DFN-Fernsprechen at a Glance

Participants using the DFN-Fernsprechen service can connect their VoIP-capable communications systems to the DFN VoIP infrastructure and transmit phone communications directly over the research network. Both incoming and outgoing calls can connect through VoIP.

General information for VoIP technology and the standards used by DFN:

·         Participants’ VoIP communications systems are connected to the central VoIP infrastructure on the research network through SIP-Trunking.

·          Telecommunications facilities are connected to redundant access points as standard practice so that the VoIP infrastructure is administered in a georedundant fashion.

·         Participant addressing is done according to E. 164.

·         The SIP-signaling is done according to RFC 3261/RFC 3398 through the use of UDP protocol over port 5060.

·         Audio codecs G.711am G.711m, G.722, and G.729ab are offered. Negotiation of the codecs takes place through establishing connections according to RFC 3264.

VoIP connections can also be encrypted upon request. The encryption of the signalling takes place over TLS (transport layer security) protocol. Encryption of media takes place through SRTP (secure realtime protocol). These encryption layers ensure confidentiality, authenticity, and integrity of your organi’ation’s VoIP connections.

More information about encryption on DFN-Fernsprechen services:

With VoIP-Centrex, participants can dispense with the use of their own telecommunications hardware. The service module VoIP-Centrex integrates wide-ranging offerings of functionality of modern VoIP telephones in the research network. In the process, the service aims to take advantage of the great potential of additional functionalities and innovations coming from the integration of these technologies and aims to take full advantage of this integration for the benefit of participants. The service also has very high availability thanks to its redundant connection to the research network
Just like with user-managed VoIP telecommunications hardware, the VoIP-Centrex platform is connected to the VoIP platform via SIP-Trunking in order to secure the connectivity within the research network as well as in public telephone networks. As standard practice, this connection and the connection to the associated end-user devices are encrypted via TLS/SRTP and can also establish both incoming and outgoing connections.
The administration of the end-user devices takes place through a web interface. On the interface, participants can administer all end-user devices and extension lines, register new end-users’ devices, or sign out old devices signed out, assign telephone numbers, and manage central address books. Every substation can also be administered by users in order to set up voicemail, set up call forwarding, or take care of user-specific address books.
You can find the portal for the VoIP-Centrex service and all relevant documentation here:

A Mobile Communications Framework Agreement for Science

The DFN association entered into a framework agreement with a mobile service operator to provide a mobile communications service. This framework agreement offers DFN participants (DFN facilities) the possibility of mobile voice, text, and data communications under conditions optimized for research and education.

Data transmission via mobile standards such as 5G or further developments plays a key role, as it facilitates being able to include mobile communications services in the convergences of previously disparate communications systems and networks.

Participants can look at the conditions of the framework agreement and cancel service through a portal provided by the mobile service provider. If you have questions, please contact the support team for DFN-Fernsprechen.

Participating institutions can reach people through mobile SMS by sending text messages via email to the SMS gateway. The SMS gateway receives the email, converts it to SMS format after checking usage authorization, then sends it through the mobile network recipients’ numbers. The SMS gateway also accepts acknowledgement and errtor messages from the mobile network and forwards them to the sender. Direct access to the SMS gateway is possible via a programming interface (API).

The SMS gateway uses a “white list” of IP addresses to ensure that emails are only forwarded from trusted devices.