On this panel, you can find the service policy attributes related to UDPTL (User Datagram Protocol Transport Level) that define the rules of setting up fax message transmission via the T.38 protocol.
To see the attribute description, hover over an attribute name and then over the question mark that appears next to it. To configure a specific attribute, select the corresponding checkbox and fill in/select the attribute value.
T38 fax max datagram
This is the maximum size (in bytes) of data accepted by PortaSIP within the UDPTL packet. The default value is 849 bytes. Here you can increase this value if data loss occurs during fax reception.
The T38 fax max datagram attribute applies within the dynamically matched service policy. Make sure that the SIP end-point pattern field is not empty.
T38 fax UDP error correction
This is the fax error correction scheme. It is used to detect and correct errors in fax page data during the reception (e.g., if some data is missing or has been altered during the transmission).
You can select one of the following options from the drop-down list:
FEC (Forward Error Correction) – PortaSIP verifies that no data is lost and it doesn’t contain errors using the parity-check information encoded in the UDPTL packets during the fax transmission. If any fragment of the received fax data is lost or contains errors, PortaSIP detects it and recovers it if it’s possible. This is the default scheme. The sender’s user agent, however, may not support it. In this case, please set Redundancy as the fax error correction scheme.
Redundancy – PortaSIP tries to recover the missing fax data using redundant data copies. This option creates overhead (due to the data copies) for each UDPTL packet. This way, more data is sent to PortaSIP.
None – PortaSIP accepts faxes without attempting to correct possible errors or incomplete data.
The T38 fax UDP error correction attribute applies within the dynamically matched service policy. Make sure that the SIP end-point pattern field is not empty.