S-CSCF ENUM Failure Handling via HSS PSTN Routing

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Solution Overview

Problem

Existing communication networks, such as VoIP networks, often fail to complete calls due to failures or degradations in non-essential network components like ENUM servers, leading to customer dissatisfaction despite the availability of other functional network components.

Innovation Solution

A method where the Serving-Call Session Control Function (S-CSCF) inserts an indication of component failure in the session request header if the ENUM server is non-responsive, allowing the call to be routed through a Home Subscriber Server (HSS) for domain information and potentially completing the call via the Public Switched Telephone Network (PSTN) if the ENUM server fails.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the network uses ENUM server for call routing, then call routing information is obtained, but call completion fails when ENUM server is non-responsive

Engineering Contradiction:

Improvecall completion reliabilityVSAvoidnetwork component dependency

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary mechanism (alternative routing path through HSS and PSTN) that mediates between the failed ENUM server and the call completion process. When ENUM server is non-responsive, the system uses the HSS to obtain domain information and routes through PSTN as an intermediary path, ensuring call completion without direct dependency on ENUM server availability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements beforehand cushioning by preparing alternative routing paths in advance. The system is designed to detect ENUM server unresponsiveness and automatically switch to pre-configured alternative routes through HSS and PSTN, cushioning against the potential failure of ENUM server before it causes call completion failure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If the network requires response from ENUM server, then routing information is validated, but call completion is blocked due to server failure

Engineering Contradiction:

Improverouting information accuracyVSAvoidcall completion rate

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies dynamics by making the routing process adaptive and flexible. The system dynamically adjusts the routing path based on ENUM server responsiveness: using ENUM server when available for accurate routing, and switching to HSS-based domain information retrieval when ENUM server fails. This dynamic adaptation maintains both routing accuracy and call completion rate.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of routing information source based on system conditions. When ENUM server is responsive, it uses ENUM-provided routing information; when ENUM server is non-responsive, it changes to using domain information from HSS. This parameter change allows the system to maintain routing accuracy while ensuring call completion.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the network follows strict ENUM server response protocol, then routing accuracy is maintained, but call completion fails when ENUM server is down

Engineering Contradiction:

Improverouting information precisionVSAvoidservice availability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements universality by making the HSS serve multiple functions: it acts as both the primary subscriber information repository and an alternative routing information source when ENUM server fails. The HSS can provide domain information for routing calls even when ENUM server is unavailable, making the system more universal and resilient.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent converts the harm of ENUM server failure into benefit by designing the system to use the failure condition as a trigger for alternative routing. The unresponsiveness of ENUM server, which would normally block call completion, is converted into a condition that activates the HSS-based alternative routing path, ultimately achieving call completion through a different but equally effective route.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS8750132B2Method and apparatus for completing a call in a network with ENUM failure

Publication Date: 2014.06.10 AT&T INTELLECTUAL PROPERTY I L P

AI summary

A method and an apparatus for processing a session request in a network are disclosed. For example, the method receives the session request by a Serving-Call Session Control Function (S-CSCF), and sends a query to a tElephone NUmbering Mapping (ENUM) server for the session request. The method determines if a response is received to the query to the ENUM server, and inserts an indication of a component failure in a header of the session request if the response is not received from the ENUM server, wherein the indication of the component failure indicates a non-responsive ENUM server.