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Sending Multiple Pages of Fax Fails on the UA5000 Side Owing to a Defect of the ECM Feature of the Fax Machine

Publication Date:  2012-07-25 Views:  55 Downloads:  0
Issue Description
The UA5000 of Operator M in Country R is deployed as follows:
Panasonic KX-FL523---->UA5000--
àSX3000---->UMG--àPSTN--àPanasonic KX-FLM653
The version of the UA5000 is PVM V100R013C03B032SP04.
The T.38 (V3) protocol is used.
During the tests, a single or multiple pages of fax data can be received on the UA5000 side, the peer side can receive a single page of fax data when it is sent on the UA5000 side, but the peer side can receive only one page or none of fax data when multiple pages of fax data are sent on the UA5000 side.
Alarm Information
Null
Handling Process
In view of the large number of terminals, it is difficult to solve a problem even if it is found. Therefore, we first eliminate the problems of the offices:

1. Analyze the signaling exchange. The analysis shows that the peer side sends a BYE message before two pages of fax data is completely received during a fax process. As a result, sending the fax ends.

2. Capture packets and perform TDM trace. The analysis shows that the processing of the UA5000 is normal.

3. Record on the UMG side and make an analysis: The sending end (upper layer) sends the PRI-EOP command after finishing sending the second page of fax data, but the receiving end fax machine (lower layer) does not respond. The sending end resends the PRI-EOP command twice, but the receiving end fax machine still fails to respond. As a result, the problem occurs.

4. Test again after the ECM function is disabled on the UMG. The problem does not appear. Therefore, it is suspected that the fax machine on the PSTN side does not support the ECM function.

5. Enable the ECM function on the UMG and meanwhile replace the fax machine on the PSTN side. Test again. The test result is OK, which proves that the previous analysis is correct.

6. After the preceding analysis, it is proved that sending multiple pages of fax data fails because the fax machine on the PSTN side does not support the ECM function.

Refer to the analysis report in the attachment. 
Root Cause
The possible causes for this problem are as follows:
1. Signaling exchange error and multipage fax error. For example, there is no MPS message.

2. UA5000 processing error.

3. UMG processing error.

4. Cooperation error between the fax machines on the two sides. 
Suggestions
Null

END