Pre-configured Next Hops for Fast EVPN Link Failure Convergence
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPN), link failures between provider edge (PE) network devices and customer edge (CE) network devices or core networks lead to high convergence times, resulting in undeliverable network traffic and data loss due to the need for reconfiguration, especially when multiple PE devices are connected in an all-active multi-homed topology.
Innovation Solution
The implementation of pre-configured primary and secondary routes within a next hop list allows PE network devices to quickly reroute traffic to other PE devices in the same Ethernet segment upon link failure, maintaining data delivery and load balancing during convergence, and sending out-of-service messages to CE devices in case of core network isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PE network devices use traditional MAC learning and routing protocol updates upon link failure, then routing correctness is maintained, but convergence time increases significantly causing data loss
Solution Approach 1:
The patent applies preliminary action by pre-configuring backup next hops and secondary routes in the forwarding plane before link failures occur. PE devices maintain alternative paths in advance, enabling immediate switchover without waiting for routing protocol convergence, thus reducing convergence time while maintaining routing correctness
Solution Approach 2:
The patent introduces an intermediary mechanism by implementing a next hop list structure that mediates between the control plane routing protocols and the data plane forwarding decisions. This intermediary layer allows independent optimization of forwarding paths from traditional routing updates, enabling faster convergence
2Stability of the object's composition
If PE network devices withdraw EVPN routes immediately upon link failure detection, then routing table consistency is maintained, but data traffic becomes undeliverable during withdrawal transient time
Solution Approach 1:
The patent applies preliminary action by pre-establishing backup forwarding paths and next hops in the forwarding plane before withdrawing routes. When link failure occurs, the device can immediately switch to alternative paths using pre-configured backup routes, maintaining data traffic delivery during the route withdrawal transient period
Solution Approach 2:
The patent ensures continuity of useful action by maintaining alternative forwarding paths that remain active during route withdrawal. The next hop list structure allows continuous data traffic delivery through backup paths while the routing table undergoes consistency updates, eliminating service interruption
3Productivity
If all PE network devices in an all-active mode topology forward traffic to and from the Ethernet segment, then load balancing is improved, but convergence complexity increases during link failures
Solution Approach 1:
The patent applies segmentation by dividing the forwarding decision process into independent per-destination next hop lists. Each PE device maintains separate backup path information for different destinations, allowing localized failure recovery decisions without coordinating complex switchover across the entire all-active topology, thus reducing convergence complexity
Solution Approach 2:
The patent applies preliminary action by pre-configuring backup next hops and secondary routes for all possible failure scenarios in the all-active topology. This advance preparation enables each PE device to independently and quickly switch to backup paths without complex coordination, maintaining load balancing capability while simplifying convergence
Data Source
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AI summary
Techniques are described for providing fast convergence in the event of a link failure in an all-active multi-homed Ethernet virtual private network. A provide edge (PE) network device may pre-configure an interface next hop and secondary next hops. The secondary next hops may be logical links to other PE network devices in the same Ethernet segment. In the event of a link failure in the interface next hop between the PE network device and a customer edge (CE) network device, the PE network device may be configured to forward data traffic to the CE network device using the secondary next hops. In the event of a link failure between the PE network device and a core network, the PE network device may be configured to send an out-of-service message to the CE network device that instructs the CE network device to stop sending traffic to the PE network device.