T-Systems is providing companies in Germany with a central SIP trunk with its "Corporate SIP Germany" service.

Corporate SIP International

Centralizing telephone connections and SIP trunks throughout Europe

  • Transnational SIP gateway as a central IP telephone connection for Europe reduces the need for external voice channels
  • Security thanks to network-based Enterprise Session Border Controller
  • Can be used flexibly for up to 50,000 parallel calls
  • Full PSTN replacement including number porting from analog connections and ISDN connections or local SIP trunks

SIP trunks modernize and centralize telephony

SIP trunks and SIP gateways from T-Systems are the VoIP successors to the former ISDN and analog connections. Depending on the network design and migration concept, local SIP trunks can be used as ISDN successors, as can central SIP gateways too – with up to 50,000 voice channels. VoIP solutions were often connected in the past in companies over ISDN gateways to the classic public telephone network and its differing technology. SIP trunking on the other hand follows a different approach and replaces classic technologies such as Public Switched Telephone Network (PSTN) telephone connections. The connection between the VoIP telephone system and the carrier network is established directly.

Central SIP gateway bundles all voice traffic

There are two main solution approaches here: the decentralized approach replaces PSTN connections with SIP trunks. The centralized approach on the other hand opts for a central SIP gateway for all locations connected to the VPN. A central SIP gateway bundles the company's external voice traffic over the in-house VPN and is therefore the central connection to the public telephone networks.
The advantages of the central SIP trunking approach are clearly evident when it comes to the topic of security for example: in the decentralized procedure, security management has to take account of each SIP trunk individually. With a centralized SIP gateway on the other hand, security management can also be performed centrally.

Technical specifications

  • Central SIP gateway for 18 European countries at present*
  • Migration of the former PSTN phone numbers of all locations and countries to the central SIP gateway
  • Consideration of all country-specific requirements
  • Emergency call function
  • Uniform transnational processes
  • Electronic billing as required – through to cost centers
  • Based on the "IntraSelect" MPLS-VPN from T-Systems: one contact for telephony and data services
* Last revised 07/2017: Austria, Belgium, Italy, Portugal, Sweden, Switzerland, Romania, Spain, Denmark, Ireland, Netherlands, Czech Republic, France, United Kingdom, Norway, Slovakia, Finland, Luxembourg. Via a dedicated gateway in Germany (Corporate SIP Germany).


All-IP migration offers companies the best opportunity to centralize their telephone infrastructure.

Corporate SIP International simplifies administration of infrastructures

Telecommunications infrastructures have evolved historically in many companies and are thus highly heterogeneous: every subsidiary, every production location, every branch and head office has its own telephone system (Private Branch Exchange, PBX). This ultimately means that administrators have to maintain each system individually – something that demands a lot of time and money, especially when different systems are also involved. The IT department has to book, install and manage the analog, ISDN or SIP connections separately. Moreover, country-specific requirements have to be taken into account and negotiations conducted with a number of local providers. This therefore makes sense especially for companies with a number of locations to standardize and centralize their telecommunications infrastructure across borders too: for example, with the new Corporate SIP International solution.

Reducing costs with a central SIP gateway

With its Corporate SIP International solution, T-Systems offers companies a central SIP gateway – currently for some 18 countries in Europe. All locations are therefore connected via the corporate network. The locations only need a single, redundant SIP gateway in the VPN – and no traditional telephone connections any more. In the case of external telephone calls, Corporate SIP International breaks out to the public telephone networks. All locations share the available voice capacities; only domestic and in-house telephone calls use the company's IP-VPN.
The central SIP gateway solution means remaining within the company's in-house network for domestic calls. No local break out to the public telephone network is required. The costs of telephone connections are thus significantly lower as a result of centralization, and the level of administration overhead is also reduced. Corporate SIP International provides up to 50,000 parallel external telephone calls, while the number of voice channels can be adjusted flexibly.

Migrating all numbers from the PSTN era

In contrast to decentralized SIP connections, the phone numbers of the previously local connections can be migrated to the SIP gateway in the case of Corporate SIP International – regardless of whether they come from analog, primary multiplex or multi-terminal connections. Redundant, central Enterprise Session Border Controllers, which are provided by T-Systems as a managed service, ensure professional VoIP security and effective routing of VoIP data packets.
On request, companies can also be provided with a central cloud PBX/hosted PBX from the secure T-Systems private cloud instead of their decentralized PBX systems. This offers the advantage of high security and availability at a low cost.

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