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Cisco Wireless Controller Configuration Guide, Release 8.1

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Book Title

Cisco Wireless Controller Configuration Guide, Release 8.1

Chapter Title

Cisco Air Time Fairness

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Updated:
December 14, 2015

Chapter: Cisco Air Time Fairness

Cisco Air Time Fairness

Information About Cisco Air Time Fairness

Cisco Air Time Fairness (ATF) for High Density Experience (HDX) allows network administrators to group devices of a defined category and enables some groups to receive traffic from the WLAN more frequently than other groups. Therefore, some groups are entitled to more air time than other groups.

Cisco ATF has the following capabilities:

  • Allocates Wi-Fi air time for user groups or device categories

  • Air time fairness is defined by the network administrator and not by the network

  • Provides a simplified mechanism for allocating air time

  • Dynamically adapts to changing conditions in a WLAN

  • Enables a more efficient fulfillment of service-level agreements

  • Augments standards-based Wi-Fi QoS mechanisms

By enabling network administrators to define what fairness means within their environments with regard to the amount of on air time per client group, the amount of traffic is also controlled.

To control air time on a percentage basis, the air time, which includes both uplink and downlink transmissions of a client/SSID, is continuously measured.

Only air time in the downlink direction, that is AP to client, can be controlled accurately by the AP. Although air time in the uplink direction, that is client to AP, can be measured, it cannot be strictly controlled. Although the AP can constrain air time for packets that it sends to clients, the AP can only measure air time for packets that it hears from clients because it cannot strictly limit their air time.

Cisco ATF establishes air time limits (defined as a percentage of total air time) and to apply those limits on a per SSID basis, where the SSID is used as a parameter to define a client group. Other parameters can be used as well to define groups of clients. Furthermore, a single air time limit (defined as a percentage of total air time) can be applied to individual clients.

If the air time limit for an SSID (or client) is exceeded, the packets that are in the downlink direction are dropped. Dropping downlink packets (AP to client) frees up air time whereas dropping uplink packets (client to AP) does not do anything to free up air time because the packet has already been transmitted over the air by the client.

Supported Access Point Platforms

Cisco ATF is supported on the following access points:

  • Cisco Aironet 1260 Series Access Points

  • Cisco Aironet 1260 Series Access Points

  • Cisco Aironet 1570 Series Access Points

  • Cisco Aironet 1700 Series Access Points

  • Cisco Aironet 2600 Series Access Points

  • Cisco Aironet 2700 Series Access Points

  • Cisco Aironet 3500 Series Access Points

  • Cisco Aironet 3600 Series Access Points

  • Cisco Aironet 3700 Series Access Points


Note
Cisco ATF is supported only on Local and FlexConnect mode APs.

Cisco ATF Modes

Cisco ATF operates in the following modes:
  • Monitor mode in which users can do the following:

    • View the air time

    • Report air time usage for all AP transmissions

    • View reports

      • per SSID/WLAN

      • per AP Group

      • per AP

    • Report air time usage at periodic intervals

    • Block ACKs are not reported

    • No enforcement as part of Monitor mode

  • Enforce Policy mode in which users can do the following:

    • Enforce air time based on configured policy

    • Enforce air time on

      • a WLAN

      • All APs connected within a Cisco WLC's network

      • an AP group

      • an AP

    • An AP can have multiple WLANs with multiple policies (1:16)

    • Strict Enforcement per WLAN—Air time used by the WLANs on a radio is strictly enforced up to the configured limits in the policies

    • Optimal Enforcement per WLAN—Share unused air time from other SSIDs

    • The sum of all policies should amount to 100 percent; there can be no oversubscription.

Restrictions on Cisco Air Time Fairness

  • ATF can be implemented only on data frames that are in the downstream direction.

  • When ATF is configured in per-SSID mode, all of the WLANs must be disabled before you can enter any ATF configuration commands. The WLANs can be enabled after all of the ATF commands have been entered.

Cisco Air Time Fairness (ATF) Use Cases

Public Hotspots (Stadium/Airport/Convention Center/Other)

In this instance a public network is sharing a WLAN between two (or more) service providers and the venue. Subscribers to each service provider can be grouped and each group can be allocated a certain percentage of air time.

Education

In this instance, a university is sharing a WLAN between students, faculty, and guests. The guest network can be further partitioned by service provider. Each group can be assigned a certain percentage of air time.

Enterprise/Hospitality/Retail

In this instance, the venue is sharing a WLAN between employees and guests. The guest network can be further partitioned by service provider. The guests could be sub-grouped by tier of service type with each subgroup being assigned a certain percentage of air time, for example a paid group is entitled to more air time than the free group.

Time Shared Managed Hotspot

In this instance, the business entity managing the hotspot, such as a service provider or an enterprise, can allocate and subsequently lease air time to other business entities.

The following are the high-level steps to configure Cisco ATF:

  1. Enable Monitor mode to determine network usage (optional)

  2. Create Cisco ATF policies

  3. Add WLAN ATF policies per network, AP group, or AP. Policies set in AP or AP group override per network polices.

  4. Determine if optimization should be enabled.

  5. Periodically check Cisco ATF statistics.

Configuring Cisco Air Time Fairness (GUI)

Configuring Cisco ATF Monitor Mode (GUI)

    Step 1   Choose Wireless > ATF > Monitor Configuration.
    Step 2   On the ATF Monitor Mode Configuration page, choose an AP, AP group, or an entire network. If you choose the entire network, specify the radio type(s).
    Step 3   Click Enable.
    Step 4   Save the configuration.

    Configuring Cisco ATF Policy (GUI)

      Step 1   Choose Wireless > ATF > Policy Configuration.
      Step 2   On the ATF Policy Configuration page, specify an ID, name, and a weight to the ATF policy, and click Create.

      Weighted ratio is used instead of percentages so that the total can exceed 100. The minimum weight that you can set is 10.

      Step 3   Save the configuration.

      Configuring Cisco ATF Enforcement SSID (GUI)

        Step 1   Choose Wireless > ATF > Enforcement SSID Configuration.
        Step 2   On the ATF Enforcement SSID Configuration page, apply the ATF policy created to an AP, an AP group, or the entire network with the radio type specified.
        Step 3   Choose the enforcement type as either Optimized or Strict.
        Step 4   Click Enable.
        Step 5   Enforce an ATF policy on a WLAN by selecting the WLAN and the ATF policy and clicking Add.
        Step 6   Save the configuration.

        Monitoring ATF Statistics (GUI)

        To monitor per WLAN per AP ATF statistics with percentage of used time, choose Wireless > ATF > ATF Statistics. Select the AP name in the drop-down list to view the statistics.

        • abs—Number of air time units being used per SSID

        • Relative Time—Percentage of time used per SSID

        • Total Air time—Total air time used per SSID


        Configuring Cisco Air Tme Fairness (CLI)

        • Configure Cisco ATF at the network level (global) by entering these commands:

          • config atf 802.11{a | b} mode disable
          • config atf 802.11{a | b} mode monitor
          • config atf 802.11{a | b} mode enforce-policy
          • config atf 802.11{a | b} optimization {enable | disable}

        • Configure Cisco ATF on a per AP group basis by entering these commands:

          • config wlan apgroup atf 802.11{a | b} mode disable ap-group-name
          • config wlan apgroup atf 802.11{a | b} mode monitor ap-group-name
          • config wlan apgroup atf 802.11{a | b} mode enforce-policy ap-group-name
          • config wlan apgroup atf 802.11{a | b} optimization {enable | disable} ap-group-name

        • Configure Cisco ATF on a per AP radio basis by entering these commands:

          • config ap atf 802.11{a | b} mode disable ap-name
          • config ap atf 802.11{a | b} mode monitor ap-name
          • config ap atf 802.11{a | b} mode enforce-policy ap-name
          • config ap atf 802.11{a | b} optimization {enable | disable} ap-name

        • Configure ATF policies by entering these commands:

          • config atf policy create policy-id policy-name policy-weight
          • config atf policy modify policy-id policy-name policy-weight
          • config atf policy delete policy-name

        • Configure WLAN with a policy ID by entering this command:

          • config wlan atf wlan-id policy policy-id

        • Configure AP group-level override for Cisco ATF policy on a WLAN by entering these commands:

          • config wlan apgroup atf 802.11{a | b} policy ap-group-name wlan-id policy-name override {enable | disable}

        • Configure AP-level override for Cisco ATF policy on a WLAN by entering these commands:

          • config ap atf 802.11{a | b} policy wlan-id policy-name ap-name override {enable | disable}

        • Monitor Cisco ATF configurations by entering these commands:

          • show atf config all
          • show atf config ap-name ap-name
          • show atf config apgroup ap-group-name
          • show atf config 802.11{a | b}
          • show atf config policy
          • show atf config wlan
          • show atf statistics ap ap-name 802.11{a | b} summary
          • show atf statistics ap ap-name 802.11{a | b} wlan wlan-id
          • show atf statistics ap ap-name 802.11{a | b} policy policy-name

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