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Wireless QoS and Fast Lane

Meraki MR access points feature enterprise-class QoS, which is important to support real-time applications. Most enterprise networks already enforce QoS by utilizing standards like differentiated services on the switching network. Differentiated services (DiffServ) standardizes the Ethernet frame marking protocol in which Ethernet switches make queuing decisions on a per frame basis. 

Wireless networks use a standard called Wireless Multi Media (WMM) for QoS which shares some concepts with DiffServ. WMM provides four different traffic classes: Voice, video, best effort, and background. Devices that support WMM and request a higher level of service, such as Wi-Fi handsets, will receive higher priority on the Meraki wireless network. 

Wireless queuing is implemented using airtime backoff timers called EDCA - Cisco Meraki Access Points use the latest 802.11-2016 EDCA standard as detailed below.

WMM Power Save allows devices to “sleep” differently when they receive critical vs. non-critical packets. Devices that support WMM Power Save should experience extended battery life when using a Meraki network.

All 802.11ac-capable Meraki APs support WMM Power Save, but some legacy APs do not support the feature. Please refer to the AP's datasheet for supported features. 

Fast Lane

Fast Lane is an implementation of all of the QoS features detailed in this article. Cisco + Apple have developed Fast Lane (a mutual agreement in implementation details) for iOS devices with the goal to improve the real-time application experience on enterprise networks. Meraki MR Access Points, in combination with a wireless profile installed on the iOS device, will enable the Fast Lane technologies. The fastest way to install a wireless profile on an iOS device is via Meraki EMM

Traffic Shaping Rules

Meraki MR Access Points feature a layer 3/7 traffic shaping feature which can identify traffic based on layer 3 or layer 7 signatures and enforce QoS. This feature is very useful for applications that do not apply the proper DSCP value. Rules can be configured in Dashboard on the Configure > Firewall and Traffic shaping page in order to overwrite or enforce custom DSCP and WMM QoS. 

Please refer to our documentation regarding Traffic Shaping and Bandwidth shaping for more details. 

Default Downstream QoS

Wireless APs are tasked with mapping Ethernet DiffServ values to WMM access categories. The standards bodies of IETF (designed DiffServe) and IEEE (designed WMM) did not align to a common QoS mapping for applications and queuing. Cisco is instrumental in determining correct QoS behaviors, markings, and practices, for the entire industry in RFC-4594, RFC-2474, and Guidelines for DiffServ to IEEE 802.11 Mapping. Meraki MR access points honor the mapping defined in Guidelines for DiffServ to IEEE 802.11 Mapping.

Below is a highlight of some of the most relevant traffic and their respective markings:

RFC 4594-Based Model

802.3 DSCP 802.3 DSCP [Decimal]

IEEE 802.11 Model [802.11e WMM-AC]

Voice + DSCP-Admit

EF + 44

46

Voice AC (AC_VO)

Broadcast Video

CS5 24 Video AC (AC_VI)

Multimedia Conferencing

AF4n 34, 36, 38 Video AC  (AC_VI)
Realtime Interactive CS4 32 Video AC (AC_VI)
Multimedia Streaming AF3n 26, 28, 30 Video AC  (AC_VI)
Signaling CS3 40 Video AC  (AC_VI)
Transactional Data AF2n 18, 20, 22 Best Effort AC (AC_BE)
OAM CS2 16 Best Effort AC (AC_BE)
Bulk Data AF1n 10, 12, 14 Background AC (AC_BK)
Scavenger CS1 8 Background AC  (AC_BK)
Best Effort DF 0 Best Effort AC  (AC_BE)

* n as used in place for the drop indication of assured forwarding matches values 1-3.  

Default Upstream QoS

Meraki Access Points honor all upstream QoS sent by the client. Clients have defaults for WMM AC and the DiffServ value for different traffic classes. Please refer to vendor documentation for more details on QoS specifics for traffic sent by the client. The DiffServ field within Ethernet traffic sent from the client will be maintained when the AP forwards it onto the Ethernet network. 

Fast Lane gives controls to administrators on what QoS they opt to employ. Refer to the Fast Lane section of this article for more details. 

Many Ethernet switches have a default configuration that does not honor ingress DSCP markings. Ensure that switchports used as uplinks for MRs are set to trust DSCP.  

Queuing on Meraki MR Access Points

Access points have a queue for each WMM access category on a per-client basis. When transmitting a frame, the Meraki APs use the following EDCA Transmit opportunity values:

These values are also included in beacons which advertise these values to associated clients. The EDCA transmit opportunity defines backoff timers for each traffic class which prioritizes traffic based on airtime. 

Additional Resources

For information regarding QoS on MS switches, please refer to our documentation on MS Switch Quality of Service

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Last modified
21:19, 13 Oct 2017

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