SDN Switch Packet Tracing via Flow Table Copying
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Solution Overview
Problem
In software-defined networking (SDN), existing packet tracing techniques consume valuable control channel bandwidth and are complex for controllers to troubleshoot packets that do not traverse their intended path, especially in complex packet processing pipelines.
Innovation Solution
Implementing a method where a single packet is sent to the controller along with the complete route it traversed through the packet processing pipeline, using a trace table to create a copy of the packet and append flow table identifiers to a recorded route, allowing efficient tracing without sending packets to every flow table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If existing packet tracing techniques send the packet to the controller at every flow table, then packet path information can be collected, but control channel bandwidth is consumed and controller complexity increases
Solution Approach 1:
The patent extracts only the essential tracing information (packet copies at ingress and egress flow tables) from the complete packet processing path, eliminating the need to send packets through every intermediate flow table. This selective extraction maintains path information while minimizing control channel usage.
Solution Approach 2:
The patent creates simplified copies of the packet at key points (ingress and egress flow tables) rather than transmitting the actual packet through every flow table. These copies contain sufficient information to reconstruct the packet path without consuming excessive bandwidth.
2Loss of information
If existing packet tracing techniques send the packet to the controller at every flow table, then packet path information can be collected, but controller complexity increases due to packet collation and path reconstruction
Solution Approach 1:
The patent performs preliminary actions at the ingress flow table by creating a packet copy and setting up tracing information before the packet traverses intermediate flow tables. This preliminary setup eliminates the need for complex real-time collation and path reconstruction at the controller.
Solution Approach 2:
The patent extracts only the necessary tracing data at key points (ingress and egress), removing the burden of processing complete packet information at every flow table. This extraction simplifies controller operations while maintaining complete path visibility.
3Adaptability or versatility
If multiple flow tables and flow entries are programmed in the packet processing pipeline, then network functionality is enhanced, but troubleshooting difficulty increases when packets do not traverse the intended path
Solution Approach 1:
The patent introduces an intermediary tracing mechanism that operates transparently within the complex packet processing pipeline. This intermediary system automatically tracks packet paths through multiple flow tables without requiring changes to the existing pipeline configuration, maintaining functionality while enabling easy troubleshooting.
Solution Approach 2:
The patent creates packet copies at strategic points in the pipeline that preserve complete path information. These copies enable troubleshooting of complex multi-table pipelines without affecting the original packet flow or requiring manual intervention.
Data Source
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Figure 3A~3B
AI summary
A method is implemented by a switch in a software defined networking (SDN) network to trace packets in a packet processing pipeline of the switch. The method includes creating a copy of a received packet to function as a trace packet. The method further includes, at each of one or more subsequent flow tables that the trace packet traverses, appending an identifier of that flow table to a recorded route of the trace packet and resubmitting the trace packet to that flow table to be processed without packet tracing. The method further includes sending, at an egress table, the trace packet to a controller along with the recorded route of the trace packet.