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553-3001-202
Standard 1.00
ITG Engineering Guidelines
This assumes no correlation and no synchronization of voice bursts in
different simultaneous calls. This assumes some statistical model of
granularity and distribution of voice message bursts due to silence
suppression.
Table 16
Example: Incremental WAN bandwidth requirement
Destination Pair
Santa Clara/Richardson
Santa Clara/Ottawa
Santa Clara/Tokyo
Richardson/Ottawa
Richardson/Tokyo
Ottawa/Tokyo
The following example illustrates the calculation procedure for Santa Clara
and Richardson. The total traffic on this route is 60 CCS. To use the preferred
codec of G.729 Annex AB with 30 ms payload, the bandwidth use on the
WAN is 11.2 kbit/s. WAN traffic is calculated using the following formula:
(60/36)*11.2 = 18.7 kbit/s. Augmenting this number by 30% would give us
the peak traffic rate of 24.3 kbit/s. This is the incremental bandwidth required
between Santa Clara and Richardson to carry the 60 CCS voice traffic during
the busy hour.
Assume that 20 CCS of the 60 CCS between Santa Clara and Richardson is
fax traffic. Of the 20 CCS, 14 CCS is from Santa Clara to Richardson, and 6
CCS is from Richardson to Santa Clara. What is the WAN data rate required
between those two locations?
Traffic between the two sites can be broken down to 54 CCS from Santa Clara
to Richardson, and 46 CCS from Richardson to Santa Clara, with the voice
traffic 40 CCS (=60-20) being the two-way traffic.
April 2000
WAN
CCS on
traffic in
WAN
kbit/s
60
18.7
45
14.0
15
4.7
35
10.9
20
6.2
18
5.6
Peaked WAN
traffic (x1.3) in
kbit/s
24.3
18.2
6.1
14.2
8.1
7.3
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