 assumed traffic mix and corresponding processor load the average time it takes to handle a call with a mix of IN and ISUP is (0.1 X 7 ms + 0.9 X 2 ms) = 2.5 ms. Appendix 4: Dimensioning Media Gateways and Associated Telephony Servers Traffic loadability (Timax) Overload margin Traffic load (Tle) Margin % d = dimensioning factor margin % of traffic loadability Usage load Tle = Example: O&M tasks Figure A4.12 CP capacity Since the processor has 900 ms per second available for traffic handling, the total number of calls/s the processor can handle is 900/2.5 = 360 cps (calls per second). This corresponds to 1.296 million busy hour call attempts (BHCA). Relationship between Group Switch Size and CP Capacity for a Telephone Exchange Figure A4.13 shows an example of a transit switch with a 64 K group switch. With the assumptions shown in the figure, this group switch can switch roughly 25 000 Erlang traffic. In order to match this switching capacity, we need a processor that can handle approximately 200 calls/second, which corresponds to 720 000 BHCA. With the assumptions that the MHT is 120 S, 200 cps corresponds to a total traffic load of 24 000 Erlang. (A = y X s). The total capacity of the switch is also given as the number of E1s that can be supported. In the example we can see that a 64 K group switch can connect approximately 2000 E1s, since an E1 has 31 speech channels. As a rule of thumb we can say that an E1 can carry roughly 24 Erlang of traffic (0.8 Erlang/channel). Assumptions: MHT (s) = 120 S 2 X 1000 E1s connected = 62000 ports ~25 000 Erl Utilization (u) = 80% Traffic = 62000 X 0.8/2 = 24800 Erl. ~200 cps 0.72 MBHCA 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 Ca