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Client count and QBSS
Client count and QBSS
Kieran Duggan avatar
Written by Kieran Duggan
Updated over a week ago

Client count method

Our 6Ghz based sensors now report client count as a metric on the sensor page. All packets between the BSSID under test and its stations are monitored and where we see an exchange between the BSSID and a Station we count a client.

The sensor has a 2x2 antenna and thus is only able to read 2x2 space-time streams.

This client count represents the number of clients contending for airtime on the medium alongside the sensor itself โ€“ and can be thought of as a measure of client congestion. If the AP is a 4x4 or greater we may not be able to see all the clients it is communicating with, however at the same time these are not clients contending with bandwidth that is available to the sensor.

Note this count is different from the QBSS Client count. As it is from the perspective of the sensor (a 2x2 client) and may miss other clients not contending directly with it. Additionally depending on how vendors choose to report client count on QBSS it may not alway represent an accurate picture of clients currently communicating, IE they may be clients cached for roaming.

QBSS Information elements

QBSS (QoS enhanced basic service set) is an 802.11e construct, when enabled on your network allows access points to transmit 3 bits of information:

QBSS Available Admission Capacity(AAC)

This field is pulled from the QoS information element and requires that QoS is enabled on your network. It represents data from the Access points perspective, showing how much time in 1 second is available for transitions.

The Higher the AAC the more available bandwidth on the network from the perspective of the BSSID reporting the measurement.

QBSS Client Count

This is the connected client count as reported by the AP and is a different perspective from that of the sensor.

If the AP has more spatial streams than a 2x2 it can support more clients that the sensor can see at any given time. This measure helps users understand how the APs themselves are loading clients onto the medium

QBSS Channel Utilization

This is the channel utilization reported by the AP, this can have a different measurement period of value depending on how vendors have defined a channel as being busy (The specific threshold set by their wireless drivers).

This measurement is local to the AP and as such would be different from the perspective of channel utilization on the sensor as they would be placed in different spaces.

This helps reveal more about the network at a distance that a sensor can not see, ie a Sensors channel usage may be missing a hidden node that is seen by the AP.

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