NAT Firewall Type Detection via SBC Message Analysis
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Solution Overview
Problem
Existing methods for determining the type of Network Address Translator (NAT) firewall are inadequate as they require special hardware and provide inaccurate results, especially since the original STUN protocol methods have been deprecated due to varying NAT implementation behaviors.
Innovation Solution
A method and system that utilize SIP messages to determine the type of NAT firewall without requiring special hardware or software, where a Session Border Controller (SBC) analyzes responses to SIP messages sent from different IP addresses and ports to accurately classify the NAT type, ensuring correct handling of SIP sessions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If STUN protocol methods are used to determine NAT type, then the client can discover NAT presence and obtained mapped IP address, but the method becomes deprecated and inaccurate due to varying NAT implementation behaviors
Solution Approach 1:
The patent introduces an SBC (Session Border Controller) as an intermediary that performs NAT type detection on behalf of the client. The SBC sends test messages through the NAT firewall and analyzes the responses to determine NAT type, eliminating the need for the client to directly interact with the NAT for detection purposes. This mediator approach resolves the contradiction by providing reliable detection without requiring special client hardware or software.
Solution Approach 2:
The patent uses SIP OPTIONS messages as test copies to probe NAT behavior. Instead of requiring special STUN client software, the system uses standard SIP messaging that can be copied and sent through the NAT firewall. The SBC analyzes the responses to these test messages to infer NAT type, providing accurate detection without modifying client-side software.
2Difficulty of detecting and measuring
If special hardware or software is used for NAT detection, then detection capability is provided, but device complexity and cost increase
Solution Approach 1:
The SBC performs NAT type detection as part of its normal session establishment process without requiring the client to install special detection software or hardware. The SBC sends test messages through the NAT and analyzes responses automatically, making the detection service self-contained within the SBC functionality rather than requiring client-side modifications.
Solution Approach 2:
The patent uses universal SIP OPTIONS messages that can be sent through any standard NAT firewall without requiring special protocol support. The same SIP messaging infrastructure used for normal VoIP communication is also used for NAT detection, eliminating the need for separate STUN client software and reducing overall system complexity.
3Measurement precision
If client-side information about NAT type is used, then detection is performed, but the client may not handle SIP sessions correctly due to limited control
Solution Approach 1:
The SBC acts as an intermediary that collects NAT type information and uses it to control SIP session handling. Rather than relying on the client to interpret and act on NAT detection information, the SBC centrally processes the test messages, analyzes the responses to determine NAT type, and then configures appropriate session parameters. This mediator approach ensures correct SIP session handling while maintaining accurate NAT type detection.
Data Source
AI summary
A method, system, and computer program product for detecting the type of NAT firewall using messages provides the capability to determine the type of NAT in use without requiring special purpose hardware or software. A method for determining a type of a NAT firewall may comprise receiving a message from a device inside the NAT firewall, the message addressed to a first IP address and port of a device outside the NAT firewall, transmitting a plurality of messages to the device inside the NAT firewall, at least one of the plurality of messages addressed from the first IP address and port and at least one of the messages addressed from a second IP address and port, receiving responses to at least some of the plurality of messages transmitted to the device inside the NAT firewall and determining the type of the NAT firewall based on the received responses.