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RFC 7494

IEEE 802.11 Medium Access Control (MAC) Profile for Control and Provisioning of Wireless Access Points (CAPWAP)

Pages: 13
Proposed Standard

 Top   ToC   RFC7494 - Page 1 
Internet Engineering Task Force (IETF)                           C. Shao
Request for Comments: 7494                                       H. Deng
Category: Standards Track                                   China Mobile
ISSN: 2070-1721                                            R. Pazhyannur
                                                           Cisco Systems
                                                                 F. Bari
                                                                    AT&T
                                                                R. Zhang
                                                           China Telecom
                                                           S. Matsushima
                                                        SoftBank Telecom
                                                              April 2015


    IEEE 802.11 Medium Access Control (MAC) Profile for Control and
            Provisioning of Wireless Access Points (CAPWAP)


Abstract


   The Control and Provisioning of Wireless Access Points (CAPWAP)
   protocol binding for IEEE 802.11 defines two Medium Access Control
   (MAC) modes for IEEE 802.11 Wireless Transmission Points (WTPs):
   Split and Local MAC.  In the Split MAC mode, the partitioning of
   encryption/decryption functions is not clearly defined.  In the Split
   MAC mode description, IEEE 802.11 encryption is specified as located
   in either the Access Controller (AC) or the WTP, with no clear way
   for the AC to inform the WTP of where the encryption functionality
   should be located.  This leads to interoperability issues, especially
   when the AC and WTP come from different vendors.  To prevent
   interoperability issues, this specification defines an IEEE 802.11
   MAC Profile message element in which each profile specifies an
   unambiguous division of encryption functionality between the WTP and
   AC.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7494.
 Top   ToC   RFC7494 - Page 2 
Copyright Notice

   Copyright (c) 2015 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents


   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  IEEE MAC Profile Descriptions . . . . . . . . . . . . . . . .   5
     2.1.  Split MAC with WTP Encryption . . . . . . . . . . . . . .   5
     2.2.  Split MAC with AC Encryption  . . . . . . . . . . . . . .   6
     2.3.  IEEE 802.11 MAC Profile Frame Exchange  . . . . . . . . .   8
   3.  MAC Profile Message Element Definitions . . . . . . . . . . .   8
     3.1.  IEEE 802.11 Supported MAC Profiles  . . . . . . . . . . .   8
     3.2.  IEEE 802.11 MAC Profile . . . . . . . . . . . . . . . . .   9
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  12
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12
 Top   ToC   RFC7494 - Page 3 
1.  Introduction


   The CAPWAP protocol supports two MAC modes of operation: Split and
   Local MAC, as described in [RFC5415] and [RFC5416].  However, there
   are MAC functions that have not been clearly defined.  For example,
   IEEE 802.11 [IEEE.802.11] encryption is specified as located in
   either the AC or the WTP with no clear way to negotiate where it
   should be located.  Because different vendors have different
   definitions of the MAC mode, 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 specification, then operators will experience interoperability
   issues with WTPs and ACs from different vendors.

   Figure 1 from [RFC5416] illustrates how some functions are processed
   in different places in the Local MAC and Split MAC mode.
   Specifically, note that in the Split MAC mode, the IEEE 802.11
   encryption/decryption is specified as WTP/AC, implying that it could
   be at either location.  This is not an issue with Local MAC because
   encryption is always at the WTP.
 Top   ToC   RFC7494 - Page 4 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions                  | 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    |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   WTP     |    WTP/AC |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   WTP     |    WTP    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EAP          |   AC      |    AC     |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AC      |    AC     |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   WTP     |    WTP/AC |
   +             |Encryption/Decryption    |           |           |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note:
     RSN - Robust Security Network
     RSNA - Robust Security Network Association
     WPA2 - Wi-Fi Protected Access 2

              Figure 1: Functions in Local MAC and Split MAC

   To solve this problem, this specification introduces the IEEE 802.11
   MAC Profile.  The IEEE 802.11 MAC Profile unambiguously specifies
   where the various MAC functionalities should be located.
 Top   ToC   RFC7494 - Page 5 
2.  IEEE MAC Profile Descriptions


   A IEEE 802.11 MAC Profile refers to a description of how the MAC
   functionality is split between the WTP and AC shown in Figure 1.


2.1.  Split MAC with WTP Encryption


   The functional split for the Split MAC with WTP encryption is
   provided in Figure 2.  This profile is similar to the Split MAC
   description in [RFC5416], except that IEEE 802.11 encryption/
   decryption is at the WTP.  Note that fragmentation is always done at
   the same entity as the encryption.  Consequently, in this profile
   fragmentation/defragmentation is also done only at the WTP.  Note
   that scheduling functionality is denoted as WTP/AC.  As explained in
   [RFC5416], this means that the admission control component of IEEE
   802.11 resides on the AC; the real-time scheduling and queuing
   functions are on the WTP.
 Top   ToC   RFC7494 - Page 6 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions                  | Profile   |
   |                                       |    0      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Distribution Service     |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Integration Service      |   AC      |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Beacon Generation        |   WTP     |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Probe Response Generation|   WTP     |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Function    |Power Mgmt/              |   WTP     |
   +             |Packet Buffering        |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Fragmentation/           |   WTP     |
   +             |Defragmentation          |           |
   |             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Assoc/Disassoc/Reassoc   |   AC      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Classifying              |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 QoS  |Scheduling               |   WTP/AC  |
   +             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |Queuing                  |   WTP     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EAP          |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AC      |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   WTP     |
   +             |Encryption/Decryption    |           |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Note:
   EAP - Extensible Authentication Protocol

           Figure 2: Functions in Split MAC with WTP Encryption
 Top   ToC   RFC7494 - Page 7 
2.2.  Split MAC with AC Encryption


   The functional split for the Split MAC with AC encryption is provided
   in Figure 3.  This profile is similar to the Split MAC in [RFC5416],
   except that IEEE 802.11 encryption/decryption is at the AC.  Since
   fragmentation is always done at the same entity as the encryption, in
   this profile, AC does fragmentation/defragmentation.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Functions                  | Profile   |
   |                                       |    1      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |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     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.1X/EAP          |   AC      |
   +   IEEE      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | 802.11 RSN  |RSNA Key Management      |   AC      |
   +  (WPA2)     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             |IEEE 802.11              |   AC      |
   +             |Encryption/Decryption    |           |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 3: Functions in Split MAC with AC encryption
 Top   ToC   RFC7494 - Page 8 
2.3.  IEEE 802.11 MAC Profile Frame Exchange


   An example of message exchange using the IEEE 802.11 MAC Profile
   message element is shown in Figure 4.  The WTP informs the AC of the
   various MAC Profiles it supports.  This happens in either a Discovery
   Request message or the Join Request message.  The AC determines the
   appropriate profile and configures the WTP with the profile while
   configuring the WLAN.

       +-+-+-+-+-+-+                             +-+-+-+-+-+-+
       |    WTP    |                             |    AC     |
       +-+-+-+-+-+-+                             +-+-+-+-+-+-+
             |Join Request[Supported IEEE 802.11       |
             |       MAC Profiles   ]                  |
             |---------------------------------------->|
             |                                         |
             |Join Response                            |
             |<----------------------------------------|
             |                                         |
             |IEEE 802.11 WLAN Config. Request [       |
             | IEEE 802.11 Add WLAN,                   |
             | IEEE 802.11 MAC Profile                 |
             |   ]                                     |
             |<----------------------------------------|
             |                                         |
             |IEEE 802.11 WLAN Config. Response        |
             |---------------------------------------->|

          Figure 4: Message Exchange for Negotiating MAC Profiles


3.  MAC Profile Message Element Definitions



3.1.  IEEE 802.11 Supported MAC Profiles


   The IEEE 802.11 Supported MAC Profile message element allows the WTP
   to communicate the profiles it supports.  The Discovery Request
   message, Primary Discovery Request message, and Join Request message
   may include one such message element.

           0               1               2               3
           0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
          +=+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
          | Num_Profiles  |  Profile_1    |   Profile_[2..N]..
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

               Figure 5: IEEE 802.11 Supported MAC Profiles

   o  Type: 1060 for IEEE 802.11 Supported MAC Profiles
 Top   ToC   RFC7494 - Page 9 
   o  Num_Profiles >=1: This refers to the number of profiles present in
      this message element.  There must be at least one profile.

   o  Profile: Each profile is identified by a value specified in
      Section 3.2.


3.2.  IEEE 802.11 MAC Profile


   The IEEE 802.11 MAC Profile message element allows the AC to select a
   profile.  This message element may be provided along with the IEEE
   802.11 ADD WLAN message element while configuring a WLAN on the WTP.

           0 1 2 3 4 5 6 7
          +=+-+-+-+-+-+-+-+
          |  Profile      |
          +-+-+-+-+-+-+-+-+

                     Figure 6: IEEE 802.11 MAC Profile

   o  Type: 1061 for IEEE 802.11 MAC Profile

   o  Profile: The profile is identified by a value as given below

      *  0: This refers to the IEEE 802.11 Split MAC Profile with WTP
         encryption

      *  1: This refers to the IEEE 802.11 Split MAC Profile with AC
         encryption


4.  Security Considerations


   This document does not introduce any new security risks compared to
   [RFC5416].  The negotiation messages between the WTP and AC have
   origin authentication and data integrity.  As a result, an attacker
   cannot interfere with the messages to force a less-secure mode
   choice.  The security considerations described in [RFC5416] apply
   here as well.
 Top   ToC   RFC7494 - Page 10 
5.  IANA Considerations


   The following IANA actions have been completed.

   o  This specification defines two new message elements: IEEE 802.11
      Supported MAC Profiles (described in Section 3.1) and the IEEE
      802.11 MAC Profile (described in Section 3.2).  These elements
      have been registered in the existing "CAPWAP Message Element Type"
      registry, defined in [RFC5415].

              CAPWAP Protocol Message Element                Type Value
              IEEE 802.11 Supported MAC Profiles              1060
              IEEE 802.11 MAC Profile                         1061

   o  The IEEE 802.11 Supported MAC Profiles message element and IEEE
      802.11 MAC Profile message element include a Profile field (as
      defined in Section 3.2).  The Profile field in the IEEE 802.11
      Supported MAC Profiles denotes the MAC Profiles supported by the
      WTP.  The Profile field in the IEEE 802.11 MAC Profile denotes the
      MAC Profile assigned to the WTP.  The namespace for the field is 8
      bits (0-255).  This specification defines two values: zero (0) and
      one (1) as described below.  The remaining values (2-255) are
      controlled and maintained by IANA, and the registration procedure
      is Expert Review [RFC5226].  IANA has created a new subregistry
      called "IEEE 802.11 Split MAC Profile" under the existing registry
      "Control And Provisioning of Wireless Access Points (CAPWAP)
      Parameters".  The registry format is given below.

               Profile                             Type Value  Reference
               Split MAC with WTP encryption       0           RFC 7494
               Split MAC with AC encryption        1           RFC 7494
 Top   ToC   RFC7494 - Page 11 
6.  References



6.1.  Normative References


   [IEEE.802.11]
              IEEE, "IEEE Standard for Information Technology -
              Telecommunications and information exchange between
              systems - Local and metropolitan area networks - Specific
              requirements Part 11: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) Specifications", IEEE Std
              802.11-2012, March 2012,
              <http://standards.ieee.org/about/get/802/802.11.html>.

   [RFC5415]  Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
              Ed., "Control And Provisioning of Wireless Access Points
              (CAPWAP) Protocol Specification", RFC 5415, March 2009,
              <http://www.rfc-editor.org/info/rfc5415>.

   [RFC5416]  Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
              Ed., "Control and Provisioning of Wireless Access Points
              (CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416,
              March 2009, <http://www.rfc-editor.org/info/rfc5416>.


6.2.  Informative References


   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008, <http://www.rfc-editor.org/info/rfc5226>.
 Top   ToC   RFC7494 - Page 12 
Acknowledgments


   The authors are grateful for extremely valuable suggestions from
   Dorothy Stanley in developing this specification.

   Guidance from the management team -- Melinda Shore, Scott Bradner,
   Chris Liljenstolpe, Benoit Claise, Joel Jaeggli, and Dan Romascanu --
   is highly appreciated.


Contributors


   Yifan Chen <chenyifan@chinamobile.com>

   Naibao Zhou <zhounaibao@chinamobile.com>


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


   Rajesh S. Pazhyannur
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA 95134
   United States

   EMail: rpazhyan@cisco.com
 Top   ToC   RFC7494 - Page 13 
   Farooq Bari
   AT&T
   7277 164th Ave NE
   Redmond, WA 98052
   United States

   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