Dynamic Multicast Forwarder Election in EVPN
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Solution Overview
Problem
Conventional Ethernet virtual private network (EVPN) designated forwarder election at a per-VLAN granularity is inadequate for many applications, leading to underutilization of communication links and preventing load balancing in all-active multi-homing scenarios, as it fails to account for the specific characteristics of multicast streams defined by group and source addresses.
Innovation Solution
Implementing dynamic designated forwarder election at a per-multicast stream granularity, using mathematical affinity functions based on provider edge addresses, Ethernet virtual private network (EVI) identifiers, and multicast stream addresses to determine the most suitable forwarder among multiple provider edges, allowing for more precise traffic distribution and load balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If per-VLAN designated forwarder election is implemented, then the system maintains simplicity in election mechanism, but communication links are underutilized and load balancing is prevented
Solution Approach 1:
The patent segments the DF election granularity from per-VLAN to per-multicast-stream level. Each multicast stream within a VLAN can have its own designated forwarder elected independently based on affinity calculations, allowing different PEs to forward different multicast streams. This segmentation enables fine-grained load distribution across multiple PEs while maintaining the all-active multi-homing architecture.
2Adaptability or versatility
If per-VLAN designated forwarder election is implemented, then the election scope is limited and easy to manage, but load balancing across provider edges is prevented
Solution Approach 1:
The patent introduces dynamic DF election where the designated forwarder for each multicast stream is determined by calculating affinity values based on PE addresses, EVI identifiers, and multicast stream addresses. This dynamic selection allows the system to adaptively distribute different multicast streams to different PEs based on affinity calculations, enabling load balancing while maintaining manageable election scope through the affinity function approach.
3Device complexity
If a single designated forwarder is selected for all multicast streams in a VLAN, then the election process is simple, but communication links between customer edge and PEs are underutilized
Solution Approach 1:
The patent applies local quality by allowing different PEs to have different roles (DF or non-DF) for different multicast streams within the same VLAN. Each PE's forwarding behavior is optimized locally for specific multicast streams based on affinity calculations, rather than having a uniform DF role across all streams. This enables multiple PEs to actively participate in forwarding different streams, increasing overall bandwidth utilization.
Data Source
AI summary
A method is performed by a first provider edge (PE) of a redundancy group including provider edges configured with an Ethernet virtual private network (EVPN) segment identifier (EVI) and an Ethernet segment identifier (ESI) and that are multi-homed to a customer edge (CE). The method includes, upon receiving from the CE a join request including a group address for a multicast stream, electing a designated forwarder (DF) for the multicast stream. The electing includes: computing for each PE a respective affinity for the DF as a function of a respective address of the PE, the EVI, and the group address; and determining which PE has a largest affinity. The method further includes, if the first PE has the largest affinity or does not have the largest affinity, configuring the first PE as the designated forwarder or not configuring the first PE as the designated forwarder for the multicast stream, respectively.