v6ops C. Tsao Internet-Draft F. Ling Intended status: Informational CHT-TL Expires: October 10, 2011 April 8, 2011 A Hybrid IPv6 Service model of Bridged and Routed Mode draft-fling-v6ops-hybrid-bridged-routed-00 Abstract The memo provides a hybrid service model including CPE for both bridged and routed mode. The purpose of this model is to simplify PE operating efforts. 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 October 10, 2011. Copyright Notice Copyright (c) 2011 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. Tsao & Ling Expires October 10, 2011 [Page 1] Internet-Draft Hybrid Bridged/Routed Mode April 2011 1. Introduction A CPE (Customer Premises Equipment) router is used to forward packets between home networking and ISP (Internet Service Provider). It connects the end-user network to PE (Provider Edge). RFC 2684[1] describes two different methods for carrying traffic over an ATM network: routed protocol data units (PDUs) and bridged PDUs. Today, the majority of the ISP deployed in home networking are in bridging mode. As home networking continues to grow in popularity and scalability, bridged mode shows shortages to support this circumstance. Routed mode would be a better solution to provide better service for growing home networking. As the growing scales of home networking, subscribers want to host services, such as a web server or an email server, will need a set of IP addresses rather than a single IP address. The problem with this is that there are not enough IPv4 addresses if ISP has to provide public IPv4 address. IPv6 has enough address space and could solve this problem. In the period of migrating bridged mode to routed mode, providing these two modes simultaneously will increase the burden of PE operators. The memo provides a hybrid service model of bridged and routed modes in order to decrease the operating efforts. 2. Requirement 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 RFC 2119[2]. 3. Scope of This Document Mixed environment of IPv4 only, dual-stack and IPv6 only hosts (behind the CPE router) can be more complex and out of the scope in the memo. It only discusses IPv6-only or dual-stack which has IPv6 nodes capability. This service model is for home networking only, not for enterprise. Every subscriber has one CPE. Multiple CPEs' case is out of scope. 4. Hybrid Model The service model we provide in the memo is that PE operator does not need to know the CPE is operating in bridging or routing mode in advance. Figure 1 shows an outline of the service architecture. Tsao & Ling Expires October 10, 2011 [Page 2] Internet-Draft Hybrid Bridged/Routed Mode April 2011 +--------+ +--------+ +---+ | AAA | | | ______| C |--Host | Server +--+ | / | P | +--------+ | | / | E |--Host | | ________ / +---+ +--------+ |Provider| / \ / Bridged Mode | DNS +--+ Edge |---| Access |-- | Server | | | | Network| \ +--------+ | | \________/ \ +---+ | | \ | C |--Host +--------+ | | \______| P | | DHCP +--+ | | E |--Host | Server | +--------+ +---+ +--------+ Routed Mode Figure 1: Hybrid Service Model Architecture This architecture describes the: o The CPE forwards traffic between hosts and PE. o The hybrid modes of CPE: bridged and routed modes. In a bridged environment, IPv6 addresses are allocated from PE to hosts directly. The relationship between PE and hosts is router-to- host. Every host establishes one connection to PE. In PE, more hosts connections mean cost increasing and more complicate operating. In order to control cost, some ISPs restrict the number of hosts to access the service at one time. In a routed environment, IPv6 address/prefix is delegate from PE to CPE router. The relationship between PE and CPE is router-to-router. Hosts use SLAAC[3] and DHCPv6 stateless [4] to get IPv6 addresses and routing information from CPE, not from PE. There is only one connection between PE and CPE router. In this mode, PE operating and cost is simpler and cheaper than bridged mode. 5. IPv6 Address Provision The address assignment between PE and CPE is router-to-host if CPE is in bridging mode. There are three methods of IPv6 address assignment in router-to-host connection: SLAACC + DHCPv6 stateless, RDNSS[6], and DHCPv6 Stateful[7]. In the first method, hosts use SLAAC to get IPv6 address, DHCP stateless to get DNS information. The second method is to add DNS parameter in RA option. In the third method, default gateway is gotten from RA and trigger hosts DHCPv6 client process to get IPv6 address and DNS information. In this memo, SLAAC + DHCPv6 stateless is used between PE and CPE. Tsao & Ling Expires October 10, 2011 [Page 3] Internet-Draft Hybrid Bridged/Routed Mode April 2011 In router-to-router connection, DHCP-PD[5] is used to delegate IPv6 prefix to CPE. In Figure 1 architecture, PE operator MUST provide two different prefixes, one is for DHCP-PD and the other is for SLAAC. The prefix length of these two methods is /64, but /60 to /63 or /48 are possible options. Prefix length depends on the number of CPE's hosts. 6. Conclusion In this service model, PE operators do not need to know CPE is in routed or bridged mode. It is convenient for management, but wastes IPv6 addresses. Because it would waste RA prefix if CPE is in routed mode, It would waste DHCP-PD prefix if CPE is in bridged mode. But for PE, it is possible to recycle unused IPv6 addresses. This service model exists when the ISP provides bridged and routed modes simultaneously. The number of routed mode subscribers will increase while bridged mode subscribers will decrease during the migration period. This is a transient model in order to simplify operating efforts and cost down. 7. Security Considerations Security issues are not addressed in this memo. 8. Acknowledgements Thanks for the following people (in alphabetical order) for their guidance and feedback: Chia-Wei Tseng, Shih-Kang Wang, Wei-Fen Hsu, and Yen-Ju Chu 9. IANA Considerations This memo has no actions for IANA. 10. References 10.1. Normative References [1] Grossman, D. and J. Heinanen, "Multiprotocol Encapsulation over ATM Adaptation Layer 5", RFC 2684, September 1999. Tsao & Ling Expires October 10, 2011 [Page 4] Internet-Draft Hybrid Bridged/Routed Mode April 2011 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [4] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, April 2004. [5] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. 10.2. Informative References [6] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 6106, November 2010. [7] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. Authors' Addresses Chih-Cheng Tsao Chunghwa Telecommunication Laboratories 12, Lane 551, Min-Tsu Rd, Sec.5 Yang-Mei, Taoyuan 326 Taiwan Email: atsao@cht.com.tw Fang-Yu Ling Chunghwa Telecommunication Laboratories 12, Lane 551, Min-Tsu Rd, Sec.5 Yang-Mei, Taoyuan 326 Taiwan Email: fancy@cht.com.tw Tsao & Ling Expires October 10, 2011 [Page 5]