The modular design of the Aarenet VoIP Switch allows an optimal adaptation to specific customer requirements. For a small, non-redundant system all system components are installed on one server. Fully redundant carrier grade systems for SIP clients have usually two Service Centres, two Config Centres and two Load Balancers. To scale up and support larger volumes additional Service Centres may be added. The architecture facilitates the realization of location redundant systems.

To support MGCP clients systems require additional components such as the Call Balancer and the Call Agent. Depending on the size of the system these components are installed on the same servers or on independent additional servers.

The software is scripted in Java with use of technologies such as Ajax and Soap


The Software is realized in a modular structure. The most important components are explained hereinafter.

Service Centre

The Service Centre supervises and controls the calls. It handles the caller authentication, routes the calls and generates call-data-records (CDR’s). Based on the CDR’s the calls will be charged to the end-users. The redundant implementation of the Service Centre increases the availability and ensures scalability of the system. To keep up with the growth of the number of subscribers the capacity is risen by an addition of new instances.

Load Balancer

The Load Balancer receives and forwards SIP messages from the CPE’s to the Service Centres. The Load Balancer forwards the messages to the Service Centre with the highest non-utilised processing capacity in consideration of the configured load distribution to manage the call.

Call Agent

This component is controlling and routing the MGCP devices. All user activities such as lifting the handset or pressing the keys are controlled by the Call Agent. The Call Agent generates the appropriate call by sending SIP messages to the Service Centre. The Call Agent converts MGCP to SIP.

Call Balancer

This component forwards the received MGCP messages from the terminals to the corresponding Call Agent. The allocation is dynamic. This means, that a terminal is allocated for one call to a distinct Call Agent and for a later call to another Call Agent. This allows the system to distribute the load to the different Call Agents.

Config Centre

The configuration of the system is handled on the Web-browser. The data is displayed and edited in an array of windows. An authorization concept provides the definition of various access levels. All system relevant configurations are maintained in the Config Centre.

CPE Centre

The optional CPE Centre generates the configuration files for the various CPEs automatically from the Aarenet VoIP Switch and downloads the settings to the CPE’s. Furthermore firmware upgrades may be executed fully automated at a predefined time. The CPE Centre offers monitoring of the connected CPEs. CPE configurations, port state, operating temperatures, etc. can be checked from the Aarenet VoIP Switch.

Use of off-the-shelf hardware without any proprietary components





Aarenet uses customarily Dell Power Edge Rack Servers with redundant power supplies and hot plug mirrored hard disks. For larger systems and on demand also Blade Servers may be used. The amount of servers depends on the size of the system and the specific requirements of the configuration.


All important system components are monitored permanently and fully automated




In case of a disruption the system may generate automated alarms via SMS or Email. The condition of all the different system components is visible at a glance. To query detailed information of a component or the generation of statistical information is very simple.

The system offers tools for preventive system monitoring and for system status checks.


Due to the modular structure of the AareSwitch there are next no limits to the scale-up of a system



Size of systems and scalability

The maximum number of subscribers which may operate on one system is determined by the performance of the deployed hardware and therefore highly scalable.

Extension Levels

Aarenet distinguishes between Test Systems, Entry Level Systems and Carrier Grade Systems.

Test Systems

Test Systems are used for evaluation purposes and as pre-production systems for customers with productive systems. The Test System supports the full functionality. All software components are mounted on a server or on two servers in the case of a redundant system. Test Systems are equipped with non-commercial licenses.

Entry Level Systems

Entry Level Systems are available with extensions from1000 up to 5000 accounts. They are available as non-redundant systems mounted on one server as well as redundant systems on two servers. Entry Level Systems may not be extended beyond the limit of 5000 accounts. For more than 5000 accounts a change to a Carrier Grade System is required.

Carrier Grade Systems

Carrier Grade Systems have an initial system size of 5000 accounts. These systems may be extended to very large systems of several hundred thousand accounts without interruption of operations. Carrier Grade Systems are always redundant and can even be built in a location redundant configuration. They are designed and built according to specific customer needs and may include additional servers for Voice Mail, Data Base, etc.