Originally presented at the WirelessLAN Professionals Conference, February 3rd, 2015

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Why Every Engineer Needs WLAN
Packet Analysis
How to solve 10 common Wi-Fi problems by
dissecting packets
Jay Botelho
Director of Product Management
WildPackets
jbotelho@wildpackets.com
Follow me @jaybotelho

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Critical Elements of a
Packet Analysis Solution
• Performance
• Multi-channel analysis
• Visualization
• Analysis modules
• High-quality decodes

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10 Common Problems
• Verifying device capabilities
‒ Networks
‒ Clients
• Verifying device
configuration
‒ Poor configuration choices
• Connection issues
‒ Authentication
• Poor VoFi quality
• Identifying network
bottlenecks
‒ Chatty clients (let me count
the ways)
‒ Probe requests
‒ Inefficient network utilization
• Roaming
‒ Sticky clients
‒ Roaming latency

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Verifying Device Capabilities
• Network capabilities – Beacons
• Client capabilities – Probe Requests

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Verifying Device Configuration
• QoS enabled/disabled
• Beacon intervals
• CTS frames sent out with 10,000 microsecond
duration field (viewed as duration attack)

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Connection Issues
Authentication – EAPOL Key Exchange
• The AP sends a nonce-value to
the STA (ANonce)
• The STA sends its own nonce-
value (SNonce) to the AP
together with a MIC, including
authentication
• The AP sends the GTK and a
sequence number together
with another MIC
• The STA sends a confirmation
to the AP

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Poor VoFi Quality
• RTP packets (g.711)
• Jitter, packet loss, latency
• Relative packet timing

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Identifying Network Bottlenecks
• Chatty clients (let me count the ways)
• Probe requests
‒ Probe Requests to all SSIDs, not just current one, flooding
device with responses
• Inefficient network utilization

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Chatty Client - Unassociated
http://www.sniffwifi.com/2012/04/phones-on-wlan.html

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Chatty Client - Associated
http://www.sniffwifi.com/2012/04/phones-on-wlan.html

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Inefficient Network Utilization
http://www.sniffwifi.com/2014/05/why-are-you-slowing-down-my-wifi-apple.html

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Inefficient Network Utilization (cont.)
http://www.sniffwifi.com/2014/05/why-are-you-slowing-down-my-wifi-apple.html

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Roaming Issues
• Sticky clients
‒ Clients make poor roaming
decisions
‒ Look for: signal strength,
data rates, etc.
• Roaming latency
‒ Criteria for determining
latency depends on your
perspective
http://revolutionwifi.blogspot.com/2012/12/wi-fi-roaming-analysis-part-3-measuring.html

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Additional Resources
• http://www.sniffwifi.com/2012/04/phones-on-wlan.html
• http://www.sniffwifi.com/2014/07/i-guess-apple-wireless-routers-dont.html
• http://www.sniffwifi.com/2014/05/why-are-you-slowing-down-my-wifi-apple.html
• http://www.sniffwifi.com/2013/12/iphones-be-chatty.html
• http://www.sniffwifi.com/2013/09/a-fish-in-desert-chomecast-sniffed.html
• http://www.sniffwifi.com/2013/08/eighteen-seconds-of-very-chatty-iphone.html
• http://www.sniffwifi.com/2012/08/testing-mobility-with-omnipeek.html
• http://www.sniffwifi.com/2011/11/how-do-i-know-if-it-really-links-me.html
• http://www.sniffwifi.com/2011/11/tell-me-whys-tell-me-sweet-little-whys.html
• http://www.sniffwifi.com/2011/11/what-is-wrong-with-this-wifi-and-what.html
• http://sc-wifi.com/2013/08/27/troubleshooting-done-motorola-style/
• http://sc-wifi.com/2012/11/12/tag-vendor-specific-nintendo/
• http://www.wifikiwi.com/cwap/a-sticky-problem-wi-fi-clients-that-wont-roam/
• http://revolutionwifi.blogspot.com/2012/12/wi-fi-roaming-analysis-part-3-measuring.html

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Thank You!
WildPackets, Inc.
1340 Treat Boulevard, Suite 500
Walnut Creek, CA 94597
(925) 937-3200