About QoS

Traditional Quality of Service (QoS) separates client traffic into queues based on traffic type, and schedule the transmission of the traffic based on data rates from the queues. In a WLAN, a slower client (802.11b) uses significantly more airtime to transmit the same amount of data as a faster client (802.11ax). To make airtime access more equitable, Extreme Networks provides airtime-based QoS scheduling. Instead of using just bandwidth in the QoS calculations, APs allocate airtime per client, traffic class, and user profile by dynamically calculating airtime consumption per packet. When multiple client types (802.11a, ac, b, g, n or ax) are active in the same WLAN, all clients receive the same amount of airtime (10 ms for example), regardless of the client type. For example, an 11ax client could send 128 Kbps of traffic in the allocated slot, while an 11b client could only send 50 Kbps, but both clients receive the same amount of airtime.

A visual representation of the difference between bandwidth-based scheduling and airtime-based scheduling when two clients are transmitting at different data rates looks like this:

Dashes ( — ) indicate airtime for frames transmitted at a low data rate.

Bullets ( • ) indicate airtime for frames transmitted at a high data rate.

Bandwidth-based scheduling:

— • — • • — • — — • — • — • — •

Airtime-based scheduling:

— • • • • — • • • • — — — — — —

The faster client might be using 802.11ax and the slower client 802.11 a, b, g, or n, or they might both be using the same protocol, but one is farther away and must use a slower speed than the other.

With bandwidth-based scheduling, both slow and fast clients finish at the same time regardless of their data rates, and they compete the entire time for the air. Because both clients have an equal opportunity to transmit frames, the faster client's throughput slows down to the rate of the slower client.

With airtime-based scheduling, both clients get their proportion of airtime. The faster client finishes four times faster, and the slower client finishes at the same time as it did with bandwidth-based scheduling. The fast client is rewarded, and the slow client is not penalized.

Note

QoS rate control and queuing on routers applies to traffic from the LAN to the WAN, but not the reverse, primarily because there is typically much less bandwidth on the WAN interface than on LAN interfaces. APs apply QoS rate control and queuing to both outbound and inbound traffic. They perform data rate limiting on incoming Ethernet and Wi-Fi interfaces, and they queue packets on outgoing Wi-Fi interfaces. APs do not queue any packets that they send out through their Ethernet interfaces because the Ethernet link is not a point of congestion; however, they do set the 802.1p or DSCP priority in the packet headers as defined in the marker map so that the next-hop router can perform QoS queuing.

The benefits of airtime-based scheduling include:

Multiple-service WLAN infrastructure: When integrated with service-based QoS scheduling in user policies, Dynamic Airtime Scheduling lets you manage the air optimally to support different application types.
Dense deployments: When there are many clients and the air is congested with wireless traffic, airtime-based scheduling ensures that faster clients get off the air faster, reducing the likelihood of collisions and contention among all client traffic.
Sparse or Partial Deployments: When a few clients are spread out at various distances from the AP, airtime-based scheduling prevents fringe or distant clients from slowing down closer, faster clients and allows for phased roll-outs.
Environments with a mixture of 802.11 a/ac/ax/b/g/n clients: When there is a mixed environment with clients using different protocols when connecting to the AP, airtime-based scheduling enables the faster clients to get the benefit of their speed without penalizing the legacy clients.

The Rate Limits table lists the following information:

Name: The name of the user profile in which traffic policing and rate limiting are enabled.
Note
Extreme Networks devices apply airtime-based scheduling to traffic assigned to admin-defined user profiles but not to traffic assigned to a predefined user profile "default-profile". To apply airtime-based scheduled QoS to client traffic, make sure that the SSIDs reference only user profiles that you or another admin created.
Used By: Hover over any number in the Used By column to see the user names of devices that are using this rate limit

You can use the icons above the table to add, modify, or clone rate limits. To delete a rate limit, select the check box for the rate limit and then select the delete icon.