EVPN Multi-Homed Network Convergence via Loopback Advertisement
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Solution Overview
Problem
In EVPN multi-homed network environments, convergence times are prolonged due to reliance on BGP route withdrawal, leading to traffic loss when a leaf node fails, as remote nodes continue to send traffic to the failed node until network reconfiguration is complete.
Innovation Solution
Implementing underlay convergence by configuring leaf nodes to advertise each other's loopback IP addresses with higher cost metrics, allowing spine nodes to reroute encapsulated packets to a backup leaf node in case of failure, thereby bypassing the failed node without requiring L2 connectivity or protocol state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BGP route withdrawal is used for convergence, then network reliability is improved, but convergence time increases and traffic loss occurs
Solution Approach 1:
The patent pre-configures backup paths and advertises loopback IP addresses with higher cost metrics before failures occur. When a leaf node fails, the backup path is already in place and can be activated immediately without waiting for BGP convergence, thus reducing convergence time while maintaining reliability
Solution Approach 2:
The patent introduces loopback IP addresses as intermediary routing targets. Instead of directly routing to leaf nodes, traffic is routed through loopback addresses that can redirect to backup leaf nodes, enabling faster failover without disrupting the overall network routing structure
2Reliability
If BGP route withdrawal is used for convergence, then network reliability is improved, but traffic loss increases
Solution Approach 1:
The patent pre-establishes backup forwarding paths by advertising loopback routes with higher cost metrics before failures occur. When a leaf node fails, traffic is immediately redirected through the pre-configured backup path, preventing traffic loss while maintaining network reliability
Solution Approach 2:
The patent prepares compensatory routing paths in advance by advertising loopback IP addresses with higher cost metrics. These pre-prepared backup paths act as a cushion that absorbs traffic during failures, preventing traffic loss while ensuring reliable delivery
3Speed
If loopback IP advertising with higher cost metrics is implemented, then convergence speed is improved, but device complexity increases
Solution Approach 1:
The patent makes leaf nodes multi-functional by enabling them to serve both as primary forwarding nodes and as backup nodes for other leaf nodes. By advertising loopback IP addresses, each leaf node can act as a backup for multiple other leaf nodes, reducing the need for dedicated backup infrastructure and simplifying the overall network design
Data Source
AI summary
Methods for assisting data forwarding during convergence in a multi-homed network are disclosed. In one aspect, a first leaf node is configured to detect when a second leaf node advertises a set of Ethernet segments which are local to the first leaf and advertise reachability information for the second leaf, indicating itself as a backup for the second leaf during convergence. A spine node that receives advertisement messages from such first and second leaf nodes programs its routing table to indicate the direct route to the second leaf as the primary path and the route to the second leaf via the first leaf as a backup path to forward encapsulated packets destined to the second leaf. Upon failure of the second leaf, when the spine node receives data packets destined to the second leaf, the spine node sends the packets to the first leaf instead of the second leaf.