EVPN Egress Fast Reroute Label Segmentation Against Transient Loops
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Solution Overview
Problem
Egress fast reroute (eFRR) in Ethernet Virtual Private Networks (EVPN) leads to transient loops between multi-home peer provider edges, causing unnecessary bandwidth consumption due to prolonged failure propagation and switchover times, especially in highly scaled environments.
Innovation Solution
A network device functioning as a provider edge (PE) in an EVPN advertises distinct EVPN labels to multi-home peer PEs and non-multi-home peer PEs, discarding traffic encapsulated with a specific label if the link is not operational to prevent loops, and forwarding traffic to a multi-home peer PE if encapsulated with another label.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If egress fast reroute (eFRR) is implemented to improve convergence speed, then switchover time is reduced, but transient loops occur between multi-home peer PEs causing bandwidth consumption
Solution Approach 1:
The patent segments the EVPN label space into two distinct sets: first EVPN labels advertised to multi-home peer PEs and second EVPN labels advertised to non-multi-home peer PEs. This segmentation allows PE devices to identify and discard traffic from multi-home peers that would otherwise create transient loops, while still enabling fast reroute functionality. The segmentation resolves the contradiction by allowing rapid switchover through eFRR while preventing the harmful transient loop traffic that consumes bandwidth.
2Reliability
If failure propagation time is reduced to improve resiliency, then network recovery speed increases, but transient loop duration increases causing more bandwidth consumption
Solution Approach 1:
The patent applies preliminary action by pre-advertising distinct first EVPN labels to multi-home peer PEs before any failure occurs. When a link failure is detected, PE devices can immediately discard traffic encapsulated with first EVPN labels from multi-home peers, preventing transient loops before they propagate. This preliminary configuration enables rapid failure response while blocking the harmful traffic paths that would consume bandwidth during the recovery period.
Data Source
AI summary
A method by a network device functioning as a provider edge (PE) in an ethernet virtual private network (EVPN) to prevent transient loops between multi-home peer PEs. The method includes advertising a first EVPN label to one or more PEs that are multi-home peer PEs of the PE, advertising a second EVPN label to one or more PEs that are not multi-home peer PEs of the PE, receiving first traffic for a CE that is encapsulated with the first EVPN label as opposed to the second EVPN label, and discarding the first traffic in response to determining that a link between the PE and the CE is not operational and the first traffic for the CE is encapsulated with the first EVPN label.