SIP C2C Module Predicts NAT Ports for VoIP
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Solution Overview
Problem
Network Address Translator (NAT) servers hinder communication efficiency in Voice over Internet Protocol (VoIP) systems by preventing direct transfer of RTP voice packets between clients behind different NAT servers, leading to significant communication failures and increased costs due to the need for bandwidth-intensive RTP-Relay solutions.
Innovation Solution
An improved SIP communication protocol with a client-to-client (C2C) module that predicts and allocates port numbers before SIP communication, allowing direct NAT traversal without the need for RTP-Relay, by conducting multiple detections to determine port allocation regularities and establishing a client-to-client RTP channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RTP-Relay is added on the SIP proxy server to enable voice packet transfer through NAT servers, then communication reliability is improved, but bandwidth cost and operational expense increase significantly
Solution Approach 1:
The C2C module performs port detection and allocation before the actual SIP communication begins. By predicting and pre-allocating port numbers based on detected regularities, the system establishes the necessary communication pathways in advance, allowing direct peer-to-peer voice packet transfer without requiring expensive RTP-Relay bandwidth during the actual communication phase
Solution Approach 2:
The C2C module acts as an intermediary that detects NAT server port allocation regularities and uses this information to predict future port numbers. This intermediary function enables clients to directly communicate through predicted ports without requiring the SIP proxy server to maintain expensive relay bandwidth, thus resolving the contradiction between communication reliability and bandwidth cost
2Adaptability or versatility
If multiple clients communicate through the SIP proxy server simultaneously, then communication coverage is improved, but communication efficiency deteriorates due to proxy server mediation
Solution Approach 1:
The communication process is segmented into two phases: setup phase (handled by SIP proxy server with C2C module for port detection and prediction) and data transfer phase (handled directly between clients). This segmentation allows the proxy server to provide necessary coordination without mediating the actual voice packet flow, thereby improving communication efficiency while maintaining coverage
Solution Approach 2:
The C2C module extracts the port detection and prediction functionality from the traditional SIP proxy server mediation model. By separating the setup function (port allocation prediction) from the data transfer function, clients can establish direct communication channels, improving efficiency while the proxy server maintains adaptability for client registration and protocol management
3Object-affected harmful factors
If virtual IP addresses are used behind NAT servers for SIP communication, then network security and address management are improved, but direct voice packet transfer between clients becomes impossible
Solution Approach 1:
The system performs preliminary detection of NAT server port allocation regularities and predicts future port numbers before actual voice communication begins. This preliminary action allows clients to know in advance which ports to use for direct communication, enabling reliable voice packet transfer while maintaining virtual IP addresses behind NAT servers for security and address management
Solution Approach 2:
The C2C module implements feedback by detecting port allocation patterns from previous communications and using this feedback to predict future port numbers. This feedback mechanism allows the system to adapt to NAT server behavior and maintain direct communication capability while clients remain behind NAT servers with virtual IP addresses, thus resolving the contradiction between network security and direct communication reliability
Data Source
AI summary
The present invention provides an improved SIP communication protocol. An NAT (Network Address Translator) traversal method is added before the SIP communication protocol, i.e. a client to client (C2C) module function is added to improve the function of SIP communication protocol, so as to solve the problem that the RTP (Real-time Transport Protocol) packets cannot traverse NAT firewall to achieve C2C communication after SIP (Session Initiation Protocol) is ended in VoIP. The major content of the present invention is to conduct a plurality of detection before SIP communication protocol, so as to predict the allocation rules of the port number by the C2C module, and open the RTP channel for C2C.