Foreign Agent Stale Challenge Code Handling

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Solution Overview

Problem

In mobile IP communication systems, congestion can lead to registration or reply messages being lost or delayed, causing an infinite loop of retransmitted registration requests with stale challenge codes, which terminates the connection.

Innovation Solution

The Foreign Agent verifies that the Mobile Node is in a registered state and that the identifier code of the retransmitted registration request is not the same as the last received message, and has a greater value, to accept and authenticate registration requests containing a stale challenge code.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the Foreign Agent rejects registration requests with stale challenge codes to prevent security issues, then security is improved, but connection continuity deteriorates during network congestion

Engineering Contradiction:

ImprovesecurityVSAvoidconnection continuity

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The Foreign Agent dynamically adjusts its acceptance criteria for registration requests based on the current communication state. When the Mobile Node is in a registered state, the Foreign Agent accepts requests with stale challenge codes if the identifier code is greater than the last received message. This dynamic behavior allows the system to maintain connection continuity during congestion while preserving security for unregistered nodes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of challenge code validity based on the Mobile Node's registration state and identifier code comparison. Instead of uniformly rejecting all stale challenge codes, the Foreign Agent evaluates the registration state and identifier code sequence, allowing stale codes to be accepted when the identifier code increases, thus adapting the security parameter to the current operational context.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the Mobile Node retransmits registration requests during congestion, then connection establishment is attempted, but infinite loops occur with stale challenge codes

Engineering Contradiction:

Improveconnection establishment attemptVSAvoidinfinite loop duration

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The Mobile Node performs a preliminary check of its registration state before retransmitting registration requests. By verifying it is still in a registered state and comparing the identifier code against the last received message, the Mobile Node prevents unnecessary retransmissions that would create infinite loops, thus avoiding time loss while maintaining connection establishment attempts.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where the Mobile Node monitors its registration state and identifier code sequence. This feedback loop allows the Mobile Node to intelligently decide whether to retransmit registration requests, preventing infinite loops by comparing current identifier codes with previously received messages, thereby optimizing connection establishment without wasting time.

Inventive Principle:

Principle #23Feedback

3Duration of action of stationary object

If the Foreign Agent accepts all registration requests during congestion, then connection continuity is maintained, but security verification deteriorates

Engineering Contradiction:

Improveconnection continuityVSAvoidsecurity verification

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The Foreign Agent applies different acceptance criteria to different registration requests based on the Mobile Node's local state. Registered nodes receive more lenient treatment (accepting stale challenge codes with increasing identifier codes), while unregistered nodes undergo strict verification. This local quality differentiation maintains connection continuity for legitimate users while preserving security verification integrity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7545766B1Method for mobile node-foreign agent challenge optimization

Publication Date: 2009.06.09 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

The present invention supports an authentication protocol on a foreign agent to avoid rejecting re-registration request when congestion has delayed receipt at a mobile node of a foreign agent challenge code in a registration reply or agent advertisement message. Upon receipt of a re-registration request message containing a stale foreign agent challenge code, the identification code of the re-registration request message is compared to the identification code of the previous valid registration request message. If the identification code is greater than and not equal to the identification code in the previous valid request message, the foreign agent authenticates the message. The authenticated registration request message is processed to reset the lifetime so the communication session can continue.