Inferring Physical Topology for IP Tunnels

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Solution Overview

Problem

Modeling IP tunnels in networks is challenging due to their virtual nature, which obscures physical topology, dynamic routing, and the lack of explicit source and destination interface information, making it difficult to determine the actual physical path between tunnel endpoints.

Innovation Solution

The method involves tracing device configuration and routing tables at routers to determine the outbound interface for each tunnel endpoint and inferring the likely return interface, using Patricia trees for efficient data processing and validation through various tests.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If IP tunnels are used to create virtual connections, then network flexibility and VPN capabilities are improved, but physical topology visibility and modeling accuracy deteriorate

Engineering Contradiction:

Improvenetwork flexibilityVSAvoidphysical topology visibility

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The patent uses packet tracing as an intermediary technique to bridge the gap between virtual tunnel operations and physical topology. By tracing packets through the network infrastructure, the system reveals the actual physical paths without disrupting the virtual tunnel functionality, thus maintaining network flexibility while recovering physical topology information.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces manual configuration-based topology discovery with automated packet tracing mechanisms. Instead of relying on static configuration data that may be incomplete or inaccurate, the system dynamically traces actual packet flows to infer physical topology, substituting mechanical configuration review with automated electronic tracing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If device configuration tracing is performed to determine physical interfaces, then physical topology discovery is improved, but processing time and computational complexity increase

Engineering Contradiction:

Improvephysical interface identification accuracyVSAvoidprocessing time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary packet tracing during network setup or maintenance windows to establish baseline physical topology information. This advance preparation creates a cached topology map that can be quickly queried later, reducing processing time during operational diagnostics while maintaining high identification accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts the depth and scope of packet tracing based on network conditions and diagnostic needs. For stable network segments, tracing is performed less frequently or with reduced granularity, while problematic areas receive more intensive tracing. This dynamic approach balances accuracy requirements with processing time constraints.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7894369B2Network physical connection inference for IP tunnels

Publication Date: 2011.02.22 RIVERBED TECH LLC

AI summary

The physical connection corresponding to IP tunnels in a network are found by tracing through the device configuration and routing tables at the routers in the network to determine the outbound interface associated with each tunnel endpoint, and then inferring a likely return interface associated with the opposite tunnel endpoint. Depending upon the particular configurations, a variety of tests can be applied to validate the inference. Patricia trees are preferably used to store and process the configuration data for efficient tracing through the routing tables at each router.