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Kofax

What is the meaning of the error "ecm_page nothing to send"

Summary

5237

Description:

  • At customer site I sometimes get "ecm_page: nothing to send" entries in the Application event log.
  • The customer wants to know what causes this problem and how it can be prevented.

Some examples of such error messages:

  • Error message as shown in the TCOSS.TRC files:

28/10:28:05.134 (86c/8a8) ID:16004 LS1(L.10.DSP0)-11:UIF1-ecm_page: nothing to send. Stat=5 0 0 7F 0 0 0 0 0 , Rsp=BC: 0 0 0 80000000
FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF , Diag=1,20 <ThreadID=57h>;11:L3,2,2,2,2,2,2,7,11;11:L2,5,5,5,5,5,5,5,8

  • Error message as shown in the ATExxxx system error messages:

***** Internal Problem Report ****** Date: 12-01-11 Time: 10:41
LS1(L.10.DSP0)-13:UTF1-ecm_page: nothing to send. Stat=4 5 0 100 5 0 0 D4 0 , Rsp=BC: 0 0 0 0 0 0 0 0 , Diag=1,24
<ThreadID=23h>;13:L3,2,2,2,2,2,2,7,11;13:L2,5,5,5,5,5,5,5,8

  • Error message as shown in the Application Event log:

An error that could be corrected (e.g. by reloading an interface) occurred. Error message: ecm_page: nothing to send.
Stat=7 0 0 47 0 0 0 1B 0 , Rsp=BC: 0 0 FFFFFF80 FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF , Diag=1,20
<ThreadID=EFh>;169:L3,2,2,2,2,2,2,7,11 in

LS1(L.19.DSP0)-G9:UIF1. Refer to TCOSS system manual for more details.

Solution:

  • This error message is logged by the KCS Server if it detects an incorrect response from the distant FAX recipient while sending a FAX message with Error correction mode (ECM).
  • The distant receiver side confirms a FAX page as 'received incorrectly' (e.g. caused by bad line quality) by sending back a Partial-Page-Request (PPR). Normally the parameters of this PPR response indicate which data have to be re-transmitted by the sender. In this specific case though the parameters of the PPR response indicate that no data have to be re-transmitted.
  • This is an incorrect behaviour of the receiver side. In the case that all data has been received correctly, the page has to be confirmed positively by using a MCF (=Message confirmation) signal instead of responding with a PPR.

You will get this "ecm_page: nothing to send" error:

  • only when sending FAX messages with Error correction mode (ECM).
  • only with specific recipients (with an incorrect ECM implementation).
  • not for every FAX message sent to this specific recipient. FAX messages that are confirmed positively, will not show this problem.

Due to the fact that the problem is detected as wrong behaviour of the receiver side, you cannot prevent this problem on KCS side. Sending, to those specific recipients causing the problems, without error correction mode is not an option. It will only omit the error message, but it does not solve the problem itself.

Technical details and some background about ECM:

  • When using Error correction mode, the FAX data are sent in so called "frames".
  • Each frame consists out of:
    • a frame header containing an Address control byte, Count, Type and sequential number.
    • 256 bytes of FAX encoded data.
    • 2 Bytes with a CRC checksum of the transmitted data.
  • A maximum number of 256 frames build a so called 'ECM page'. So one ECM page is a data block containing max. 256 Frames * 256 Bytes Fax coded Data (FCD) / Frame = 64 kByte FAX encoded data.
  • A physical FAX page typically uses less than 256 frames, so it can be transmitted in one ECM page. It can also happen that the graphical data sent on one physical fax page is rather complex and therefore needs more than 256 frames. In this case the physical FAX page is split into 2 or more ECM pages.
  • After the page data have been transmitted, the sender side either sends a PPS-EOP (Partial page signal - End of Procedure) or a PPS-MPS (Partial page signal - Multiple page signal).
    • PPS-EOP is sent if this was the last transmitted data page,
    • PPS-MPS will be used if additional (multiple) pages have to be transmitted.
  • Each ECM page must be confirmed by the FAX receiver side in accordance with the T.30 FAX protocol.
    There are 2 possible responses to confirm a transmitted ECM page:
    • Message confirmation (MCF): everything was received correctly.
    • Partial page request (PPR). This response is used to indicate that parts of the data have been received incorrectly. To find out whether the received data are correct or wrong, the receiver side recalculates the CRC checksum based on the received data and compares it with the received checksum in the CRC bytes. This check is done for each frame. If there is mismatch in the checksum, this specific frame must be requested to be resent by the sender.
  • The PPR response contains a status report for all received frames, one bit for each frame.
    • If a specific frame was received correctly the appropriate bit in the PPR response is set to 0
    • If a specific frame was not received correctly or not received at all (e.g. because the ECM page contains less frames than 256) the appropriate bit in the PPR response is set to 1.
  • The sender side, which receives the PPR response, knows how many frames have been transmitted initially for this ECM page. It will re-transmit those frames which are marked as not received correctly in the PPR response.

What happens exactly in the situation where the "ecm_page nothing to send" error is reported:

  • The receiver side sends back a PPR response.
  • But in the PPR response all frames which had been sent by the sender side are marked as 'received correctly'.
  • So in this case KCS, acting as sender, does not know which frames have to be re-transmitted and therefore the error message "ecm_page nothing to send" is logged.
  • It is obvious that this situation is caused by a wrong ECM implementation on the receiver side: If all frames are confirmed as received correctly, why is the response PPR and not MCF?

Technical Analysis of the error message:

  • This part describes the important parameters shown in the error message. It is most likely only interesting for developers and 2nd Level support engineers:

    Example Error message:
    LS1(L.10.DSP0)-13:UTF1-ecm_page: nothing to send. Stat=7 2 1 76 2 0 0 E4 0 , Rsp=BC: 0 0 0 FFC00000 FFFFFFFF
    FFFFFFFF FFFFFFFF FFFFFFFF , Diag=2,20
    <ThreadID=23h>;13:L3,2,2,2,2,2,2,7,11;13:L2,5,5,5,5,5,5,5,8

  • The 4th parameter in the "Stat=7 2 1 76 2 0 0 E4 0" line defines how many frames have been sent in this ECM page. In this case the parameter shows 76. This value has to be interpreted as a hexadecimal number, so this specific page contained 0x76 = 118 frames.
  • The "Rsp=BC: 0 0 0 FFC00000 FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF" line shows the details of the PPR response. "BC" is the code for "PPR". Each of the next parameters must be seen as 32-bit value. Each bit in these 32-bit values defines whether the appropriate frame was received correctly (bit set to 0) or if it was not received respectively received with CRC errors (bit value=1). The bit-values must be swapped, so you have to read them starting from the right-hand side.

    Let's now check each parameter:
Parameter value in Error message Binary representation Meaning
0 0000 0000 0000 0000 0000 0000 0000 0000 The first 32 Frames were received correctly
0 0000 0000 0000 0000 0000 0000 0000 0000 The 2nd 32 Frames were received correctly
0 0000 0000 0000 0000 0000 0000 0000 0000 The 3rd 32 Frames were received correctly
FFC00000 1111 1111 1100 0000 0000 0000 0000 0000 The next 22 Frames were received correctly 10 Frames are marked as "not received"
FFFFFFFF 1111 1111 1111 1111 1111 1111 1111 1111 All 32 Frames are marked as not received
FFFFFFFF 1111 1111 1111 1111 1111 1111 1111 1111 All 32 Frames are marked as not received
FFFFFFFF 1111 1111 1111 1111 1111 1111 1111 1111 All 32 Frames are marked as not received
FFFFFFFF 1111 1111 1111 1111 1111 1111 1111 1111 All 32 Frames are marked as not received
  • So in total 32 + 32 + 32 + 22 = 118 Frames were marked as 'received correctly' (Bit value = 0).
  • 118 Frames have been transmitted in total, so all of them were marked as 'received correctly'.
  • PPR is an in-proper response if all sent frames are marked as received correctly.

Applies to:

  • KCS all versions:

Keywords: ecm, nothing to send,details, ppr, isdn, transmissionsystem error message, system alert