DAHDI error: Got DAHDI event: HDLC Bad FCS (8) on D-channel of span 1

Hi All,

I know error mentioned in subject line is very common, and there are many discussions found on net; but none of them clearly tell what is the solution for this and may vary case to case. So I am creating this new topic here.

My environment:
Ubuntu: 14.4 LS
Asterisk: 13.9.1
DAHDI version: 2.10.2 Echo Canceller
PRI version: 1.5.0
DAHDI hardware: Allocard 4aCP1e (3rd Gen) (alloPL4xxp+)

When I connect PRI line to above hardware, it seems D channel is not coming up and keeps throwing below error on CLI, but light turns green on DAHDI hardware card which indicates it is getting proper TX and RX signals.

[2016-08-08 10:39:24] NOTICE[4296]: chan_dahdi.c:2788 my_handle_dchan_exception: Got DAHDI event: HDLC Abort (6) on D-channel of span 1
[2016-08-08 10:39:25] NOTICE[4296]: chan_dahdi.c:2788 my_handle_dchan_exception: Got DAHDI event: HDLC Bad FCS (8) on D-channel of span 1
[2016-08-08 10:39:27] NOTICE[4296]: chan_dahdi.c:2788 my_handle_dchan_exception: Got DAHDI event: HDLC Abort (6) on D-channel of span 1
[2016-08-08 10:39:31] NOTICE[4296]: chan_dahdi.c:2788 my_handle_dchan_exception: Got DAHDI event: HDLC Bad FCS (8) on D-channel of span 1
[2016-08-08 10:39:32] NOTICE[4296]: chan_dahdi.c:2788 my_handle_dchan_exception: Got DAHDI event: HDLC Bad FCS (8) on D-channel of span 1

Below are some of the outputs:
root@asterisk-server:~# dahdi_scan
[1]
active=yes
alarms=OK
description=T4XXP (PCI) Card 0 Span 1
name=ALLOPL4/0/1
manufacturer=Allo
devicetype=Allocard 4aCP1e (3rd Gen)
location=Board ID Switch 0
basechan=1
totchans=31
irq=0
type=digital-E1
syncsrc=0
lbo=0 db (CSU)/0-133 feet (DSX-1)
coding_opts=AMI,HDB3
framing_opts=CCS,CRC4
coding=HDB3
framing=CCS/CRC4

root@asterisk-server:~# cat /proc/dahdi/1
Span 1: ALLOPL4/0/1 “T4XXP (PCI) Card 0 Span 1” (MASTER) CCS/HDB3/CRC4
CRC4 error count: 5361
E-bit error count: 1785

       1 ALLOPL4/0/1/1 Clear (In use)
       2 ALLOPL4/0/1/2 Clear (In use)
       3 ALLOPL4/0/1/3 Clear (In use)
       4 ALLOPL4/0/1/4 Clear (In use)
       5 ALLOPL4/0/1/5 Clear (In use)
       6 ALLOPL4/0/1/6 Clear (In use)
       7 ALLOPL4/0/1/7 Clear (In use)
       8 ALLOPL4/0/1/8 Clear (In use)
       9 ALLOPL4/0/1/9 Clear (In use)
      10 ALLOPL4/0/1/10 Clear (In use)
      11 ALLOPL4/0/1/11 Clear (In use)
      12 ALLOPL4/0/1/12 Clear (In use)
      13 ALLOPL4/0/1/13 Clear (In use)
      14 ALLOPL4/0/1/14 Clear (In use)
      15 ALLOPL4/0/1/15 Clear (In use)
      16 ALLOPL4/0/1/16 HDLCFCS (In use)
      17 ALLOPL4/0/1/17 Clear (In use)
      18 ALLOPL4/0/1/18 Clear (In use)
      19 ALLOPL4/0/1/19 Clear (In use)
      20 ALLOPL4/0/1/20 Clear (In use)
      21 ALLOPL4/0/1/21 Clear (In use)
      22 ALLOPL4/0/1/22 Clear (In use)
      23 ALLOPL4/0/1/23 Clear (In use)
      24 ALLOPL4/0/1/24 Clear (In use)
      25 ALLOPL4/0/1/25 Clear (In use)
      26 ALLOPL4/0/1/26 Clear (In use)
      27 ALLOPL4/0/1/27 Clear (In use)
      28 ALLOPL4/0/1/28 Clear (In use)
      29 ALLOPL4/0/1/29 Clear (In use)
      30 ALLOPL4/0/1/30 Clear (In use)

asterisk-server*CLI> pri show spans
PRI span 1/0: Down, Active

root@asterisk-server:~# asterisk -rx “dahdi show status”
Description Alarms IRQ bpviol CRC Fra Codi Options LBO
T4XXP (PCI) Card 0 Span 1 OK 0 0 501121 CCS HDB3 CRC4 0 db (CSU)/0-133 feet (DSX-1)
root@asterisk-server:~#

Attached are the DAHDI config files.

Please review and advise what am I missing here as the PRI line works well when connected thru service provider’s Schmid modem.

Thank you.

The solution is to fix your hardware (or configure DAHDI to match your hardware).

The message means that a call control (signalling) message had a bad check sum. That means the message was corrupted in transit, or mis-decoded at the physical layer, i.e. when translating the pattern of voltage variations on the cable into as series of zeroes, ones, and message (frame) boundaries.

In any case, for such problems you should be seeking the support of your ISDN card hardware supplier. For current DIgium products, that is provide on the Digium commercial web site.

HDLC is High Level Data Link Control, which is the specification for how a signalling messages are actually put onto the wire.

FCS is frame check sequence, which is the checksum for a single message.

D channel is the channel which carries such messages, rather than actual speech.

Span 1 is the first or only cable attached.

Thank you David. Could you please let me know what exact help i should be seeking from ISDN card hardware providers. Because I contacted them earlier, and they put a loopback test which came up fine and concluded that their hardware is correct along with DAHDI configuration.
Also my ISDN line provider has also concluded that their line is fine because it is working fine with their modem and other test.
I am really in no-man’s land to understand where is the problem and where to look for. Please help.

any chance on this issue be resolved?

If this is intermittent, call you service provider and ask them to repair the cable to you, as this is indicative of hardware failures corrupting the signal on the wire…

If it has happened since you first configured asterisk, you have probably misconfigured it. The supplier of your ISDN card should be able to support you, but you will need to provide the correct technical information about your service provider. Because they always involve specialist hardware, DAHDI issued are not supported on the open source forum.