SIP Proxy Enforcement via 305 Use Proxy Response

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Solution Overview

Problem

In enterprise communication systems, ensuring that the proxy server is included in SIP signaling between terminal devices and other SIP entities, such as PBX, is challenging due to security concerns and limitations in PBX vendors' support for certain SIP extensions like RFC 3327, which prevents multiple SIP URIs from sharing a common contact address.

Innovation Solution

The method involves a client device sending a SIP 305 Use Proxy response message to the PBX if the SIP request message was not sent via the enterprise voice application server, referencing the enterprise voice application server in the Contact field, thereby forcing all subsequent SIP requests and responses to route through the enterprise voice application server, even when PBXs do not support multiple registration bindings or RFC 3327.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If PBX uses traditional SIP routing without proxy enforcement, then call routing is simple and fast, but the proxy server cannot be forced to participate in SIP signaling for security and control

Engineering Contradiction:

Improveproxy server participation in SIP signalingVSAvoidSIP signaling path management

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The client device sends a SIP 305 Use Proxy response message back to the PBX after receiving a SIP request, providing feedback that forces the PBX to route subsequent requests through the proxy server. This feedback mechanism ensures proxy participation without requiring complex pre-configuration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Instead of the PBX actively forcing traffic through the proxy (which would require complex routing configurations), the client device actively requests to use the proxy by sending a 305 response. This inverted approach puts the burden on the client to ensure proxy participation, simplifying PBX operations.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If PBX supports multiple SIP URIs sharing common contact address (RFC 3327), then multiple registrations are possible, but many PBX vendors do not support this extension

Engineering Contradiction:

Improvemultiple SIP URI registration capabilityVSAvoidPBX vendor support compatibility

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The proxy server acts as an intermediary that resolves the conflict between multiple SIP URIs and a single contact address. The proxy receives requests for different URIs and routes them appropriately while maintaining a single contact address in the registration, enabling compatibility with PBXs that don't support RFC 3327.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the multi-URI handling logic from the PBX and places it in the proxy server. The PBX simply performs standard SIP routing, while the proxy server handles the complexity of managing multiple URIs and directing traffic to the correct destination, separating concerns between the two components.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If client device sends SIP request directly to PBX without proxy, then signaling is direct and efficient, but enterprise control and security monitoring are reduced

Engineering Contradiction:

Improveenterprise control over VoIP communicationsVSAvoidSIP signaling path length

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The client device performs preliminary action by sending a SIP 305 Use Proxy response message to establish proxy participation before the actual call setup. This preliminary routing instruction ensures that all subsequent SIP signaling for that call will go through the proxy, establishing enterprise control in advance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The proxy server serves multiple functions: it enforces enterprise security policies, monitors SIP signaling for compliance, performs authentication, and maintains call routing control. This multi-functionality justifies the additional signaling path length by providing comprehensive enterprise control capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9270707B2Method and system for enforcing proxy use within an enterprise communications system

Publication Date: 2016.02.23 MALIKIE INNOVATIONS LTD

AI summary

A method and system for enforcing the user of a proxy server within an enterprise communication system. The system includes an enterprise voice application server configured to act as a SIP proxy to client devices, and a private branch exchange configured to act as a SIP registrar. The client devices are configured to evaluate incoming SIP requests to determine whether they were received via the enterprise voice application server and, if not, to respond with a SIP 305 Use Proxy message referencing the enterprise voice application server in a Contact field. The 305 Use Proxy message forces the PBX or other intermediate SIP server to reroute the SIP request and any subsequent SIP requests in the dialog through the enterprise voice application server.