I am testing the TA908E connected to a Cisco UC540 PBX for SIP-PRI and I have noticed that occasionally when there are not active calls - the IAD is sending B-channel restarts for every channel in the PRI. I am trying to time it and see if it happens every hour as a "refresh" or "keepalive" or if there is actually an interoperability issue between the two devices. I'm not seeing slips, code violations etc.
Show commands below and snippet of PRI config.
#SHOW COMMANDS
TA908e#sh int pri 3
pri 3 is UP
Switch protocol: National ISDN 2
Signaling role: network (NT) b-channel-restarts enabled
b-channel-restarts: enabled
Calling-party override: disabled
Calling-party presentation: allowed
Calling-party screening: auto
Calling-party number: (no number configured)
Digits transferred all
Name-delivery: via Setup msg / Facility IE
Progress indicator #8 in alerting message: enabled
Progress indicator #2 in connect message: disabled
Progress indicator #1 in setup message: disabled
Progress indicator #3 in setup message: disabled
Progress indicator location: public
resource-selection: linear descending
TBCT: enabled
area code:
Transmission of redirecting numbers is enabled
Redirecting numbers: sent as received
Connected interface: t1 0/3 tdm-group 1
Channel status 123456789012345678901234
.......................D
Legend: - = Unallocated . = Inactive
A = Active B channel B = Backup D channel
D = Active D channel M = Maintenance
R = Restart
Last clearing of "show interface" counters: never
36235 packets input, 173906 bytes, 0 no buffer
0 runts, 0 giants, 0 throttles
1 input errors, 0 CRC, 0 frame
1 abort, 0 discards, 0 overruns
36215 packets output, 173885 bytes, 0 underruns
TA908e#
TA908e#
TA908e#sh int t1 0/3
t1 0/3 is UP
Receiver has no alarms
T1 coding is B8ZS, framing is ESF
Clock source is system, FDL type is disabled
Line build-out is 0dB
No remote loopbacks, No network loopbacks
Acceptance of remote loopback requests enabled
Tx Alarm Enable: rai
Last clearing of counters 3d 19:18:18
loss of frame : 1, last occurred 01:56:15
loss of signal : 1, last occurred 01:56:15
AIS alarm : 0
Remote alarm : 0
DS0 Status: 123456789012345678901234
XXXXXXXXXXXXXXXXXXXXXXXX
Status Legend: '-' = DS0 is not allocated
'X' = DS0 is allocated (nailed)
Signaling Bit Status: 123456789012345678901234
RxA: 000000000000000000000000
RxB: 000000000000000000000000
TxA: 000000000000000000000000
TxB: 000000000000000000000000
123456789012345678901234
Line Status: -- No Alarms --
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
Current Performance Statistics:
0 Errored Seconds, 0 Bursty Errored Seconds
0 Severely Errored Seconds, 0 Severely Errored Frame Seconds
0 Unavailable Seconds, 0 Path Code Violations
0 Line Code Violations, 0 Controlled Slip Seconds
0 Line Errored Seconds, 0 Degraded Minutes
TDM group 1, line protocol is not set
Encapsulation is not set
#PRI CONFIG
! ADTRAN, Inc. OS version R11.10.1.E
! Boot ROM version R10.9.3.B2
! Platform: Total Access 908e (3rd Gen), part number 4243908F2
! Serial number CFG1444961
!
interface t1 0/3
fdl none
tdm-group 1 timeslots 1-24 speed 64
no shutdown
!
interface t1 0/4
shutdown
!
!
interface pri 3
role network b-channel-restarts enable
isdn name-delivery setup
connect t1 0/3 tdm-group 1
isdn supplementary-service tbct
no shutdown
!
!
isdn-group 1
min-channels 1
max-channels 12
connect pri 3
!
voice codec-list USERS
default
codec g711ulaw
!
!
voice trunk T02 type isdn
description "PRI to PBX"
resource-selection linear descending
connect isdn-group 1
no early-cut-through
modem-passthrough
rtp delay-mode adaptive
codec-list USERS
!
!
voice grouped-trunk "PRI TRUNK GROUP"
trunk T02
accept $ cost 0
!
I understand that the command is in place actually making it restart b-channels I was looking more for why b-channel-restarts would be needed at all every 60 minutes. I received the answer from support.
B channel restarts is an ISDN spec. If it is enabled, we will send a restart message every hour for inactive B channels. It requires that the device receiving the restart , send an ACK to the restart. If it does not the ISDN spec calls for that B channel to be locked out.
The advantage of restart messages is that it helps prevent B channel lock out conditions. Either side of the PRI can send them.
The disadvantages of restarts are, that in a high call volume environment , you have a short period where calls can't be made or received. Also it is possible that a PBX does not support
restart messaging because, either 1 it is not configured or 2 the firmware is out of date on the PBX.
George, it appears you have b-channel restarts enabled:
interface pri 3
role network b-channel-restarts enable
If you want them disabled, just change that command to "role network".
Thanks
Jay
I understand that the command is in place actually making it restart b-channels I was looking more for why b-channel-restarts would be needed at all every 60 minutes. I received the answer from support.
B channel restarts is an ISDN spec. If it is enabled, we will send a restart message every hour for inactive B channels. It requires that the device receiving the restart , send an ACK to the restart. If it does not the ISDN spec calls for that B channel to be locked out.
The advantage of restart messages is that it helps prevent B channel lock out conditions. Either side of the PRI can send them.
The disadvantages of restarts are, that in a high call volume environment , you have a short period where calls can't be made or received. Also it is possible that a PBX does not support
restart messaging because, either 1 it is not configured or 2 the firmware is out of date on the PBX.