T.38 Ced Retransmission - Patton electronics SmartWare R.3.20 Software Configuration Manual

SmartWare Software Configuration Guide
Step
4 node (pf-voip)[ name ]#fax volume
volume
(optional)
node (pf-voip)[ name ]# fax max-bit-
5
(optional) rate { 2400 | 4800 | 7200 | 9600 |
12000 | 14400 }
6 node (pf-voip)[ name ]# fax detection
(optional) { ced-tone | fax-frames }
node (pf-voip)[ name ]#no fax error-
7
(optional) correction
8 node (pf-voip)[ name ]#no fax hdlc
(optional)

T.38 CED retransmission

Even if the user has configured redundant transmission for low-speed and high-speed packets the T.30 Indica-
tor messages are not included in this process. If the CED message gets lost, the remote device only receives the
CED Tone that is sent in-band. But the transmitted in-band tone may be short due to T.38 switchover or too
much distortion, such as by using a low bit-rate voice coder like G.723. In this case it is possible that the
remote device never starts the initial T.30 procedure, because it has never received the CED tone. For that rea-
son SmartWare sends the CED three times in an interval of 100ms with the same sequence number. With this
command, you can disable this feature or set the number of retransmissions to a user defined value.
VoIP profile configuration task list
Command
40 • VoIP profile configuration
Purpose
Adjusts the volume of the fax signals re-generated
on the receiver side. The volume is in dB, in the
range -18.5 ... -3.5 (Default: -9.5dB).
Sets maximum allowed bit-rate for fax relay
(Default 14400 Bit/sec).
Selects the method when fax transmissions are
detected: By CED tone or by fax frames (Default:
ced-tone). It takes longer to detect Fax frames than
CED tones, but the risk of misdetection is mini-
mized.
Disables error correction mode (Default: enabled).
If the error correction mode is disabled, the con-
nected fax devices cannot negotiate error correc-
tion mode. Connections with error correction mode
enabled are more sensitive to packet loss. Disable
error correction mode when packet loss is more
than 2–3%.
Error correction mode does
Note
not cancel IP packet loss.
Disables HDLC image transfer (Default: enabled).
If HDLC mode is enabled, the SmartNode removes
bit-stuffing, checks CRCs of fax frames arriving
from the PSTN and regenerates the CRCs before
sending fax frames towards the PSTN. HDLC can
only be enabled together with error correction.
Disable HDLC when the fax peer does not support
this mode.
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