ESI Label Allocation for EVPN Multihoming Loop Prevention
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Solution Overview
Problem
Current ESI labeling methods in EVPN MPLS multihoming networks lead to transient loops during DF elections, as devices may not correctly identify the designated forwarder, resulting in bridging loops when ESI labels are not consistently applied across redundant network devices.
Innovation Solution
Implementing a method where all redundant network devices advertise and use the same ESI label for an Ethernet segment, allowing them to replicate and forward packets with this label, ensuring that only the designated forwarder device forwards packets and preventing loops by dropping or not forwarding packets without the label.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different ESI labels are used by redundant network devices for the same Ethernet segment, then each device can independently identify packets, but transient loops occur during DF elections due to inconsistent label application
Solution Approach 1:
The patent applies homogeneity by requiring all redundant network devices to use the same ESI label for a given Ethernet segment. This ensures that packet identification is consistent across all devices, eliminating the transient loops that occur during DF elections when devices have different label values. The designated forwarder and non-designated forwarders all reference the identical ESI label, providing uniform packet filtering behavior throughout the multihomed group.
2Reliability
If ESI labels are consistently applied across all redundant network devices, then bridging loops are prevented, but the complexity of label management and synchronization increases
Solution Approach 1:
The patent implements self-service through the ESI label advertisement mechanism where each network device autonomously advertises its ESI label to other members of the multihomed group via EVPN signaling. Devices automatically synchronize their label knowledge through this peer-to-peer advertisement process, eliminating the need for centralized label management or complex manual synchronization procedures. The system self-regulates to ensure all devices have consistent ESI label information.
3Stability of the object's composition
If redundant network devices use the same ESI label, then network stability is maintained during DF elections, but the ability to differentiate device-specific packet handling is reduced
Solution Approach 1:
The patent applies segmentation by separating the ESI label function into two distinct roles: identification and forwarding decision. The ESI label itself remains identical across all devices for identification purposes, while the forwarding decision is segmented by the DF election state machine that each device independently maintains. This allows devices to use the same label while still performing device-specific packet handling based on their DF status, combining consistency with operational flexibility.
Data Source
AI summary
Systems and methods are provided herein for allocating the same ESI label on multihomed peers for a given ES. In some embodiments, each network device that provides multihoming to a host using an ES, advertises EVPN AD per ES routes to each other, wherein the EVPN AD per ES routes comprise an ESI label associated with the ES. Because the network devices advertise the same ESI label for the ES, a first network device generates a bitmap. The first network device uses the bitmap to include the advertised ESI label in replicated packets that the first network device forwards to the other network devices that provide multihoming to the host via the ES. The network devices that consider themselves non-DF devices will drop the packet. The network devices that consider themselves the DF device will not forward the packet to the host via the ES because of the ESI label.