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 routers, leading to inefficient bandwidth utilization and potential overload on designated forwarders, as non-designated forwarders typically drop multicast traffic rather than forwarding it.
Innovation Solution
Each provider edge router deterministically determines whether it should act as an elected multicast forwarder for specific multicast groups, regardless of its designated forwarder status, by using algorithms such as dividing network addresses by the number of multi-homed routers or applying hash functions, allowing it to configure forwarding states and ignore designated forwarder elections, thereby forwarding multicast traffic across multiple routers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a designated forwarder election is implemented in multi-homed EVPN networks, then a single router is responsible for forwarding multicast traffic, but this leads to overload on the designated forwarder and inefficient bandwidth utilization
Solution Approach 1:
The patent segments the single forwarder responsibility into multiple elected forwarders based on multicast group address ranges. Each PE router is assigned responsibility for specific multicast groups through deterministic election algorithms, distributing the forwarding load across multiple routers rather than concentrating it on a single designated forwarder.
Solution Approach 2:
The patent implements dynamic forwarder election where PE routers can become elected forwarders based on current network conditions and multicast group requirements. The forwarding responsibility is not static but can change dynamically through the election process, allowing the system to adapt to varying traffic patterns and router capacities.
2Device complexity
If non-designated forwarders drop multicast traffic, then forwarding control is simplified, but this results in loss of multicast traffic and reduced network efficiency
Solution Approach 1:
The patent implements a feedback mechanism where PE routers exchange election status information through BGP join synch routes. Routers receive feedback about which peers are elected forwarders for specific multicast groups and adjust their forwarding behavior accordingly, ensuring that multicast traffic is forwarded by the appropriate elected forwarder without duplication or loss.
3Productivity
If deterministic election algorithms are implemented for multicast forwarder selection, then load balancing across multiple routers is achieved, but this increases control plane complexity
Solution Approach 1:
The patent uses parameter changes in the form of hash functions and modular arithmetic operations on multicast group addresses to deterministically select elected forwarders. By changing the selection criteria from static designated forwarder assignment to dynamic parameter-based election, the system achieves load balancing while maintaining deterministic and reproducible forwarder selection across all PE routers.
Data Source
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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.