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    <p>Hello,</p>
    <p>Keep-Alive works like a charm. Don't open any ports, because they
      won't give you any official IP addresses - only domain names. What
      I know so far: DTAG don't support T38 and transport was always
      UDP.</p>
    <p>You may find out additional information about the trunk when
      querying DNS for SRV and NAPTR records.</p>
    Sincerely,<br>
    Paul<br>
    <br>
    <div class="moz-cite-prefix">Am 27.01.2018 um 18:55 schrieb Paul
      Muaddib:<br>
    </div>
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cite="mid:CAEjNe_HQP+O8sNvStR7MG4JLmupndY=GESLRBe5qwL0vmGWgKA@mail.gmail.com">
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          <div>Hi,<br>
            <br>
            does anyone here have experience with the SIP trunk service
            from the German Telekom: "DeutschlandLAN SIP-Trunk"? There
            is little information from Deutsche Telekom on the Internet
            besides the "Technical Technical Specification of the SIP -
            1TR114" As I have read so far, Deutsche Telekom has not
            necessarily been sticking to the standard. <br>
            <br>
            What I know so far<br>
            <br>
            Transport protocol is probably TCP instead of UDP<br>
            Codecs: G. 711a and G. 722<br>
            Fax either via G. 711a or T. 38<br>
            <br>
            My Setup<br>
            Internet <-----> Router/Firewall(NAT) <---->
            Freeswitch<br>
            <br>
            According to the instructions, they require you to open
            several ports in the firewall. Is that really necessary?
            Does the Keep-Alive function work without opening any port?<br>
            <br>
            At the Federal Office for Information Security (BSI) it is
            additionally recommended to use a SIP proxy such as kamailio<br>
            <br>
            At the moment we are still using an ISDN gateway. I don't
            like to run into problems when we switch over, because I
            can't go back then.<br>
            <br>
          </div>
          Best regards,<br>
        </div>
        Paul</div>
      <br>
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