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Versions: 00 01

Network Working Group                                             L. Xue
Internet-Draft                                                     Z. Du
Intended status: Standards Track                                  Huawei
Expires: April 24, 2014                                           D. Liu
                                                            China Mobile
                                                                R. Zhang
                                                           China Telecom
                                                    John. Kaippallimalil
                                                                  Huawei
                                                        October 21, 2013


  Capability Announcement and AR Discovery in CAPWAP Control and Data
                           Channel Separation
            draft-xue-opsawg-capwap-separation-capability-01

Abstract

   In centralized IEEE 802.11 Wireless Local Area Network (WLAN)
   architecture, the Access Controller (AC) isn't intelligent enough
   actually to aggregate all the wireless frames, even the bandwidth
   requirement in the access point is increasing.  Thus it is a general
   case in the existing operator's network that WTPs forward the
   wireless frames directly to Access Router (AR) to avoid overload on
   the AC.  In this scenario, CAPWAP Control Channel and CAPWAP Data
   Channel are separated from each other.  This document extends CAPWAP
   for applicability of CAPWAP Control and Data Channel separation.

Requirements Language

   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].

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."



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   This Internet-Draft will expire on April 24, 2014.

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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Split CAPWAP-CTL and CAPWAP-DATA Establishment  . . . . . . .   3
     2.1.  AR Discovery  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Split Mode Capability Announcement  . . . . . . . . . . .   4
   3.  CAPWAP Message Elements for Split Mode  . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In centralized IEEE 802.11 Wireless Local Area Network (WLAN)
   architecture, Control and Provisioning of Wireless Access Points
   (CAPWAP) protocol is defined to enable Access Controller (AC) to
   manage a collection of Wireless Termination Points (WTPs), specified
   in [RFC5415] and [RFC5416].  In the existing specifications, CAPWAP
   Control Channel and Data Channel are setup and managed as a converged
   procedure between a WTP and AC.  CAPWAP Control messages are
   exchanged for management between a WTP and AC; meanwhile, CAPWAP data
   messages encapsulate forwarded wireless frames from/to WTP.

   Actually, it is a general case in the existing operator's network
   that WTPs forward the wireless frames directly to Access Router (AR)
   to avoid overload on the AC.  AC isn't intelligent enough to
   aggregate all the wireless frames, even the bandwidth requirement in
   the access point is increasing continually.  In this scenario, CAPWAP



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   Control Channel and CAPWAP Data Channel should be separated from each
   other, shown in the following figure.

            CAPWAP-CTL +--------+
             ++========+   AC   |
            //         +--------+
           //
   +-----+//   CAPWAP-DATA           +--------------+
   | WTP |===========================| Access Router|
   +-----+                           +--------------+

          Figure 1: Split CAPWAP Control and CAPWAP DATA Channel

   However, up to now, there is only one entire procedure for both
   CAPWAP Control Channel and CAPWAP Data Channel setup [RFC5415]
   between a WTP and AC.  It is not suitable if CAPWAP Control Channel
   and CAPWAP Data Channel split.  This document extends CAPWAP for
   applicability of CAPWAP Control Channel and CAPWAP Data Channel
   seperation.

2.  Split CAPWAP-CTL and CAPWAP-DATA Establishment

   This section describes the session establishment process for CAPWAP
   Control Channel and CAPWAP Data Channel seperation, named as CAPWAP
   Split Mode.  In this architecture, the CAPWAP protocol should concern
   with not only interface between the WTP and the AC, but also the
   interface between the WTP and the AR.

   On the bases of the existing CAPWAP procedure [RFC5415], additional
   phases should be considered, specified in following sub sections.

2.1.  AR Discovery

   In CAPWAP Split Mode, AR discovery should be the Preliminary phase
   for CAPWAP Data Channel.  The WTPs MUST obtain the AR information,
   such as IP address which to establish the CAPWAP Data Channel.  The
   AR information may be configured manually on the WTPs.

   However, it is difficult to operate when there are large numbers of
   WTPs in the network.  Auto-configuration method is required to enable
   AR discovery.  Several dynamic methods such as DHCP or DNS could be
   useful, but this document does not discuss these methods in detail.
   Actually, AR Discovery can be completed in the process of CAPWAP
   Control Channel procedure defined in [RFC5415].

   It's known that AC and AR are deployed centralized in operators'
   network.  Always, AC can acquire AR information in the network via
   manual configuration.  After the Discovery Response messages



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   received[RFC5415], a WTP can select an AC with which to establish a
   secure DTLS session for CAPWAP Control Channel.  Then AC configures
   the WTP with AR address appropriately via Configuration Status
   Response.  When a WTP receives the Configuration Status Response
   message carrying AR address, it checks and restores the AR address
   for CAPWAP Data Channel.

   In order to support AR discovery on a WTP, a new CAPWAP message
   element, the AR Information Element is defined in section 3.

   Additionally, the AR discovery process may also support load-sharing
   and recovery from a single AR point of failure.

2.2.  Split Mode Capability Announcement

   In order to support CAPWAP Split Mode, the split mode capability MUST
   be announced with agreement between a WTP and AC.  Otherwise, the
   CAPWAP Data messages will be sent to AC instead of AR, which violates
   the split mode .

   The CAPWAP Split Capability announcement can be achieved during Join
   Operations [RFC5415]between a WTP and AC.  A new CAPWAP message
   element, the CAPWAP Mode Element is included in the Join Request
   message and Join Response message between WTP and AC in order to
   negotiate about the CAPWAP Mode.  The element format is defined in
   Section 3.

   Besides, the decision about the CAPWAP mode between a WTP and AC can
   be made based on operator's requirements.  For example, if the CAPWAP
   Mode Element included in either Join Request message or Join Response
   message, or both is set as Split Mode value, the CAPWAP will work in
   Split mode.  Or, the agreement is consistent the value of CAPWAP Mode
   element carried in Join Request messages send by WTP.  In this
   document, the methods to arrive decision agreement about the CAPWAP
   mode between a WTP and AC are not mandatory.

3.  CAPWAP Message Elements for Split Mode

   As aforementioned, two new CAPWAP message elements are defined in
   this section for CAPWAP Split Mode.

   The AR Information Element is used by the AC to configure the AR
   information to WTP.  The format is shown as follows.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Type                 |          Length               |



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
   .                     AR Information                            .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          AR Information Element

   Type: TBD

   Length: >=8

   AR Information: The IP address of AR served for WTP in the network.
   In order to support load-sharing and recovery from a single AR point
   of failure.  The AR information can be formatted via TLV for sub-
   elements, the sub-element format is:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Type                 |          Length               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
    | Prefer|              AR Address                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       .
    +-+-+-+-+


                  Load-sharing AR Information sub-element

   Type: 1

   Length; >= 9

   AR Address: the IP address of AR served for WTP in the network.

   The CAPWAP Mode element is used for the split mode capability which
   MUST be announced with agreement between a WTP and AC.  The format is
   shown as follows.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Type                 |          Length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
   |         CAPWAP Mode           |          Reserved             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            CAPWAP Mode Element




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   Type: TBD

   Length: 8

   CAPWAP Mode: If the value is 0, the CAPWAP mode is converged defined
   in [RFC5415].  If the value is 1, the CAPWAP mode is split mode,
   defined in this document.

   Reserved: It can be used by operators to define the rule for making
   CAPWAP mode decision.

4.  IANA Considerations

   This document defines two CAPWAP elements used in CAPWAP Split Mode.
   IANA is requested to allocate the following type.

   o  The type for AR Information Element

   o  The type for CAPWAP Mode Element

5.  Security Considerations

   This document does not constrain the use of encryption mechanisms to
   protect the data channel.  If there is security requirement for
   CAPWAP Data Channel, Datagram Transport Layer Security (DTLS)
   [RFC4347] and the IPSec mechanism [RFC2401] can be used to guarantee
   the security of the CAPWAP Data Channel.

   If DTLS is used for CAPWAP Data Channel in CAPWAP Split Mode, the
   DTLS procedure is required between a WTP and AR.

6.  References

6.1.  Normative References

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

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, November 1998.

   [RFC4347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security", RFC 4347, April 2006.

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




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   [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.

6.2.  Informative References

   [I-D.cao-capwap-eap]
              Zhang, R., Cao, Z., and H. Luo, "Encapsulation of EAP
              Messages in CAPWAP Control Plane", draft-cao-capwap-eap-00
              (work in progress), October 2012.

Authors' Addresses

   Li Xue
   Huawei
   No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan, HaiDian District
   Beijing  100095
   China

   Email: xueli@huawei.com


   Zongpeng Du
   Huawei
   No.156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan, HaiDian District
   Beijing  100095
   China

   Email: duzongpeng@huawei.com


   Dapeng Liu
   China Mobile
   Unit 2, 28 Xuanwumenxi Ave, Xuanwu District
   Beijing  100053
   China

   Email: liudapeng@chinamobile.com


   Rong Zhang
   China Telecom
   No. 109 Zhongshandadao avenue
   Guangzhou  510630
   China

   Email: zhangr@gsta.com




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   John Kaippallimalil
   Huawei
   5430 Legacy Drive, Suite 175
   Plano, TX  75024

   Email: john.kaippallimalil@huawei.com













































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