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 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." This Internet-Draft will expire on November 10, 2013. Shao, et al. Expires November 10, 2013 [Page 1] Internet-Draft CAPWAP May 2013 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. 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 Shao, et al. Expires November 10, 2013 [Page 2] Internet-Draft CAPWAP May 2013 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. Shao, et al. Expires November 10, 2013 [Page 3] Internet-Draft CAPWAP May 2013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 | Shao, et al. Expires November 10, 2013 [Page 4] Internet-Draft CAPWAP May 2013 + 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 | Shao, et al. Expires November 10, 2013 [Page 5] Internet-Draft CAPWAP May 2013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |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 | |<-------------------------------------------------------->| Shao, et al. Expires November 10, 2013 [Page 6] Internet-Draft CAPWAP May 2013 | 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. Shao, et al. Expires November 10, 2013 [Page 7] Internet-Draft CAPWAP May 2013 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 Shao, et al. Expires November 10, 2013 [Page 8]