Pre-configured Forwarder Ordering for Fast EVPN Failover
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPN), network failures lead to significant flooding of Ethernet frames until a new designated forwarder is elected, causing traffic loss and inefficiency due to the lack of pre-configuration of next hops in multi-homed environments with multiple PE routers.
Innovation Solution
The PE routers determine and pre-configure an ordering of designated forwarders before a network failure, allowing remote PE routers to automatically update forwarding next hops without waiting for the designated forwarder election process, thereby reducing traffic loss and flooding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the designated forwarder election process is performed after a network failure, then the system ensures correct forwarding through formal election, but network flooding and traffic loss occur during the election period
Solution Approach 1:
The patent applies preliminary action by having PE routers pre-determine and pre-configure the ordering of designated forwarders before any network failure occurs. Each PE router calculates and stores the failure order sequence in advance, so when a failure happens, the remote PE router can immediately switch to the pre-configured next designated forwarder without waiting for the election process, thus eliminating flooding and traffic loss during failover
Solution Approach 2:
The patent applies preliminary anti-action by pre-configuring the failure order sequence to counteract the potential harm of network flooding. By having the ordering information ready beforehand, the system prevents the harmful flooding effect that would otherwise occur during the election period, as the remote PE router can immediately update its forwarding table to the next designated forwarder upon detecting a failure
2Reliability
If the remote PE router waits for the designated forwarder election to complete, then the correct next forwarder is identified, but significant flooding and traffic loss occur during the waiting period
Solution Approach 1:
The patent applies preliminary action by having all PE routers pre-calculate and share their failure order sequences with remote PE routers before any failure occurs. This allows the remote PE router to have the complete ordering information available immediately when needed, eliminating the waiting period and associated flooding while ensuring correct next forwarder identification
3Reliability
If multiple PE routers are configured in multi-homed environment, then redundancy and reliability are improved, but the complexity of managing designated forwarder election increases
Solution Approach 1:
The patent applies parameter changes by transforming the complex dynamic election process into a static pre-configured parameter (failure order sequence). Instead of managing complex real-time elections among multiple PE routers, each router simply uses its pre-calculated failure order index to determine the next designated forwarder, significantly simplifying the forwarding configuration while maintaining redundancy
Data Source
AI summary
In general, techniques are provided for receiving a first control plane message that indicates the reachability of the second PE network device as a designated forwarder in an Ethernet segment. The techniques include receiving a second control plane message comprising information that indicates, in the event of a network failure at the second PE router, that the third PE network device of the plurality of PE network devices is the designated forwarder in the layer two segment. The techniques also include forwarding layer two frames to the second PE network device identified as the designated forwarder in the layer two segment; and responsive to determining a network failure at the second PE network device, configuring, based at least in part on the second control plane message, a forwarding plane of the first PE network device to forward layer two frames to the third PE network device as the designated forwarder.