Local Non-Secure Warning Tone Generation on VoIP Phones
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Solution Overview
Problem
Current methods for supporting Non-Secure Warning Tones (NSWT) in packet-switched networks, particularly across multiple security domains, face limitations such as unreliable audibility, bandwidth constraints, and inability to distinguish between multiple security domains, leading to ambiguous security warnings and restricted interoperability with VoIP and Circuit Switched phones.
Innovation Solution
Enhanced VoIP signaling between a Multi-Level Secure (MLS) system and phones allows local generation of NSWT, independent of voice codec bandwidth and network routing, and introduces Remote Security Domain Warning (RSDW) to clearly inform users of security domains, ensuring unambiguous warnings across multiple domains without bandwidth or quality degradation constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If NSWT is issued in-band in VoIP calls, then security warning can be provided, but NSWT may be lost or degraded and becomes unintelligible
Solution Approach 1:
The patent segments the security warning function into two independent parts: NSWT generation is separated from the voice codec processing. The NSWT is generated locally by the VoIP phone based on signaling from the MLS system, rather than being embedded in the voice stream. This segmentation ensures that NSWT clarity is independent of voice quality degradation.
Solution Approach 2:
The patent introduces signaling as an intermediary mechanism between the MLS system and the VoIP phone. The MLS system sends signaling instructions to the phone, which then autonomously generates the NSWT locally. This intermediary approach allows reliable NSWT delivery without being affected by voice stream degradation.
2Reliability
If high bandwidth codec (G.711/64 kbps) is used to ensure NSWT clarity, then NSWT audibility is improved, but substantial bandwidth is consumed
Solution Approach 1:
The patent extracts the NSWT generation function from the voice codec processing. Instead of requiring high-bandwidth codecs to preserve NSWT quality, the NSWT is generated independently by the phone based on signaling. This extraction eliminates the need for excessive bandwidth while ensuring reliable NSWT delivery.
3Reliability
If VoIP call routing is controlled to keep destination phone on the same IP network, then NSWT audibility is improved, but routing flexibility is reduced
Solution Approach 1:
The patent enables the VoIP phone to autonomously generate NSWT based on signaling received from the MLS system. This self-service capability means the phone can reliably produce NSWT regardless of its network location or routing path, eliminating the need to constrain call routing to the same IP network.
4Device complexity
If single NSWT is used to distinguish between multiple security domains, then system complexity is reduced, but security domain identification becomes ambiguous
Solution Approach 1:
The patent applies different NSWT characteristics (such as different tones, patterns, or associated signaling data) to represent different security domains. This local differentiation allows each security domain to have its distinct warning signature, enabling unambiguous identification while maintaining a relatively simple overall system structure.
Data Source
AI summary
A method for supporting non-secure warning tones on packet-switched networks involves receiving a call attempt from a source phone to a destination phone, checking if a connection of the security domains of the source phone and the destination phone via a MLS voice gateway is allowed, and checking if a generation of a non-secure warning tone locally by the source phone is required. A call is established from the source phone to the destination phone upon acknowledgement of the local generation of the non-secure warning tone by the source phone.