Support for Deutsche Telekom’s CompanyFlex SIP Trunks
Our clients can now use additional Deutsche Telekom trunks for our PBX. Since the end of 2024 we support Deutsche Telekom’s CompanyFlex SIP trunks in addition to its predecessor, Deutschland LAN trunks, on PBX 1.5. This new possibility is a significant step forward, enabling clients to integrate even more external trunks into our Voxbi PBX.
A challenge worth tackling
In 2020 Deutsche Telekom implemented a new product, called CompanyFlex, based on different specifications than their previous trunks. In fact, Deutsche Telekom’s new SIP trunks, not only change administrative processes but also require significant technical adjustments. To sum up, since Deutsche Telekom’s new CompanyFlex trunks follow a different set of rules, our team had to rework how our system communicates with them, similar to updating a phone system to speak a new language.
Following a client’s request to integrate said Trunks, our Voice Backbone Team embarked on a deep dive into the new setup. We want to take you on the journey of how we implemented all the necessities for the new Trunk.
We pored over the 32-page specification document (1TR119), which detailed every requirement needed to properly configure these trunks. Balancing this task with our ongoing operations was challenging, involving extensive research, troubleshooting sessions, wireshark analysis and code changes to make sure our system was setting the right values in the right places.
Talk to an expert
Speak directly with our experts who are ready to provide insights and answers.
Key modifications for Telekom trunk registration
To fulfill the requirements for the registration of Telekom trunks, we implemented several key modifications on our core voice platform, including the following:
- DNS Resolution
- Proxy Identification:
- Client URI: The
client_urirequires a different layout, and we have adapted it to be explicitly set using the SIP user. - Contact Settings: The
contact_userformat required adjustments, so we adapted the retrieval process from the database. The SIP contact address is now determined based on either the authentication part or the entire user value. - Qualify:
qualify_frequencyand expiration timers are set to match their needs and ensure timely registration checks - Security Mechanisms: The code enforces security by setting
security_mechanismsto use SDES-SRTP and mediasec, and it specifiessecurity_negotiationas mediasec.
The outbound proxy isn’t resolved using a simple DNS A record. Instead, a DNS query first returns a NAPTR record, which then leads to SRV records that define the transport protocol (and possibly TLS encryption). This process ultimately provides multiple A records for redundancy.
An outbound proxy must be used for the CompanyFlex product to ensure proper connectivity
These changes necessitated significant adaptations and extensive testing to ensure full compliance with Deutsche Telekom’s CompanyFlex trunks specifications and requirements.
While working on the integration, we took the opportunity to further enhance the TLS configuration to improve security and performance. While more adjustments may be needed for certain installations, we are continuously refining our setup to deliver the best possible service.
Commitment to innovation
This integration highlights our adaptability and technical expertise. We continuously align with evolving telecommunications standards to keep our solutions reliable and future-ready.
If you are interested in acquiring your own integration with an external trunk, please do not hesitate to contact our team to get further information and arrange your own integration with our Voxbi PBX.