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Optimizing WLANs Peter Lane
March 14, 2013
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Inventory your network Monitor the health of your network Alert on critical issues Optimize RF Optimize Applications
Agenda
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• Voice/video optimization • High Density/Large Public Venue • Outdoor • Advanced RF troubleshooting
Topics not covered
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• APs – Single radio or dual radio – a/b/g, 2 stream 11n, 3 stream 11n
• Switches – AP uplink speed – Switch uplink speed
• Applications – Voice – Video – Cloud based (Salesforce, Box, Hulu, YouTube, etc.) – Gaming – File sharing
Routinely Inventory your network
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• Clients – Types – Densities – Locations
• Physical locations – Odd construction materials – Old buildings – Sources of Interference
Routinely Inventory your network
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ArubaOS Dashboard - Performance
Noise Floor
Channel Utilization
Interference
SNR
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AOS RF Dashboard – Security
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AOS RF Dashboard – WLAN
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AOS RF Dashboard – Access Points
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AirWave – AP Monitoring
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Radio Details
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AppRF AirWave Screenshots
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• Prioritize cloud based Applications – Create a stateful firewall destination – Add a policy using that destination to prioritize – Pause ARM scanning for extremely latency sensitive or UDP
heavy applications (not common)
Controller ACLs and policy updates
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• Limit the bandwidth per user/role • Limit the bandwidth used per VAP.
Bandwidth contracts and Traffic shaping
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Use Reports to identify trends over time
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RF Health
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Rogue Client Connections
• Don’t get blamed for other networks performance
• Identify clients that are misconfigured
• Identify underserved locations
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Capacity planning
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Use alerts to reduce work and gain visibility
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Channel Utilization
• Why is the Radio low on air time? – Special event – Other APs down – Change in user behavior – Lots of multicast
• Frequent occurrence? – Add APs – Upgrade APs – Implement bandwidth contracts – AirGroup
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• >-85 is a concern – Look at the SNR of
associated clients to determine impact
• Look at nearby APs – Is it an area wide problem or
restricted to a single AP?
Noise Floor monitoring
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Radius Auth Issues
• Find Auth issues before clients report them – Restrict to Device or user – Tweak levels for your
environment – Verify RADIUS server
performance and config if problems are seen
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IDS Events can cause client disruption
• Some attacks simply disrupt the network – Very rare – Not an issue if only seen
once – Repeated detections imply
someone is causing network problems
– Don’t waste time looking for other problems when this one is purposely created
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Interface Usage Monitoring
• A saturated uplink leads to slow wireless performance
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Device Event Monitoring
• Catchall Alert – Temp – Fan speed – Crash – Etc.
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• Sticky clients – Station handoff assist – Lower TX power levels
• Interference – Non-wifi interference immunity (use with caution) – Channel Reuse and Cell size reduction – Lower TX power levels – ARM channel changes – Replace microwaves
• Old clients – Match AP min/max TX power to +- 3 db of client
Common Problems
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Standard recommendations from VRD
Feature Setting Profile ARM Assignment Single band (default)
Multiband (for single-radio APs) ARM
Client-Aware ARM Enabled ARM Voice-Aware Scanning Enabled ARM Video-Aware Scanning Enabled ARM Load-Aware Scanning 10 Mb/s (default) ARM Power-Save-Aware Scanning
Disabled ARM
Rogue-Aware Scanning Disabled except for high security environments
ARM
Band Steering Enabled, prefer 5 GHz (default) VAP Adjusting Receive Sensitivity
Disabled Radio
Station Handoff Assist Disabled RF Optimization Intelligent Rate Adaptation
Always on, not configurable N/A
Fair Access Enabled Radio
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Deployment specific settings from the VRD
Feature Sparse AP with Data Only
Dense AP with Data Only
When Enabling Video
When Enabling Voice
Spectrum Load Balancing
Disabled Enabled Enabled Disabled
Mode-Aware ARM Disabled Disabled Disabled Enable only to solve client issues
Local Probe Request Threshold
Disabled Enabled (value = 25 dB)
Enabled (value = 25 dB)
Enabled (value = 25 dB)
Dynamic Multicast Optimization
Disabled Disabled Enabled – higher of 40 or 3 x number of VLANs
Disabled
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• Know your network – How is it used – Where is it used
• Monitor the health of your network – RF health of the APs – Client health – Authentication issues
• Alert on critical issues – Leverage tools to get notified about issues
Keep Optimizing
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Thank You
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Essential Elements of Healthy RF
Signal Strength Good Noise Floor
Channel Utilization
Client NIC
Low Interference
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• AP Characteristics – Number and type of Radios (a/b/g/n) – Max Tx Power – Receive Sensitivity – Number of Spatial Streams – Antenna – Internal/External – Antenna Pattern – Number of clients supported
What Affects Signal Strength?
APs are not created equal Choose the right AP for the occasion
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AP-135 Antenna Pattern
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AP-93 Antenna Pattern
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AP Radiated Power (EIRP)
What Affects Signal Strength?
= Radio Transmit Power (dBm)
+ Transmit Antenna Gain (dBi)
• AP Regulatory Domain • Country Code • Radio Band (2.4GHz/5GHz) • Channel (different channel has different
allowed Max EIRP)
Antenna is PASSIVE – Does Not ADD energy Higher Gain just means energy more focused
Not always a good thing
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• Attenuation (Path Loss) – Distance from AP/Line-of-sight – Building materials (walls, windows, partitions) – Furniture – People
What Affects Signal Strength?
Client Received Power (dBm) = Radiated Power/EIRP (dBm)
- Path Loss (dB)
+ Receiver Antenna Gain (dBi)
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Attenuation of Common Building Material
2.4GHz 5.0GHz Fabric, blinds, ceiling tiles ~1dB ~1.5dB Interior drywall 3-4 dB 3-5 dB Cubicle wall 2-5 dB 4-9 dB Wood door (Hollow – Solid) 3-4 dB 6-7 dB Brick/Concrete wall 6-18 dB 10-30 dB Glass/Window (not tinted) 2-3 dB 6-8 dB Double-pane coated glass 13 dB 20 dB Steel/Fire exit door 13-19 dB 25-32 dB
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• Disable Bcast if possible • AirGroup when possible – Management frames – Lowest data rates – Large subnets bring in large bcast domains
• SSID profile – Bcast/mcast on the SSID • Set to ARP
Broadcast Optimization
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• Watch out for DHCP lease issues • Short leases recommended depending on usage – 30-60 min for guest networks – 6 to 8 hours for .1x
DHCP
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