Egress Node Protection Labels for BUM Traffic Failover
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPN), network failures can lead to traffic black-holing during the global repair process, causing dropped packets and reduced traffic forwarding performance due to the time required for a new designated forwarder to be elected after a failure.
Innovation Solution
Implementing egress node protection labels, where backup PE devices can forward Broadcast, Unknown Unicast, and Multicast (BUM) traffic even before being elected as the new designated forwarder, by advertising protection labels and using Bidirectional Forwarding Detection (BFD) to quickly detect failures and reduce false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a new designated forwarder is elected after a failure using traditional global repair process, then network stability is maintained through proper DF election, but traffic forwarding performance deteriorates due to traffic black-holing and packet loss during the election time
Solution Approach 1:
The patent applies preliminary action by pre-configuring backup PE devices with protection labels and enabling them to forward BUM traffic proactively before the global repair process completes. When a DF failure is detected, backup PE devices immediately start forwarding traffic using their protection labels, eliminating the waiting period for new DF election and preventing traffic black-holing while maintaining network stability
2Productivity
If backup PE devices forward BUM traffic before being elected as new designated forwarder using protection labels, then traffic forwarding performance improves by minimizing downtime, but device complexity increases due to label management and detection mechanisms
Solution Approach 1:
The patent implements feedback through BFD (Bidirectional Forwarding Detection) sessions that continuously monitor DF health and provide real-time failure detection. This automated feedback mechanism triggers the protection label forwarding process only when actually needed, allowing backup PE devices to maintain simple forwarding behavior during normal operation while automatically activating advanced protection mechanisms upon failure detection, thus improving traffic forwarding performance without permanently increasing device complexity
Solution Approach 2:
The patent uses protection labels as intermediaries that enable backup PE devices to forward BUM traffic without requiring full DF election procedures. These labels act as a mediator mechanism that simplifies the failure response process by providing a pre-established forwarding path, reducing the complexity of implementing fast failover while maintaining improved traffic forwarding performance
3Ease of operation
If traditional global repair process is used for DF election, then device operation simplicity is maintained through standardized protocols, but loss of time increases due to the duration required for new DF election and traffic resumption
Solution Approach 1:
The patent applies preliminary action by pre-configuring backup PE devices with protection labels and enabling them to forward BUM traffic proactively before the global repair process completes. When a DF failure is detected, backup PE devices immediately start forwarding traffic using their protection labels, eliminating the waiting period for new DF election and preventing traffic black-holing while maintaining network stability
Data Source
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AI summary
Techniques are described for facilitating node protection for Broadcast, unknown Unicast, and Multicast (BUM) traffic for a multi-homed node failure. For example, multi-homed provider edge (PE) devices each advertise egress node protection labels to an ingress PE device. In the event one of the multi-homed PE devices fails, the ingress PE device sends a BUM packet including the egress node protection labels for the failed node. When an egress PE device receives the BUM packet, the egress PE device determines whether the BUM packet includes the egress node protection labels and whether the egress PE device is operating as a backup designated forwarder (DF) on an Ethernet segment identifier (ESI) for which the failed node was the DF. If the BUM packet includes the egress node protection labels and the egress PE device is operating as a backup DF, the egress PE device forwards the BUM traffic to the ESI.