This document provides two traces: a Cisco IOS® Software debug and a fax analyzer trace. The Cisco IOS debugs work on the Cisco 3660 in Cisco IOS Software Release 12.2(5.8)T and later. Debug formats for this command were improved in later Cisco IOS Software releases, possibly 12.2(7a) and 12.2(5.8)T.
For more information on document conventions, see the Cisco Technical Tips Conventions.
There are no specific prerequisites for this document.
The information in this document is based primarily on Cisco IOS Software Release 12.2(5), although most of the information should also be useful for other Cisco IOS Software releases.
The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.
debug fax relay t30 all - Originating Router |
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3660A Oct 25 14:33:02.001: 6/0:1:8 3698358 fr-entered (10ms) Oct 25 14:33:03.193: 6/0:1:8 3699550 fr-msg-tx NSF Oct 25 14:33:03.433: 6/0:1:8 3699790 fr-msg-tx CSI Oct 25 14:33:04.125: 6/0:1:8 3700480 fr-msg-tx DIS Oct 25 14:33:05.905: 6/0:1:8 3702260 fr-msg-det TSI Oct 25 14:33:06.701: 6/0:1:8 3703060 fr-msg-det DCS Oct 25 14:33:11.201: 6/0:1:8 3707560 fr-msg-tx CFR Oct 25 14:35:47.261: 6/0:1:8 3863620 fr-msg-det EOP Oct 25 14:35:49.601: 6/0:1:8 3865960 fr-msg-tx MCF Oct 25 14:35:51.157: 6/0:1:8 3867510 fr-msg-det DCN Oct 25 14:35:53.304: 6/0:1:8 3869660 fr-end-dcn |
debug fax relay t30 all - Terminating Router |
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Oct 25 10:33:01.801: 6/0:1 (8) 3183322 fr-entered (10ms) Oct 25 10:33:02.885: 6/0:1 (8) 3184410 fr-msg-det NSF Oct 25 10:33:03.125: 6/0:1 (8) 3184650 fr-msg-det CSI Oct 25 10:33:03.817: 6/0:1 (8) 3185340 fr-msg-det DIS Oct 25 10:33:06.205: 6/0:1 (8) 3187730 fr-msg-tx TSI Oct 25 10:33:07.009: 6/0:1 (8) 3188530 fr-msg-tx DCS Oct 25 10:33:10.897: 6/0:1 (8) 3192420 fr-msg-det CFR Oct 25 10:35:47.565: 6/0:1 (8) 3349090 fr-msg-tx EOP Oct 25 10:35:49.293: 6/0:1 (8) 3350820 fr-msg-det MCF Oct 25 10:35:51.469: 6/0:1 (8) 3352990 fr-msg-tx DCN Oct 25 10:35:53.457: 6/0:1 (8) 3354980 fr-end cause unknown 0x1 |
It is important to know the following information:
Phase in which the fax transmission error occurred.
Whether the router or fax machines terminated the connection, and if it was a fax machine, which one.
What fax protocol events took place prior to the connection being terminated.
An example of the fax analyzer trace for a successful ECM-mode transmission (but with a high error rate) may look like the following:
Fax Analyzer Trace |
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===================================================================== # Phase dBm Elapse Duration Optimum Size Type --------------------------------------------------------------------- 0 >> Dialed digits 0.0 -7.909 4.220 0.000 32 DTMF 1 >> quiet -- -3.689 3.689 0.000 0 2 << Answer Tone -19.0 0.000 2.938 2.650 0 Tone 3 << quiet-mod chg *** -- 2.938 0.153 0.060 0 4 << NSF, CSI, DIS * -17.8 3.091 4.079 3.040 126 FSK 5 << quiet -- 7.170 0.558 0.060 0 6 >> TSI, DCS * -13.8 7.728 2.104 1.813 74 FSK 7 >> quiet-mod chg -- 9.832 0.088 0.060 0 8 >> V.29 9600 TRAIN * -11.3 9.920 1.843 1.655 1853 9600 9 >> quiet -- 11.763 1.555 0.060 0 10 << FTT * -17.7 13.318 1.437 1.013 50 FSK 11 << quiet * -- 14.755 0.589 0.060 0 12 >> TSI, DCS * -13.8 15.344 2.107 1.813 74 FSK 13 >> quiet-mod chg -- 17.451 0.091 0.060 0 14 >> V.29 7200 TRAIN * -11.4 17.542 1.843 1.655 1389 7200 15 >> quiet -- 19.385 2.078 0.060 0 16 << CFR * -18.1 21.463 1.438 1.013 50 FSK 17 << quiet * -- 22.901 0.626 0.060 0 18 >> V.29 7200 DATA * -11.5 23.527 16.390 0.000 14004 7200 19 >> quiet-mod chg -- 39.917 0.069 0.060 256 20 >> PPS-EOP *** -13.8 39.986 1.353 1.120 43 FSK 21 >> quiet * -- 41.339 1.853 0.060 0 22 << PPR * -17.9 43.192 2.454 1.866 87 FSK 23 << quiet -- 45.646 0.636 0.060 0 24 >> V.29 7200 DATA * -11.2 46.282 1.148 0.000 783 7200 25 >> quiet-mod chg -- 47.430 0.062 0.060 256 26 >> PPS-EOP -13.8 47.492 1.354 1.120 44 FSK 27 >> quiet * -- 48.846 1.849 0.060 0 28 << RNR * -17.8 50.695 1.437 1.013 50 FSK 29 << quiet -- 52.132 0.583 0.060 0 30 >> RR -13.8 52.715 1.235 15.210 43 FSK 31 >> quiet * -- 53.950 1.995 0.060 0 32 << MCF * -17.8 55.945 1.456 1.013 50 FSK 33 << quiet * -- 57.401 0.596 0.060 0 34 >> DCN -13.8 57.997 1.791 1.013 43 FSK 35 >> Call end * 0.0 59.788 0.000 0.000 0 |
The exchange of DIS/DCS (CSI,DIS / TSI,DCS) messages:
DIS is the initial message stating the capabilities of the answering end. The accompanying CSI frame has the phone number.
DCS defines the transmit parameters and starts an image transfer sequence. The accompanying TSI frame has the phone number.
The fax machines go into training mode and can attempt more than once to agree on a transmission speed. For instance, the fax machines may first train to a speed of 9600 bps, fail, and then train to a speed of 7200 bps.
In the fax trace output above, the transmission starts with:
The exchange of DIS/DCS (CSI,DIS / TSI,DCS) messages:
DIS is the initial message stating the capabilities of the answering end. The accompanying CSI frame has the phone number.
DCS defines the transmit parameters and starts an image transfer sequence. The accompanying TSI frame has the phone number.
The fax machines go into training mode and can attempt more than once to agree on a transmission speed. For instance, the fax machines may first train to a speed of 9600 bps, fail, and then train to a speed of 7200 bps.
Successful training is followed by a CFR message.
Transmission starts following the CFR message.
If there is a high number of errors, a good fax analyzer will detect them.
Also, if ECM mode is enabled, there will be a high number of retransmissions and partial page request (PPR) messages. When the terminating fax machine considers the error rate too high, it will terminate the connection.
MCF is the normal response to an end-of-image message sequence by the receiving end. It indicates that the image was received with less than five percent of lines in error. It is normally followed by the DCN (disconnect) message.
If there is no MCF message, the transmission was not completed successfully. It may suggest a high error rate caused by one of the following:
Digital line errors (clocking, cabling)
VoIP packet loss (queueing, prioritization, fragmentation, compression)
Hardware fault
Cisco IOS/DSPW incompatibility (rarely occurs)
If the DIS or DCS messages are retransmitted several times, it may be that they are not passed across the VoX connection correctly or only passed in one direction—a software or configuration problem.
If training repeats multiple times, each time at a lower speed and then the transmission fails, it may be that the fax codec was not loaded and the voice gateways handle the fax transmission as a normal voice conversation, again a configuration or software issue.
Revision | Publish Date | Comments |
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1.0 |
02-Feb-2006 |
Initial Release |