802.11r MAC Functions 
=========================


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        **What is the role of the MAC layer in 802.11r?**

        The MAC layer manages fast transitions between access points by coordinating authentication and key management for seamless roaming.

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        **How does MAC handle fast BSS transitions in 802.11r?**

        It uses Fast Transition (FT) protocols to pre-authenticate with target APs and cache keys to reduce handoff latency.

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        **What MAC frames are introduced by 802.11r?**

        802.11r introduces FT Action frames used for exchanging mobility domain and fast transition information between stations and APs.

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        **How does the MAC layer support key caching in 802.11r?**

        The MAC layer caches PMK (Pairwise Master Key) and PTK (Pairwise Transient Key) to quickly resume security contexts during roaming.

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        **What is the Mobility Domain Identifier in MAC?**

        It is a unique identifier included in MAC frames to define a group of APs where fast transitions are allowed.

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        **How does the MAC layer coordinate pre-authentication?**

        The MAC layer sends FT Action frames to the target AP for pre-authentication before the client roams.

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        **What is the role of the MAC sublayer management entities in 802.11r?**

        They manage the fast transition state machine, triggering handoffs and managing security contexts during roaming.

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        **Does 802.11r change the MAC authentication process?**

        Yes, it streamlines authentication by enabling fast reauthentication and key establishment via FT.

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        **How are MAC timings affected by 802.11r?**

        802.11r reduces MAC timing delays during handoff by minimizing message exchanges needed for authentication.

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        **What MAC frame exchanges are involved in FT?**

        Key exchanges include FT Authentication Request and Response frames carrying mobility and security parameters.

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        **How does the MAC layer handle roaming decision signaling in 802.11r?**

        It uses FT Action frames to notify target APs and coordinate seamless transitions.

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        **Are MAC layer encryption methods impacted by 802.11r?**

        No, 802.11r maintains standard encryption methods but optimizes key distribution for fast roaming.

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        **How does the MAC layer ensure security during fast transitions?**

        It uses FT Key Hierarchy and secure FT message exchanges to protect against replay and man-in-the-middle attacks.

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        **What is the MAC layer’s role in managing the PMK cache?**

        It stores and retrieves PMKs associated with APs in the mobility domain to speed up handoffs.

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        **How does MAC interact with the PHY during fast transitions?**

        MAC coordinates with PHY to switch channels and maintain timing synchronization during roaming.

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        **Does 802.11r affect the MAC’s management of power saving?**

        802.11r can impact power saving by requiring quick channel switches, but mechanisms exist to minimize power consumption.

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        **How does the MAC layer handle coexistence with legacy devices in 802.11r?**

        It falls back to standard roaming for legacy devices while enabling fast roaming only for 802.11r-capable clients.

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        **Are there any new MAC timing parameters introduced in 802.11r?**

        Yes, 802.11r defines specific timing requirements for FT message exchanges to ensure minimal handoff delays.

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        **How does the MAC layer handle FT reassociation?**

        It uses FT Reassociation Request/Response frames to finalize the fast transition after pre-authentication.

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        Topics in this section,

                * :ref:`Reference links <802_11r_mac_functions_step17>`


.. _802_11r_mac_functions_step17:

.. tab-set::

    .. tab-item:: Reference links

       * Reference links