Hash-Based Forwarder Selection for Multihomed EVPN Traffic
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Solution Overview
Problem
Current VPN technologies face challenges in efficiently handling multidestination traffic at provider edge switches in network fabrics, particularly in cloud-based models, due to resource-intensive designated forwarder elections and limited scalability.
Innovation Solution
The implementation of a hashing function to determine a designated forwarder among multiple options for a multihomed host, utilizing a shadow hash forwarding table to efficiently manage multidestination traffic in EVPN networks, enabling Active-Active multihoming and ensuring in-order packet delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional VPN technologies are used to provide secure multi-tenant networking, then security and compartmentalization are improved, but network resource consumption increases and scalability deteriorates
Solution Approach 1:
The patent changes the fundamental parameters of VPN operation by transitioning from traditional encapsulation-based VPN to EVPN with hash-based forwarding. This involves changing the forwarding mechanism from complex VPN routing tables to simplified hash-based destination selection, and changing the security model from per-tenant encryption to EVPN overlay with MAC mobility. These parameter changes enable maintaining security while dramatically improving resource efficiency and scalability.
2Ease of operation
If designated forwarder election is implemented in traditional VPN, then traffic forwarding is achieved, but resource utilization increases and scalability deteriorates
Solution Approach 1:
The patent replaces the mechanical system of traditional designated forwarder election (which requires complex state tracking and control plane involvement) with a hash-based forwarding mechanism. The hash function deterministically selects the forwarder based on packet characteristics, eliminating the need for complex election protocols and reducing resource utilization while maintaining ease of operation.
Solution Approach 2:
The hash-based forwarding mechanism is self-service in nature - each switch independently computes the hash and determines the forwarder without requiring coordination with other switches or control plane intervention. This self-service approach simplifies the system and reduces resource consumption compared to traditional election mechanisms.
3Reliability
If multihomed host connectivity is provided, then connectivity reliability is improved, but packet ordering may deteriorate without proper designated forwarder selection
Solution Approach 1:
The patent changes the forwarding selection parameter from dynamic election-based choices to deterministic hash-based selection. The hash function consistently maps specific traffic flows to specific forwarders, ensuring that packets from the same flow always take the same path. This deterministic approach maintains connectivity reliability through multihoming while guaranteeing packet order within flows.
Data Source
AI summary
Embodiments for handling multidestination traffic in a network are described. It is determined that a destination of a packet, received at a network device, is a multihomed destination. In response to determining that the destination of the packet is a multihomed destination, a hash value is determined from one or more header values of the packet using a hash function. The device refrains from forwarding the packet to the destination using a shadow hash forwarding table and the has value based on determining that the network device is not a designated forwarder for the packet, where the shadow hash forwarding table is used rather than a hash forward table based at least in part on determining that an updated forwarding table has not converged in the network.