solution Approach 2:
The system prepares compensatory measures in advance by maintaining backup paths in forwarding tables. When a primary link fails, these pre-prepared backup paths provide immediate cushioning to prevent traffic disruption, eliminating the need for time-consuming route propagation delays
2Speed
If backup paths are pre-configured and stored in forwarding tables for immediate switching, then recovery speed increases upon link interruption, but device complexity increases due to additional forwarding table management
Solution Approach 1:
The system applies self-service by automatically computing and populating backup paths in forwarding tables without requiring manual configuration. The network devices autonomously manage the backup path information, reducing operational complexity while enabling fast recovery switching
3Stability of the object's composition
If extensive route withdrawals and updates are propagated across the network for failover, then routing consistency is maintained across all devices, but network resource consumption increases during failover events
Solution Approach 1:
The patent extracts the routing update function from the failover process. By maintaining pre-computed backup paths locally in forwarding tables, the system removes the need for extensive route withdrawal and update propagation across the network during failover events, significantly reducing network resource consumption while maintaining routing consistency
Data Source
AI summary
Techniques described herein provide for expediting routing convergence in EVPN with multihomed ethernet segment when one of the redundant devices loses connection to the ethernet segment. When a first redundant device receives EVPN auto discovery (AD) route advertising an ethernet segment from a second redundant device, it creates an entry for a forwarding table. The entry has, for an advertised MAC address, a local identifier of the ethernet segment (marked as active next hop) and the identifier of the second network device (marked as backup next hop). When a packet for that MAC address is received, the first redundant device routes the data using data from the entry. In particular, the first redundant device uses the local identifier of the ethernet segment as next hop when the ethernet segment link is active; and uses the identifier of the second network device as next hop when the ethernet segment is down.