Network Working Group CJ. Shao Internet-Draft H. Deng Intended status: Informational China Mobile Expires: April 18, 2013 R. Zhang China Telecom October 15, 2012 Enhancement of CAPWAP Problem Statement draft-shao-capwap-plus-ps-00 Abstract With the recent widely deployment of large public Wifi network, and the integration with cellular network. EAP based authentication has been considered as the good candidate to improve the Wifi user experience similarly to the extend of GSM network. Couple of new functions which could enhance CAPWAP protocol have been raised to improve the large carrier grade Wifi network. 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 April 18, 2013. Copyright Notice Copyright (c) 2012 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 Shao, et al. Expires April 18, 2013 [Page 1] Internet-Draft DMM October 2012 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. Conventions used in this document . . . . . . . . . . . . . . . 3 3. Supporting EAP authencation in Wifi network . . . . . . . . . . 3 3.1. Scenario Description . . . . . . . . . . . . . . . . . . . 3 4. The scope of definition of split MAC mode . . . . . . . . . . . 4 5. 802.11n support . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Channel auto reconfiguration . . . . . . . . . . . . . . . . . 5 7. Power auto reconfiguration . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Shao, et al. Expires April 18, 2013 [Page 2] Internet-Draft DMM October 2012 1. Introduction Public Wifi service has been paid more attention due to the growth of cellular data traffic, this is mainly originated from faster mobile network and more smart terminals. It is predcited that such growth will continue even with the deployment of LTE network. The capacity and coverage of LTE network still needs the complementation of public wifi network because Wifi spectrum is free, limited and globally available. and almost all smart terminal has the Wifi equiped. Recent efforts have been made to let Wifi roaming similar to as easy as legacy cellular GSM network by deploying EAP based authentication mechanism, and to let mobile to Wifi integration is seamless and transparent to the customer; Toward this two directions, current CAPWAP protocol could be enhanced to improve better user experiences. There have been lots of propritary implementations between AP and AC interfaces, some of them have very strong capability which could be used to improve the wifi performance. Once Standard interface is specified, such merits may be not exist, but it benefit for operators deployment with such sacrifice. 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. Supporting EAP authencation in Wifi network Current EAP message is designed to be transmited in CAPWAP data plane, AC in the middle of data path will act as the authenticator to transmit this EAP message to AAA server, but sometime, operator would like to let AC to be in the bypass of the data plane which could help to improve the performance of AC, allow it can manage more APs once the network is growing. In order to allow AC be bypassed, the capwap control message could be extended to support EAP messages. 3.1. Scenario Description The following figure shows where and how the problem arises. In many operators' network, the Access Controller is placed remotely at the central data center. In order to avoid the traffic aggregation at the AC, the data plane out of the AP is directed to the Access Router (AR). In this scenario, the CAPWAP-CTL tunnel and CAPWAP-DATA tunnel are separated from each other. Shao, et al. Expires April 18, 2013 [Page 3] Internet-Draft DMM October 2012 Because there are no explict message types to support the encapsulation of EAP packets in the CAPWAP-CTL tunnel, the EAP messages are tunneled via the CAPWAP-DATA plane to the AR. AR acts as authenticator in the EAP framework. After authentication, the AR receives the keying message for the session. But AC is supposed to delieve these keying messages to the AP, and AR has no standard interface to ship them to the AP or the AC. This is unacceptable in the scenario of EAP-based auto-authentication. CAPWAP-CTL +--------+ ++========+ AC | // +--------+ // +-----+// CAPWAP-DATA +--------------+ | AP |===========================| Access Router| +-----+ +--------------+ Figure 1: Split between CAPWAP-CTL and CAPWAP-DATA Plane So it is desirable to encapsulate EAP messages in the CAPWAP-CTL plane, to avoid data aggregation and improve WLAN system scalability. 4. The scope of definition of split MAC mode There are many functions hasn't been clearly defined whether they belong to either AP and AC in the split mode. Operation needs to configure differently handle the various implementation of split MAC mode. if there is no clear scope definition of split MAC and local MAC, then operator has the diffculty to interoperate different vendors. 5. 802.11n support There are couple of capabilities of 802.11n need to be supported by CAPWAP control message such as radio capability, radio configuration and station information. IEEE 802.11n standard was published in 2009 and it is an amendment to the IEEE 802.11-2007 standard to improve network throughput. The maximum data rate increases to 600Mbit/s physical throughput rate. In the physical layer, 802.11n use OFDM and MIMO to achive the high throughput. 802.11n use multiple antennas to form antenna array which can be dynamically adjusted to imporve the signal strength and extend the coverage. 802.11n support two modes of channel usage: 20MHz mode and 40Mhz Shao, et al. Expires April 18, 2013 [Page 4] Internet-Draft DMM October 2012 mode.802.11n has a new feature called channel binding. It can bind two adjacent 20MHz channel to one 40MHz channel to improve the throughput.If using 40Mhz channel configuration there will be only one non-overlapping channel in 2.4GHz. In the large scale deployment scenario, operator need to use 20MHz channel configuration in 2.4GHz to allow more non-overlapping channels. In MAC layer, a new feature of 802.11n is Short Guard Interval(GI). 802.11a/g use 800ns guard interval between the adjacent information symbols. In 802.11n, the GI can be configured to 400nm under good wireless condition. Another feature in 802.11 MAC layer is Block ACK. 802.11n can use one ACK frame to acknowledge several MPDU receiving event. CAPWAP need to be extended to support the above new 802.11n features. For example, CAPWAP should allow the access controller to know the supported 802.11n features and the access controller should be able to configure the differe channel binding modes. One possible solution is to extend the CAPWAP information element for 802.11n. 6. Channel auto reconfiguration Channel auto reconfiguration could imporve the Wifi performance, CAPWAP message could be extended to support this function. Each channel may provide different quality of service, when WTP works. WTP can be active or passive scanning and monitoring each channel, form the report of measurement results to the Access Controller. WTP can periodically send configure status request to the AC. According to the current channel quality and other channel quality scanning report, ACs decide whether modify the channel to be used, send the configure status response packet to set up a new channel for the WTP. 7. Power auto reconfiguration Power auto reconfiguration could imporve the Wifi performance. CAPWAP message could be extended to achieve following outcome. o Maximize Spectrum Usage: Real-world Wi-Fi deployments are depending on the features of shared media. Three channels available in the 2.4GHz band and 23 channels in the 5GHz band. Power auto reconfiguration could help these channels be fully utilized. As the results, clients could be distributed across all available channels. Shao, et al. Expires April 18, 2013 [Page 5] Internet-Draft DMM October 2012 o Reduce Interference: when multiple devices attempt to simutaneously access the same channel at the same time, a co- channel interference likely happned. It reduces overall performance of the channel. The reconfiguration via CAPWAP could efficiently mitigate the interference. That is essential to proper network operation o Optimize Coverage: Simply increasing AP power may not help to maximize converage because it creates an unbalanced condition in which more distantly located clients may perforIm poorly due to their lower transmit output power. The power reconfiguration could achieve a balanced environment, where configuration could ensure that coverage is uniform and adequate throughout the service area. 8. Security Considerations BD 9. IANA Considerations None 10. Contributors Yifan Chen chenyifan@chinamobile.com Bocun Deng 13316090701@189.cn 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. Shao, et al. Expires April 18, 2013 [Page 6] Internet-Draft DMM October 2012 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 Rong Zhang China Telecom No.109 Zhongshandadao avenue Tianhe District, Guangzhou 510630 China Email: zhangr@gsta.com Shao, et al. Expires April 18, 2013 [Page 7]