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ITG Engineering Guidelines Page 83 of
378
ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation
A configuration with 120 VoIP users each generates 4 calls using IP network
(originating and terminating) with an average holding time of 150 seconds in
the busy hour.
In the same hour, 25 faxes were sent and 20 faxes received. The faxes sent
averaged 3 pages, while the faxes received averaged 5 pages. The average
time to set up and complete a fax page delivery is 48 seconds.
The codec of choice is G.729 Annex AB, voice packet payload is 30 ms.
The fax modem speed is 14.4 kbit/s, and payload is 16.6 ms. How many ITG
ports are needed to meet P.01 blocking Grade of Service? What is the traffic
in kbit/s generated by this node to T-LAN?
1 Calculate Voice on IP Traffic during busy hour
CCS/user = 4*150/100 = 6 CCS
Tv = 120*6 = 720 CCS
2 Calculate fax on IP Traffic during busy hour
CCS/fax sent = 3*48/100 = 1.44 CCS
CCS/fax received = 5*48/100 = 2.4 CCS
Total fax CCS (Tx + Rx) = 1.44*25 + 2.4*20 = 36+ 48= 84 CCS
3 ITG Traffic during busy hour
Total traffic (T) = Tv + Tx = 720 + 84 = 804 CCS
4 Refer to the Poisson P.01 table (Table 12) to find the number of ITG
ports required for 1% blocking Grade of Service. For P.10 blocking
Grade of Service, refer to Table 13.
804 CCS can be served by 35 ITG ports with P.01 blocking Grade of
Service. Two 24 -port ITG cards are needed to serve this customer.