Multicast Load Balancing in Multihomed EVPN Networks
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPNs), existing technologies face challenges in load-balancing multicast traffic across multiple provider edge (PE) routers, leading to inefficient bandwidth utilization and potential overload on designated forwarders, as non-designated forwarders typically drop multicast traffic despite having available bandwidth.
Innovation Solution
Each PE router deterministically determines whether it should act as an elected multicast forwarder for specific multicast groups, regardless of its designated or non-designated status, by using algorithms such as dividing network addresses by the number of multi-homed PE routers or applying modulo operations, to configure forwarding states and ignore designated forwarder elections, thereby forwarding multicast traffic across multiple PE routers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single designated forwarder is elected for the Ethernet segment, then the network simplicity and control are maintained, but the load-balancing capability and bandwidth utilization are reduced
Solution Approach 1:
The patent segments the single designated forwarder role into multiple elected forwarders based on multicast group addresses. By dividing the multicast group address space and assigning different forwarders to different segments, the system achieves load-balancing while maintaining simple per-segment control mechanisms. This resolves the contradiction by segmenting the forwarding responsibility without complex coordination.
Solution Approach 2:
The patent applies local quality by making each PE router's forwarding behavior dependent on its local multicast group address assignments. Each router independently determines its role based on local conditions (received join requests and local multicast groups) rather than global coordination, enabling load-balancing while keeping control simple at each node.
2Ease of operation
If non-designated forwarders drop multicast traffic, then the network control is simplified, but the bandwidth utilization and load-balancing are inefficient
Solution Approach 1:
The patent introduces dynamic forwarding behavior where PE routers change their role from static designated/non-designated to dynamic elected forwarders based on multicast group assignments. This dynamic adaptation allows any router to forward traffic when needed, improving bandwidth utilization while maintaining simple control through local deterministic selection algorithms.
Solution Approach 2:
The patent changes the parameter of forwarding decision from based on designated forwarder election to based on multicast group address hashing. This parameter change enables non-designated forwarders to participate in traffic forwarding for specific groups, improving bandwidth utilization without complex control mechanisms.
3Productivity
If all PE routers forward multicast traffic, then the load-balancing and bandwidth utilization are improved, but the control complexity and potential conflicts increase
Solution Approach 1:
The patent implements self-service by enabling each PE router to independently determine its forwarding role through local deterministic algorithms based on received join requests and local multicast groups. Routers autonomously select whether to forward traffic for specific groups without requiring coordination or complex control, achieving load-balancing while keeping control simple at each node.
4Stability of the object's composition
If designated forwarder election is used, then the network stability is maintained, but the overload on designated forwarders and underutilization of others occurs
Solution Approach 1:
The patent segments the forwarding load across multiple routers by assigning different multicast groups to different elected forwarders. This segmentation distributes traffic quantity across multiple devices while maintaining network stability through deterministic selection algorithms that ensure consistent and predictable forwarding decisions.
Solution Approach 2:
The patent applies partial action by having only selected PE routers forward traffic for specific multicast groups rather than all routers forwarding everything. This partial forwarding approach distributes the workload and prevents overload on any single designated forwarder while maintaining stable network operation.
Data Source
AI summary
In general, techniques are described for load-balancing responsibility for forwarding of multicast traffic into an active-active Ethernet segment between two or more multi-homed provider edge (PE) routers in an Ethernet Virtual Private Network (EVPN). In one example, a PE router may receive an Internet Group Management Protocol (IGMP) join report for a multicast group. The PE router may send join synch routes used to synchronize the join report for the multicast group across the Ethernet segment. The PE router may deterministically determine whether the PE router is configured to be an elected multicast forwarder for one of a plurality of multicast groups. If the PE router is elected a multicast forwarder, the PE router may configure a forwarding state of the PE router to ignore a designated forwarder calculation and to forward the multicast traffic into the Ethernet segment regardless of whether the PE router is a designated forwarder.