Downlink Control via Uplink Protocol State in Multi-Homed EVPN
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Solution Overview
Problem
In multi-homed Ethernet virtual private network (EVPN) configurations, network traffic blackholing occurs when protocols have not finished initializing on the uplinks of the primary provider edge device, preventing effective communication between the customer edge device and the network.
Innovation Solution
A customer edge device connected to both a primary and a secondary provider edge device determines the interface status of the uplinks. If an uplink has an inactive interface status, the device causes the downlink to be down, and when an uplink becomes active, it causes the downlink to be up, thereby preventing network traffic blackholing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the downlink is activated when uplinks are physically active but protocols are not initialized, then the downlink can transmit traffic, but network traffic blackholing occurs
Solution Approach 1:
The system performs preliminary action by checking protocol initialization status on uplinks before activating the downlink. The controller determines whether protocols have finished initializing on uplinks prior to allowing downlink traffic transmission, preventing blackholing by ensuring proper protocol state beforehand
Solution Approach 2:
The system implements feedback by continuously monitoring the interface status of uplinks and using this information to control downlink activation. The controller receives feedback about protocol initialization status and adjusts downlink state accordingly, creating a closed-loop control system that prevents traffic blackholing
2Reliability
If the downlink is kept down until protocols initialize, then traffic blackholing is prevented, but network communication is delayed
Solution Approach 1:
The system performs preliminary protocol initialization checks on uplinks before activating the downlink. By checking protocol status in advance and only activating the downlink when protocols are ready, the system avoids delayed communication establishment while maintaining reliable traffic delivery
Solution Approach 2:
The continuous monitoring of protocol initialization status provides real-time feedback that enables timely downlink activation. When protocols finish initializing, the feedback mechanism triggers immediate downlink activation, minimizing communication establishment time while ensuring traffic delivery reliability
3Productivity
If the device monitors uplink interface status continuously, then downlink activation is optimized, but computing resource usage increases
Solution Approach 1:
The controller implements feedback by monitoring uplink interface status and using this information to control downlink activation. This selective monitoring approach optimizes downlink activation timing while managing computing resource consumption by only checking status when relevant to traffic flow decisions
Data Source
AI summary
A customer edge device is connected, in a multi-homed configuration, to a device via a downlink of the device and to another device via another downlink of the other device. The device may determine that each of one or more uplinks of the device has an inactive interface status and may thereby cause the downlink of the device to be down. This may cause the customer edge device to communicate network traffic via the other downlink of the other device. The device may determine that at least one uplink, of the one or more uplinks, has an active interface status and may thereby cause the downlink to be up. This may cause the customer edge device to communicate network traffic via the downlink of the device.