Nortel ISDN Signaling Link Description, Installation And Operation page 117

Table 20
Sample Measurement Results for G.729A codec
Destination pair
Santa Clara/
Richardson
Santa Clara/
Ottawa
Santa Clara/
Tokyo
Richardson/
Ottawa
Richardson/
Tokyo
Ottawa/
Tokyo
ITG Trunk 2.0 ISDN Signaling Link (ISL)
Table 20 provides a sample measurement of network delay and packet loss
for the G.729A codec between various nodes.
Measured One way
delay (ms)
Mean
Mean+
171 179
120 132
190 210
220 235
305 345
260 286
As an example, the delay and loss pair of traffic from Santa Clara to
Richardson (171 ms and 1.5%) will meet "excellent" criterion, but their
counter part with standard deviation (179 ms and 2.1%) can achieve only
"good" QoS.
Since the algorithm implemented in ITG will calculate mean only and not
standard deviation, it will confirm the "excellent" rating (if the objective is
set for excellent, it will not fallback to alternate facilities), but the customer
will have up to 50% chance to experience a service level inferior to
"excellent" level.
As a contrast, the site pair Santa Clara/Ottawa which has both QoS levels of
mean and mean+σ falling in the excellent region. The customer will have
more confidence that (better than 84% chance under the assumption of
Normal distribution) during peak traffic period, the "excellent" service level
is likely to be upheld.
ITG Engineering Guidelines
Measured Packet
loss (%)
σ
Mean
Mean+
1.5 2.1
1.3 1.6
2.1 2.3
2.4 2.7
2.2 2.6
2.4 2.8
Description, Installation and Operation
Page 117 of 378
Expected QoS level
(See page 143)
σ
Mean
Mean+
Excellent Good
Excellent Excellent
Good Good
Good Good
Good Fair
Good Fair
σ