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Technology Brief
Auto Healing
NSBU
ZyXEL Communications Corp.
November, 2013
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Contents
Introduction
How It Works
Benefits for Users and SIs
Technical Details
Deployment Notes
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Introduction
What’s Auto Healing?
A high-availability WLAN feature that:
Automatically detects AP failures
Compensates by increasing the wireless coverage of nearby APs
This technology helps:
Minimize outage impact
Maximize WLAN availability
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
How It Works
ScenarioA floor in a campus with six rooms. Each room is covered by an AP. The teachers and students are using tablet computers in class.
Campus
AP3AP2
AP4 AP5 AP6
AP1
Room1 Room2 Room3
Room4 Room5 Room6
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
How It Works
Without Auto HealingRoom2 loses wireless service when AP2 fails. The IT staff needs to rush to the classroom and fix the failed AP to recover the wireless service. The class is interrupted.
Campus
AP3AP2
AP4 AP5 AP6
AP1
Room1 Room2 Room3
Room4 Room5 Room6
FAIL
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
How It Works
With Auto HealingWith Auto Healing, the WLAN is scanned periodically. When AP1, AP3 and AP5 finds that AP2 is “dead”, they will increase their output power to cover the wireless “dead zone”.
Campus
AP3AP2
AP4 AP5 AP6
AP1
Room1 Room2 Room3
Room4 Room5 Room6
FAIL
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
How It Works
RecoveryWhen AP1, AP3 and AP5 finds that AP2 has recovered (via periodic scanning), they will automatically decrease their output power to the original state.
Campus
AP3AP2
AP4 AP5 AP6
AP1
Room1 Room2 Room3
Room4 Room5 Room6
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Benefits for Users and SIs
Minimize outage impactIT staff can continue to provide wireless services to the users in Room2 and replace the failed AP when the class has ended, or when the new AP has been delivered by the SI.
Maximize WLAN availabilitySIs do not need to be on site right away to replace the AP and restore the wireless service.
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Technical Details
How does the scanning work?Scheduled scan
By default, an AP scans the availability of its neighbor APs (in its neighbor list) with an interval of 5 minutes*
Each scan takes 1 minute to complete
When an AP failure is detected, 2 more confirm scans will be conducted before increasing output power
Neighbor APs will increase output power within 3 minutes of detecting an AP failure (1 scheduled scan + 2 confirm scans)
When an AP recovery is detected, neighbor APs will decrease output power immediately after the scan (within 1 minute)
*The scan interval can be configured between 5 to 30 minutes
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
How does the scanning work?Scheduled scan
Technical Details
Increase output power Decrease output power
3 minutes total
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Technical Details
How does the scanning work?Event scan
When the WLAN controller detects a CAPWAP connection from a failed AP (possible recovery), it will initiate a event scan immediately to check the availability of it’s wireless signal
When a wireless signal is detected, neighbor APs will decrease output power immediately after the scan (within 1 minute)
Decrease output power
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Technical Details
More detailsThe scan interval can be configured between 5 to 30 mins
By default, an AP will include neighbor APs that have an RSSI of -85 or better into its neighbor list
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Deployment Notes
Output power adjustmentTo enable Auto Healing, each AP needs to reserve some output power to cover neighbor APs in cases of AP failures
Before deploying Auto Healing, please ensure the AP’s output power is adjusted to less than 100% (for example 60%)
It is not possible for an AP to transmit more than its max. output power
(100%), so reducing the AP’s output power is necessary for Auto
Healing to work
By default, an APs output power is set to maximum level (100%)
The reserved output power will be used to maximize WLAN availability when a neighbor AP fails
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Deployment Notes
RF planningFor Auto Healing to function correctly, please make sure that APs are not too far away from each other
The functioning AP may not be able to cover the “dead zone”
AP1 AP2
AP1 AP2
Initial output power
Increased output power
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Copyright © 2013 ZyXEL Communications Corporation. All rights reserved.
Deployment Notes
RF planningFor Auto Healing to function correctly, please make sure that APs are not too close to each other
The functioning AP may not increase its output power because it may already cover the “dead zone”
AP1 AP2
Initial output power
AP1 AP2
Initial output power
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