Directed Echo Requests for Multipoint Tunnel Failure Detection

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Solution Overview

Problem

Conventional traceroute techniques in computer networks, especially in multipoint tunnels, face processing burdens and false positives due to the large number of replies from nodes, making it difficult to accurately determine failures, especially when failures are limited to a few egress nodes.

Innovation Solution

Implementing a directed echo request mechanism where a first node sends an out-of-band message to a second node to initiate an in-band echo request for a specified tunnel, allowing the second node to inject echo requests and responses, and using reverse traceroute to work backwards to discover in-band failures, thereby reducing the processing burden and improving failure determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional traceroute techniques are used in multipoint tunnels, then connectivity verification can be performed, but the processing burden increases and false positives occur due to the large number of replies from nodes

Engineering Contradiction:

Improvefailure determination accuracyVSAvoidprocessing burden

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent segments the multipoint tunnel into individual point-to-point links by sending directed echo requests to each intermediate node separately. This divides the complex multipoint verification into manageable segments, allowing the source node to process replies individually and accurately determine failure locations without being overwhelmed by the total number of replies from all egress nodes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses directed echo requests as intermediary messages that are sent through intermediate nodes to verify connectivity. These intermediary requests allow the source node to indirectly verify connectivity to specific egress nodes through intermediate nodes, reducing the processing burden by filtering out unnecessary replies and focusing only on relevant connectivity verification.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of information

If conventional traceroute is used to verify connectivity in multipoint tunnels, then connectivity information can be obtained, but the time required increases due to processing multiple replies

Engineering Contradiction:

Improveconnectivity information accuracyVSAvoidverification time

Core Design Contradiction:

Loss of informationVSLoss of time

Solution Approach 1:

The patent performs preliminary actions by pre-configuring the directed echo request mechanism and using pre-established tunnels. The source node sends directed echo requests with specific TTL values to intermediate nodes before actual failure detection is needed, allowing connectivity verification to be performed more efficiently and reducing the time required for failure determination.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of sending echo requests from the source node to all egress nodes simultaneously (conventional approach), the patent inverts the approach by sending directed echo requests from intermediate nodes back to the source node. This inversion allows the source node to receive and process replies in a more manageable manner, reducing verification time while maintaining accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

3Difficulty of detecting and measuring

If conventional traceroute is used in multipoint tunnels, then route tracing is possible, but device complexity increases due to handling multiple reply messages

Engineering Contradiction:

Improvefailure location detectionVSAvoidmessage processing complexity

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The patent applies local quality by tailoring the echo request parameters (such as TTL values and target egress node identification) to the specific local conditions of each segment being verified. This allows the source node to handle replies in a standardized manner while adapting the verification process to the specific topology and failure conditions of each segment, reducing overall processing complexity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7746796B2Directed echo requests and reverse traceroute

Publication Date: 2010.06.29 CISCO TECHNOLOGY INC

AI summary

In one embodiment, a first node may send an out-of-band message to a second node to request that the second node initiate an in-band echo request for a specified tunnel, e.g., toward one or more third nodes. Upon receiving the in-band echo request, one or more responding nodes (e.g., generally the third nodes) may send a response to the first node. This “directed echo request” technique may also be used in conjunction with a “reverse traceroute” technique.