[asterisk-users] Asterisk 10/1.6.1 and Dahdi/Libpri compatilities in BRI /PtmP

[Richard Mudgett]

> >> > This is the option I will try.
> >> > I'll report my findings here.
> >>
> >> My findings, after setting layer1_presence=ignore in
> >> chan_dahdi.conf
> >> are :
> >>
> >>   == Starting D-Channel on span 1
> >>   == Starting D-Channel on span 2
> >>   == Primary D-Channel on span 1 up
> >>   == Primary D-Channel on span 2 up
> >> foo*CLI> pri show spans
> >> PRI span 1/0: Up, Active
> >> PRI span 2/0: In Alarm, Down, Active
> >> foo*CLI> pri show spans
> >> PRI span 1/0: In Alarm, Down, Active
> >> PRI span 2/0: Down, Active
> >> foo*CLI> pri show spans
> >> PRI span 1/0: Down, Active
> >> PRI span 2/0: Down, Active
> >> foo*CLI> pri show spans
> >> PRI span 1/0: Down, Active
> >> PRI span 2/0: Down, Active
> >>
> >>
> >> So basically, "pri show spans" still reports lines being down,
> >> though
> >> they are not.
> >
> > The "pri show spans" command is not useful for PTMP lines if the
> > *telco*
> > brings layer 2 and layer 1 down while idle.  These lines really are
> > down.
> > The *only* difference between an unplugged line and layer 1 being
> > down is
> > that they come back up on demand.
> 
> Do you imply that instead of being afraid of the word "Down"
> presence,
> I should stand assured by
> the word "Active" presence, the later one meaning "this line can be
> back up on demand" ?

For your PTMP setup, the only useful information pri show spans is
going to give you is the fact that the span is configured.

PRI span v/w: x, y, z
v = span number
w = span D channel index (Will be non-zero if there is more than one
    D channel per span. (NFAS redundant D channel setup))
x = Can be: "In Alarm" (Layer 1 down) or not present if layer 1 up
y = Can be: "Down" (Layer 2 down), "Up" (Layer 2 up)
z = Can be: "Active" (This D channel is the active NFAS D channel
    or only D channel), "Standby" (This D channel is in backup standby
    mode for NFAS)

> What would the wording for such situation in 1.4.13, with these layer
> 1 and 2 features ?
> Still something like "Down, Active" ?
> And what about using something more specific like "Energy save,
> Active" ?

The layer1_presence option just causes Asterisk to ignore layer 1 alarms
from DADHI on the span when considering the ability of the B channels
to be usable for outgoing and incoming calls.  The option only has an
effect on PTMP lines because some telcos drop layer 1 for power saving
reasons.  When in power saving mode, you will not be able to tell if the
line is out of service until you attempt to make a call.

The layer2_persistence option causes libpri to bring layer 2 back up when
the telco drops it.  Because layer 2 is not allowed to remain down, the
telco cannot bring layer 1 down.  Some telcos may have an issue with this
behavior because the line cannot go into power saving mode.

> What surprised me a lot is the speed with which each line is put in
> energy save mode : a line remainded up during 20s or so and then put
> down for a while.

The line will come back up on demand in less than a second.

Richard