igure A4.17 shows that one call handler has enough capacity to handle all the voice traffic. Regarding data it is assumed that the traffic is switched through the backbone network using PVCs, which means that the load on the processor in the MSG is very little. Appendix 4: Dimensioning Media Gateways and Associated Telephony Servers Voice Assumptions 900 Mbit/s 2000 erl 2000 erl Voice: 50 0 000 subs (200 E1) 0.10 erl./subs 20% MSG-internal 80% utilization 120 S mht Data: 1500 Mbits/s 1500 Mbits/s 2500 erl 2500 erl 40% MSG-internal CP-calls 38 cps<50 Voice: 2500/120 + 2000/120 = 38cps Figure A4.17 Processor capacity in an MSG - numerical example TASK 3: TELEPHONY SERVER DIMENSIONING Telephony Server Processors In the telephony server there are two types of processors, both types having limitations when it comes to call handling. The central processor, exemplified in Figure A4.18, han- dles the normal signalling for setting up calls through the network, and the ML processor handles the communication with the involved distributed MSGs. Figure A4.18 shows an example of maximum number of ISUP calls per second that can be handled by the different processors. If there is a mixture of IN calls and ordinary calls, as well as a mixture of accesses, the call handling figures will be lower. The maximum figures will also be reduced if there are calls including announcement devices and conference call devices. Central processor ML 10G ML 20G Only ISUP Only ISUP, no XT, no IN IN-factor IN-factor Access mix factor Access mix factor XT-factor (announcement devices, conference calls etc.) Figure A4.18 Example of call-handling capacity for processors in a telephony server Understanding Changing Telecommunications - Building a Successful Telecom Business Input Data for Dimensioning In order to dimension the telephony server we need to calculate the number of calls per second that has to be handled by the telephony server. The input data we need is the traditional traffic volume (in Erlang), the distribution of the calls and the comp