BFD Echo Session for Non-BFD Edge Device Failure Detection
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Solution Overview
Problem
In computer networks, particularly in MPLS/VPN environments, many CE devices are not configured for Bidirectional Forwarding Detection (BFD), leading to delayed failure detection and convergence times, as BFD benefits are only realized by enabled devices, while non-configured devices remain unaware of link failures until other mechanisms detect them.
Innovation Solution
Establishing a BFD Echo session from a BFD-enabled device to a non-configured device via a monitored path and using an external BGP session over an alternate path to notify the non-configured device of path failures, allowing both devices to detect failures without requiring the non-configured device to be BFD-enabled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If BFD is configured on all edge devices, then failure detection speed is improved, but device complexity and configuration effort increase
Solution Approach 1:
The patent introduces an intermediary mechanism where a BFD-capable device acts as a mediator to provide failure detection services to non-BFD devices. The BFD-capable device establishes BFD sessions with other BFD-capable devices and uses BFD Echo functionality to enable failure detection involving non-BFD devices without requiring them to be configured with BFD, thus resolving the contradiction between fast failure detection and configuration complexity
Solution Approach 2:
The patent makes the BFD-capable device universal by enabling it to serve both BFD-configured and non-BFD devices. Through BFD Echo sessions and alternative notification paths, a single BFD-capable device can provide failure detection services to any device regardless of its BFD configuration status, eliminating the need for widespread BFD deployment while maintaining fast failure detection
2Loss of time
If BFD is configured on all edge devices, then convergence time is improved, but administrative time and costs increase
Solution Approach 1:
The BFD-capable device serves as an intermediary that accelerates convergence for the entire network segment by implementing BFD only where needed. It rapidly detects failures through BFD sessions and quickly notifies dependent devices via alternative paths, achieving fast convergence without requiring configuration on all devices, thus reducing administrative time and costs
Solution Approach 2:
Instead of configuring BFD on all edge devices (excessive action), the patent applies BFD selectively only to devices that need or can support it (partial action). This selective deployment achieves sufficient convergence improvement while minimizing configuration effort and costs, as the BFD-capable device handles the detection work for the entire group
3Reliability
If BFD Echo session is established to a non-configured device, then failure detection is enabled for both devices, but requires alternative notification path
Solution Approach 1:
The patent uses existing routing protocols (OSPF, IS-IS, BGP) as intermediary notification mechanisms. When a BFD Echo session detects a failure involving a non-BFD device, the BFD-capable device leverages these existing protocol sessions to notify the non-BFD device of the failure condition, enabling reliable failure detection for both devices without requiring direct BFD capability on the non-BFD device or complex custom notification mechanisms
Data Source
AI summary
A technique enables bidirectional forwarding detection (BFD) between first and second edge devices in a computer network, wherein the second edge device is not configured for BFD. According to the novel technique, a BFD Echo session is established from the first edge device to the first edge device via the second edge device, i.e., along a monitored path (e.g., a single link). Also, an external border gateway protocol (eBGP) session is established between the first and second edge devices over an alternate path (e.g., an eBGP multi-hop session). The first edge device determines that the monitored path is down upon not receiving a returned BFD Echo message from the second edge device. In response, the first edge device notifies the second edge device that the monitored path is down through the eBGP session over the alternate path. Notably, upon notifying the second edge device that the monitored path is down, the first edge device breaks the eBGP session, and upon receiving the notification, the second edge device also breaks the eBGP session.