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

[Karsten Wemheuer]

Hi Olivier,

Am Freitag, den 11.06.2010, 14:27 +0200 schrieb Olivier:
> 
> 
> 2010/6/11 Karsten Wemheuer <kwem at gmx.de>
>         Hi,
>         
>         Am Freitag, den 11.06.2010, 11:54 +0100 schrieb Gareth Blades:
>         > Olivier wrote:
>         > > Hello,
>         > >
>         > > I've got a running system in which logs are full of
>         messages such as:
>         > > [Jun 10 07:24:14] NOTICE[2414] chan_dahdi.c: PRI got
>         event: HDLC Bad FCS
>         > > (8) on Primary D-channel of span 2
>         > >
>         > > The strange thing is those messages are coming from a
>         single span.
>         > >
>         > > My setup is :
>         > >
>         > > Asterisk 1.6.1.18
>         > > Junghanns OctoBRI
>         > > with wcb4xxp driver
>         > > libpri 1.4.10.2
>         > > dahdi 2.3.0
>         > > 3 BRI lines in PtMP mode
>         > >
>         > >
>         > > What does this "PRI got event: HDLC Bad FCS (8) on Primary
>         D-channel of
>         > > span 2" roughly mean ?
>         > > Why could it happen on a single port and not on the
>         others ?
>         > >
>         > > Regards
>         > Basically it means that one of the messages it received on
>         the PRI D
>         > channel failed the checksum.
>         >
>         > I take it that in your span command you have 'crc4' or
>         similar specified
>         > as an option for all of your spans?
>         >
>         > If thats the case its probably a faulty port on the card,
>         cable, or a
>         > card in the local telephone exchange,
>         
>         
>         AFAIK CRC4 is for PRI only. The setup of Olivier is BRI in
>         PTmP mode.
>         Many providers drive Layer 1 down in case of inactivity. Maybe
>         the
>         driver has a problem with such lines.
> 
> Would that explain why only a single port is hit ?

No, except if this port is configured differently from the others (on
the provider site)...

> 
> This port is the 2nd and the dialing pattern is DAHDI/g1 which means
> "start with channel 1 on span 1, then channel 2 on span 1, then
> channel 4 on span 2, ....".
Ok, but dialing is Layer 3. You are observing layer 2 errors on the
D-Channel (LAPD-protocol).


> What I observed is that provider sends incoming calls alternatively to
> each span :
> if an inbound call comes through span 2 (channel 4 or 5), then the
> provider would send the next one to span 3 (channel 7 or 8) if
> available, etc ...
To my experience a provider do not send incoming calls to different
ports on PTmP lines. Each line gets his own numbers, there is no
overflow (at least in germany). But again: Your original problem are
layer 2 errors. Reasons could be:
- line broken
- port broken
- driver do not handle layer 1 down in case of inactivity

> I'll try to swap cables and see if messages are "moving" from span 2
> to another span.

Good idea.

Have a nice weekend.

Karsten