That's what I had in mind + some other techniques to address things to help with answering machines and recorded messages.

Vasilis rightly states some of the challenges in doing this, and he is also right on the legal and effort/benefit ratio.

My aim behind all of this is not to really prosecute or dispute issues with carriers - we have an active policy of barring FAS routes after the second offence, so that's covered. The aim is to be able to detect such routes as an when they arise, and be proactive rather than reactive in dealing with this horrendous and disgusting practice that plagues the telecom industry.

Best regards,

Ahmed.


2010/1/8 Anthony Minessale <anthony.minessale@gmail.com>
you could use the existing tone_detect app after the false answer to xfer to an extension of your choice if ring tone was detected.


2010/1/8 Ahmed Naji <a.alalousi@gmail.com>

Hi Valsis,

Thanks for this.

My line of thought is to tone-detect secondary ringing tones post 200(OK) to detect FAS (False Answer Supervision). This should eliminate at least a good proportion of calls, and it can be done real time through a script/modules/...etc.

Working along this thought, at least you are minimising the hit cost-wise to a few seconds at most.

As to answering machines and fake conferences, fake network messages ...etc, one can possibly use voice detection, perhaps with heuristic and statistical training.

Just a thought ..

Regards,

Ahmed.


2010/1/8 Vlasis Hatzistavrou (KTI) <vhatz@kinetix.gr>

Hello Ahmed,

I don't think there is a reliable way to detect FAS on a per call basis. Even audio detection software can be confused by strange ringtones, answering machines, etc.

The most reliable way we have found is to use statistics from CDRs and see if the INVITE-to-200(OK) delay averaged over a number of calls appears to be too small. If it is, then it is possible that you got FAS for those calls.

But this can only tell you if you have been experiencing FAS in past calls, ie you will not know you are getting FAS in real time.

It is still useful however: after you detect a possible FAS case via statistics you can place a few test calls yourself to verify that there actually exists FAS (and this is the only information that a carrier will accept in a trouble ticket to prove to them that they actually give you FAS).

I hope this helps. 
Best regards,
Vlasis Hatzistavrou.

On 8/1/10 3:05 рм, Ahmed Naji wrote:
Hi everyone,

Was just wondering what/if anyone is doing any work on FAS detection and spoofed ring tones. Be great to discuss some ideas.

Regards,

Ahmed.

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