Configuration Files Parameters - 3Com VCX V7122 User Manual

always a sample in the buffer for the coder to use. If there is more than 70 msec of delay at
any time during the call, the packet arrives too late. The coder tries to access a frame and is
not able to find one. The coder must produce a voice sample even if a frame is not available.
It therefore compensates for the missing packet by adding a Bad-Frame-Interpolation (BFI)
packet. This loss is then flagged as the buffer being too small. The dynamic algorithm then
causes the size of the buffer to increase for the next voice session. The size of the buffer
may decrease again if the gateway notices that the buffer is not filling up as much as
expected. At no time does the buffer decrease to less than the minimum size configured by
the Minimum delay parameter.
Special Optimization Factor Value: 13
One of the purposes of the Jitter Buffer mechanism is to compensate for clock drift. If the two
sides of the VoIP call are not synchronized to the same clock source, one RTP source
generates packets at a lower rate, causing under-runs at the remote Jitter Buffer. In normal
operation (optimization factor 0 to 12), the Jitter Buffer mechanism detects and compensates
for the clock drift by occasionally dropping a voice packet or by adding a BFI packet.
Fax and modem devices are sensitive to small packet losses or to added BFI packets.
Therefore to achieve better performance during modem and fax calls, the Optimization
Factor should be set to 13. In this special mode the clock drift correction is performed less
frequently - only when the Jitter Buffer is completely empty or completely full. When such
condition occurs, the correction is performed by dropping several voice packets
simultaneously or by adding several BFI packets simultaneously, so that the Jitter Buffer
returns to its normal condition.

Configuration Files Parameters

The configuration files (Call Progress Tones, PRT, Voice Prompts and CAS) can be loaded
to the VCX V7122 via the Embedded Web Server (see
TFTP session.
To load the configuration files via TFTP, follow these steps:
1 In the ini file, define the files to be loaded to the device. You can also define in the ini file
whether the loaded files should be stored in the non-volatile memory so that the TFTP
process is not required every time the device boots up.
2 Locate the configuration files you want to load and the ini file in the same directory.
3
Invoke a BootP/TFTP session; the ini and configuration files are loaded onto the device.
Table 31 below describes the ini file parameters that are associated with the configuration
files.
Table 31 Configuration File Parameters
ini File Field Name
CallProgressTonesFilename
VoicePromptsFileName
3Com VCX V7122 SIP VoIP Gateway User Manual
Valid Range and Description
The name of the file containing the Call Progress Tones definitions. See
Configuration Files on page
this file.
The name (and path) of the file containing the Voice Prompts definitions. See
Prerecorded Tones (PRT) File
create and load this file.
Auxiliary Files on page 86), or via
139 for additional information on how to create and load
on page 141 for additional information on how to
Chapter 7:
137