Survivable Media Server Dial Plan Routing for WAN Failures
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Solution Overview
Problem
Converged communications networks face challenges in providing alternate communication paths when the Wide Area Network (WAN) fails, limiting users' ability to dial extensions across different network regions and lacking feature transparency and seamless routing.
Innovation Solution
Establishing public or private network inter-gateway connections via trunks, allowing for automatic detection of WAN failures and routing voice calls over alternative networks like the PSTN, using abbreviated dial strings and Uniform Dial Plans to maintain seamless communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the WAN is available and a single primary media server controls all gateways, then abbreviated extension dialing works across network regions, but the system lacks redundancy and reliability when the WAN or primary server fails
Solution Approach 1:
The system divides the enterprise network into multiple autonomous network regions, each with its own survivable media server that can independently control local gateways. This segmentation allows the network to continue operating in fragmented regions without requiring a single centralized controller, thereby improving reliability while maintaining manageable complexity through distributed autonomy.
Solution Approach 2:
The patent implements dynamic dial plan modification based on network conditions. When the WAN fails or a region becomes autonomous, the system automatically changes dialing parameters by translating abbreviated extension strings into full PSTN dial strings, enabling calls to traverse public networks instead of requiring direct WAN connectivity. This parameter change resolves the contradiction by adapting the dialing behavior to the current network topology.
2Ease of operation
If media gateways register with local survivable media servers during WAN failure, then each region operates autonomously, but subscribers cannot dial extensions across different network regions
Solution Approach 1:
The patent introduces PSTN trunks as an intermediary communication path between autonomous network regions. When the WAN fails, calls destined for extensions in other regions are automatically routed through the public network infrastructure. The survivable media servers act as mediators that translate internal extension numbers into external PSTN addresses, enabling cross-region communication while maintaining the simplicity of abbreviated dialing for users.
3Reliability
If manual PSTN dialing is used during network failure, then calls can be placed over public networks, but users must manually recognize problems and dial complex numbers
Solution Approach 1:
The system implements automatic detection of WAN failures and self-service routing of calls through the PSTN. The survivable media servers monitor network conditions and automatically translate abbreviated extension dial strings into full PSTN dial strings without user intervention. This self-service mechanism maintains ease of operation by keeping the user interface simple while automatically providing reliable alternate paths when needed.
Solution Approach 2:
The patent pre-configures dial plan translation rules and PSTN trunk relationships before failures occur. When a WAN failure happens, the system has already prepared the alternate routing paths and translation mappings, enabling immediate switch to PSTN dialing without requiring users to manually look up or construct complex dial strings. This preliminary preparation resolves the contradiction by making the alternate path as easy to use as the primary path.
4Reliability
If subscribers without DID numbers are reached during PSTN fallback, then feature transparency is lost and calls appear as simple PSTN calls
Solution Approach 1:
The patent implements in-band signaling that provides feedback between the calling and called parties during PSTN routed calls. This signaling mechanism preserves feature transparency by transmitting call control information, caller identification, and service features through the voice path itself. The feedback loop maintains awareness of the call's true nature and enables features like call transfer, conferencing, and detailed call reporting even when calls traverse the public network, thereby preventing loss of information while ensuring reliable call completion.
Data Source
AI summary
In one configuration, the present invention is directed to an enterprise network that includes geographically dislocated first and second network regions communicating with one another through first and second networks and respectively comprising first and second gateways and first and second groupings of trunks. A media server is positioned in the first network region that includes a routing agent. When a WAN outage occurs, the routing agent, using a dial plan, maps the dialed digits to an electronic address addressable over the PSTN and routes the call over the PSTN to the destination second communication device in the second network region.