local mac和split mac

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CAPWAP协议支持Split和Local MAC两种操作模式。Split MAC模式中，所有L2无线数据和管理帧通过CAPWAP协议在AC和WTP间交换。Local MAC模式允许数据帧被本地桥接或隧道化为802.3帧。两种模式下，无线管理帧均由WTP本地处理后转发给AC，但数据帧处理方式不同，影响了无线网络的管理和控制。

阅读RFC 5415，关于split mac和 local mac的描述如下：

The CAPWAP protocol supports two modes of operation: Split and Local MAC (medium access control).

In Split MAC mode, all L2 wireless data and management frames are encapsulated via the CAPWAP protocol and exchanged between the AC and the WTP. As shown in Figure 1, the wireless frames received from a mobile device, which is referred to in this specification as a Station (STA), are directly encapsulated by the WTP and forwarded to the AC.(split mac 方式意味着所有的2层无线数据和管理帧都封装为capwap协议包后在ac与ap之间传送。)

       +-+         wireless frames        +-+
              | |--------------------------------| |
              | |              +-+               | |
              | |--------------| |---------------| |
              | |wireless PHY/ | |     CAPWAP    | |
              | | MAC sublayer | |               | |
              +-+              +-+               +-+
              STA              WTP                AC

Figure 1: Representative CAPWAP Architecture for Split MAC

The Local MAC mode of operation allows for the data frames to be either locally bridged or tunneled as 802.3 frames. The latter implies that the WTP performs the 802.11 Integration function. In either case, the L2 wireless management frames are processed locally by the WTP and then forwarded to the AC. Figure 2 shows the Local MAC mode, in which a station transmits a wireless frame that is encapsulated in an 802.3 frame and forwarded to the AC.（local mac方式下数据帧或者被本地桥接或者作为802.3帧被隧道化传输。后者意味着AP终结了802.11帧。无论是哪一种情况，二层的无线管理帧都被AP本地封装后转发给AC。）

       +-+wireless frames +-+ 802.3 frames +-+
              | |----------------| |--------------| |
              | |                | |              | |
              | |----------------| |--------------| |
              | |wireless PHY/   | |     CAPWAP   | |
              | | MAC sublayer   | |              | |
              +-+                +-+              +-+
              STA                WTP               AC

Figure 2: Representative CAPWAP Architecture for Local MAC

Provisioning WTPs with security credentials and managing which WTPs are authorized to provide service are traditionally handled by proprietary solutions. Allowing these functions to be performed from a centralized AC in an interoperable fashion increases manageability and allows network operators to more tightly control their wireless network infrastructure.

总结：

local mac： 802.11无线管理帧 AP-（capwap）-AC

802.11数据帧 AP 本地桥接（本地转发,AP完成802.11->802.3帧格式转换后发送给路由器）或者capwap 封装802.3帧给AC （集中转发）

split mac：　所有802.11帧（数据帧 + 管理帧） capwap 封装后发送给AC （集中转发，AP进行加解密，capwap封装的802.11帧发送给AC，AC收到后转换为802.3帧后发出；或者集中转发，AC收到capwap封装的802.11帧，加解密之后，转换为802.3的帧后发出）