Nortel Meridian 1 Description, Installation And Operation page 57

IP Telecommuter Engineering Guidelines
Due to the capacity limitation of an ITG Line Card processor, a card can
process 15 simultaneous calls with minimum packet delay or loss. To protect
QoS of calls in progress, when the 16th call comes in, it will be blocked and
not allowed into the system under the flow control rule implemented in the
ITG software. Assuming 4 calls per hour per client, and a holding time of 300
seconds, the probability of blocking to occur is less than 0.001. This critical
load amounts to 12 CCS per client with a 20% peaking allowance.
With the loading of 6 CCS or less per set in a typical office model, the
blocking probability is negligible. However, users should take care not to
engineer an application beyond the stated capacity.
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• Obtain total subnet traffic: Number of clients*CCS/client
• Convert to erlangs: total CCS/36
• Find T-LAN kbps number from bandwidth table
• Bandwidth per subnet: total erlangs*T-LAN kbps
• Repeat the procedure for each subnet
• Sum us total T-LAN bandwidth
• ITG cards = total H.323 clients/24
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Subnet A: 36 clients, average 6 CCS/client.
Total erlangs =36*6/36 =6
Subnet B: 72 clients, average 5 CCS/client.
Total erlangs =72*5/36 =10
Subnet C: 12 clients, average 6 CCS/client.
Total erlangs =12*6/36 =2
T-LAN Bandwidth = 25.6*(6+10+2)= 460.8 kbps
Number of ITG cards=(36+72+12)/24=5
ITG Line 1.0/IP Telecommuter Description, Installation and Operation
Page 57 of 262