Telephony Servers (front-end servers)
The front end servers terminate TDM and/or SIP traffic on location. The locations can be anywhere and are not restricted to a city, country or continent. The single requirement is that the POPs can reach the centralized application servers or local application.

Intelligent Networking (IN) Servers
Using intelligent networking in your solution for example for "Intelligent Roaming" requires a separate IN server to control and steer the IN messages and to control the status of each message.

Application Servers
In order to achieve high availability, the application servers on the central site are installed N+1. Application servers can also be used for mass calling load circumstances. The servers are located behind two active/standby load balancers which route the requests in a balanced way to the available application servers.

Messaging (SMS-C, USSD, etc) Servers
Using Messaging (SMS, USSD, MMS, etc) in your solution requires a separate messaging server to send and receive the messages and to control the status of each message.

Database Servers
Centralized database servers are used to store statistical information. The CDRs and CERs are inserted from the application servers. Next to statistical information, dialogue settings are stored in the central database.

Web Servers
In a number of cases it is important for customers to interact with the system using web browsers. This can for example be needed for the Service Creation Environment or for changing parameters, Ring Back Tone, VoiceMail, etc.

Text To Speech (TTS) Servers
Using Text to Speech in your solution requires a separate TTS server to process the slang and do conversion of the text into voice files of the correct language and with the correct voice.

Automatic Speech Recognition (ASR) Servers
Using Automatic Speech Recognition in your solution requires a separate ASR server to remove the noise, etc and to process the recognition in the correct language or dialect and return the recognizers result.

Server Combinations
For small applications all the separate server functions can be combined on one system. For a distributed solution or for greater capacity, spreading the functions on different servers is a better idea.

In a 2 server configuration, one server would be front end, the other server would handle the application and database functions. For greater robustness and redundancy more than one server for each function can be used. Many different combinations are possible, and the best solution will be determined for each customer.