Problem with PRI ISDN Layer 2 Q.921

Asterisk Asterisk Support
1

Hi. I’ve got a problem with my Asterisk installation, v1.4.9 as part of AsteriskNOW.

Everything starts up fine when Asterisk is run. However, my T1 provider informs me that they only see ISDN Layer 2 RR messages when I reboot the server, but then they stop and no further L2 responses are received to their messages. We are also finding that the PRIs go down after what appears to be random idle intervals.

We can make and receive calls to and from the system when the PRIs are up, and can see the status as Up, with everything working.

I am based in Hong Kong, as are the circuits.

I have two T1 lines attached to a Digium TE205P card, and both are configured according to our telco provider’s spec. The settings I have are:

zapata.conf:

trunkgroup => 1,24
spanmap => 1,1,1
language=en
context=default
switchtype=ni1
signalling=pri_cpe
rxwink=300
usecallerid=yes
hidecallerid=no
callwaiting=yes
usecallingpres=yes
callwaitingcallerid=yes
threewaycalling=yes
transfer=yes
canpark=yes
cancallforward=yes
callreturn=yes
echocancel=yes
echocancelwhenbridged=yes
rxgain=0.0
txgain=0.0
group=1
callgroup=1
pickupgroup=1
immediate=no

callerid=asreceived
group=1
signalling=pri_cpe
channel => 1-23,25-47

zaptel.conf:

span=1,1,0,esf,b8zs
span=2,0,0,esf,b8zs
bchan=1-23
dchan=24
bchan=25-47
dchan=48
loadzone=us
defaultzone=us
channels=1-23,25-47

In my “pri intense debug” log, I get the following messages, which seem to indicate the RR is being sent and received correctly, but our telco says not.

> [ 00 01 01 39 ]

> Supervisory frame:
> SAPI: 00  C/R: 0 EA: 0
>  TEI: 000        EA: 1
> Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
> N(R): 028 P/F: 1
> 0 bytes of data
-- Restarting T203 counter

< [ 00 01 01 37 ]

< Supervisory frame:
< SAPI: 00  C/R: 0 EA: 0
<  TEI: 000        EA: 1
< Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
< N(R): 027 P/F: 1
< 0 bytes of data
-- ACKing all packets from 26 to (but not including) 27
-- Since there was nothing left, stopping T200 counter
-- Stopping T203 counter since we got an ACK
-- Nothing left, starting T203 counter
-- Got RR response to our frame
-- Restarting T203 counter
T203 counter expired, sending RR and scheduling T203 again
Sending Receiver Ready (1)

> [ 00 01 01 03 ]

> Supervisory frame:
> SAPI: 00  C/R: 0 EA: 0
>  TEI: 000        EA: 1
> Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
> N(R): 001 P/F: 1
> 0 bytes of data
-- Restarting T203 counter

< [ 00 01 01 05 ]

< Supervisory frame:
< SAPI: 00  C/R: 0 EA: 0
<  TEI: 000        EA: 1
< Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
< N(R): 002 P/F: 1
< 0 bytes of data
-- ACKing all packets from 1 to (but not including) 2
-- Since there was nothing left, stopping T200 counter
-- Stopping T203 counter since we got an ACK
-- Nothing left, starting T203 counter
-- Got RR response to our frame
-- Restarting T203 counter
T203 counter expired, sending RR and scheduling T203 again
Sending Receiver Ready (28)

> [ 00 01 01 39 ]

> Supervisory frame:
> SAPI: 00  C/R: 0 EA: 0
>  TEI: 000        EA: 1
> Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
> N(R): 028 P/F: 1
> 0 bytes of data
-- Restarting T203 counter

< [ 00 01 01 37 ]

< Supervisory frame:
< SAPI: 00  C/R: 0 EA: 0
<  TEI: 000        EA: 1
< Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
< N(R): 027 P/F: 1
< 0 bytes of data
-- ACKing all packets from 26 to (but not including) 27
-- Since there was nothing left, stopping T200 counter
-- Stopping T203 counter since we got an ACK
-- Nothing left, starting T203 counter
-- Got RR response to our frame
-- Restarting T203 counter
T203 counter expired, sending RR and scheduling T203 again
Sending Receiver Ready (1)

> [ 00 01 01 03 ]

> Supervisory frame:
> SAPI: 00  C/R: 0 EA: 0
>  TEI: 000        EA: 1
> Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
> N(R): 001 P/F: 1
> 0 bytes of data
-- Restarting T203 counter

< [ 00 01 01 05 ]

< Supervisory frame:
< SAPI: 00  C/R: 0 EA: 0
<  TEI: 000        EA: 1
< Zero: 0     S: 0 01: 1  [ RR (receive ready) ]
< N(R): 002 P/F: 1
< 0 bytes of data
-- ACKing all packets from 1 to (but not including) 2
-- Since there was nothing left, stopping T200 counter
-- Stopping T203 counter since we got an ACK
-- Nothing left, starting T203 counter
-- Got RR response to our frame
-- Restarting T203 counter

Am I missing something in the configuration here? I’m quite at a loss as to how to solve the issue and the telco insists that our end is at fault, and not their equipment.

I hope you can help, and thanks for any assistance in advance.

reax

2

Just as a suggestion, I’d try setting your switchtype to “national” (which is NI-2) instead of NI-1. As I understand it, PRI doesn’t work reliably using the NI-1 switchtype. (In fact, I’ve heard a PRI expert say that it shouldn’t really work at all.)

Jared Smith
Community Relations Manager
Digium, Inc.[/quote]

3

Hello Jared,

I have made this change, as you suggested, and will await the telco’s report on what they see before I can be sure if this has changed anything.

We were actually told by our telco to use NI-1, as they said they didn’t support NI-2. However, we’ll see what occurs with the next round of diagnostics.

Thanks for getting back to me.

Jack