Forked Call Routing via Endpoint Reachability Feedback
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Solution Overview
Problem
Call forking in telephony systems often fails due to policy restrictions, network limitations, or unavailable resources, leading to unreachable endpoints, where the caller and subscriber remain unaware of the failure, resulting in incomplete alerting across designated devices.
Innovation Solution
The originating server receives notification of an unreachable endpoint from the destination server, which then creates a new forked call using a different routing algorithm to ensure all endpoints are alerted, synchronizing call states and allowing the call to be answered from any available device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If call forking is implemented to ring multiple endpoints, then the subscriber can be reached on various devices and locations, but some endpoints may become unreachable due to policy restrictions or network limitations
Solution Approach 1:
The originating server proactively creates alternative forked calls with different routing algorithms before the initial forking attempt completes, ensuring that unreachable endpoints are compensated for by alternative routing paths that bypass policy restrictions or network limitations
Solution Approach 2:
The system changes routing parameters by implementing multiple routing algorithms with different paths to reach the same endpoint, allowing the call to bypass restrictions imposed on specific routes while maintaining the ability to reach all designated endpoints
2Difficulty of detecting and measuring
If the destination server determines an endpoint is unreachable, then the failure can be identified, but the caller and subscriber remain unaware of the failure without notification mechanisms
Solution Approach 1:
The system implements feedback by having the destination server send notifications to the originating server about unreachable endpoints, which then creates alternative forked calls to ensure all endpoints are alerted, closing the information loop about call delivery status
3Reliability
If a different routing algorithm is used to reach unreachable endpoints, then parallel simultaneous alerting can be provided on all endpoints, but the system complexity increases
Solution Approach 1:
The system segments the forking process by having the originating server create separate forked calls for different routing algorithms, allowing each algorithm to independently attempt to reach endpoints without interfering with others, thereby managing complexity through modular separation
Data Source
AI summary
Call forking allows for a subscriber to receive an incoming call and have that call ring on a number of endpoints identified by the subscriber. The call may then be answered on any one of the endpoints without the calling party needing to know which device is most likely to be answered. Call forking is not always available, such as due to regulatory prohibition or technical issues. As a result, a call may be designated to be forked to a particular endpoint, but that particular endpoint may fail to receive the call. The called and calling parties are often unaware of the issue. However, by providing the address of the endpoint back to an originating server associated with the calling party, the call may be forked from the originating server via a path different from the one that caused the endpoint to be unreachable. Once the call is answered, on any ringing endpoint, all other forked calls are terminated.