[Freeswitch-users] DeutschlandLAN SIP Trunk

[Paul Muaddib]

Hi,

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.

What I know so far

Transport protocol is probably TCP instead of UDP
Codecs: G. 711a and G. 722
Fax either via G. 711a or T. 38

My Setup
Internet <-----> Router/Firewall(NAT) <----> Freeswitch

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?

At the Federal Office for Information Security (BSI) it is additionally
recommended to use a SIP proxy such as kamailio

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.

Best regards,
Paul
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