ISDN/RBS Trunk Busy-Out Feature Guide
Overview
With the release of AOS 16.01, AOS voice devices support the capability to actively disable a PRI or E&M/RBS trunk based on an IP connectivity test. This feature can be used to notify a local PBX that connectivity to a SIP trunk has been lost so the PBX can attempt to route calls in an alternate direction.
This feature utilizes network-monitor. For more detail, please see this guide:
Configuration Steps
1. Create a probe
Configure a probe that will monitor your primary data connection in order verify that it's still active. Usually an icmp-probe is the simplest option here, and sending a ping directly to your softswitch would obviously be the best target, assuming your softswitch accepts ICMP. From global configuration mode:
!
probe drop-trunk icmp-echo
destination 192.168.1.1
period 5
tolerance consecutive fail 3 pass 2
no shutdown
!
This probe, named "drop-trunk", sends an icmp echo-request to 192.168.1.1 every 5 seconds. If the probe fails to receive 3 consecutive responses, the probe will enter a FAIL state. Two consecutive responses will put the probe back into a PASS state. Adjust the period and tolerance values as needed. The command ‘show probe’ can be used to see the probe’s current status.
2. Create a track that references the probe
!
track test-track
test if probe drop-trunk
no shutdown
!
This track, named "test-track", simply watches the probe and determines whether or not it's in a failed or passed state. The track is listed separately because you can reference multiple probes in a single track. The command "show track" will let you see the configured track’s status.
3. Configure ‘busy-out’ on RBS or ISDN voice trunk
For PRI:
!
voice trunk T02 type isdn
busy-out monitor track test-track
connect isdn-group 1
!
or for RBS:
!
voice trunk T03 type t1-rbs supervision wink role network
busy-out monitor track test-track
connect t1 0/2 tdm-group 1
!
Sample Debugs
PRI
When the track fails on an ISDN trunk, the busy-out option will take down the D channel.
NETMON.PROBE drop-trunk: value changed to fail
NETMON.PROBE drop-trunk: Request timed out. (failed)
NETMON.TRACK test-track: Controlling account T02 New state: FAIL
NETMON.TRACK test-track changed from pass to fail.
ISDN.EP PRI 1 D channel is DOWN
INTERFACE_STATUS.pri 1 changed state to down
NETMON.PROBE drop-trunk: Request timed out. (failed)
The D channel negotiation resumes when the track returns to a passed state.
NETMON.PROBE drop-trunk: Reply from 192.168.1.1: bytes=92 time=14ms (passed)
NETMON.PROBE drop-trunk: value changed to pass
NETMON.PROBE drop-trunk: Reply from 192.168.1.1: bytes=92 time=12ms (passed)
NETMON.TRACK test-track: Controlling account T02 New state: PASS
NETMON.TRACK test-track changed from fail to pass.
ISDN.L2_FMT PRI 1 ======================================
ISDN.L2_FMT PRI 1 Sent = Sapi:00 C/R:C Tei:00
ISDN.L2_FMT PRI 1 Ctl:SABME
ISDN.L2_FMT PRI 1 ======================================
ISDN.L2_FMT PRI 1 Recd = Sapi:00 C/R:C Tei:00
ISDN.L2_FMT PRI 1 Ctl:UA
ISDN.EP PRI 1 D channel is UP
INTERFACE_STATUS.pri 1 changed state to up
RBS
When the track fails on an RBS trunk, the AOS voice product unit will send an AIS (blue) alarm to the destination, effectively preventing the PBX from routing calls toward the AOS unit.
NETMON.PROBE drop-trunk: value changed to fail
NETMON.PROBE drop-trunk: Request timed out. (failed)
NETMON.TRACK test-track: Controlling account T03 New state: FAIL
NETMON.TRACK test-track changed from pass to fail.
T1.t1 0/2 Tx Blue
T1.t1 0/2 Yellow, Tx Blue
INTERFACE_STATUS.t1 0/2 changed state to down
NETMON.PROBE drop-trunk: Request timed out. (failed)
NETMON.PROBE drop-trunk: Request timed out. (failed)
The alarm clears when the track passes.
NETMON.PROBE drop-trunk: Reply from 192.168.1.1: bytes=92 time=14ms (passed)
NETMON.PROBE drop-trunk: value changed to pass
NETMON.PROBE drop-trunk: Reply from 192.168.1.1: bytes=92 time=13ms (passed)
NETMON.TRACK test-track: Controlling account T03 New state: PASS
NETMON.TRACK test-track changed from fail to pass.
T1.t1 0/2 Yellow
T1.t1 0/2 No Alarms
INTERFACE_STATUS.t1 0/2 changed state to up
