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UniFi - Wi-Fi Issues with Debugging Metrics

 Overview


This article will explain how to understand the Debugging Metrics statistics view, and how to use the data therein to troubleshoot and resolve common Wi-Fi issues. 

Table of Contents


1. Introduction

2. Using Debugging Metrics

2.1 Most Active APs

2.2 Retries

2.3 Channel Utilization

2.4 Top Clients

2.5 Top Interference

2.6 Most Active Clients

2.7 Longest Connected Clients

2.8 Top Memory Usage

2.9 Top CPU Usage

3. Related Articles

Introduction


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 In UniFi Controller version 5.6.x, we have introduced an additional statistics dashboard- Debugging Metrics. This new view presents administrators with a collection of data that we think should make it easier to identify and fix common Wi-Fi performance issues.

To access Debugging Metrics (on UniFi v.5.6.x and later):
-Open your UniFi controller
-Click Statistics
-In dropdown box, choose “Debugging Metrics”. 



Including in Debugging Metrics are the following data tables:

·  Most Active APs

·  Retries

·  Channel Utilization

·  Top Clients

·  Top Interference

·  Most Active Clients

·  Longest Connected Clients

·  Top Memory Usage

·  Top CPU Usage

Each category contains a table that summarizes the data and can be shown for either 2.4GHz band or 5GHz band. All that is requires in terms of hardware to use this table is a UniFi access point, though this feature can be supplemented with additional helpful data with the use of a UniFi Security Gateway and UniFi Switch.

This article will explain how to use each of the fields in this Debugging Metrics view to identify and resolve common issues. In the following section, we will what in each table points to a potential issue and what are some of the most common causes/resolution of these issues. 

Using Debugging Metrics Data


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Most Active APs 


In this view we see the APs on your network that are sending/receiving the most traffic. Tx indicates packets transmitted, and Rx indicates packets received. This helps you see if there may be clients violating the terms of use, or areas with higher demand that could use another AP. Excessive use on an AP can lead to over-utilized memory/CPU, as well as poorer performance for over-active APs.

Common Causes/How to Fix

  • Not enough APs to meet density demands- If traffic appears consistently too high on a given access point, to resolve, add an additional AP to help handle the traffic. Alternatively, consider placing nearby APs closer to the over-utilized AP to help handle some of the client load.
  • Problematic Clients- Sometimes what may look like an over-active AP may be more the result of a client device using up excessive traffic with P2P applications, media streaming, intentional spamming, etc. Identify clients that use too much traffic, and if enabled, use Deep-Packet Inspection to identify whether the traffic being used violates what is acceptable terms of use of your network. You can then decide to either limit by adding to a client group with controlled bandwidth limits, or block the problematic client devices altogether.
  • Poor Configuration on AP- If an AP is set to broadcast to high, and nearby APs are set to broadcast at lower levels, one AP can attract client devices with better signal strength but fail to deliver optimal Wi-Fi experience. To fix this, make sure all nearby devices are sharing the load with the over-active AP, and try lowering Tx power on the active AP/raising that of the nearby less active APs.


Retries 


In this view, you can see the retry rate both for transmitting (packets that had to be resent to the client) and receiving (rx) packets (packets that had to be resent to the access point). Retry rate indicates packets that had to be re-sent because they were corrupted upon arriving at the proper destination.

Common Causes/How to Fix

  • Interference- This is the most common cause of packet loss/retransmissions. Identify whether retry rate is higher in 2.4GHz/5GHz or both, and then look for other nearby APs to see how local the interference is. This can point to a rogue access point, a very congested RF environment, a problematic client device near to the AP, etc. To fix, try doing an RF Scan, and placing APs on less congested channels. Also, eliminate adjacent channel overlap on nearby UniFi APs. Another option would to be identify the problematic device causing the interference and re-configure/remove it.
  • Client/AP Tx Power mismatch- Another common cause of packet retries is the mismatch of broadcast power levels (Tx Power), if an AP and client device are communicating at much different broadcast strengths, then this can cause packet retries. Look for packet retries on Rx specifically as this would indicate the more likely issue of the AP broadcasting too strongly for ideal behavior with the client.


Channel Utilization 


This view shows you which APs are utilizing the most of their assigned channel on 2G or 5G. This portion also shows you what portion of the utilization is due the the AP itself.

Common Causes/How to Fix

  • Interference: If you see an access point with 59% Channel utilization but only 15% combines self Tx/Rx, this can indicate channel re-use/interference is the culprit. In a high-density environment, make sure you are minimizing the number of APs using each respective channel.
  • Legacy Clients/Poor Data Rates: If you see high channel utilization on an AP that largely comes from Self Tx/Rx, check the Most Active APs table to see if it is handling excessive traffic. If not, it is possible that poor data rates of older Wi-Fi clients are slowing down the AP and eating up a disproportionate amount of airtime. If this is causing adverse behavior you may opt to not provide connectivity to the lower data rates on this AP to prevent these older clients from causing issues. 



Top Clients 


Top clients shows what APs are handling the most client devices, and whether one band is more in use than the other. An overutilized AP can limit network performance, and having too many devices on a particular band may also be undesirable.

Common Causes/How to Fix

  • Tx Power Levels: In a higher density environment, if clients are connecting to an AP but should be connecting to another nearby AP, this can indicate the the access point in question is broadcasting at a higher strength than other nearby APs and may benefit from decreasing the Tx power on either band. It could also indicate that the other device(s) should have the Tx power increased. Typically this is more of an issue for 5G given the limited range. If devices are connecting to 2G heavily, this can indicate the need to lower 2G Tx levels on the overutilized AP.
  • 2.4GHz Band Overutilized: In cases where you see the AP has too many clients on 2.4GHz, you may opt to enable Bandsteering on the AP. Once advanced settings are enabled in the controller, you can enable band steering by clicking on the AP with high # of clients, then Configuration > Bandsteering, and select “Prefer 5G”. After you’ve applied this setting monitor the AP to see whether performance improves, you should begin to see more clients on 5G.
  • AP Placement/Density: If one AP seems to have more clients connected to it than all the others, consider moving other APs closer, or adding another AP to ease the burden on the AP.


Top Interference 


This table shows the APs that have the most RF interference. RF interference results from other wireless communications disrupting normal wireless communication to/from your APs. Excessive interference can cause a number of adverse effects on your Wireless network. Look out for sustained interference levels of double-digits and higher, to indicate that your performance may be impacted.

Common Causes/How to Fix

  • Poor Channel Assignment: Interference levels are specific to individual channels on each band, based on local RF environment. If you see high interference levels, do an RF Scan on your APs, then manually assign the AP to a channel on 2.4G/5G that is less saturated with wireless. If your network is dealing with severe interference, consider narrowing your channels (2.4GHz channels should in most cases stay at HT20 channel width, and 5GHz in noisy/high-density environments may warrant being narrowed to HT20 as well). Remember that channels must also be assigned to avoid from interference of other UniFi APs. Make sure to stagger channels and avoid using the same and adjacent channels on adjacent APs.
  • Tx Levels: If interference is exceptionally high in a location, even with devices located local to the device, and is assigned to the optimal channel, this may indicate that your device is broadcasting too quietly- try tweaking the Tx power up to medium/high, or using custom levels to see if interference levels are lower with a stronger Tx level. Sometimes excessively high Tx levels in certain environments can cause self-interference. If the AP is placed on a stone/brick/metal surface, self interference can severely impact performance. In such cases, try lowering Tx power to see if wireless then performs better. 


Most Active Clients 


This table shows which clients on your network are using the most bandwidth. Look out for highly utilized APs that are being over-used by a small number of clients.

Common Causes/How to Fix 

  • Network Abuse/Misuse- Abnormally high traffic from individual clients often points to client devices that are either using the network for things that they shouldn’t like torrenting, excessive media downloads, downloading large applications, etc. and can also point to clients that may be seeking to intentionally bring down or negatively impact your network. When this occurs in environments with a USG deployed, use Deep Packet Inspection (DPI) to find out what kind of traffic these clients are using and identify violations of your network terms of use. Problematic clients can be added to a user group in UniFi with maximum bandwidth limits. Admins also can ban these users from the wireless network altogether.
  • High Demand Clients- Sometimes the high bandwidth may be expected, if a client device is a media server, camera, etc. In such cases, if normal client use is adversely affected, you may opt to confine high-demand clients to their own wireless network/dedicated access point. This can ensure that other clients have the optimal Wi-Fi experience, while still serving the most demanding clients. 


Longest Connected Clients 


This table shows which clients on your network have been connected for the longest time. This is useful in that it can both identify widespread network issues, i.e. if client uptime is low across the board. It can also help identify devices that should not be staying on the network i.e. in a coffee shop.


Top Memory Usage 


Top memory usage indicates the % of AP hardware memory that is being used by its operations. Devices that may be dealing with abnormally high demand or may be encountering an error of some sort, may have the top memory usage. Typically high memory usage will accompany high utilization/demand, if you see abnormally high amounts of memory utilization i.e. >80%, your clients may see adverse performance. 


Top CPU Usage 


Top memory usage indicates the % of AP hardware processing resources in use by the AP at a given time. Similarly to memory usage, higher CPU usage will typically indicate the AP is more heavily in use. Abnormally high levels of CPU usage may point to a bug or an error on the AP.  

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