Configuration Guide for RFMS 3.0 Initial Configuration XXX-XXXXXX-XX WiNG 5.x Feature Guide QoS April, 2011 Revision 1.0
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Table of Contents 1. Overview... 5 1.1 WMM... 5 1.2 Further Considerations... 6 2. Radio QoS Policies... 6 2.1 Creating Radio QoS Policies... 6 2.1.1 Editing Radio QoS Policies... 7 2.1.2 Deleting Radio QoS Policies... 8 2.2 Radio QoS Parameters... 9 2.2.1 WMM Tab... 9 2.2.2 Admission Control Tab... 10 2.2.3 Multimedia Optimizations... 12 2.3 Applying Radio QoS...13 3. WLAN QoS Policies...16 3.1 Creating WLAN QoS Policies...16 3.1.1 Editing WLAN QoS Policies... 18 3.2 WLAN QoS Parameters...19 3.2.1 WLAN WMM Tab... 20 3.2.2 WLAN QoS Rate Limit Tab... 21 3.2.3 WLAN QoS Multimedia Optimizations Tab... 22 3.3 Apply WLAN QoS to the WLAN...24 4. Airtime Fairness...26 4.1 Prefer High-Throughput...26
Index of tables: Table 1 - WMM Access Categories... 5 Table 2 802.1p to 802.11e Mapping... 6 Table 3 - WMM AC Category Parameters... 10 Table 4 - Admission Control Settings... 11 Table 5 - Admission Control Parameters... 12 Table 6 - Accelerated Multicast Parameters... 13 Table 7 - WMM Tab Settings Parameters... 21 Index of CLI Examples: CLI Example 1 - radio qos policies... 6 CLI Example 2 - editing radio qos policies... 7 CLI Example 3 - deleting radio qos policies... 8 CLI Example 4 - radio qos admission control... 11 CLI Example 5 - radio qos master configuration... 11 CLI Example 6 - applying radio qos policies... 13 CLI Example 7 - creating wlan qos policies... 16 CLI Example 8 - editing wlan qos policies... 18 CLI Example 9 - deleting wlan qos policies... 19 CLI Example 10 - wlan accelerated multicast... 24 CLI Example 11 - applying wlan qos... 25 CLI Example 12 - disabling airtime fairness... 26 CLI Example 13 - preference for high-throughput rates... 26 Index of figures: Figure 1 - UI Policy Creation... 7 Figure 2 UI Policy Editing... 8 Figure 3 - UI Deleting Policies... 9 Figure 4 - WMM AC Categories... 10 Figure 5 UI Admission Control Parameters... 12 Figure 6 - Multimedia Optimizations UI... 13 Figure 7 - Applying Radio Policies... 14 Figure 8 - Selecting the desired radio... 15 Figure 9 - Applying the policy... 16 Figure 10 - WLAN QoS Policy Create... 17 Figure 11 - Naming WLAN QoS Policy... 17 Figure 12 - WLAN QoS UI Edit... 18 Figure 13 - Deleting WLAN QoS Policies... 19 Figure 14 - WLAN QoS WMM Tab... 20 Figure 15 - WLAN QoS Rate Limiting... 22 Figure 16 - WLAN QoS Multimedia Optimizations... 23 Figure 17 - WLAN QoS Accelerated Multicast... 24 Figure 18 - Selecting WLAN for QoS... 25 Figure 19 - Select QoS Policy... 26
1. Overview WiNG 5 supports WMM and QoS standards to provide traffic prioritization and scheduling for voice, video and other, less stringent traffic categories. Beyond enabling WMM traffic classifications and general qos support, other features are necessary to provide an optimal experience. Establishing voice admission control, traffic rate limiting and multicast optimizations, especially for video applications may be required in a variety of environments. This paper will discuss these features and explain their part in maximizing client and application communications. 1.1 WMM Though not officially standardized, the Wifi Alliance implementation of Wireless Multimedia extensions (WMM) has become widely accepted as the standard means of providing QoS on 802.11 networks. WMM defines four Access Categories with different levels of prioritization for voice, video, best effort and background traffic types. Access Categories Voice (AC_VO) Video (AC_VI) Best Effort (AC_BE) Background (AC_BK) Table 1 - WMM Access Categories These categories map to the different levels of priority on wired networks as well, so that a consistent level of importance can be maintained on a packet as it traverses the network. So a VoWifi phone conversation can be given the correct level of priority on the wireless medium and transition to the wired medium and on to its destination while maintaining its priority throughout the network. Of course, this is contingent on having QoS established on the LAN as well. Table 1 below shows the mapping relationship between 802.1p traffic categories and WMM access categories: Mapping of 802.11e AC s to 802.1d Class of Service priority levels Priority 802.1p Priority 802.1d Designation Access Category (AC) Lowest 1 BK AC_BK 2 Spare AC_BK 0 BE AC_BE 3 EE AC_BE 4 CL AC_VI 5 VI AC_VI 6 VO AC_VO
Highest 7 NC AC_VO 1.2 Further Considerations Table 2 802.1p to 802.11e Mapping We will contain our discussion to QoS and airtime as it pertains to wireless networks. Simply enabling QoS in and of itself does not necessarily guarantee priority levels. If a wireless network has been oversubscribed, as in a high number of client associations per access point, this can affect resources at the AP before QoS can even come into effect. Another consideration is MU data rates; it may be desirable to give more airtime to clients with faster data rates than for those who hold the network back by transmitting at slower data rates. WiNG 5 s attention to QoS features at the radio and WLAN level, as well as Airtime Fairness, admission control and rate limiting can benefit the WLAN carrying diverse traffic types. Further, special consideration and handling of shared traffic types, such as multicast video make the WiNG 5 network capable of delivering the best, most consistent user experience for time sensitive applications. 2. Radio QoS Policies Radio QoS policies are applied to individual radios within an access point. The policies are applied to radios either through group device profiles or as device overrides and are inherited throughout an RF-Domain as applied. Radio QoS parameters enforce WMM and police the different traffic types at the radio level. Perhaps the most important aspect of configuring these parameters is with regards to Admission Control, which will be detailed in section 2.2. 2.1 Creating Radio QoS Policies Policies are created via the CLI by issuing the radio-qos-policy <policy_name> command. Executing this command creates the policy and enters the configuration context for the policy. However it is not applied to the running-configuration until a commit is issued. Creating Radio QoS Policies rfs4000-22a3ac(config)#radio-qos-policy <radio_qos_policy_name> rfs4000-22a3ac(config-radio-qos-<policy_name>)# CLI Example 1 - radio qos policies The radio qos policies can be created via the WiNG 5.x UI by navigating to Configuration > Wireless > Radio QoS Policy and then clicking Add as shown in table 4. Upon entering the configuration parameter page, enter a name for the policy in the main work space frame.
Configuration > Wireless > Radio QoS Policy 2.1.1 Editing Radio QoS Policies Figure 1 - UI Policy Creation Policies are modified via the CLI by issuing the radio-qos-policy <policy_name> command. Executing this command enters the configuration context for the policy. Editing Radio QoS Policies rfs4000-22a3ac(config)#radio-qos-policy <radio_qos_policy_name> rfs4000-22a3ac(config-radio-qos-<policy_name>)# CLI Example 2 - editing radio qos policies Similarly, the radio qos policies can be modified via the WiNG 5.x UI by navigating to Configuration > Wireless > Radio QoS Policy, selecting the desired policy and then clicking Edit as shown in table 6.
Configuration > Wireless > Radio QoS Policy 2.1.2 Deleting Radio QoS Policies Figure 2 UI Policy Editing Policies are deleted via the CLI using the no option with the radio-qos-policy <policy_name> command. Deleting Radio QoS Policies rfs4000-22a3ac(config)#no radio-qos-policy <radio_qos_policy_name> CLI Example 3 - deleting radio qos policies Within the WiNG 5.x UI this is accomplished simply by navigating to Configuration > Wireless > Radio QoS Policy, selecting the desired policy and then clicking Delete.
Configuration > Wireless > Radio QoS Policy 2.2 Radio QoS Parameters Figure 3 - UI Deleting Policies By default, WiFi Alliance WMM extensions are supported when radio qos policies are enabled on a radio. In order for the policing to be effective, wireless client devices and applications must also support wireless QoS and the LAN infrastructure should have 802.1p or DSCP prioritization enabled as well. 2.2.1 WMM Tab The first tab within the policy configuration relates to the four WMM access categories and the values present will be applied against the individual traffic class queues as those types of traffic are detected.
Radio QoS Policy WMM Tab Figure 4 - WMM AC Categories WMM Access Category Parameters TxOps the amount of time a client is allowed to transmit upon receiving it s opportunity on the medium. Higher priority traffic should have a lower value. Arbitrary Interframe Spacing Number a wait period between frames, based on the specific access category (AC). ECW Min The minimum contention window backoff period. A random value between ECW min and max will be selected. ECW Max The maximum contention window backoff period. A random value between ECW min and max will be selected. Table 3 - WMM AC Category Parameters The default values within the WMM tab will rarely require manipulation. This is the purpose of WMM to take guess work granularity out of configuration. However it is important to understand the various elements. 2.2.2 Admission Control Tab Admission control governs access to the medium, imposing limits on clients for access. By checking the Enable box for each category type, AC is imposed for that category. Thus, each type must be enabled individually if that is what is required. Note that it is not recommended to enable admission control for best effort or background traffic categories. Admission control will most likely come into play on networks supporting voice. Since voice is such a sensitive application, easily degraded by latency, jitter or congestion, it will be necessary to understand how to control the wireless medium in favor of voice traffic for customers.
2.2.2.1 Settings Two important parameters are found under the Settings heading relating to firewall detected traffic and client traffic specifications. See table 7 for details. Admission Control Parameters Enable admission control for firewall detected traffic Implicit TSPEC 2.2.2.2 Voice Admission Control Enables the WiNG 5 firewall Application Layer Gateway (ALG) detection of traffic types and to mark detected packets with the correct WMM AC. Enabled by default when qos policy is applied to the radio. Requires that clients communicate requirements for traffic to be sent by setting the Traffic Specifications within the packets. Clients not specifying or not supporting TSPEC will not receive priority from the radio. Table 4 - Admission Control Settings On wireless networks supporting VoWifi, it is important to enforce Admission Control and to configure the parameters governing subscription and airtime. Examples for CLI and web UI follow. CLI Voice Admission Control rfs4000-22a3ac(config)#radio-qos-policy default rfs4000-22a3ac(config--radio-qos-default)#admission-control voice? max-airtime-percent max-clients max-roamed-clients reserved-for-roam-percent CLI Example 4 - radio qos admission control The options under admission control will not show in the master configuration file unless the default values are modified. However, enabling admission control will show up under the radioqos policy: Radio-QoS Policy - Master Configuration! radio-qos-policy default admission-control voice! CLI Example 5 - radio qos master configuration
Radio QoS Policy Admisson Control Tab Figure 5 UI Admission Control Parameters Voice Admission Control Enable Voice: Enable AC on this radio specifically for voice traffic as determined by WMM extensions or detected by the firewall ALG Max Airtime: Specifies airtime in the form of bandwidth %, up to 150% to accommodate over-subscription. This ensures that radio bandwidth is available for the specified traffic type (shown is voice). Max Wireless Clients: Sets a limit on clients allowed on the radio and is useful to mitigate over-subscription Max Roamed Clients: Setting a hard-limit for supported clients on a radio would be detrimental in roaming environment. Thus, this setting sets a limit for new clients who have roamed to the radio. Reserved for Roam: Sets the % of radio bandwidth allotted to admission control for clients who have roamed. 2.2.3 Multimedia Optimizations Table 5 - Admission Control Parameters Multimedia Optimizations relates to multicast traffic and clients subscribed to multicast streams; this typically is the case with real-time video applications. Accelerated Multicast refers to multicast-to-unicast conversion, which increases the quality of video traffic multicast packets. The parameters within the radio qos-policy work together with those defined in the WLAN qospolicy, which will be covered in a later section. The multicast-to-unicast conversion process is resource intensive, so it should not be performed for an exorbitant number of clients / streams. Additionally, it is only supported for local radios and not for those located remotely. Radio Multimedia Optimizations Max wireless clients allowed: Sets the number of clients allowed for accelerated multicast, or multicast-to-unicast conversion clients. When count exceeds: If the above limit is exceeded, new multicast clients can be rejected (default) or revert can be selected, which will revert back to normal multicast streams. Max multicast streams: Sets the maximum number of multicast streams that can be subscribed to per client. Packets per second: Once a flow is established to a client, the conversion process can be started once a rate threshold is reached.
Timeout for clients: This value, measured in seconds, establishes the timeout period for a client to reaffirm its subscription via IGMP. If the client fails to do so, it will be removed from the list of sessions to optimize. Table 6 - Accelerated Multicast Parameters Radio QoS Policy Multimedia Optimizations Tab 2.3 Applying Radio QoS Figure 6 - Multimedia Optimizations UI Policies are applied at the individual radio and each radio can only have a single policy applied to it, thus 2 per AP. The policies can be applied to profiles (recommended) which then will be automatically inherited by the AP s using the profile. Alternatively, the policies can be applied as device overrides to specific radios individually. For reasons of future management and troubleshooting, device overrides are not recommended. At the command line, execute the following commands on the desired hardware profile or device to enable a policy on a radio: Applying Radio QoS Policies rfs4000-22a3ac(config)#profile ap650 default-ap650 rfs4000-22a3ac(config-profile-default-ap650)#interface radio <n> rfs4000-22a3ac(config-profile-default-ap650-if-radio1)#use radio-qospolicy <radio-qos-policy-name> rfs4000-22a3ac(config-profile-default-ap650-if-radio1)#commit CLI Example 6 - applying radio qos policies Likewise the policy can be applied through the web UI. Navigate to Configuration > Profiles and select the desired profile, then click Edit:
Device Profiles Applying Radio QoS Policies Figure 7 - Applying Radio Policies Once in the desired profile, select Radios, choose the radio you wish to apply the policy to and then click Edit:
Device Profiles Applying Radio QoS Policies Figure 8 - Selecting the desired radio Once the Radios main window appears, select the desired radio qos policy from the drop down, under the Radio Settings tab, then click >>OK:
Device Profiles Applying Radio QoS Policies 3. WLAN QoS Policies Figure 9 - Applying the policy WLAN QoS allows for policing of traffic on the WLAN as a whole and for the clients associated to the WLAN. The WLAN QoS policies are used to specify and manipulate the types of traffic on the WLAN, perform rate-limiting and perform further optimizations on multicast type traffic, such as video streams. 3.1 Creating WLAN QoS Policies Policies are created via the CLI by issuing the wlan-qos-policy <policy_name> command. Executing this command creates the policy and enters the configuration context for the policy. However it is not applied to the running-configuration until a commit is issued. Creating WLAN QoS Policies rfs4000-22a3ac(config)#wlan-qos-policy <wlan_qos_policy_name> rfs4000-22a3ac(config-wlan-qos-<policy_name>)# CLI Example 7 - creating wlan qos policies The wlan qos default policy can be edited or a new one can be created via the WiNG 5.x UI by navigating to Configuration > Wireless > WLAN QoS Policy and then clicking Add as shown
in figure 10. Upon entering the configuration parameter page, enter a name for the policy in the main work space frame and click >>OK to activate the parameter tabs for configuration. WLAN QoS Policy Create in UI Figure 10 - WLAN QoS Policy Create Name the QoS Policy Web UI Figure 11 - Naming WLAN QoS Policy
Once you have clicked the OK button, the WMM tab becomes active and the parameters can be adjusted as necessary. This will be covered in section 3.2. 3.1.1 Editing WLAN QoS Policies Policies are modified via the CLI by issuing the wlan-qos-policy <policy_name> command. Executing this command enters the configuration context for the policy. Editing WLAN QoS Policies rfs4000-22a3ac(config)#wlan-qos-policy <wlan_qos_policy_name> rfs4000-22a3ac(config-wlan-qos-<policy_name>)# CLI Example 8 - editing wlan qos policies Likewise they are edited through the UI by highlighting the target policy and clicking Edit as shown in figure 11: Editing WLAN QoS Policy Web UI Figure 12 - WLAN QoS UI Edit Deleting a WLAN QoS policy via the command line is a simple, 2-step process. Using the no form of the command, remove the policy and then perform a commit to apply to runningconfig.
Deleting WLAN QoS Policies rfs4000-22a3ac(config)#no wlan-qos-policy <wlan_qos_policy_name> rfs4000-22a3ac(config)#commit CLI Example 9 - deleting wlan qos policies Perform this action at the web UI simply by highlighting the desired QoS policy and then clicking on Delete : Deleting WLAN QoS Policy Web UI Figure 13 - Deleting WLAN QoS Policies As with any configuration performed, it will not take effect in the running-config until a commit has been performed. Then clicking on Save will save the configuration to the startup-config. 3.2 WLAN QoS Parameters Once a policy is created and named, the administrator will have access to the WMM, Rate Limiting and Multimedia Optimizations tabs and can customize accordingly.
3.2.1 WLAN WMM Tab Like the Radio QoS WMM screen, this page deals with details for manipulating transmit opportunities and wait periods for WMM classified traffic. The Settings area allows the administrator to specify what type of traffic the WLAN will be comprised of. If it is a mix of clients and support for WMM, then the default of WMM should be accepted. However it is also possible to treat all traffic on the WLAN as a specific category and have the appropriate prioritizations applied. This would be the case if traffic types are being segmented at the network level; i.e. dedicated voice VLAN, data VLAN, etc and WLAN s mapped accordingly. Typically, only the parameters under Settings will be manipulated. WLAN QoS Policy WMM Tab Figure 14 - WLAN QoS WMM Tab
WLAN QoS WMM Tab Settings Area 3.2.2 WLAN QoS Rate Limit Tab Wireless Client Classification implies what type of traffic is expected on the radio. Unless the WLAN is dedicated to a specify client traffic type, leave the default setting of WMM. The Non-Unicast Classification specifies how to categorize non-unicast traffic so the correct prioritization will be applied. Enable Voice Prioritization is for legacy Motorola VOIP phones and will apply voice prioritization to the traffic type. Enable SVP Prioritization is for legacy Polycom VOIP phones utilizing the SVP protocol. Enable WMM Power Save allows for honoring of the unscheduled automatic power save delivery mechanism for QSTA s Enable QBSS Load IE enables the load information element within the QoS BSS frames to inform clients of load. Configure Non WMM Client Traffic specifies how to treat traffic not marked as one of the WMM access category types. Table 7 - WMM Tab Settings Parameters The rate limit tab allows for rate limiting on the WLAN as a whole, as well as imposing limits on the clients specifically. Limiting can be enabled in upstream and / or downstream directions and for one, the other or both directions as desired. First the rate limit function is enabled on the desired direction, the maximum rate is set and then a maximum burst is configured to accommodate traffic bursts that happen when initial traffic sessions are established. The Random Early Detection mechanism is a means of randomizing traffic queues and packet drops among the queues Tail Drop does not occur. Tail Drop happens when queues are full and additional incoming packets are simply dropped. On a congested network where queues are always full, this causes anomalies across the network which RED mitigates. The default settings are typically sufficient and further modification should not be necessary.
WLAN QoS Policy Rate Limit Tab Figure 15 - WLAN QoS Rate Limiting 3.2.3 WLAN QoS Multimedia Optimizations Tab Normally on wireless networks, multicast traffic is buffered until the DTIM period, at which point clients come out of power save mode and check for traffic destined to them that has been buffered at the AP. On WLAN s supporting multimedia applications that also support use of the DTIM period, a primary and secondary multicast mask can be configured, specifying what frames are transmitted immediately without waiting for the DTIM interval. The primary use case for this feature would be video streaming, however since accelerated multicast has been introduced as a new feature, it will likely be the primary method of optimizing video applications.
WLAN QoS Policy Multimedia Optimizations Tab 3.2.3.1 WLAN QoS Accelerated Multicast Figure 16 - WLAN QoS Multimedia Optimizations On networks where multicast packets are being bridged, the Accelerated Multicast area allows for conversion of multicast streams into unicast for overall better utilization and performance. All multicast streams can be automatically detected and converted, or the administrator can specify what streams to convert. This can be especially useful in education markets where real-time video and various testing methods may be delivered over the WLAN or in large global enterprises where company announcements and other training may be delivered in a like manner. The accelerated multicast parameters within the WLAN qos policy work in tandem with the same settings within the radio qos policy.
Completely disabling multicast streaming on the WLAN is option 1. The second option is to automatically detect streams and then apply a classification. By default, the classification given upstream will be inherited or trusted. As another alternative, an administrator may also designate specific destination address ranges and then apply customized classifications for each configured destination. When packets matching the destination are encountered, acceleration (unicast conversion) takes effect. CLI and UI examples follow: Applying WLAN QoS rfs4000-22a3ac(config)#wlan-qos-policy default rfs4000-22a3ac(config-wlan-qos-default)#accelerated-multicast? A.B.C.D configure the multicast address in A.B.C.D Autodetect Let system automatically detect multicast streams rfs4000-22a3ac(config-wlan-qos-default)#accelerated-multicast <mcast- IP-addr> classification video rfs4000-22a3ac(config-wlan-qos-default)#commit CLI Example 10 - wlan accelerated multicast WLAN QoS Policy Accelerated Multicast Figure 17 - WLAN QoS Accelerated Multicast 3.3 Apply WLAN QoS to the WLAN Once the WLAN qos policy has been created, it is simple to apply the policy to a specific WLAN. From the CLI, simply enter WLAN configuration mode and perform the use command as shown below:
Applying WLAN QoS Policies rfs4000-22a3ac(config)#wlan wlan1 rfs4000-22a3ac(config-wlan-wlan1)#use wlan-qos-policy <policy-name> rfs4000-22a3ac(config-wlan-wlan1)#commit CLI Example 11 - applying wlan qos To apply the qos policy through the web UI, navigate to Configuration > Wireless > Wireless LANs, highlight the desired WLAN and click Edit: Applying WLAN QoS Policy Select WLAN Figure 18 - Selecting WLAN for QoS In the main configuration window, select Basic Configuration, and go to the QoS Policy drop down under the WLAN Configuration area as shown below:
Select the QoS Policy under WLAN Configuration 4. Airtime Fairness Figure 19 - Select QoS Policy Airtime Fairness is enabled by default at the radio-level within profiles or individual devices. Turning off AF results in round-robin packet transmission scenario, however it does not mean that all MU s are able to transmit the same number of bytes in a given period. Clients utilizing higher byte-count packets will transmit more than those using smaller packets. Disabling Airtime Fairness rfs4000-22a3ac(config-profile-default-ap650-if-radio)#no airtime-fairness 4.1 Prefer High-Throughput CLI Example 12 - disabling airtime fairness Obviously disabling airtime fairness does not make much sense in an environment where there is voice and video traffic to schedule. But what about giving more airtime to MU s that are transmitting at the higher 802.11n rates? It may often be desirable to establish airtime governed unfairness to give more time to higher-rate clients, allowing them access to the HOV lane of the wireless highway. This is a configurable option, allowing for 1-10 times the airtime as that of slower rate clients. Airtime Un-Fairness rfs4000-22a3ac(config-profile-default-ap650-if-radio)#airtime-fairness prefer-ht weight <n> (where n is a factor of 1-10) CLI Example 13 - preference for high-throughput rates