CTI Products EXB Network Manager - Manual (Page 12)

Hot-Standby EXB / Network Manager Software Manual Hot Standby
CTI Products, Inc. EXB Operation
8
68-11707-100
2.5 Open Reverse (Holdoff) Link Condition
Figure 4 Open Reverse (Holdoff) Link
1. The Main EXB Control Neuron issues a Probe packet to the Standby EXB
Control Neuron
2. The Standby Control Neuron returns a Probe ACK.
3. When the Main EXB Control Neuron receives the Probe ACK, it issues a Holdoff
packet to the Standby EXB Control Neuron.
4. There is a break on the Central MCN Tie line.
5. The Holdoff Packet is not received.
6. Since the Standby EXB Control Neuron does not receive a Holdoff packet
(timeout), it closes its switch and passes MCN packets back and forth between the
Central site and Remote Site on the bottom path.
7. Both Central EXBs will have their switches closed.
The MCN traffic to and from the IN port of the Central Main (Top) EXB will pass
over the top link.
The MCN traffic to and from the OUT port of the Central Standby (Bottom) EXB
will pass over the bottom.
8. Since the Main EXB does not receive a Holdoff Acknowledge, it informs the
EXB Network Management Software of a problem.
Central EXBs Remote EXBs
Hot Standby -- Open Reverse (Holdoff) Link CC-80599-100
WAN Links
Router
Control Neuron
Port 1
B A
Switch
In
Out
Router
Control Neuron
Port 1
B A
6. Switch Closes
In
Out
Router
Control Neuron
Port 1
B A In
Out
Router
Control Neuron
Port 1
B A In
Out
Main
Standby
1. Probe Packet
2. Probe Ack
2. Probe Ack
1. Probe Packet
3. Holdoff Packet
A
B
D
C
5. No Holdoff Packet
X
4. Break at D