Locating Traffic Origin in LAN Using Subnet Discovery
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Solution Overview
Problem
Existing methods for locating an offending network device in a LAN, such as those using Link Layer Discovery Protocol (LLDP), are hindered by non-configured switches that obstruct the propagation of discovery protocol frames, preventing complete network scanning and requiring manual intervention in large networks.
Innovation Solution
The system employs IP subnet communication to broadcast a discovery message across all switches within the same subnet, allowing unconfigured switches to receive and respond to the message, and uses spanning tree protocol and LLDP frames to identify ports associated with the offending device, even if they define an edge of a searchable space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LLDP discovery protocol frames are used to locate offending network devices, then the location information can be obtained, but non-configured switches obstruct the propagation of discovery protocol frames, preventing complete network scanning
Solution Approach 1:
The patent introduces an intermediary mechanism where configured switches act as mediators to forward discovery requests across the network. When a discovery request reaches a non-configured switch, the last configured switch that received the request forwards it to neighboring configured switches, enabling the discovery protocol to traverse through unconfigured switches and reach all parts of the network.
Solution Approach 2:
The patent segments the network into configured and non-configured switch zones. The discovery process is divided into segments where configured switches handle protocol processing and forwarding, while non-configured switches simply pass through traffic. This segmentation allows the system to work around the limitations of non-configured switches without requiring them to be fully capable.
2Productivity
If manual log-in into each network switch is performed to locate offending devices, then detailed network architecture knowledge is required and the process is lengthy, but automated discovery methods require all switches to be configured with specific software
Solution Approach 1:
The patent implements partial automation where only some switches (a subset) need to be configured with the discovery software, not all switches in the network. This partial action approach achieves automated discovery functionality without requiring complete configuration of every switch, thus improving productivity while reducing the complexity burden.
Solution Approach 2:
The discovery mechanism is designed to be universal, working with both configured and non-configured switches. Configured switches perform multiple functions: processing discovery requests, maintaining MAC address tables, and forwarding requests to neighboring switches. This multi-functionality allows the system to achieve automated discovery without requiring every switch to have the same configuration.
3Loss of information
If discovery protocol frames are propagated through the network using LLDP, then offending device location can be determined, but the method is impeded when switches are not configured with the requisite software
Solution Approach 1:
The patent implements a feedback mechanism where configured switches monitor the propagation of discovery requests and provide feedback about which switches have been reached and which have not. This feedback allows the system to identify gaps in coverage caused by non-configured switches and adjust the discovery process accordingly, ensuring complete information gathering while maintaining reliable operation.
Solution Approach 2:
The system performs preliminary actions by having configured switches pre-forward discovery requests to neighboring configured switches before the requests would naturally propagate through non-configured switches. This preliminary action ensures that discovery information is collected from all accessible switches without being blocked by unconfigured devices, maintaining both completeness and reliability.
Data Source
AI summary
The switch port at which traffic associated with a specified media access control (MAC) address originates is searched for in a local area network (LAN). One or more switches receive a broadcast discovery message on a LAN subnet. Each switch determines whether the MAC address identified by the discovery message is associated with one of its ports. If the switch determines that the MAC address is associated with one of its ports, then the switch determines whether that port defines an edge of a searchable space. If the switch determines that that port defines an edge of the searchable space, then the switch issues a response message identifying the switch and the port.