Network Device Pipeline Testing via Probe Reflection
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Solution Overview
Problem
Testing network switches is challenging as existing methods are ineffective in verifying forwarding states, leading to potential packet loss due to undetected incorrect forwarding states.
Innovation Solution
A deterministic model is implemented to test forwarding states by injecting probes into network devices' switching logic, using demultiplexers and agents to control probe routing and reflection, allowing for local management and verification of forwarding behaviors across multiple pipelines and ECMP links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test probes are sent from source host device through network switches to destination host device, then paths and links in the network are tested, but forwarding states of the network devices themselves are not tested
Solution Approach 1:
The patent introduces an intermediary testing mechanism where test probes are injected into the switching logic of network devices and reflected back by neighbor devices. This intermediary approach allows the source device to verify forwarding states by analyzing the reflected probes, thereby obtaining forwarding state information that would otherwise be inaccessible through conventional end-to-end probing.
Solution Approach 2:
The patent implements a feedback mechanism where neighbor devices reflect test probes back to the source device. This feedback loop enables the source device to receive information about the forwarding states of its own switching logic, allowing for verification and correction of forwarding behavior based on the reflected probe data.
2Reliability
If multiple pipelines are tested for forwarding states, then comprehensive verification is achieved, but testing complexity increases
Solution Approach 1:
The patent creates a universal testing mechanism that can test multiple pipelines through a single integrated approach. The test probe injection and reflection system serves multiple functions: it can test any pipeline by controlling which pipeline receives the injected probe, and the same reflected probe mechanism works for all pipelines, eliminating the need for separate testing systems for each pipeline.
Solution Approach 2:
The patent uses parameter changes to control pipeline selection during testing. By modifying parameters such as the destination address or pipeline selection bits in the test probes, the system can direct probes to different pipelines for testing without changing the fundamental testing mechanism, thereby managing complexity through parameter control rather than structural complexity.
Data Source
AI summary
A source network device can inject a probe into any one of multiple pipelines by supplying control bits for controlling a demultiplexer through which the probe passes. The control bits of the probe are coupled to the demultiplexer select lines so as to couple an input port of the demultiplexer to one of multiple output ports. As a result, an agent operating on the source network device can test any desired pipeline. In a one-hop embodiment, the source network device redirects the probe back to the agent without transmission to a neighbor. A two-hop embodiment uses a neighbor device to reflect the probe back to the source device in order to test forwarding states of the source network device.