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--></style></head><body bgcolor="white" lang="EN-CA" link="#0563C1" vlink="#954F72" style="line-height:initial"><div class="WordSection1"><p class="MsoNormal"><a name="_MailEndCompose"><span style="mso-fareast-language:EN-US">For us, the bigger problem is the ‘what to do’ rather than ‘how to’. </span></a></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US"> </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US">I’ve struggled with putting together meaningful and effective requirements for TDOS. There are a few companies that sell ‘voice firewalls’ but their materials are heavy on marketing-speak and “we enable you to do this and that”, rather than “This is what we do and how we do it”. </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US"> </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US">In my view, the main problem with TDOS is to identify it and be able to differentiate between TDOS calls and regular call volume.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US"> </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US">It seems to be more of an art, making it inherently difficult to programmatically pre-empt it. </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US"> </span></span></p><div><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="color:#1f497d">Best Regards,</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="color:#1f497d"> </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="color:#1f497d">Ivan Kovacevic</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span lang="EN-US" style="color:#1f497d">Vice President, Client Services</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="color:#1f497d">Star Telecom | </span></span><a href="http://t.sidekickopen61.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg1qMvVnW3LjyBM63K6FlW63JXmj56dLPjf6TyZWx02?t=http%3A%2F%2Fwww.startelecom.ca%2F&si=6470560385859584&pi=46813559-c184-4aa3-a9f0-b4d5979660e8"><span style="mso-bookmark:_MailEndCompose"><span style="color:blue">www.startelecom.ca</span></span><span style="mso-bookmark:_MailEndCompose"></span></a><span style="mso-bookmark:_MailEndCompose"><span style="color:#1f497d"> | SIP Based Services for Contact Centers | </span></span><a href="http://t.sidekickopen61.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg1qMvVnW3LjyBM63K6FlW63JXmj56dLPjf6TyZWx02?t=https%3A%2F%2Fwww.linkedin.com%2Fcompany%2Fstar-telecom-www-startelecom-ca-%3Ftrk%3Dbiz-companies-cym&si=6470560385859584&pi=46813559-c184-4aa3-a9f0-b4d5979660e8"><span style="mso-bookmark:_MailEndCompose"><span style="color:blue">LinkedIn</span></span><span style="mso-bookmark:_MailEndCompose"></span></a><span style="mso-bookmark:_MailEndCompose"></span></p></div><p class="MsoNormal"><span style="mso-bookmark:_MailEndCompose"><span style="mso-fareast-language:EN-US"> </span></span></p><span style="mso-bookmark:_MailEndCompose"></span><div><div style="border:none;border-top:solid #e1e1e1 1.0pt;padding:3.0pt 0cm 0cm 0cm"><p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> VoiceOps [mailto:<a href="mailto:voiceops-bounces@voiceops.org">voiceops-bounces@voiceops.org</a>] <b>On Behalf Of </b>Victor Chukalovskiy<br><b>Sent:</b> May 15, 2017 11:06 AM<br><b>To:</b> Matthew Yaklin <<a href="mailto:myaklin@firstlight.net">myaklin@firstlight.net</a>>; <a href="mailto:voiceops@voiceops.org">voiceops@voiceops.org</a><br><b>Subject:</b> Re: [VoiceOps] Mitigating or stopping TDOS attacks - any advice?</span></p></div></div><p class="MsoNormal"> </p><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">Hi,</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">You are talking PSTN --> customer call flow scenario in CLEC setting. Usually a class 4/5 switch is set to "transparently" pass all incoming calls from PSTN side to whatever customers trunk or line the DID or range is pointed to. And then either that resource gets full due to call volume or your switch starts failing or lagging due to CPS.</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">You have two options however:</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">If you were to pass all your traffic through a SIP proxy, like Kamallio or OpenSIPS like Alex suggested, that proxy can be programmed to do any kind of fancy call admissions control, dynamic filtering, number pattern etc. This however means you put an extra box in the call path between your PSTN switch and a customer.</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">Alternatively, you may try to see if all your PSTN switches can do some kind of external dip or routing query on incoming calls (radius, SIP refer etc). If they can, you can set a server or a cluster that would answer all those dips and decide on per-call basis wether the call should be admitted or not. So think external "brain" for your switches. This way call admission controll decision is made externally, but enforced right at your PSTN switch, and you don't have extra box in the call path. Making it somewhat more elegant.</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">This is pretty high-level, but if I understood your topology right, these are basically your two options.</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">-Victor</span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d"> </span></p></div><div><p class="MsoNormal" style="background:white"><span lang="EN-US" style="color:#1f497d">Sent from my BlackBerry 10 smartphone.</span></p></div><table class="MsoNormalTable" border="0" cellspacing="4" cellpadding="0" width="100%" style="width:100.0%;background:white;border-spacing:0px"><tr><td style="padding:.75pt .75pt .75pt .75pt;font-size:initial;text-align:initial"><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm"><div><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">From: </span></b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">Matthew Yaklin</span></p></div><div><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">Sent: </span></b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">Monday, May 15, 2017 10:44</span></p></div><div><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">To: </span></b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif"><a href="mailto:voiceops@voiceops.org">voiceops@voiceops.org</a></span></p></div><div><p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">Subject: </span></b><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif">[VoiceOps] Mitigating or stopping TDOS attacks - any advice?</span></p></div></div></td></tr></table><p class="MsoNormal"><span lang="EN-US"> </span></p><div id="_originalContent"><div id="divtagdefaultwrapper"><p><span lang="EN-US" style="color:black">Hello all,</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">I am curious what others have in place or actions they take when a customer is the target of a TDOS attack?</span></p><p><span lang="EN-US" style="color:black">TDOS being Telephony Denial of Service. An attack where the perp uses whatever means to flood a customer's telephone service with unwanted calls. </span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">Say you are a multi state CLEC. You have multiple brands of switches (Meta, Taqua, DMS, Genband, etc...) as well as ACME and Perimeta SBCs in use. You have legacy TDM as well as SIP trunks. Your customers are served via legacy and modern methods. You have hosted PBX as well (Broadsoft). Many customers are on your LAN but many are on the internet. So that is our situation. Or you can be bigger or smaller. No matter the size I would welcome how you handle it.</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">We have asked our manufacturers for advice but they have only provided the basic number blocking available by default on the switch. Meta and Genband have provided little other than pointing to existing features. If you have any thoughts on whether there is something we can provide based upon SIP messaging or other creative solutions that would be awesome!</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">So I welcome a discussion on this and any advice other operators can give.</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">Thank you very much,</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black">Matt</span></p><p><span lang="EN-US" style="color:black"> </span></p><p><span lang="EN-US" style="color:black"> </span></p></div><p class="MsoNormal" style="margin-bottom:12.0pt"><span lang="EN-US"> </span></p></div><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif"><img border="0" width="1" height="1" style="width:.0104in;height:.0104in" id="_x0000_i1025" src="http://t.sidekickopen61.com/e1t/o/5/f18dQhb0S7ks8dDMPbW2n0x6l2B9gXrN7sKj6v4LCS0Vf6xNj7dSCJWW64Jplz1pctGFW55kbNc1k1H6H0?si=6470560385859584&pi=46813559-c184-4aa3-a9f0-b4d5979660e8" alt="http://t.sidekickopen61.com/e1t/o/5/f18dQhb0S7ks8dDMPbW2n0x6l2B9gXrN7sKj6v4LCS0Vf6xNj7dSCJWW64Jplz1pctGFW55kbNc1k1H6H0?si=6470560385859584&pi=46813559-c184-4aa3-a9f0-b4d5979660e8"></span><span style="font-size:12.0pt;font-family:"Times New Roman",serif"></span></p></div></body></html>