BGP EVPN MAC Address Retention for Link Failure Resilience
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Solution Overview
Problem
In EVPN networks, temporary withdrawal of multi-homed MAC addresses can lead to unwanted traffic loss due to premature removal from all provider edge devices, even if the address is still reachable from other devices, necessitating a method to dampen such withdrawals and only remove addresses that are genuinely non-reachable.
Innovation Solution
Implementing a failure recovery process that causes multi-homed peers to advertise local customer MAC addresses in the BGP EVPN control plane, using a timer to control the re-advertisement of host MAC addresses and regeneration of Ethernet VPN routes, thereby preventing temporary traffic loss during link failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-homed MAC address is removed from one provider edge device due to link failure, then link resiliency is improved, but temporary traffic loss occurs because the MAC address is withdrawn from all provider edge devices even when still reachable
Solution Approach 1:
The system performs preliminary actions by having remaining provider edge devices continue to advertise the multi-homed MAC address in BGP EVPN routes even after link failure. This preliminary maintenance of MAC address advertisements prevents temporary traffic loss by ensuring the MAC address remains reachable through alternative paths before any withdrawal occurs.
Solution Approach 2:
The system implements feedback mechanisms where provider edge devices monitor the reachability of multi-homed MAC addresses and adjust their advertising behavior accordingly. When a link fails, the feedback loop detects that the MAC address is still reachable through other provider edge devices, preventing premature withdrawal and associated traffic loss.
2Speed
If MAC addresses are quickly removed from the control plane upon link failure, then network convergence speed is improved, but temporary traffic loss occurs before the removal is complete
Solution Approach 1:
The system performs preliminary maintenance of MAC address advertisements in the control plane even after link failure detection. By keeping the MAC address advertised until confirmation of complete unreachability, the system avoids the temporary traffic loss that would occur during the convergence process, while still achieving rapid convergence once the MAC address is confirmed lost.
3Reliability
If BGP EVPN control plane advertising is used for MAC address learning, then MAC address reachability is improved across the network, but temporary withdrawals cause traffic loss despite the address being reachable from other devices
Solution Approach 1:
The system uses feedback from BGP EVPN control plane advertisements to determine whether a multi-homed MAC address should be withdrawn. By monitoring whether remaining provider edge devices continue to advertise the MAC address, the system can distinguish between genuine unreachability and temporary link failures, preventing premature withdrawal and associated traffic loss.
Data Source
AI summary
Embodiments are directed to a process and system for avoiding temporary traffic loss in a network having first and second computers and provider edge devices, by retaining, in each provider edge device, path information including a MAC address for the first host computer in a control plane as a dynamic address, and maintaining, in each provider edge device, its own routing table listing network addresses of the other provider edge devices as multi-homed peers. A failure recovery process in each provider edge devices advertises all multi-homed peer network addresses as addresses that each respective provider edge device has dynamically learnt in the control plane such that when a provider edge device receives a route with a locally connected host, it re-advertises the host address on its own.