105
operation.
10. (Optional.) Specify an output
interface for UDP packets.
out interface
interface-type
interface-number
By default, the output interface for
UDP packets is not specified. The
NQA client determines the output
interface based on the routing table
lookup.
This command is available in
Release 1121 and later.
11.
source port of UDP packets.
source port
port-number
By default, no source port number is
specified.
12.
source IP address of UDP
packets.
• Specify the IP address of
the specified interface as
the source IP address:
source interface
interface-type
interface-number
•
address:
source ip ip-address
By default, t
he packets take the
primary IP address of the output
interface as their source IP address.
If you execute the
source ip
and
source interface
commands
multiple times, the
configuration
takes effect.
The specified source interface must
be up. The source IP address must
be the IP address of a local
interface, and the local interface
must be up. Otherwise, no probe
packets can be sent out.
Configuring the voice operation
To ensure successful voice operations and avoid affecting existing services, do not perform the
operations on well-known ports from 1 to 1023.
The voice operation measures VoIP network performance.
The voice operation works as follows:
1. The NQA client sends voice packets at sending intervals to the destination device (NQA
server).
The voice packets are of one of the following codec types:
ï‚¡ G.711 A-law.
 G.711 µ-law.
ï‚¡ G.729 A-law.
2. The destination device time stamps each voice packet it receives and sends it back to the
source.
3. Upon receiving the packet, the source device calculates the jitter and one-way delay based on
the timestamp.
The following parameters that reflect VoIP network performance can be calculated by using the
metrics gathered by the voice operation:
• Calculated Planning Impairment Factor (ICPIF)—Measures impairment to voice quality in a
VoIP network. It is decided by packet loss and delay. A higher value represents a lower service
quality.
• Mean Opinion Scores (MOS)—A MOS value can be evaluated by using the ICPIF value, in the
range of 1 to 5. A higher value represents a higher service quality.