Configuring Voice
Managing Caller ID Services
Cisco SRP500 Series Services Ready Platforms Administration Guide (SRP520 Models)
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Optimizing Fax Completion Rates
Issues can occur with fax transmissions over IP networks, even with the T.38
standard, which is supported by the SRP. You can adjust several settings on your
SRP to optimize your fax completion rates.
STEP 1
Ensure that you have enough bandwidth for the uplink and the downlink.
•
For G.711 fallback, it is recommend to have approximately 100 kbps.
•
For T.38, allocate at least 50 kbps.
STEP 2
To optimize G.711 fallback fax completion rates, set the following on the Line tab
of your SRP:
•
Network Jitter Buffer
: very high
•
Jitter buffer adjustment
: disable
•
Call Waiting
: no
•
3 Way Calling
: no
•
Echo Canceller
: no
•
Silence suppression
: no
•
Preferred Codec
: G.711
•
Use pref. codec only
: yes
If you are using a Cisco media gateway for PSTN termination, disable T.38 (fax
relay) and enable fax using modem passthrough. For example:
modem passthrough nse payload-type 110 codec g711ulaw
fax rate disable
fax protocol pass-through g711ulaw
STEP 3
Enable T.38 fax on the SRP by configuring the following parameter on the Line tab
for the FXS port to which the FAX machine is connected:
FAX_Passthru_Method: ReINVITE
NOTE
If a T.38 call cannot be set-up, then the call automatically reverts to G.711 fallback.
STEP 4
If you are using a Cisco media gateway use the following settings:
