EVPN Port Extender Convergence via Aggregated Ethernet Segments
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Solution Overview
Problem
In Ethernet Virtual Private Networks (EVPN), the current implementation of port-extenders leads to inefficiencies such as large BGP route tables and granular designated forwarder elections, resulting in increased traffic convergence time and resource utilization.
Innovation Solution
Modeling a port-extender as an Ethernet segment and advertising EVPN routes with port granularity information, which reduces the number of Ethernet segment advertisements and Designated Forwarder elections, allowing for faster traffic convergence and smaller BGP tables by including port granularity information in packet headers and using split-horizon techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If port-extenders are modeled with granular port-level Ethernet segments, then forwarding precision is improved, but BGP route table size increases and device complexity increases
Solution Approach 1:
The patent merges multiple port-level Ethernet segments associated with a single port-extender into a single aggregated Ethernet segment. This consolidation reduces the number of BGP route advertisements from one per port to one per port-extender, significantly decreasing BGP route table size while maintaining adequate forwarding precision through the use of 802.1BR headers that carry port identification information.
Solution Approach 2:
The patent implements a nested structure where port-level information is embedded within the aggregated Ethernet segment representation through 802.1BR headers. The header contains an ingress port identifier that provides fine-grained port-level information nested within the coarser aggregated segment structure, enabling precise forwarding without requiring separate BGP routes for each port.
2Measurement precision
If designated forwarder elections are performed at port granularity, then forwarding accuracy is improved, but traffic convergence time increases
Solution Approach 1:
The patent merges multiple port-level DF elections into a single DF election at the port-extender level. Instead of performing separate DF elections for each port (which would result in multiple elections and longer convergence time), a single DF is elected for the entire port-extender. The 802.1BR header then ensures accurate port-level forwarding by identifying the ingress port, maintaining forwarding accuracy while reducing convergence time.
3Measurement precision
If port granularity information is included in all BGP advertisements, then routing precision is improved, but resource utilization increases
Solution Approach 1:
The patent applies local quality by including port granularity information only where needed - specifically in the 802.1BR headers for packets requiring precise port-level forwarding, rather than embedding it in all BGP advertisements. This selective application reduces overall resource utilization while maintaining routing precision for packets that require it.
Solution Approach 2:
The patent merges port granularity information into the aggregated Ethernet segment model, where a single BGP advertisement represents multiple ports. Port-level differentiation is achieved through 802.1BR headers rather than through separate BGP routes, reducing the quantity of BGP data while preserving routing precision through header-based port identification.
4Measurement precision
If multiple MPLS ESI labels are allocated for each port-extender port, then forwarding accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple port-specific MPLS ESI labels into a single aggregated ESI label for the entire port-extender. This single label is used for all ports associated with the port-extender, significantly reducing MPLS label management complexity. Port-level forwarding accuracy is maintained through the 802.1BR header that identifies the specific ingress port, eliminating the need for separate labels per port.
Data Source
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AI summary
Techniques are described for forwarding traffic within an Ethernet Virtual Private Network (EVPN) fabric of port-extenders by modeling a port-extender as a port-extender Ethernet segment. For example, a method includes receiving, by a provider edge (PE) device of a plurality of PE devices configured with an EVPN instance reachable by a port-extender Ethernet segment connecting the plurality of PE devices to a port-extender device, an EVPN route including information identifying an extended-port of the port-extender device associated with the port-extender Ethernet segment; storing, by the PE device, the information identifying the extended-port of the port-extender device associated with the port-extender Ethernet segment; and generating, by the PE device, a packet header of a data packet to be forwarded toward the extended-port of the port-extender device, the packet header including the information identifying the extended-port of the port-extender device.