120 ITG engineering guidelines
Table20 "Example: Incremental WAN bandwidth requirement" (page
120) summarizes the WANtraffic in kbit/s for each route. Therecommended
incremental bandwidth requirement is included in the column adjusted
for 30% traffic peaking in busy hour. 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 2 0
Example: Incremental WAN bandwidth requirement
Destination Pair CCS on
WAN
WAN
traffic in
kbit/s
Peaked WAN
traffic (x1.3) in
kbit/s
Santa Clara/Richardson 60 18.7 24.3
Santa Clara/Ottawa 45 14.0 18.2
Santa Clara/Tokyo 15 4.7 6.1
Richardson/Ottawa 35 10.9 14.2
Richardson/Tokyo 20 6.2 8.1
Ottawa/Tokyo 18 5.6 7.3
The following exampleillustrates the calculation procedurefor Santa Clara
and Richardson. The total traffic on thisroute is 60CCS. To use the
preferred codec of G.729AB with a 30 ms payload, the bandwidth on the
WAN is 11.2kbit/s. WANtraffic is calculated using the following formula:
(60/36)*11.2 = 18.7 kbit/s
Augmenting this number by 30% givesa peaktraffic 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?
Trafficbetween 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-waytraffic.
The bandwidth requirement calculation would be:
(40/36)*11.2 + (14/36)*33.6 = 25.51 kbit/s
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
.