Configures the WLAN traffic rate limits using the WLAN QoS policy
Excessive traffic causes performance issues or brings down the network entirely. Excessive traffic can be caused by numerous sources including network loops, faulty devices or malicious software such as a worm or virus that has infected one or more devices at the branch. Rate limiting limits the maximum rate sent to or received from the wireless network (and WLAN) per wireless client. It prevents any single user from overwhelming the wireless network. It can also provide differential service for service providers. The uplink and downlink rate limits are usually configured on a RADIUS server using vendor specific attributes. Rate limits are extracted from the RADIUS server‘s response. When such attributes are not present, settings defined on the controller (access point, wireless controller, or service platform) are applied. An administrator can set separate QoS rate limits for upstream (data transmitted from the managed network) and downstream (data transmitted to the managed network).
Before defining rate limit thresholds for WLAN upstream and downstream traffic, it is recommended that you define the normal number of ARP, broadcast, multicast and unknown unicast packets that typically transmit and receive from each supported WMM access category. If thresholds are defined too low, normal network traffic (required by end-user devices) are dropped resulting in intermittent outages and performance problems.
Connected wireless clients can also have QoS rate limit settings defined in both the upstream and downstream direction.
rate-limit [client|wlan] [from-air|to-air]
{max-burst-size|rate|red-threshold}
rate-limit [client|wlan] [from-air|to-air] {max-burst-size <2-1024>|
rate <50-1000000>}
rate-limit [client|wlan] [from-air|to-air]
{red-threshold [background <0-100>| best-effort <0-100>|video <0-100>|
voice <0-100>]}
rate-limit [client|wlan] [from-air|to-air] {max-burst-size <2-1024>|
rate <50-1000000>}
|
rate-limit |
Configures traffic rate limit parameters |
|
client |
Configures traffic rate limiting parameters on a per-client basis |
|
wlan |
Configures traffic rate limiting parameters on a per-WLAN basis |
|
from-air |
Configures traffic rate limiting from a wireless client to the network |
|
to-air |
Configures the traffic rate limit from the network to a wireless client |
|
max-burst-size <2-1024> |
Optional. Sets the maximum burst size from 2 - 1024 kbytes. The chances of the upstream or downstream packet transmission getting congested for the WLAN's client destination are reduced for smaller burst sizes. The default for WLAN Rate Limit is 320 kbytes. The default for Client Rate limit is 64 kbytes. Note: Smaller the burst, lesser are the chances of upstream packet transmission resulting in congestion for the WLAN's client destinations. By trending the typical number of ARP, broadcast, multicast and unknown unicast packets over a period of time, the average rate for each access category can be obtained. Once a baseline is obtained, administrators should then add a 10% margin (minimally) to allow for traffic bursts at the site. |
|
rate <50-1000000> |
Optional. Sets the traffic rate from 50 - 1000000 kbps. This limit is the threshold value for the maximum number of packets received or transmitted over the WLAN from all access categories. Any traffic that exceeds the specified rate is dropped and a log message is generated. The default is 5000 kbps. |
rate-limit [client|wlan] [from-air|to-air]
{red-threshold [background <0-100>| best-effort <0-100>|video <0-100>|
voice <0-100>]}
|
rate-limit |
Configures traffic rate limit parameters |
|
client |
Configures traffic rate limiting parameters on a per-client basis |
|
wlan |
Configures traffic rate limiting parameters on a per-WLAN basis |
|
from-air |
Configures traffic rate limiting from a wireless client to the network |
|
to-air |
Configures the traffic rate limit from the network to a wireless client |
|
red-threshold |
Configures random early detection threshold values for a designated traffic class |
|
background <0-100> |
The following is common to the ‘from-air' and ‘to-air' parameters: Optional. Sets a percentage value for background traffic in the upstream or downstream direction. Background traffic exceeding the defined threshold is dropped and a log message is generated. The default threshold is 50% for traffic in both directions. |
|
best-effort <0-100> |
The following is common to the ‘from-air' and ‘to-air' parameters: Optional. Sets a percentage value for best effort traffic in the upstream or downstream direction. Best effort traffic exceeding the defined threshold is dropped and a log message is generated. The default threshold is 50% for traffic in both directions. |
|
video <0-100> |
The following is common to the ‘from-air' and ‘to-air' parameters: Optional. Sets a percentage value for video traffic in the upstream or downstream direction. Video traffic exceeding the defined threshold is dropped and a log message is generated. The default threshold is 25% fro traffic in both directions. |
|
voice <0-100> |
The following is common to the ‘from-air' and ‘to-air' parameters: Optional. Sets a percentage value for voice traffic in the upstream or downstream direction. Voice traffic exceeding the defined threshold is dropped and a log message is generated. The default threshold is 0% for traffic in both directions. 0% means no early random drops will occur. |
The following information should be taken into account when configuring rate limits:
Background traffic consumes the least bandwidth of any access category, so this value can be set to a lower value once a general downstream rate is known by the network administrator (using a time trend analysis).
Best effort traffic consumes little bandwidth, so this value can be set to a lower value once a general upstream rate is known by the network administrator (using a time trend analysis).
Video traffic consumes significant bandwidth, so this value can be set to a higher value once a general upstream rate is known by the network administrator (using a time trend analysis).
Voice applications consume significant bandwidth, so this value can be set to a higher value once a general upstream rate is known by the network administrator (using a time trend analysis).
nx9500-6C8809(config-wlan-qos-test)#rate-limit wlan from-air max-burst-size 6
nx9500-6C8809(config-wlan-qos-test)#rate-limit wlan from-air rate 55
nx9500-6C8809(config-wlan-qos-test)#rate-limit wlan from-air red-threshold best-effort 10
nx9500-6C8809(config-wlan-qos-test)#rate-limit client from-air red-threshold background 3
nx9500-6C8809(config-wlan-qos-test)#show context wlan-qos-policy test classification non-wmm video multicast-mask primary 11-22-33-44-55-66/22-33-44-55-66-77 classification non-unicast normal rate-limit wlan from-air rate 55 rate-limit wlan from-air max-burst-size 6 rate-limit wlan from-air red-threshold best-effort 10 rate-limit client from-air red-threshold background 3 qos trust dscp qos trust wmm accelerated-multicast autodetect classification voice nx9500-6C8809(config-wlan-qos-test)#