Centralized Server Session Routing in VoIP Transit Networks

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Solution Overview

Problem

In large-scale VoIP transit networks, traditional methods for session routing are inefficient due to the lack of real-time availability information about session control edge nodes, leading to increased processing and bandwidth overhead and potential call failures when nodes become unavailable or faulty.

Innovation Solution

A centralized server system that stores and updates application layer routing policies based on status messages from session control edge nodes, selecting available nodes and interconnects for routing requests, reducing unnecessary status message exchanges and ensuring quicker, more efficient session setup.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bilateral heartbeat messages are exchanged between all session control nodes to detect node availability, then node status detection reliability is improved, but network message overhead and processing load increase quadratically with the number of nodes

Engineering Contradiction:
Improvenode status detection reliabilityVSAvoidnetwork message overhead
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent introduces a central routing server as an intermediary that consolidates the heartbeat monitoring function. Instead of each node exchanging messages with every other node (n*(n-1) messages), all nodes send their status to the central server, which maintains availability information. This reduces message complexity from O(n²) to O(n), resolving the contradiction between reliable status detection and message overhead.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Loss of information

If session control nodes exchange frequent status messages to maintain real-time availability information, then routing accuracy is improved, but bandwidth consumption and processing overhead increase

Engineering Contradiction:
Improverouting information accuracyVSAvoidbandwidth and processing overhead
Core Design Contradiction:
Loss of informationVSLoss of energy

Solution Approach 1:

The patent merges the status reporting function into a centralized routing server that aggregates availability information from all session control nodes. Instead of multiple redundant status messages being exchanged between nodes, a single centralized entity collects and maintains the status information, reducing overall message traffic while preserving routing accuracy.

Inventive Principle:
Principle #5Merging (Combining)

3Adaptability or versatility

If a flat architecture with centralized routing servers is used instead of hierarchical switches, then network flexibility and scalability are improved, but the system loses the ability to make distributed local routing decisions

Engineering Contradiction:
Improvenetwork flexibilityVSAvoidrouting decision complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the routing function into two parts: a centralized routing server that maintains global availability information and makes policy decisions, and distributed session control nodes that execute routing decisions based on server instructions. This segmentation allows the system to benefit from both centralized information gathering and distributed execution, resolving the contradiction between flexibility and decision complexity.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP2901651B1Application layer session routing
Publication Date: 2018.07.18 BRITISH TELECOM PLC
  • EP2901651B1 patent drawingFigure 1
  • EP2901651B1 patent drawingFigure 2
  • EP2901651B1 patent drawingFigure 3

AI summary

A method and server system for providing application layer session routing based on network element availability. A server system (12, 18) is arranged to monitor the abilities of session control edge nodes (21A-D) within a large VoIP and Multimedia transit network (20) to handle session set-up requests. A status module (38) in the server system receives status messages (22, 24) from the edge nodes and based on these messages a selection and modification module (40, 41) selects which edge nodes (21A-D) as well as which of their associated interconnects to other networks to include in a response (5) to a routing request (4) from a source node (21A-D).