321 Studios (ITG) Trunk 2.0

ITG Engineering Guidelines Page 89 of 378

ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation

assumptions are made to project the Leader Card rea l time capacity: the

number of probe packets per Leader Card is 25, the average holding time is

180 seconds, the number of calls per hour per port (on the Fo llower Ca rds) is

15.3.

8-Port Leader and DCHIP Card Real Time Capacit

The 8-Port ITG Trunk Card is the NTCW80 based on the Intel 486 CPU.

Table 7 shows the forecast for the number of nodes, ports and calls per hour

that can be supported by the 8 -Port IT G Trunk Lea der/DCHIP C ard when t he

Leader Card is not conf igured with any ports. Cas e I assumes that the cal l mix

is 50% call origination and 50% call termination and as a result it take s

approximately 200 ms per call on average for the Leade r Card to a ssi st in t he

call setup/tear-down process. If, for example, the network size is 25 nodes,

then the Leader Card can support 10648 calls per hour (or 19166 CCS,

assuming 180 second average holding time). Assuming 15.3 calls per hour

per port, that translates into 695 ports, which is approxim ately 87 Follower

Cards. If, however, the ca ll s are 100% incoming calls (s ee Ca s e I I bel o w ) ,

then the call processing assistance re al ti me is app roxim ate ly 400 ms per cal l

and the Leader Card can support 43 Follower Cards.

Note that the Lea der Card capacit y that is express ed in terms of th e number

of calls per hour is derived from the real time measurements and is

independent of customer traffic assumptions. The Leader Card capacity

expressed in terms of the number of CCS and the number of ports (and the

number of Follower Cards) is derived from the cal ls per hou r va lue, b ased on

the traffic assumptions of 180 second average holding time (AHT) and 15.3

calls per hour per port, respectively. If these parameters do not reflect a

specific customer’s traffic requirements, the capacities in te r ms of CCS, the

number of ports, and the number of Followe r Cards c an be re-com puted using

the following procedures:

Number_of_Ports = Calls_per_ hour / Customer_calls_per_hour_p er_port

Number_of_Follower_Cards = Number_of_Ports / 8

Table 8 shows the fore cast of the Leader Card rea l time capacity for the ca se

that four or eight ports are configured to carry voic e traff ic with G. 711 c odec

and 10 ms voice sample size and Table 9 shows th e forec ast for the cas e with

the G.729A codec with Voice Activity Detection (VAD) and Silence

Suppression, and 30 ms voice sample s ize. For both tables , 40% voi ce ac tivity

is assumed.