XPhone Call Controller

The XPhone Call Controller handles the IP-based switching of media streams (comparable to an IP multimedia subsystem). In a standard installation, it is located on the same machine as the XPhone server. However, it can be run on a separate machine under Linux. Outsourcing can be done for several reasons:

  • Distribution of computing load

    In very communication-intensive applications with media transcoding requirements (many simultaneous connections from softphone to PSTN), CPU load is shifted to the separate system that provides dedicated resources for this task (CPU, network). Whether offloading makes sense for load reasons is determined by whether the Windows server system of the XPhone server can meet the necessary resource requirements.

  • Isolate the switching system in a DMZ:

    The XPhone Call Controller encapsulates all switching processes and has a dedicated connection channel to the XPhone server (TCP/IP). The connection is established from the XPhone server to the call controller. This constellation meets increased corporate security requirements when Softphone Mobile is used, since ports on the Internet must be exposed for this application.

This section describes the hardware & software requirements for the outsourced XPhone Call Controller. If you are running the SingleServer deployment, where the XPhone Call Controller is run on the XPhone Server, you will need the System requirements for the XPhone Server.

The XPhone Call Controller can be downloaded as Hyper-V or as VMware (virtual) hard disk respectively. This virtual hard disk is preconfigured and contains a free Debian 10 OS. I.e. basically you need a Windows Server from 2019 or VMware ESXi from version 7 as hypervisor.

After setup, a fixed IP address is required for this system. This system must be able to reach the XPhone Connect server via the network (and vice versa) and requires access from/to the public Internet (if Softphone Mobile and/or Payload Separation from the public network is used).

Basic requirements for the system

  • 4 CPU cores

  • 8 GByte RAM

  • 20 GByte hard disk space

When using Softphone Mobile from the public Internet.

  • A public IP address

  • External accessibility (e.g. port 3478 for STUN requests)


When using Softphone Mobile, it is recommended to outsource the XPhone Call Controller to the DMZ. Here you can find the Hosting concepts.

Additional performance requirements

In case of simultaneous, internal (1:1) softphone calls

These system requirements are in addition to the basic requirements.



CPU cores

from 750

+ 1 GB

+ 2

from 1000

+ 1,5 GB

+ 3

from 2000

+ 3 GB

+ 6

from 3000

+ 4,5 GB

+ 9

For simultaneous, external softphone calls

These system requirements are in addition to the basic requirements.


CPU cores

from 40

+ 2

from 80

+ 4

from 120

+ 6

from 160

+ 8

from 200

+ 10

These are general recommendations. The actual demand depends on many factors. Some additional parameters are difficult to quantify (e.g. hard disk performance, network performance, telephony behavior, etc.), so the recommendations might have to be adjusted when used in practice.

The provision of sufficient CPU and RAM plays a crucial role for the smooth use of XPhone Connect. This is especially true when using the XPhone Call Controller (XCC), e.g. for real-time voice transmission in the conference service, AnyDevice and Follow-Me, TeamDesk, Softphone.

Have you found an mistake on this page?

Please send us a hint about this error by mail to doku@c4b.de. Thank you very much!