SIP Provider Deutsche Telekom, VoiceData Connection(DE) (kb4706)

The information in this article applies to:

  • SwyxWare 2015

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Information und configuration hints for SIP provider Deutsche Telekom, VoiceData Connection (Germany).


General information

The Deutsche Telekom is offering the possibility to perform telephony on a SIP base to their business customers, when using their VoiceData connection. This is not a traditional SIP trunk, but nevertheless the SwyxWare can be configured accordingly use this connection for telephony. This can only be used when it is combined with internet access from Deutsche Telekom, it cannot be used an any other internet connection.

For a reliable operation of a SwyxWare on a VoiceData connection, at least SwyxWare2015R with a CHF has to be installed.

A detailed configuration guide (in German) can be downloaded at the end of this article.


Required information:

  • Access number (previously T-Online Number) or its alias, i.e. 11223344
  • Personal password for the Telekom VoiceData connection
  • assigned numbers (usually threei), i.e.. 040112233, 04011223334, 040112235

These information is provided by Deutsche Telekom when the connection is created or can be accessed through the Telekom customer center.

For each single assigned number, a dedicated SIP trunk group with the profile  "Telekom VoiceData (DE)" must be created. When configuring the user data for each SIP trunk, the associated public number must be entered as User ID in format canonical with plus, i.e. +4940112233. As UserName, the Access number must be configured. In order to enable forwarding of inbound external calls to another external destination, the number of simultanous call on each trunk must at least be '2'.

After the public calling number was assigned to a user, the exclusive usage of this trunk for that specific user must be configured through the routing records of the SIP trunk.

If an external, inbound call needs to be forwarded to another external destination, it is necessary to signal the public number of the forwarding party. This has to be configured in the tab 'NUmber signaling' of the trunk properties (Use: Originator's number, if assigned to this trunk, otherwise: Number of the transferor.)

Tested Features

  • Incoming/outgoing national calls
  • Incoming/outgoing international calls
  • Correct Calling Line Identificaion (CLI) on national and international calls
  • Holding and retrieving calls
  • Toggeling between two calls
  • Call transfer
  • Conferencing
  • Mutually supported codec:
    • G.711a
  • Incoming/outgoing DTMF signaling in accordance with via RFC2833
  • FAX tarnsmission via G.711

FAX transmission

The VoiceData connection does not support the T.38 protocol, which is strongly recommended for FAX transmission in an IP environment. The alternative method for FAX transmission via G.711 is supported from SwyxWare2015R3 on. In oder to prevent the intended T.38 stream switch, it is necessary to remove the T.38 codec from the list of supported codecs.
Note: Quality and reliability of a FAX transmission via G.711 strongly depends on the end-to-end network connection. Since the control and redundancy information from the T.38 protocol are missing, especially the transmission of larger documents may fail.


  • CLIP No Screening is not supported

Test date:
27/04/2015 with SwyxWare2015 R2 with CHF
28/09/2015 with SwyxWare2015 R3

Overview of tested SIP provider


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