Call intensity (y) = A/s = 24800/120 = 207 calls/s Figure A4.13 Example of switching and processing capacity in a transit switch Understanding Changing Telecommunications - Building a Successful Telecom Business TeS (200 cps) CP etc ML/MGW 1000 E1s 1000 E1s Figure A4.14 Capacity analysis of a telephony server domain Relationship between a Virtual ATM Group Switch Size and Telephony Server Capacity These basic principles for a telephony exchange also apply to a telephony server domain, where the group switch has been replaced by an ATM network. Figure A4.14 shows a telephony server domain with distributed MGWs handling all the voice traffic. A MGW is here defined as the voice-handling part of an MSG. From the server view, the ports in the MGWs are seen as ports in a virtual group switch. With 2 X 1000 Els having 0.8 Erlang/channel connected to this 'virtual group switch', this corresponds to 24 000 Erlang. With a mean holding time of 120 S, 200 calls per second can be handled. This can be compared with a traditional transit switch with a 64 K group switch. TASK 2: MSG PROCESSOR DIMENSIONING Assumptions and Definitions The processor in a typical MSG can handle approximately 55 calls/s in the MSG versions considered here. This means that we have to calculate the call intensity (calls/s) for the voice traffic. As mentioned, PVCs are assumed for data traffic through the backbone network with little load on the MSG processors. Therefore, as well as for reasons of simplicity, we will disregard the data traffic in the following calculations. Voice The processor in the MSG will handle all the originating calls plus all the incoming calls. The assumed objective is that it shall be possible to handle 55 calls/s per call handler, where a call handler corresponds to one CP pair in one MSG sub-rack. A 10G MSG with two CP pairs can thus handle 110 calls/s. These values are valid for the reference call type, inter-MSG call and ISUP signalling. Appendix 4: Dimensioning Media Gateways and Associated Telephony Servers In the calcul