Multicast Join Processing for EVPN Shortest-Path Forwarding
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPN), conventional multicast forwarding techniques fail to deliver multicast traffic along a shortest-path tree when the specified upstream neighbor is not the designated forwarder, leading to incomplete traffic distribution and increased latency due to reliance on rendezvous-point trees.
Innovation Solution
A provider edge (PE) device in an EVPN network processes and installs multicast forwarding state even if it is not identified as the upstream neighbor in a multicast Join message, enabling it to forward multicast traffic along the shortest-path tree, thus eliminating the need for resource-intensive PIM Register tunnels and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PE device only processes multicast Join messages when it is the specified upstream neighbor, then the forwarding state installation is simple and straightforward, but multicast traffic cannot be delivered along the shortest-path tree when the specified upstream neighbor is not the designated forwarder, leading to incomplete traffic distribution and increased latency
Solution Approach 1:
Instead of only processing Join messages when the PE device is the specified upstream neighbor (conventional approach), the invention inverts the logic to process Join messages even when the PE device is not the specified upstream neighbor. This allows the PE device to install multicast forwarding state and forward traffic along the shortest-path tree, improving multicast traffic delivery completeness while maintaining manageable processing complexity through standardized processing procedures.
2Loss of time
If multicast traffic is delivered via rendezvous-point trees, then the forwarding process is simpler to implement, but latency increases and resource utilization decreases due to the indirect path
Solution Approach 1:
The invention performs preliminary actions by having PE devices install multicast forwarding state in advance based on received Join messages, even before becoming the designated forwarder. This pre-establishment of forwarding state enables direct shortest-path tree forwarding when the PE device becomes the designated forwarder, reducing latency and improving resource utilization while maintaining implementation simplicity through standardized processing procedures.
3Use of energy by moving object
If PIM Register tunnels are used to deliver multicast traffic, then traffic can be delivered to the rendezvous point, but resource utilization decreases due to the resource-intensive tunnel establishment and maintenance
Solution Approach 1:
The invention extracts the unnecessary PIM Register tunnel establishment and maintenance from the multicast forwarding process. By having PE devices directly install multicast forwarding state and forward traffic along the shortest-path tree, the solution eliminates the need for resource-intensive PIM Register tunnels while maintaining reliable traffic delivery capability, thus improving network resource utilization.
Data Source
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AI summary
In some examples, a method includes receiving, by a first provider edge (PE) device of a layer 3 network, configuration data configuring the PE device to provide, via an Ethernet segment with an edge device, active-active multi-homing layer 2 (L2) virtual bridge connectivity to the edge device using an Ethernet Virtual Private Network (EVPN) instance; receiving, by the first PE device, a multicast Join message for multicast traffic, the multicast Join message identifying a second PE device that also participates in the EVPN instance; processing, by the first PE device, the multicast Join message to generate multicast forwarding state; and forwarding, by the first PE device based at least on the multicast forwarding state, the multicast traffic.