Subject: [Capwap] Proposed Resolution for Issue 77: Update figure 1 to depict a generic CAPWAP architecture

From: "Pat Calhoun (pacalhou)" <[email-masked]>
Date: Mon, 22 May 2006 07:12:44 -0700

All,

Here is my proposed resolution for the above mentioned issue. While the
original issue submitted included a proposed resolution, it was a
combined figure that attempted to show all possible modes of operation,
which I found confusing. Instead, I prefer to have a separate figure
(and text) to discuss local MAC.

Comments appreciated.

1.  Introduction
[...]

   CAPWAP assumes a network configuration consisting of multiple WTPs
   communicating via the Internet Protocol (IP) to an AC.  WTPs are
   viewed as remote RF interfaces controlled by the AC.  The CAPWAP
   protocol supports two modes of operation: split and local MAC.  The
   Split MAC mode is one where all L2 wireless data and management
   frames are encapsulated via the CAPWAP protocol and exchanged between
   the AC and the WTP.  In the example of 802.11, as shown in Figure 1,
   the 802.11 frames received from a mobile node (STA) are directly
   encapsulated by the WTP and forwarded to the AC.

              +-+         802.11 frames          +-+
              | |--------------------------------| |
              | |              +-+               | |
              | |--------------| |---------------| |
              | |  802.11 PHY/ | |     CAPWAP    | |
              | | MAC sublayer | |               | |
              +-+              +-+               +-+
              STA              WTP                AC

   Figure 1: Representative CAPWAP Architecture for Split MAC

   The Local MAC mode of operation diffs from Split MAC as it 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 bridging
   function.  In either case, however, the management frames are
   processed locally by the WTP, and then forwarded to the AC.  Figure 2
   provides an example using the IEEE 802.11 binding, where a station
   transmits an 802.11 frame, which is encapsulated as 802.3 and
   forwarded to the AC.

              +-+ 802.11 frames +-+ 802.3 frames +-+
              | |---------------| |--------------| |
              | |               | |              | |
              | |---------------| |--------------| |
              | |  802.11 PHY/  | |     CAPWAP   | |
              | | MAC sublayer  | |              | |
              +-+               +-+              +-+
              STA               WTP               AC

   Figure 2: Representative CAPWAP Architecture for Local MAC
[...]

Pat Calhoun
CTO, Wireless Networking Business Unit
Cisco Systems
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From: "Dorothy Stanley" <[email-masked]>
Date: Wed, 24 May 2006 08:26:47 -0700

Pat,

Overall - Fine by me also, a couple of suggested edits:

Change "split and local MAC" to "Split and Local MAC"
Change "The Split MAC mode is one where" to "In Split MAC Mode"

Below Figure 1, delete "diffs from Split MAC as it"

Change "In either case, however, the management frames are
   processed locally by the WTP"

to
In either case, the L2 wireless management frames are
   processed locally by the WTP"

Dorothy