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Versions: (draft-shao-opsawg-capwap-hybridmac) 00 01 02 03 04 05 06 07 08 RFC 7494

Network Working Group                                            C. Shao
Internet-Draft                                                   H. Deng
Intended status: Informational                              China Mobile
Expires: November 10, 2013                                       F. Bari
                                                                    AT&T
                                                                R. Zhang
                                                           China Telecom
                                                           S. Matsushima
                                                        SoftBank Telecom
                                                            May 09, 2013


                      Hybrid-MAC Model for CAPWAP
                 draft-ietf-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
   WTP (Wireless Termination Points) 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 WTP
   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 WTPs 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
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   This Internet-Draft will expire on November 10, 2013.





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Copyright Notice

   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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   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  . . . . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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 WTP.  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.
   Unfortunately, there are many functions that have not yet been
   clearly defined whether they belong to either the WTP 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 WTP 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



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   continue to experience difficulty in interoperating WTPs 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 WTP 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.

   Wireless control frames, such as TS, CTS, ACK, PS-POLL, etc., are
   processed locally by WTP 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 WTP or the AC.  In the case
   of Split MAC, the real-time part of wireless frames are processed in
   WTP, while the non-real-time frames are processed in the AC.  This is
   shown in Figure 1 quoted from [RFC5416].  In Split MAC mode, the
   wireless data frames received from a mobile device are directly
   encapsulated by the WTP and forwarded to the AC.  The Local MAC mode
   of operation allows data frames to be processed locally by the WTP
   and then forwarded to the AC.



















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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Local MAC          |              Split MAC        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |               |   802.3 MAC    |              |
   +   802.3 MAC   +       AC      +-+-+-+-+-+-+-+-+-      AC      +
   |               |               | 802.11MAC NonRT|              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   802.11 MAC  |               | 802.11 MAC RT  |              |
   +-+-+-+-+-+-+-+-+       WTP     +-+-+-+-+-+-+-+-+-      WTP     +
   |   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 quoted from [RFC5416], 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 WTP or the AC.
   Therefore the location of these features becomes vendor specific and
   this increases the difficulty of interoperability between WTPs and
   ACs from different vendors.


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions describe         | Local MAC | Split MAC |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Distribution Service     |  WTP/AC   |     AC    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Integration Service      |   WTP     |     AC    |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Beacon Generation        |   WTP     |     WTP   |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Probe Response Generation|   WTP     |     WTP   |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Function    |Power Mgmt               |   WTP     |     WTP   |
   +             |/Packet Buffering        |           |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Fragmentation            |   WTP     |    WTP/AC |
   +             |/Defragmentation         |           |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Assoc/Disassoc/Reassoc   |  WTP/AC   |     AC    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Classifying              |   WTP     |     AC    |



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   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   WTP     |    WTP/AC |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   WTP     |    WTP    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EWTP         |   AC      |    AC     |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   WTP     |     AC    |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   WTP     |    WTP/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 WTP 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.


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions describe         | Hybrid-MAC|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Distribution Service     |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Integration Service      |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Beacon Generation        |   WTP     |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Probe Response Generation|   WTP     |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Function    |Power Mgmt               |   WTP     |
   +             |/Packet Buffering        |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Fragmentation            |   AC      |
   +             |/Defragmentation         |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Assoc/Disassoc/Reassoc   |   AC      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Classifying              |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   WTP     |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   WTP     |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EWTP         |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AC      |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   WTP     |
   +             |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.


   +-+-+-+-+-+-+               +-+-+-+-+-+                    +-+-+-+-+-+-+
   |    STA    |               |    WTP  |                    |    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                     |
         |<-------------------------------------------------------->|



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         |                DATA Frame Exchange                       |
         |    802.11 Data           |       802.11 or 802.3 Data    |
         |<-------------------------+------------------------------>|


                Figure 4: Hybrid-MAC model Frames Exchange

7.  Security Considerations

   This document doesn't specify security risk difference from
   [RFC5416].  It could directly refer to Security section of [RFC5416]

8.  IANA Considerations

   This document make no request for IANA registration.

9.  Contributors

   Naibao Zhou zhounaibao@chinamobile.com

10.  Acknowledgments

   The author thanks the kind advices from Dorothy Stanley in the
   development of this document.

   The efforts of Margaret Wasserman, Wes George in reviewing this
   document are gratefully acknowledged.

   Guidance from management team: Melinda Shore, Scott Bradner, Chris
   Liljenstolpe, Benoit Claise, Joel Jaeggli, Romascanu Dan are highly
   appreciated.

11.  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.

   [RFC5416]  Calhoun, P., Montemurro, M., and D. Stanley, "Control and
              Provisioning of Wireless Access Points (CAPWAP) Protocol
              Binding for IEEE 802.11", RFC 5416, March 2009.



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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


   Rong Zhang
   China Telecom
   No.109 Zhongshandadao avenue
   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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