Hi Valsis,<br><br>Thanks for this.<br><br>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.<br>
<br>Working along this thought, at least you are minimising the hit cost-wise to a few seconds at most.<br><br>As to answering machines and fake conferences, fake network messages ...etc, one can possibly use voice detection, perhaps with heuristic and statistical training.<br>
<br>Just a thought ..<br><br>Regards,<br><br>Ahmed.<br><br><br><div class="gmail_quote">2010/1/8 Vlasis Hatzistavrou (KTI) <span dir="ltr"><<a href="mailto:vhatz@kinetix.gr">vhatz@kinetix.gr</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
Hello Ahmed,<br>
<br>
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.<br>
<br>
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. <br>
<br>
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. <br>
<br>
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).<br>
<br>
I hope this helps. <br>
<pre cols="72">Best regards,
Vlasis Hatzistavrou.</pre><div><div></div><div class="h5">
<br>
On 8/1/10 3:05 πμ, Ahmed Naji wrote:
</div></div><blockquote type="cite"><div><div></div><div class="h5">Hi everyone,<br>
<br>
Was just wondering what/if anyone is doing any work on FAS detection
and spoofed ring tones. Be great to discuss some ideas.<br>
<br>
Regards,<br>
<br>
Ahmed.<br clear="all">
<br>
-- <br>
Ahmed Naji<br>
</div></div><pre><fieldset></fieldset>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Ahmed Naji<br>