Transparent PSTN Failover for VoIP Switches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current VoIP systems lack effective failover capabilities to ensure 100% protection against all outage possibilities, as they rely on data networks that are not as redundant as the traditional PSTN, leading to inadequate call handling during connectivity losses between the SBC and IP PBX, requiring manual interception by operators or auto attendants.
Innovation Solution
Implementing a transparent PSTN failover method where a VoIP switch routes calls through a PSTN number associated with the called party or premises, using a voice gateway to convert VoIP calls to TDM format and replace redirect numbers with original called numbers, allowing calls to be terminated by the IP PBX without operator intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If VoIP systems use data networks for call transmission, then cost is reduced and adaptability is improved, but reliability deteriorates due to lack of redundancy compared to PSTN
Solution Approach 1:
The system dynamically switches between VoIP and PSTN networks based on connectivity status. When the SBC loses connection to the IP PBX, the system automatically transitions call routing from the data network to the PSTN network, and vice versa when connectivity is restored. This dynamic adaptation resolves the contradiction by maintaining reliability through automatic fallback while preserving the cost benefits of VoIP during normal operation.
Solution Approach 2:
The system pre-configures PSTN failover capabilities and maintains PSTN connectivity as a backup pathway. By having the PSTN route prepared in advance and the failover logic pre-programmed in the SBC and IP gateway, the system cushions against potential VoIP network failures, ensuring reliability is maintained without permanently incurring PSTN costs.
2Reliability
If standard PSTN failover is implemented using call forwarding to a single PSTN number, then reliability is improved by providing backup call routing, but device complexity and ease of operation worsen due to requiring manual interception by operators or auto attendants
Solution Approach 1:
The system performs automatic failover without requiring manual intervention. The SBC detects connectivity loss and automatically redirects calls through the PSTN. The IP gateway automatically detects PSTN failover calls and replaces the redirect number with the original called number, enabling the IP PBX to terminate calls directly. This self-service automation eliminates the need for operators or complex auto attendant programming, reducing device complexity while maintaining reliability.
Solution Approach 2:
The IP gateway acts as an intermediary between the PSTN and IP PBX during failover. It receives calls from the PSTN with the redirect number, automatically replaces it with the original called number, and forwards the call to the IP PBX. This intermediary function automates what would otherwise require manual operator intervention, simplifying the system while ensuring reliable call delivery.
3Reliability
If call forwarding to a single PSTN number is used for failover, then reliability is improved by providing backup routing, but productivity deteriorates due to overwhelming call volumes that require manual handling
Solution Approach 1:
The system automatically routes failover calls directly to the intended destination without requiring manual interception. The IP gateway's automatic number replacement and the IP PBX's direct call termination enable calls to be handled systematically, preventing operator overload and maintaining productivity even during failover events.
Solution Approach 2:
The system replaces the manual mechanical process of operator interception with automated electronic processes. The IP gateway automatically performs number replacement and call routing, substituting human labor with automated telephony protocols and logic, thereby maintaining productivity during failover conditions.
4Ease of operation
If transparent PSTN failover is implemented with automatic number replacement, then ease of operation is improved by eliminating manual interception, but device complexity increases due to requiring coordination between SBC, IP gateway, and IP PBX
Solution Approach 1:
The IP gateway performs multiple functions: it converts between VoIP and TDM formats, detects failover conditions, replaces call numbers, and routes calls to the IP PBX. By consolidating these diverse functions into a single multi-functional device, the system achieves transparent failover with ease of operation while limiting the increase in overall system complexity.
Solution Approach 2:
The system uses feedback mechanisms where the SBC monitors connectivity to the IP PBX and triggers failover when connection is lost. The IP gateway monitors incoming calls for failover indicators and automatically responds by replacing numbers and routing calls. This feedback-driven automation simplifies operation while the standardized feedback protocols between components keep complexity manageable.
Data Source
AI summary
Novel tools and techniques for implementing Transparent PSTN Failover. In some embodiments, a VoIP switch might receive a call request for connection between a calling party at a calling telephone number (“TN”) and a called party at a called TN. Based on a determination that connection via a session border controller (“SBC”) between the VoIP switch and an Internet Protocol (“IP”) gateway has been lost, the VoIP switch might route the call request to a PSTN redirect TN through the PSTN. One of the Class 5 switch of the PSTN or the IP gateway might replace the redirect TN with the called TN, based on a determination that the redirect TN represents a PSTN failover. The IP gateway may then route the call request to an IP PBX for terminating (establishing) the call connection between calling party and called party, without interception by an operator, receptionist, or auto attendant.