[asterisk-users] busy hangup HDLC Bad FCS (8) on Primary D-channel

[Steve Davies]

On 1 June 2011 15:10, randall <randall at songshu.org> wrote:
> On 06/01/2011 03:55 PM, randall wrote:
>> On 06/01/2011 03:41 PM, Tzafrir Cohen wrote:
>>> On Wed, Jun 01, 2011 at 08:06:02AM +0200, randall wrote:
>>>> Hi all,
>>>>
>>>> After running fine for a few months now asterisk seems to hang
>>>> frequently , still functioning but the DAHDI channels seem busy  (users
>>>> report a busy signal when calling or being called)
>>>>
>>>> A reboot will allow it to run for another day or maybe 2  or 3 till the
>>>> problem occurs again.
>>>>
>>>>
>>>> running stock Asterisk 1.6.2.9-2+squeeze2 on Debian with stock kernel
>>>> 2.6.32-5-686
>>>>
>>>> i get the following errors:
>>>> pri_dchannel: PRI got event: HDLC Bad FCS (8) on Primary D-channel of span 2
>>>>
>>>> (happens on all 4 spans)
>>>>
>>>> and the following in dmesg:
>>>> [ 9004.635323] NOTICE-xpd_bri: XBUS-00/XPD-01: D-Chan RX DROP: BADFCS: 252
>>>> [ 9004.635332] NOTICE-xpd_bri: XBUS-00/XPD-01: D-Chan RX:    current
>>>> packet[0..2]: 55 55 FC
>>>> [ 9004.635340] NOTICE-xpd_bri: XBUS-00/XPD-01: Multibyte Drop: errno=-71
>>>>
>>>>
>>>> Channel 0/1, span 1 got hangup, cause 18
>>>
>>> Is this happening in the middle of a call? Or only a while after the
>>> call ended?
>>>
>>
>> the "bad fcs" messages seem to happen random
> there seems to be a relation indeed, have seen them happen randomly
> quite spurious, but they indeed tend to happen a while after the call is
> made.
>>
>> the hangup happens when a call through DAHDI is attempted,
>> (usually after it has been working fine for a while a day or 2)

In my experience, FCS errors are caused by line quality issues, and
usually (not always) are in the telco's equipment. If they are only
happening occasionally, it may be a marginal, but mostly-OK signal on
the wire.

Do you also get occasional poor-quality audio on calls? The issue will
happen more when a call is being setup, or is progressing because
there are more frames being exchanged when a call is in progress.

I have also seen a bad component or dry solder on a voice card cause
this, and even a badly made ISDN cable can be part of the problem. If
none of that helps, I would ask the telco to put a trace on the line.

Hope that helps,
Steve