Network Working Group Jie Hu Internet Draft Yunqing Chen Intended status: Informational Huiling Zhao Expires: April 18, 2011 Dongfeng Mao China Telecom October 18, 2010 PPPv6 Problem statement and requirements draft-hu-pppext-ipv6cp-requirements-00 Abstract The IPv6 Control Protocol (IPv6CP) is a NCP that allows for the negotiation of parameters for an IPv6 interface over PPP. In IPv6 networks, PPP (PPPoE) will still be an important mechanism for connecting broadband access users. However, IPv6CP only defines the Interface-Identifier option, other parameters such as IPv6 Address, Primary and alternative DNS server addresses, and delegated prefix have to be configured by other methods rather than IPv6CP. This document describes problems the ISPs faced and lists requirements related when deploying IPv6 in broadband access network over PPP. 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on April 18,2011. Hu Expires April 18, 2011 [Page 1] Internet-Draft PPPv6 Problem statement and requirements October 2010 Copyright Notice Copyright (c) 2010 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 1.1. Requirements Language................................... 2 2. Current Practice in IPv4............................................. 3 3. Problem Statement ................................................... 3 4. Requirements ............................................................ 4 5. Security Considerations............................................ 5 6. Acknowledgments ..................................................... 5 7. References ................................................................. 5 7.1. Normative References........................................ 5 7.2. Informative References....................................... 5 Authors' address..............................................................6 1. Introduction The Point-to-Point Protocol (PPP) provides a standard method for transporting multi-protocol datagrams over point-to-point links. PPP defines an extensible Link Control Protocol (LCP) and a family of Network Control Protocols (NCPs) for establishing and configuring different network-layer protocols. In current practice, after the LCP and the authentication (if required) phases are completed, the corresponding network-layer control protocol, IPCP will be used to negotiate IP layer elements between subscriber devices and the BNGs. 1.1. Requirements Language The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119]. Hu Expires April 18, 2011 [Page 2] Internet-Draft PPPv6 Problem statement and requirements October 2010 2. Current Practice in IPv4 In current practice, after the LCP and the authentication (if required) phases are completed, the corresponding network-layer control protocol, IPCP will be used to negotiate IP layer elements between subscriber devices and the BNGs. As in IPv4, PPP is adopted to provide Internet service by a great many ISPs (both fixed and mobile providers) over a wide area. It is a simple protocol with following advantages: 1. Robust authentication and authorization functions integrated (PAP or CHAP), can effectively prevent non-authorized users from accessing network. 2. Each PPP session is regarded as a separate logical link/interface, and the process of link establishment is divided into several orderly phases which are scalable and feasible to be implemented. 3. As a part of PPP, IPCP is fairly efficient. Typically, all the elements needed for establishing IP connectivity can be configured through "Configuration Options" defined in IPCP, with no extra control protocols or devices running these protocols introduced. 4. As a stable method of configuring IP elements, IPCP works well for the Dial-on-Demand subscriber whose link may be terminated/re- dialed up anytime. 5. Then, PPP can provide accurate timing and traffic flow statistics of network access for each subscriber. Base on that, ISPs can apply various kinds of policies according to different marketing activities. 6. Broadband user can initiate multiple PPP sessions simultaneously, each PPP session is dedicated for one service, by this way services are distinguished and separated by PPP session, in this case ISP can provide different QoS profile for different service (PPP session). 3. Problem Statement While in IPv6, it is not straightforward as in IPv4. Additionally, in the scenario where the PPP link is initiated by a Residential Gateway, delegated prefix is required on the CPE as the address pool. Currently, the configuration of IPv6 link can't be accomplished by the NCP (IPv6CP) itself. The lack of Configuration Options defined in IPv6CP results in following problems: Hu Expires April 18, 2011 [Page 3] Internet-Draft PPPv6 Problem statement and requirements October 2010 o The process of IP elements configuration is quite complicated. After entering the IPv6CP phase, one or more extra control protocols such as ND, DHCPv6, (and/or DHCPv6-PD) must be introduced, as currently there is only one configuration option define in IPv6CP for interface-ID negotiation. o The co-existence of multiple mechanisms with functionalities partially overlapped will lead to interoperation problems in the implementation. o More transaction steps caused by extra control protocols introduced will result in longer response time and higher risk of exception. o How to determine the moment when the status of IPv6CP negotiation comes to "OPEN", so as to get corresponding AAA activities started? o ISPs have to change current network infrastructure accordingly, such as installing DHCPv6 server somewhere in the network (standalone or embedded) which will not only increase both CAPEX and OPEX, but result in scalability problems when the number of subscribers grows. o Some unnecessary functions will be involved. For example, functions like Address Resolution, On-link Prefix List Advertisement, Default Router Advertisement, etc. defined in ND are actually not needed for a simple PPP link. o Individual active state machine has to be maintained for each protocol, and conflicts may exist (such as multiple lifetime counters) 4. Requirements To keep the implementation simple and stable, the problems described above must be solved. During the transition from IPv4 to IPv6, if ISPs choose to run IPv4 and IPv6 over one single PPP link for dual stack subscribers, it is more feasible to unify the way of configuring both IPv4 and IPv6. From the ISP's point of view, it is more reasonable to extend the IPv6CP functions needed for PPP by the same means of IPCP which is mature and widely implemented rather than introducing extra control protocols. To establish basic IPv6 connectivity over PPP, the following Configuration Options need to be defined: 1. IPv6 address, DNS server addresses (primary and alternative), and Delegated-Prefix; Hu Expires April 18, 2011 [Page 4] Internet-Draft PPPv6 Problem statement and requirements October 2010 Also, Configuration Options for other fucntions may be considered in the future: 2. DS-Lite AFTR Address, NTP server address, etc. 5. Security Considerations There are no security considerations in this document. 6. Acknowledgments Part of this text borrows from the previous RFCs and I-Ds. And as such is partially based on previous work done by the PPP working group. Thanks to Jacni Qin, Qian Wang and Qiong Sun for useful feedback. 7. References 7.1. Normative References [RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51, RFC 1661, July 1994. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3315] R. Droms, Ed, J. Bound, B. Volz, T. Lemon, C. Perkins, and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3633] O. Troan, R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC3646] R. Droms, Ed, "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003. [RFC4861] T. Narten, E. Nordmark, W. Simpson, and H. Soliman, " Neighbor Discovery for IP version 6 (IPv6)", RFC4861, September 2007. [RFC5072] S.Varada, Haskins, D., and E. Allen, "IP Version 6 over PPP", RFC 5072, September 2007. 7.2. Informative References [RFC1332] McGregor, G., "The PPP Internet Protocol Control Protocol (IPCP)", RFC 1332, May 1992. Hu Expires April 18, 2011 [Page 5] Internet-Draft PPPv6 Problem statement and requirements October 2010 [I-D.ietf-pppext-ipv6-dns-addr] Hiller, T. and G. Zorn, "PPP IPV6 Control Protocol Extensions for DNS Server Addresses", draft-ietf-pppext-ipv6-dns-addr-03 (work in progress), June 2003. [draft-qin-pppext-ipv6-addr-pref] Y. Li, J. Qin, and L. Yuan, " PPP IPv6 Control Protocol Extensions for Address and Prefix", draft-qin-pppext-ipv6-addr-pref-00, January 2010. [draft-huang-ipv6cp-options] J. Huang, " IPv6CP Options for PPP Host Configuration", draft-huang-ipv6cp-options-00, February 3, 2010. Authors' Addresses Jie Hu China Telecom Beijing Research Institute Room 708 No.118, Xizhimenneidajie, xicheng District Beijing 100035 China Phone: <86 10 58552808> Email: huj@ctbri.com.cn Yunqing Chen China Telecom Beijing Research Institute Room 708 No.118, Xizhimenneidajie, xicheng District Beijing 100035 China Phone: <86 10 58552102> Email: chenyq@ctbri.com.cn Huiling Zhao China Telecom Beijing Research Institute Room 502 No.118, Xizhimenneidajie, xicheng District Beijing 100035 China Phone: <86 10 58552002> Email: zhaohl@ctbri.com.cn Dongfeng Mao China Telecom No.31, Jinrong Ave, Xicheng District,100032 Phone: <86 10 58501809> Email: maodf@chinatelecom.com.cn Hu Expires April 18, 2011 [Page 6]