3 aruba arm and cm

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CONFIDENTIAL
© Copyright 2014. Aruba Networks, Inc.
All rights reserved
CONFIDENTIAL
© Copyright 2014. Aruba Networks, Inc. All rights
reserved
Adaptive Radio Management and Client
match

CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved
What is ARM?
•Adaptive Radio Management (ARM) is an RF spectrum
management technology that dynamically provides a stable, high
performing, self-healing wireless LAN deployment.
•Distributed algorithm approach:
• For each AP the controller determines the best 802.11 channel
and transmit power settings.
• Based on the frequency configured in regulatory domain (from the
perspective of the AP and neighbors).
• Results in a highly-scalable & reliable RF
environment:
• Significantly reduces time the AP takes to adapt to changes in the
RF environment.

Lobby Cafeteria
Conference
Rooms
Offices/Cubicles
Adaptive Radio Management (ARM)
RF Spectrum Management
•ARM manages the
network’s RF
–Adaptive RF: automates RF
setup and optimization
–Self-Healing: adjusts
channel/power to fix coverage
holes
–Adapts to interference in real-
time
•Application Aware
–Voice Aware Scanning
–Load Aware Scanning
–Rogue AP Aware Scanning
–Client Aware Assignment
•Infrastructure-Based
Control

Before ARM is Enabled
•All 5GHz radios
on channel 36
•All 2.4GHz
radios on
channel 1
•All power levels
at 50%

After ARM is Enabled
•Network learns
optimal channel
plan to avoid
interference
•Learns optimal
power levels to
avoid coverage
holes

Infrastructure-Based Control
• Adaptive Radio Management (ARM) adds
infrastructure-based control of wireless clients
1. Band Steering – Steers clients to higher capacity 5GHz band
when clients are capable to do so
2. Spectrum Load Balancing - load balance clients across multiple
APs
3. Co-channel Interference Mitigation - APs with excess capacity
revert to air monitors
4. Airtime Fairness - assures 802.11n performance in presence of
legacy clients
5. Coordinated Access to A Single Channel - co-channel
interference adaptation for radios on a single channel
6. Client Match - feature to match a wireless client to the best AP in
its vicinity to improve the overall throughput in a WLAN

Band Steering
•Increase performance by automatically moving clients to 5GHz
band when capable
– Fingerprint clients that are 5GHz capable
– Encourage these clients to move to 5GHz band by “hiding” APs in
2.4GHz band from them (suppressing probe response from AP)
•Reserve 2.4GHz band for single-band clients
– Many voice over WLAN handsets
802.11b/g
802.11a/n
Actively steer
clients to
appropriate band
20MHz Channels 24 3
40MHz Channels 11 1
X

Spectrum Load Balancing
•By default, a client selects the AP with which to associate based on the AP
with the strongest signal
•With ARM, the AP/controller insures an intelligent distribution of clients
across available channel capacity
– Dynamically assesses channel loading routing clients to APs on channels with
available bandwidth
– AP will send an association response with error code 17 to new clients trying to
associate
– No manual configuration of
thresholds required
X

Airtime Fairness
• Prevent throughput reduction for faster clients in the presence of
slower clients
•Air time Allocation Policies
– Default Access – Disable Air Time allocation
– Fair Access – Allocate same air time to all clients
– Preferred Access – Allocate air time based on client capabilities
• Gives higher priority to faster clients (802.11n > 802.11a/g > 802.11b) while
ensuring no clients are starved
– Works with mixed-mode clients in both 2.4 and 5GHz spectrums, across 11b/g/n
and 11a/n client

Co-Channel Interference Mitigation
• Goal: Minimize co-channel interference
• How it works: In situations with excess AP capacity, the extra APs automatically revert
into Air Monitors
• Auto detection of edge APs to prevent them from turning into AMs
• Required for effective Vo WLAN deployments
2.4 GHz
Ch 1
2.4 GHz
Ch 1 2.4 GHz
Ch 115 GHz
Ch 36
5 GHz
Ch 149
5 GHz
Ch 52
5 GHz
Ch 161
2.4 GHz
Ch 6

ARM Functional Description
•ARM constantly monitors the network
– APs continuously scan other channels during dead intervals
– AP analyzes BSSIDs and interference seen on current and other channels
and reports back to controller
•Controller collects and classifies information obtained during
scans from all AP’s
•Create two indices for each AP, for each channel
• Interference Index (sum of SNRs)
• Coverage Index (number representing overlap)
•Compare the indices to the “Ideal Index” (configurable)
•Controller picks the best channel and power level towards the
“Ideal Index”
•Back off parameter is a dampening factor so that the AP and
clients do not flap.

Scanning
•ARM monitors and services wireless devices on the current
channel while scanning other channels periodically.
• APs scan during dead periods (limited to configured intervals)
• Air Monitors will scan by default each channel in it’s regulatory
domain for 1 second
•Scanning behavior is controlled via the ARM profile (It is
highly recommended to keep default settings)
AP-800) #show rf arm-profile default
Adaptive Radio Management (ARM) profile "default"
-------------------------------------------------
Parameter Value
--------- -----
Scan Interval 10 sec
Scanning Enabled
Scan Time 110 msec

Indices
• Coverage Index: Metric that the AP uses to measure for RF coverage
calculated and weighted for all Aruba APs seen on a specified channel
• Interference Index: Metric the AP uses to measure co-channel
interference which is calculated and weighted for all APs including 3rd
party APs on a specific channel and it’s neighbors

What exactly ARM will gather from APs?
•Amount of Retry frames (measured in %)
•Amount of Low-speed frames (measured in %)
•Amount of Non-unicast frames (measured in %)
•Amount of Fragmented frames (measured in %)
•Amount of Bandwidth seen on the channel (measured in kbps)
•Amount of Phy errors seen on the channel (measured in %)
•Amount of Mac errors seen on the channel (measured in %)
•Noise floor value for the specified AP

When exactly ARM will trigger the AP to change the channel ?
1. The Interference Index metric on a new channel is at least “arm free-
channelindex” value less than its current channel interference index value
2. The ARM noise-threshold value is reached
3. The ARM error-rate-threshold is reached
4. When a Radar is detected
5. If the AP is initially on a non-valid channel
6. If “arm rogue-ap-aware” is enabled and an active client is found using the
Rogue AP

What AP will do once it receives a trigger from ARM ?
1. Then it will wait for “arm wait-time” (default is 15 seconds) before it makes a
change.
2. It will not make a change if “arm assignment” is set to disabled, maintain, or if
“arm client-aware” is enabled and wireless clients are associated to the AP
3. Once it moves to a new channel that has the least interference then it will restart
its scanning process on all Regulatory Domain channels for “arm min-scan
time”
4. It won’t change to another channel until “arm backoff-time” (default is 240
seconds) is reached.

When exactly ARM will trigger the AP to change the Tx power ?
1. If the coverage index ,cov-idx (X/Y), metric “x” value is less than “arm
idealcoverage-index” (default is 5).
2. If the coverage index table (cov-idx) metric “x” value is more than “arm
idealcoverage-index” (default is 5)

What AP will do once it receives a trigger from ARM ?
1. AP will wait for “arm wait-time” (default is 15 seconds) before it increases or decrease its
transmit power by one level.
2. If a value of “arm max-tx-power” has been configured then the AP will not increase its
transmit power beyond that configured value
3. If a value of “arm min-tx-power” has been configured then the AP will not decrease its
transmit power less than that configured value
4. The AP will not make any power change if “arm assignment” is set to disabled or
maintain.
5. Once an AP increases or decreases its transmit power in accordance with the value of
“arm ideal-coverage-index” value then it will not change its transmit power again until
“arm backoff-time” (default is 240 seconds) is reached

What do you mean by one level ?
802.11b/g :
Transmit Power 0 = 0 dBm / 1 mW
Transmit Power 1 = 11 dBm / 12.589 mW
802.11a :

Understanding the knobs !

Understanding the knobs ! Cont…

Client Match Vs ARM 2.0
ARM 2.0 Steering Client Match Steering
Entry time (one-time) decision on
whether to accept clients.
Continuous monitoring on whether the
client is on the best radio
Decision made at association Decision made after understanding
client behaviour (4min)
Decision without knowledge of client's
view
Decision to move using virtual beacon
report
Blind steering Directed steering
Multiple knobs in different profiles Single feature that makes cohesive
decision
No client location VBR helps to get client location

ClientMatch: How It Works
Client AP1 SNR AP2 SNR AP3
AA:BB 13 35 15

How it Works
• Each AP monitors SNR for its associated clients
• If a client SNR is above a good threshold (25dB SNR), no action is taken.
• If the client SNR is below the good threshold, find a “better” AP for the client.
• “Better” AP needs to be at least 10 dB stronger than signal of current AP &
“Better” AP needs to be have signal of at least -70dBm .If “Better” AP is found,
moves the client to it.
• AP's would build a beacon report which is shared information and it is based on
the probes being sent from the client to the AP.
• Decision to move the client from one AP to the other is taken by using this table
as a baseline.
• The clients are continuously monitored and steered as per matching factors
listed above.

802.11K Beacon Report
• AP sends Beacon Request directing client to get list of beacons / probe
response that can be heard by it on a specific channel.
• Client prepares report with details including SSID, Encryption Type, Received
Signal Strength and sends to AP
• 802.11k only defines way to retrieve information from the station
• The ability to configure the station is not in its scope.
• “show ap association” would show “K: 802.11K client” for capable client
• Dot11k disabled by default as most clients don’t support it yet and have
compatibility issues.

VBR – 11k emulation for incapable clients
Collection:
AP maintains a Probe Report table of all clients whose Probe request it received in last
2min and shares it with controller every 30sec (configurable under cm-report-interval).
Use “show ap arm client-match probe-report” to see Probe Report Table.
Assimilation:
Controller assimilates information received from multiple APs to build VBR table like
Below example. Use “show ap virtual-beacon-report” to fetch data from Controller PoV.
Distribution:
To each AP; controller distributes the VBR entries of all associated clients. Use “show
ap arm virtual-beacon-report” from AP PoV. With VBR, AP monitors client and makes
steering decisions using built-in logic and configuration.
Client MAC SNR Timestamp
11:22:33:44:55:66 27 11:48:51.002
Client MAC AP1 AP2 AP3 ..
AA:BB:CC:DD:EE:FF (*)(BSSID, SNR,
Timestamp)
(BSSID, SNR,
Timestamp)
(BSSID, SNR,
Timestamp)
11:22:CC:DD:EE:FF (BSSID, SNR,
Timestamp)
(BSSID, SNR,
Timestamp)
(*) (BSSID, SNR,
Timestamp)
AA:BB:CC:11:22:33 (BSSID, SNR,
Timestamp)
(BSSID, SNR,
Timestamp)
(*) (BSSID, SNR,
Timestamp)

CM - Sticky Client Steering Logic
• Check if client drops below configured SNR threshold. Default (25);
configurable using “cm-sticky-snr”.
• If client does, check association time is < 4min. If yes; don’t do
anything.
• If client drops below threshold and association time above 4min
window
a) Check VBR for AP which meets below criteria
I. Better signal strength as configured in “Client Match SNR
threshold”. Default 10. configurable with “cm-sticky-snr-
delta”
II. The signal level is above “Client Match Sticky Min Signal”.
Default 70. configurable with “cm-sticky-min-signal”
b) Once AP is found; inform Controller to coordinate client steer

CM – Band Steering / Balancing Logic
• Use VBR to identify dual-band clients.
• If client is in ‘g’ & SNR is above threshold (25); don’t do anything
• If client is in ‘g’ & SNR is below threshold; check if ‘a’ signal on same AP is above
“Band Steer a Band Min Signal”. Default 75. Available from 6.3.1.3 (Bug # 90048).
Configurable with “cm-band-a-min-signal”
• If there is more than 15 clients; min 3 ‘g’ clients and ‘a’ clients > 4 x ‘g’ clients; then
don’t Band Steer (i.e. Band Balance)

CM – Load Balance Steering Logic
• Find good location to move : Create “Client View” by filtering VBR of clients which
can see other APs with signal stronger than -70 dBm . Use command “show ap
arm client-match neighbors ap-name”
• Don’t move clients if the AP is loaded less than “Load Balancing client threshold”.
Default 10, Configurable using “cm-lb-client-thresh”.
• For each Client View; find the clients on each channel and the average client per
channel.
• Identify overloaded channels i.e. channels which exceed average by (Load
Balancing threshold) and underloaded channels. Default 20%. Configurable using
“cm-lb-thresh”
• Move client from overloaded to underloaded AP; if it will meet “Load Balancing
SNR threshold”. Default 30. Configurable using “cm-lb-snr-thresh”.

Co-ordinating client move
• To initiate move; Controller sends blacklist report to all APs except target AP of client
with hard (Deauth) / soft steer flag. Hard steer is sent to the associated AP alone.
• AP maintains a Blacklist table. Can be viewed using “show ap arm client-match
restriction-table ap-name” .
• Default duration for which client is blacklisted is 10s. Configurable under “cm-steer-
timeout”.
• To move the client; Source AP does a deauth of the client.
• When the client tries to associate; non-desired APs which have client in blacklist
would
• Not respond to Probe Request
• Send Resource Constrained Response to 802.11 Auth Req or Ignore
• Send Resource Constrained Response to 802.11 Assn Req
• The Target AP would be the only AP which respond to client and it will associate to it.
• 802.11v BSS Transition would be the alternative when it’s supported by clients.
Rightnow; we don’t have any clients which do.
•

ACE Recommended Config for less Aggressive Roaming
Option Recommended
(Default)
Reason
Client Match Sticky client
check SNR
18 (25) Sticky steer will kick in only when
SNR drops to 18 i.e. later
Client Match Sticky Min
Signal
65(70) Client won’t be moved till client can
find target AP of -65dBm i.e. less
often
Client Match Restriction
timeout (sec)
3(10) Less time for which client can’t
associate to other APs
Client Match Max steer
failures
2(3 in 6.3) Unsteerable client would be
classified quicker
Client Match Load
Balancing client threshold
30(10) All APs can easily handle 30 clients.
Load Balancing happen less often

ClientMatch for Link Optimization (L1)

ClientMatch for Traffic Optimization (L2-3)

Knobs of Client Match in ARM profile

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