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Network Working Group                                            C. Shao
Internet-Draft                                                   H. Deng
Intended status: Informational                              China Mobile
Expires: August 22, 2013                                         F. Bari
                                                                    AT&T
                                                                R. Zhang
                                                           China Telecom
                                                           S. Matsushima
                                                        SoftBank Telecom
                                                       February 18, 2013


                      Hybrid-MAC Model for CAPWAP
                 draft-shao-opsawg-capwap-hybridmac-00

Abstract

   The CAPWAP protocol supports two modes of operation: Split and Local
   MAC (medium access control), which has been described in
   [RFC5415].There are many functions in IEEE 802l.11 MAC layer that
   have not yet been clearly defined whether they belong to either the
   AP (Access Point) or the AC (Access Controller)in the Split and Local
   modes.  Because different vendors have their own definition of these
   two models, depending upon the vendor many MAC layer functions
   continue to be mapped differently to either the AP or AC.  If there
   is no clear definition of split MAC and local MAC, then operators
   will not only need to perform vendor specific configurations in their
   network but will continue to experience difficulty in interoperating
   APs and ACs from different vendors.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 22, 2013.

Copyright Notice



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   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions used in this document . . . . . . . . . . . . . . . 3
   3.  The difference between Local MAC and Split MAC  . . . . . . . . 3
   4.  Functions in Local MAC and Split MAC  . . . . . . . . . . . . . 4
   5.  Hybrid-MAC model recommendation . . . . . . . . . . . . . . . . 5
   6.  Hybrid-MAC model Frames Exchange  . . . . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   10. Normative References  . . . . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8
























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1.  Introduction

   The CAPWAP protocol supports two modes of operation: Split and Local
   MAC (medium access control), which has been described in [RFC5415].In
   Split MAC mode, all L2 wireless data and management frames are
   encapsulated via the CAPWAP protocol and exchanged between the AC and
   the AP.  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 AP performs the 802.11 Integration function.
   Unfortunately, there are many functions that have not yet been
   clearly defined whether they belong to either the AP or the AC in the
   Split and Local modes.  Because different vendors have their own
   definition of the two models, many MAC layer functions are mapped
   differently to either the AP or the AC by different vendors.
   Therefore, depending upon the vendor, the operators in their
   deployments have to perform different configurations based on
   implementation of the two modes by their vendor.  If there is no
   clear definition of split MAC and local MAC, then operators will
   continue to experience difficulty in interoperating APs and ACs from
   different vendors.


2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


3.  The difference between Local MAC and Split MAC

   The main difference between Local MAC and Split MAC lies in the
   processing of the wireless frames.  This is shown in Figure 1 where
   depending upon the mode, either the AP or the AC performs the 802.11
   Integration function.  According to the 802.11 protocol definition,
   the 802.11 wireless frame is divided into three kinds of frames,
   including wireless control frames, wireless management frames, and
   wireless data frames.

   WWireless control frames, such as TS, CTS, ACK, PS-POLL, etc., are
   processed locally by AP in both Local MAC and Split MAC.  However,
   wireless management frames, including Beacon, Probe, Association,
   Authentication, are processed differently in the Local MAC and the
   Split MAC.  In the Local MAC, depending upon the vendor wireless
   management frames can be processed in the AP or the AC.  In the case
   of Split MAC, the real-time part of wireless frames are processed in
   AP, while the non-real-time frames are processed in the AC.  This is
   shown in Figure 2.  In Split MAC mode, the wireless data frames



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   received from a mobile device are directly encapsulated by the AP and
   forwarded to the AC.  The Local MAC mode of operation allows data
   frames to be processed locally by the AP and then forwarded to the
   AC.


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Local MAC          |              Split MAC        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |               |   802.3 MAC    |              |
   +   802.3 MAC   +       AC      +-+-+-+-+-+-+-+-+-      AC      +
   |               |               | 802.11MAC NonRT|              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   802.11 MAC  |               | 802.11 MAC RT  |              |
   +-+-+-+-+-+-+-+-+       AP      +-+-+-+-+-+-+-+-+-      AP      +
   |   802.11 PHY  |               |   802.11 PHY   |              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



         Figure 1: The comparison between Local MAC and Split MAC


4.  Functions in Local MAC and Split MAC

   As shown in Figure 2, main functions are processed in different
   places in the Local MAC and Split MAC.  In addition, for some
   functions (for example, the Frag. / Defrag.  Assoc. / Disassoc /
   Reassoc., Etc.) the protocol does not explicitly map processing of
   such functions to the AP or the AC.  Therefore the location of these
   features becomes vendor specific and this increases the difficulty of
   interoperability between APs and ACs from different vendors.



















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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions describe         | Loacal MAC| Split MAC |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Distribution Service     |  AP/AC    |     AC    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Integration Service      |   AP      |     AC    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Beacon Generation        |   AP      |     AP    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Probe Response Generation|   AP      |     AP    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Function    |Power Mgmt               |   AP      |     AP    |
   +             |/Packet Buffering        |           |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Fragmentation            |   AP      |     AP/AC |
   +             |/Defragmentation         |           |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Assoc/Disassoc/Reassoc   |  AP/AC    |     AC    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Classifying              |   AP      |     AC    |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   AP      |     AP/AC |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   AP      |     AP    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EAP          |   AC      |     AC    |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AP      |     AC    |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   AP      |     AP/AC |
   +             |Encryption/Decryption    |           |           |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 2: Functions in Local MAC and Split MAC


5.  Hybrid-MAC model recommendation

   As discussed above, if the functions have been clearly defined to be
   implemented in AP or AC, the interoperability will be much better
   between different vendors products.  To achieve this goal a common
   Hybrid-MAC model, as shown in Figure 3, is proposed.








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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions describe         | Hybrid-MAC|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Distribution Service     |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Integration Service      |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Beacon Generation        |   AP      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Probe Response Generation|   AP      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Function    |Power Mgmt               |   AP      |
   +             |/Packet Buffering        |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Fragmentation            |   AC      |
   +             |/Defragmentation         |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Assoc/Disassoc/Reassoc   |   AC      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Classifying              |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   AP      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   AP      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EAP          |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AC      |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   AP      |
   +             |Encryption/Decryption    |           |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 3: Functions in Hybrid MAC


6.  Hybrid-MAC model Frames Exchange

   An example of frame exchange using the proposed Hybrid-MAC Model
   shown in Figure 4.










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+-+-+-+-+-+-+               +-+-+-+-+-+                    +-+-+-+-+-+-+
|    STA    |               |    AP   |                    |    AC     |
+-+-+-+-+-+-+               +-+-+-+-+-+                    +-+-+-+-+-+-+
      |                          |                               |
      |        Beacon            |                               |
      |<-------------------------|                               |
      |        Probe             |                               |
      |<------------------------>|                               |
      |              802.11 AUTH/Association                     |
      |<-------------------------------------------------------->|
      |                          |Station Configuration Request [|
      |                        Add Station (Station MAC Address),|
      |                        IEEE 802.11 Add Station (WLAN ID),|
      |                        IEEE 802.11 Session Key(Flag=A)]  |
      |                          |<------------------------------|
      |                          |                               |
      |                          |Station Configuration Response |
      |                          |------------------------------>|
      |       802.1X Authentication & 802.11 Key Exchange        |
      |<-------------------------------------------------------->|
      |                          |Station Configuration Request [|
      |                        Add Station (Station MAC Address),|
      |                        IEEE 802.11 Add Station (WLAN ID),|
      |                        IEEE 802.11 Station Session Key]  |
      |                          |<------------------------------|
      |                          |                               |
      |                          |Station Configuration Response |
      |                          |------------------------------>|
      |                 802.11 Action Frames                     |
      |<-------------------------------------------------------->|
      |                DATA Frame Exchange                       |
      |    802.11 Data           |       802.11 or 802.3 Data    |
      |<-------------------------+------------------------------>|


                Figure 4: Hybrid-MAC model Frames Exchange


7.  Security Considerations

   TBD


8.  IANA Considerations

   None





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9.  Contributors

   Naibao Zhou zhounaibao@chinamobile.com


10.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4564]  Govindan, S., Cheng, H., Yao, ZH., Zhou, WH., and L. Yang,
              "Objectives for Control and Provisioning of Wireless
              Access Points (CAPWAP)", RFC 4564, July 2006.

   [RFC5415]  Calhoun, P., Montemurro, M., and D. Stanley, "Control And
              Provisioning of Wireless Access Points (CAPWAP) Protocol
              Specification", RFC 5415, March 2009.


Authors' Addresses

   Chunju Shao
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  100053
   China

   Email: shaochunju@chinamobile.com


   Hui Deng
   China Mobile
   No.32 Xuanwumen West Street
   Beijing  100053
   China

   Email: denghui@chinamobile.com


   Farooq Bari
   AT&T
   7277 164th Ave NE
   Redmond WA 98052
   USA

   Email: farooq.bari@att.com





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   Rong Zhang
   China Telecom
   No.109 Zhongshandadao avenue
   Tianhe District,
   Guangzhou  510630
   China

   Email: zhangr@gsta.com


   Satoru Matsushima
   SoftBank Telecom
   1-9-1 Higashi-Shinbashi, Munato-ku
   Tokyo
   Japan

   Email: satoru.matsushima@g.softbank.co.jp


































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