Network Working Group L. Xue Internet-Draft Z. Du Intended status: Informational Huawei D. Liu China Mobile R. Zhang China Telecom John Kaippallimalil Huawei July 10, 2013 Capability Announcement and AR Discovery in CAPWAP Control and Data Channel Separation draft-xue-opsawg-capwap-separation-capability-00 Abstract In a centralized IEEE 802.11 Wireless Local Area Network (WLAN) architecture, the Access Controller (AC) does not have the intelligence to aggregate all the wireless frames. In addition, increasing amounts of traffic handled by each access point would require even more processing at an AC. Thus it is normal in an existing operator's network for the WTPs to forward the wireless frames directly to AR to avoid overloading the AC. In this scenario, CAPWAP Control Channel and CAPWAP Data Channel are separated from each other. This document provides extensions to CAPWAP for the split scenario where CAPWAP Control and Data Channel are separated. 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 Xue, et al. Expires January 11, 2014 [Page 1] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 material or to cite them other than as "work in progress." Xue, et al. Expires January 11, 2014 [Page 2] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 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. 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 . . . . . . . . . . . . . . . . . . 7 6.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction In a 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 between a WTP and AC are setup and managed in a converged procedure. CAPWAP Control messages are management messages exchanged between a WTP and AC; meanwhile, CAPWAP data messages encapsulate forwarded wireless frames. In practice, it is a general case in existing operator networks that WTPs forward the wireless frames directly to AR to avoid overload on the AC. This requirement is also mentioned in [I-D.cao-capwap-eap]. The AC does not have the intelligence to aggregate all the wireless frames. In addition, increasing amounts of traffic handled by each access point would require even more processing at an AC. In this scenario, CAPWAP Control Channel and CAPWAP Data Channel should be Xue, et al. Expires January 11, 2014 [Page 3] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 separated from each other, as 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 common procedure for both CAPWAP Control Channel and CAPWAP Data Channel setup [RFC5415] between a WTP and AC. This is not sufficient if CAPWAP Control Channel and CAPWAP Data Channel are split. This document extends CAPWAP for applicability in split CAPWAP Control Channel and CAPWAP Data Channel. 2. Split CAPWAP-CTL and CAPWAP-DATA Establishment This section describes the session establishment process for split CAPWAP Control Channel and CAPWAP Data Channel, called CAPWAP Split Mode. In this architecture, the CAPWAP protocol should be concerned with not only the interface between the WTP and the AC, but also the interface between the WTP and the AR. Using existing CAPWAP procedure [RFC5415] as the basis, additional phases are needed, and these are specified in following sub sections. 2.1. AR Discovery In CAPWAP Split Mode, AR discovery should be the Preliminary phase for CAPWAP Data Channel procedures. The WTPs MUST obtain the AR information, such as IP address which are used to establish the CAPWAP Data Channel. It is possible for the AR information to be configured manually on the WTP. However, it is difficult to operate when there are large numbers of WTPs in the network. An auto-configuration method is required to enable AR discovery in larger networks. Several dynamic methods such as DHCP or DNS could be used, but this document does not discuss these methods in detail. It is also possible for AR Discovery to be completed in the process of CAPWAP Control Channel procedures defined in [RFC5415]. Xue, et al. Expires January 11, 2014 [Page 4] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 A common deployment is for the AC and AR to be in a centralized location in the operators network. In all cases, the AC can default to acquiring AR information in the network via manual configuration. After the Discovery Response messages 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 the AC instead of the AR, which is not the expected outcome in 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 requirements. For example, if the CAPWAP Mode Element is included in either Join Request message or Join Response message, or both are set to Split Mode value, CAPWAP will operate in Split mode. Alternatively, the agreement that is consistent with the value of CAPWAP Mode element carried in Join Request messages send by WTP may be acceptable. This document does not prescribe a single method to arrive at an agreement about the CAPWAP mode. 3. CAPWAP Message Elements for Split Mode As mentioned in earlier sections, 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 Xue, et al. Expires January 11, 2014 [Page 5] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 information to WTP. The format is 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+ . 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 that is used for the split mode capability 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Xue, et al. Expires January 11, 2014 [Page 6] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+ | CAPWAP Mode | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ CAPWAP Mode Element Type: TBD Length: 8 CAPWAP Mode: If the value is 0, the CAPWAP operates in converged mode 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 are security requirements 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 Xue, et al. Expires January 11, 2014 [Page 7] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 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. [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 Xue, et al. Expires January 11, 2014 [Page 8] Internet-Draft CAPWAP-CTL and CAPWAP-DATA Separatio July 10, 2013 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 John Kaippallimalil Huawei 5430 Legacy Drive, Suite 175 Plano TX 75024 Email: john.kaippallimalil@huawei.com Xue, et al. Expires January 11, 2014 [Page 9]