A high-performance infrastructure for a new business area
In the summer of 2013, toplink GmbH was the first German network operator to certify its SIP trunks for the Unified Communication product “Microsoft Lync 2013”. Xantaro provided advice and support to the pioneer in IP telephony at all stages of implementing the solution. Today, toplink provides innovative IP telephony services based on this infrastructure.

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With Lync 2013, Microsoft launched in 2013 a new version of its platform for Unified Communications and Collaboration (UCC) for busi-nesses. The environment brings together features such as VoIP, video and conferencing, instant messaging or presence information, enabling colleagues to work together optimally, no matter where they happen to be. “Microsoft has launched a premium product on the market with Lync 2013”, reports Jens Weller, Managing Director at toplink GmbH founded in 1995 in Darmstadt, Germany.

Based on an efficient NGN infrastructure (Next Generation Network), toplink provides its customers  with a wide range of ITC services: from voice and data communications, SIP trunking through to UCC, IT outsourcing and IT consulting to individually developed VoIP solutions for carriers, service providers and portal operators. “We are a pioneer in the field of SIP trunks in Germany and we now offer an innovative IP telephony solution for Lync 2013 – including consulting, installation and operation, if requested by companies. We know that the telecommunications market is rapidly changing, and we are delighted to be able to embark on a new sustainable business area with this offer.” Prior to the implementation, however, the technical prerequisites needed to be set up.


Xantaro develops a SIP-trunk concept for Lync 2013

To enable the new IP telephony service for Microsoft Lync 2013, toplink’s existing NGN-based infrastructure had to be supplemented with SIP trunks for Lync 2013. As a matter of course, these needed to be highly scalable and designed for a variety of customers and thousands of parallel sessions. For this task, toplink called on the in-house advice and support of service integrator Xantaro. “We opted to collaborate with Xantaro” says Stanislav Vikulov, VoIP Engineer at toplink, “because Xantaro has the specific expertise for this project and is also very familiar with the market and the range of services of the different providers and products.”

Xantaro accompanied toplink throughout all phases of the project: from the solution concept for the new SIP trunks, through to the selection of the vendor and devices, testing and finally the implementation of the new infrastructure.


Efficient test environment thanks to Xantaro’s XT³Lab 

The core of the new SIP trunks were to be high-performance session border controllers (SBC) which have been integrated into toplink’s NGN infrastructure. In particular, it was necessary to ensure compatibility with MS Lync and interworking with the NGN. Xantaro advised toplink on the selection of products which in the end resulted in AudioCodes‘ Mediant 4000. This SBC with its outstanding Lync-specific properties has been designed for the professional usage of providers and supports thousands of parallel sessions.

For the extensive testing of functionalities, a Mediant 800 MSBR – a smaller model out of Xantaro’s XT³Lab providing the same functional range as the planned SBC – was installed on site at toplink initially. Thereby, the functionality of the SBC in conjunction with Microsoft Lync 2013 could be put through its paces and various use cases could be simulated. In numerous tests, the engineers in charge worked in cooperation with Xantaro to check all possible telephony scenarios and different functions such as call forwarding or conference calls, every which way across various networks such as PSTN, IP or mobile communications. Acting as an interface to the technology vendor, Xantaro also took responsibility for the communication with AudioCodes – for example, in the case of specific feature requests and to coordinate the necessary adjustments. And then the time had come.


First certification for Microsoft Lync 2013 in Germany 

In summer 2013, toplink was the first network operator to receive a certification for its SIP trunks for Microsoft Lync 2013. “Lync 2013 offers numerous improvements compared to the previous version,” explains Stanislav Vikulov. For the first time, the communication platform is equipped for equal treatment of mobile and landline devices, it features compatibility with Thin Clients, connects easily with non-Lync users and boasts many improvements for video conferencing and a higher quality of transmission. “That’s why Microsoft puts its partners and licensed providers through a strict inspection”, explains the VoIP Engineer.

In the end, the new SIP trunks for Lync 2013 at toplink underwent 122 individual tests in accordance with the “Unified Communications Open Interoperability Programs”. “With the support of Xantaro we have successfully passed the tests and received the Microsoft certification”, reports Vikulov with pleasure. In addition to just the certification for Microsoft Lync 2013, toplink today is the only provider in Germany which has also received the coveted certification for encryption – and can therefore now provide SIP trunking for Lync 2013 including TLS/SRTP.


Ideally positioned thanks to new services for Lync 2013

In toplink’s NGN network, there are now two redundant Mediant 4000 SBCs from AudioCodes which are optimised for Lync 2013 and form the heart of the new SIP trunks. They create the technical foundation upon which toplink can now offer new services for enterprises and telecommunications providers: Companies operating Lync 2013 themselves or hosting it for their customers – such as Deutsche Telekom AG – can use toplink’s SIP trunks to ensure a smooth connection to the PSTN network for their customers, covering all the functions. And companies that work with Lync 2013, but do not want to administer it, can get continuous advice and support including Lync 2013 hosting from toplink. “The successful testing of our SIP trunks was confirmation for us of the efficiency of our business product”, explains Vikulov. “Xantaro has accompanied us in this important project and contributed its in-depth expertise to give us an efficient, reliable and scalable infrastructure, with which we will now be able to conquer a new business area.”

For further information please visit www.toplink.de and www.audiocodes.com





  • Microsoft Lync is popular UCC platform in businesses
  • launch of the new version Microsoft Lync 2013 with innovations and improvements
  • possibility to extend the business area by new IP telephony services for Lync 2013


  • utilisation of 2 redundant AudioCodes Mediant 4000 SBCs for the implementation of scalable SIP trunks
  • intensive pre-testing within a pilot installation
  • functionality optimisation and modification in direct cooperation with the vendor


  • graduation of 122 tests and successful certification if the SIP trunks for Microsoft Lync 2013
  • positioning as the first German network operator in a new business area
  • portfolio extension by providing new telephony services based on Lync 2013
  • end users benefit from equal treatment of mobile and fixed devices, compatibility with Thin Clients and non-Lync users, improved transmission quality