Matt FosterChannel Acct Mgr.

Aust/NZ

Netscout

matt.foster@netscout.com

Wi-Fi troubleshooting

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5 ghz

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802.11a/b .11n .11ac

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The Wi-Fi Industry is Growing with Speed

• Speeds are getting faster

• Industry is growing

• Technology is getting more complex

• Performance expectations increasing

Wi-Fi Troubleshooting is Complex

Involves more than Wi-Fi network packets

Need to understand the channels and how they’re allocated

Non-Wi-Fi devices can also impact the system

Resolving User Complaints

How to get from complaints…

• “The wireless doesn’t work”• “The Internet is slow”• “I can’t connect to the

wireless”

• “I keep getting disconnected”

… To the source of the problem

• Mis-configuration of an AP or client

• Interference

• Rogue AP

• Unauthorized client

• Channel overlap

• Network congestion

• Wired network problems

How to make this fast and efficient?

Understanding Wi-Fi Bandwidth demand

• Video Streaming – Large BW demand, but can buffer slightly

• Voice services – Small BW demand, but must be low latency, highest priority

• General Business applications – Low/Medium BW demand, low priority

• SaaS – Low BW demand medium priority

• General internet traffic – Medium BW demand medium priority

• Large file transfers (FTP)- Medium BW demand, low priority

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To calculate bandwidth demand requirements, we need to firstly look at

the applications running over the Wi-Fi network and each of their

network requirements.

What is my weakest link in Bandwidth delivery?

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Ask yourself 3 questions-

1. What is the maximum bandwidth my current

airspace can deliver (per location)?

2. What is the maximum bandwidth my current AP

can deliver (in reality)?

3. What is the maximum bandwidth my current

backhaul can deliver?

Analysing the Air space

Do you have good Signal coverage?

Do you have overlapping channels?

Do you have external interference?

Do you have roaming issues?

Are you connecting or roaming to the correct AP?

Do you have high utilization?

What does yours look like?

Analysing the Air space

• Plan – map out your desired signal coverage

• Predictive – Understand your expected outcome

• Active/Passive surveys- what does reality look like?

• Troubleshoot/Optimise your Wi-Fi network for performance

• Verify Co/Adj channel interference

• Verify non-wifi interference

Wi-Fi best practices

Signal coverage is only the first step, plan for performance

Let’s look at Video Streaming – Analyse the Air space

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- Idle Channel, basically 0% Utilisation

- One device streaming 4KHD, 30% Utilisation

Let’s look at Video Streaming -Education

• The amount of bandwidth required will depend on the quality of the stream. For a ballpark estimate of the speed required for stream live video or cached video.

– 1.5Mbps, minimum speed for quality viewing (eg. DivX)

– 3Mbps, Standard Definition

– 5-8Mbps, 720p and 1080p High Definition

– 25Mbps, 4K Ultra High Definition

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Video streaming is a popular method used in today’s syllabus and

always delivered over the Wi-Fi network

Media typeMinimum BW req.

(Mbps)Number of Students

Maximum demand (Mbps)

DivX 1.5 25 37.5

SD 3 25 75

HD 7 25 175

UHD 25 25 625

Common Wi-Fi Problems

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• Poor wireless performance due to congestion or interference

• Cannot connect due to mis-configurations

• Locating unauthorized access points and devices

• Disconnects due to interference or congestion

• Can connect, but no internet

• Roaming failures

• Validate coverage

• Interfering technologies

Common Wi-Fi Problems

Most common Wi-Fi problems and why they occur

Complaint Common Cause Examples

No Wi-Fi Access Coverage Dead spots, failed APs or radios

Slow Wi-Fi Congestion Wi-Fi or channel interference

Internet is down Configuration Authentication, services (DHCP, DNS)

Losing connection Configuration Misconfigured network, interference

All of the above Rogues Unauthorized APs and clients

Key Tests and Measurements

• Channel Utilization: Wi-Fi and non-Wi-Fi

• Signal/Noise Ratio

• Visibility into all clients – connected and probing

• Co-Channel and Adjacent Channel Interference

• Connectivity to networks and access points

• Network Performance

• AP backhaul connectivity

• Interfering technologies

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Some examples

Over-utilized Channels

“I keep getting kicked off the wireless network”

Check channel utilization:

- 2.4 GHz and 5 GHz channels

- Number of APs per channel

- Number of clients per channel

Cannot Connect to the Network

“I can connect to Wi-Fi but internet is down”

Check misconfigured services:- Authentication

- DHCP, DNS

- Ping and TCP port tests

- Signal/Noise/SNR

Does Roaming Work?

“I can connect to Wi-Fi but disconnect when I roam”

Verify roaming:

- Connect to a network

- Start Roaming Test

- Verify which AP you are connected to

- See where Client roams to, or where it gets disconnected

Is there a pirate on the ship?

Rogue APs and unauthorized client devices cause Wi-Fi interference and poses a security risk to your network

Detect View Locate

Unauthorized Devices

Validating the AP Backhaul

Does the AP have connectivity to the WLAN Controller or to the network?

• Verify POE and a link to the switch/VLAN• Verify basic network services

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Questions?