ALG NAT STUN Interworking for SIP Routing
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Solution Overview
Problem
The existing Network Address Translation (NAT) techniques face challenges in supporting Internet applications by not being able to analyze higher-layer packet information, leading to issues with NAT-traversal and inefficient SIP message routing across networks with different IP addressing schemes, resulting in unnecessary processes and resource wastage.
Innovation Solution
An interworking system that includes an Application Layer Gateway (ALG) for routing SIP messages, a Network Address Translator (NAT) for packet analysis, and a STUN server for providing global IP binding information, which performs NAT translation and minimizes terminal load by integrating STUN client functionality within the network node, optimizing SIP message routing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NAT technique is used to translate private IP addresses into global IP addresses, then the capacity of global IP addresses is improved and network security is enhanced, but the NAT cannot analyze higher-layer packet information leading to NAT-traversal problems
Solution Approach 1:
The patent introduces an Application Layer Gateway (ALG) as an intermediary component that works in conjunction with NAT. The ALG analyzes higher-layer packet information (Layer 7) that NAT cannot process, enabling proper translation of application-layer addresses while NAT handles IP address translation. This mediator resolves the contradiction by dividing responsibilities between NAT (for IP translation) and ALG (for application-layer analysis).
Solution Approach 2:
The patent segments the address translation function into multiple components: NAT handles Layer 3 IP address translation, while ALG handles Layer 7 application-layer address translation. This segmentation allows each component to specialize in its layer, with NAT focusing on IP address capacity and ALG providing the necessary adaptability for higher-layer analysis.
2Reliability
If STUN-client is driven on each terminal to acquire NAT-translated global IP address, then the NAT-traversal problem is solved, but it creates terminal load and is difficult to apply to the network
Solution Approach 1:
Instead of placing the STUN client functionality on each terminal (as in conventional approaches), the patent inverts the architecture by implementing STUN client functionality within the ALG itself. This inversion centralizes the traversal capability at the network level rather than the terminal level, eliminating terminal load while maintaining NAT-traversal reliability.
Solution Approach 2:
The ALG performs NAT-traversal functions autonomously without requiring external STUN clients on terminals. The ALG itself acts as the STUN client, acquiring and utilizing NAT-translated global IP addresses to enable proper routing, thereby making the system self-sufficient at the network gateway level.
3Reliability
If STUN server is accessed through NAT for every call, then global IP address is obtained, but unnecessary processes are generated and radio channels are wasted when call receiving terminal is on the same network
Solution Approach 1:
The patent implements preliminary action by having the ALG acquire and cache NAT binding information (global IP addresses) in advance, before actual call traffic needs to route through NAT. This pre-acquisition allows the ALG to use cached binding information for subsequent calls, avoiding repeated STUN server accesses and eliminating unnecessary radio channel usage when terminals are on the same network.
Solution Approach 2:
The system implements feedback mechanisms where the ALG monitors network conditions and terminal locations. When terminals are detected to be on the same network, the feedback loop prevents unnecessary STUN server communications, optimizing resource usage while maintaining the capability to acquire global IP addresses when needed.
Data Source
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AI summary
Disclosed are an interworking system between IP networks using different IP addressing scheme, an application layer gateway (ALG), a network address translator, an interworking method, and a SIP message routing method. The interworking system between a local network using a private IP and a global network using a global IP includes a STUN server and an application layer gateway (ALG). The STUN server provides binding information of header information of a global IP binding request. The application layer gateway (ALG) performs a global IP binding request with header information changed by IP masquerading, and performs routing by applying the received binding information to media receiving address information of a SIP message.