Network Device Interface Identification via Packet Analysis
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Solution Overview
Problem
External tapping devices cannot determine the input and output interfaces of a routing device, as this information is unknown to them and cannot be identified based on packet data alone.
Innovation Solution
A network device taps into the network, receives packets, and uses a processing unit to determine the input and output interfaces of the routing device by analyzing packet addresses and running discovery protocols like CDP or LLDP, comparing CRCs to identify matching packets, and storing this information for further processing or storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If external tapping devices are used to obtain packets from the network, then packet copying capability is improved, but the ability to determine input and output interfaces deteriorates
Solution Approach 1:
The patent introduces an intermediary mechanism (discovery protocol packets and interface mapping tables) that bridges the gap between external tapping devices and routing device interface information. The tapping device sends discovery protocol packets through the network to the routing device, which responds with interface identification information, allowing the external device to determine input/output interfaces without direct access to routing device internals
Solution Approach 2:
The patent implements preliminary action by pre-establishing interface mapping tables that correlate packet source/destination addresses with routing device interfaces. Before normal packet monitoring begins, the system performs discovery protocol exchanges to populate these mapping tables, enabling subsequent packets to be analyzed for interface determination without requiring real-time communication with the routing device
2Measurement precision
If discovery protocols are run to determine interface information, then interface identification capability is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by implementing a multi-functional discovery protocol mechanism that serves multiple purposes: identifying input interfaces, identifying output interfaces, and building interface mapping tables. The same discovery protocol infrastructure handles all interface determination tasks, reducing overall system complexity compared to implementing separate mechanisms for each function
Solution Approach 2:
The patent uses copying by creating simplified representations of interface information in the form of mapping tables. Instead of implementing complex real-time communication with the routing device for each packet analysis, the system copies interface identification data into local tables that can be queried efficiently, reducing the complexity of ongoing interface determination operations
Data Source
AI summary
A method performed by a network device that taps to a network having a routing device, includes: receiving a first packet tapped from the network; determining a first information regarding an input interface of the routing device based on a destination address of the first packet; receiving a second packet tapped from the network; determining a second information regarding an output interface of the routing device based on a source address of the second packet; determining a first CRC for the first packet; determining a second CRC for the second packet; and comparing the first CRC with the second CRC at the network device to determine whether the first packet and the second packet are the same.