[Asterisk-Dev] Who looks after PRI Layer 1 framing?

[Haigh, Michael]

I'm having a problem getting Asterisk to talk to Cable and Wireless PRIs
in the UK.  After a lot of looking at bits on the wire and looking at
the carrier switch, it seems that the carrier switch is seeing an
"unintentional loopback" condition and taking the PRA out of service.
 
This occurs when bit Sa5 (in frames without the frame alignment signal)
is set to 0 by the TE.  In the original ETSI PRI Layer 1 specification
(ETS 300 011) there was obscurity about what bits Sa4 through Sa8 should
be set to by the TE, however in rev 2 of the specification there is a
note (Note 4 to Table 3) which specifies that Sa4 through Sa8 should be
set to ONE by a TE.
 
I'm not sure if looking after framing at this level is looked after by
libpri, zaptel or the specific card driver.  I'm guessing it's one of
libpri or zaptel, since these links used to work just fine with older
versions of the CVS tree (like from 2005-04-28).  I've also tried this
with both a Sangoma AFT104 and a Digium TE110P with the same problems.
 
Cheers
Mick
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