3 aruba arm and cm

9 - 1CONFIDENTIAL© Copyright 2014. Aruba Networks, Inc.All rights reserved

CONFIDENTIAL © Copyright 2014. Aruba Networks, Inc. All rights reserved

Adaptive Radio Management and Client match


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 GHzCh 1

2.4 GHzCh 1 2.4 GHz

Ch 115 GHzCh 36

5 GHzCh 149

5 GHzCh 52

5 GHzCh 161

2.4 GHzCh 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 ishighly recommended to keep default settings)

AP-800) #show rf arm-profile defaultAdaptive Radio Management (ARM) profile "default"-------------------------------------------------Parameter Value--------- -----Scan Interval 10 secScanning EnabledScan 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 likeBelow 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 Timestamp11:22:33:44:55:66 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)

AA:BB:CC:11:22:33 (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 criteriaI. 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

3 aruba arm and cm

Engineering

aruba networks

singleband clients

rights reservedafter

rights reservedbefore

networks rfadaptive

rights reservedwhat

wlanconfidential copyright

xconfidential copyright