Configuring A Voice Test - 3Com S7906E Configuration Manual

To do...
Configure the source IP
address of a probe request in a
test operation
Configure common optional
parameters

Configuring a Voice Test

It is recommended not to perform an NQA UDP jitter test on known ports, namely, ports from 1 to 1023.
Otherwise, the NQA test will fail or the corresponding services of these ports will be unavailable.
A voice test is used to test voice over IP (VoIP) network status, and collect VoIP network parameters so
that users can adjust the network according the network status. The procedure of a voice test is as
follows:
1) The source (NQA client) sends voice packets of G.711 A-law, G.711 µ-law or G.729 A-law codec
type at regular intervals to the destination (NQA server).
2) The destination affixes a time stamp to each packet that it receives and then sends it back to the
source.
3) Upon receiving the packets, the source calculates the delay jitter and delay by calculating the
difference between the interval for the destination to receive two successive packets and the
interval for the source to send these two successive packets, and thus the network status can be
analyzed.
The voice parameter values that indicate VoIP network status can also be calculated in a voice test,
including:
Calculated Planning Impairment Factor (ICPIF): Measures attenuation of voice data in a network,
depending on packet loss and delay. A higher value represents a lower network quality.
Mean Opinion Scores (MOS): Measures quality of a VoIP network. A MOS value can be evaluated
by using the ICPIF value, in the range 1 to 15. A higher value represents a higher quality of a VoIP
network.
The evaluation of voice quality depends on users' tolerance to voice quality, and this factor should be
taken into consideration. For users with higher tolerance to voice quality, you can use the
advantage-factor command to configure the advantage factor. When the system calculates the ICPIF
value, this advantage factor is subtracted to modify ICPIF and MOS values and thus both the objective
and subjective factors are considered when you evaluate the voice quality.
Use the command...
source ip ip-address
Refer to Configuring Optional
Parameters Common to an
NQA Test Group
1-16
Remarks
Optional
By default, no source IP
address is specified.
The source IP address must be
that of an interface on the
device and the interface must
be up. Otherwise, the test will
fail.
Optional