Network Working Group Dayong Guo Internet Draft Sheng Jiang Intended status: Standards Track Huawei Technologies Co., Ltd Expires: January 8, 2010 July 13, 2009 Softwire Concentrator Discovery Using DHCP draft-guo-softwire-sc-discovery-01.txt Status of this Memo This Internet-Draft is submitted to IETF 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 January 8, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Guo & Jiang Expires January 8, 2010 [Page 1] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 Abstract Several types of Carrier-Grade-NATs (CGNs) have been proposed to simplify IPv4/IPv6 transition of the edge network by integrating tunnels and NAT. A very common scenario is that many users set up softwires (i.e. tunnels) to a softwire concentrator for public or private access services. In order to establish softwires successfully, a new mechanism is required to enable users in the edge network to discover the information of the concentrator. This document describes how a host or CPE (Customer Premises Equipment) discovers the remote softwire concentrator or CGN in a hub and spoke network using DHCP. Based on two new Softwire Concentrator or CGN Discovery DHCP Options, proposed in the document, a user can obtain softwire concentrator or CGN information and then set up a tunnel to the softwire concentrator or CGN. Table of Contents 1. Introduction.................................................3 2. DHCP Solution for Softwire Concentrator Discovery............4 2.1. DHCPv4 Softwire Concentrator Discovery (SCD) Option.....4 2.2. DHCPv6 Softwire Concentrator Discovery (SCD) Option.....5 3. Security Considerations......................................7 4. IANA Considerations..........................................7 4.1. DHCPv4 SCD Option SC Types..............................7 4.2. DHCPv6 SCD Option SC Types..............................7 4.3. Tunnel Types............................................8 5. Acknowledgments..............................................8 6. References...................................................8 6.1. Normative References....................................8 6.2. Informative References..................................8 Author's Addresses.............................................10 Guo & Jiang Expires January 8, 2010 [Page 2] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 1. Introduction Transition is an important factor for user experience in IPv4 and IPv6 coexistence phase. The transition of the edge network is the most complicated because it is near lots of users and uses multiple network technologies. Recently, several types of Carrier-Grade-NATs (CGNs) have been proposed to simplify IPv4/IPv6 transition of the edge network by integrating tunnels and NAT. Incremental CGN [Incremental CGN] describes how dispersed IPv6 users bridge with the IPv6 Internet by tunnel spanning ipv4 infrastructure. The dual-stack lite technology [Ds-lite CGN] is intended for maintaining connectivity to legacy IPv4 devices and networks using IPv4-over-IPv6 softwires while a service provider deploys an IPv6-only network. A very common scenario is that many users set up softwires or tunnels to a softwire concentrator for public or private access services. In order to establish a softwire successfully, users must know the information of a softwire concentrator or CGN, such as address, tunnel type, protocol type in tunnel. Additionally, the discovery process may also support load-sharing and recovery from a single point of failure. The aforementioned scenarios have been abstracted as hub and spoke networks in the IETF Softwire working group, and several encapsulation techniques have been defined [RFC4925] [RFC5512] [RFC5571] discloses a mechanism in mesh network by BGP extension for users to discover the information of a tunnel end point. However, the nodes in an edge network do not have BGP capability generally. Manual configuration is not suitable because the address and other attribute of the concentrator may change. A new mechanism is required to enable users in edge network to discover the information of the concentrator automatically. The Dynamic Host Configuration Protocol (DHCP [RFC2131], [RFC3315]) is widely used in edge networks to enable auto-configuration. This document extends DHCP to support discovery of a softwire concentrator or CGN. This mechanism is general for incremental CGN, DS-Lite and Port-range Router [Port-range, PR-v6]. It can also be extended to support the discovery of other concentrators with tunnels. In the absence of DHCP, PPP or Router Advertisements could be used to find a softwire concentrator or CGN automatically, but this document does not discuss these methods in detail. Guo & Jiang Expires January 8, 2010 [Page 3] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 2. DHCP Solution for Softwire Concentrator Discovery In order to support softwire concentrator or CGN discovery, two new DHCP options are defined. When a DHCP server answers a client request message, softwire concentrator information can be carried in a DHCP reply message. Thus a client is configured the address and other attribute of a softwire concentrator or CGN and can automatically set up a tunnel. For load sharing or single-point failure recovery purposes, a DHCP reply message may carry information of more than one softwire concentrators. Section 2.1 defines a new DHCPv4 Softwire Concentrator Discovery (SCD) option while Section 2.2 defines DHCPv6 SCD option. 2.1. DHCPv4 Softwire Concentrator Discovery (SCD) Option The DHCPv4 Softwire Concentrator Discovery (SCD) Option is mainly used when an IPv6 host or CPE in an IPv4 ISP network wants to obtain an IPv4 address of an IPv6 access point or an incremental CGN. The Option is carried in DHCPv4. A DHCP message may carry more than one SCD Option. The DHCPv4 SCD Option is structured 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Len | SC Type | Preference | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Softwire Concentrator or CGN Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tunnel Type | Protocol Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . Sub Options . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Code TBD1. Len 6 + length of sub options in octets. SC Type SC type, 0 for softwire concentrator, 1 for Incremental CGN, 2 for Port-range PRR. Guo & Jiang Expires January 8, 2010 [Page 4] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 Preference This indicates the preference level for a softwire concentrator or CGN. 0 is the highest. When receiving multiple options, the user chooses a primary softwire concentrator among them based on the preference. The others are backup softwire concentrators. The service provider assigns different preference for each softwire concentrator to support traffic engineering. Softwire Concentrator or CGN Address The outer layer IPv4 address of softwire concentrator, which is used to establish tunnel. Tunnel Type Tunnel type which users connect to softwire concentrators or CGN. 1 for L2TPv2, 2 for L2TPv3, 3 for GRE, 4 for IP in IP, 5 for IPsec. Protocol Type This designates either IPv4 or IPv6 packet encapsulated in tunnel, of the types defined in [IANA-ET] as ETHER TYPEs. Sub Options An optional, variable length field is used to carry other information, such as GRE Key. 2.2. DHCPv6 Softwire Concentrator Discovery (SCD) Option The DHCPv6 Softwire Concentrator Discovery (SCD) Option is mainly used when an IPv4 host or CPE in an IPv6 ISP network wants to learn an IPv6 address of an IPv4 access point or a DS-lite CGN. The Option is carried in DHCPv6. A DHCPv6 Reply message can carry more than one SCD Option. The DHCPv6 SCD Option is structured as follows: Guo & Jiang Expires January 8, 2010 [Page 5] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option_SCD | Option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Softwire Concentrator or CGN Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SC Type | Preference | Tunnel Type | Protocol Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol Type | | +-+-+-+-+-+-+-+-+ Sub Options | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option-code Option_SCD (TBD2). Option-len 20 + length of sub options in octets. Softwire Concentrator or CGN Address The outer layer IPv6 address of softwire concentrator, which is used to establish tunnel. SC Type SC type, 0 for softwire concentrator, 1 for ds-lite CGN, and 2 for Port-range PRR. Preference This indicates the preference level for a softwire concentrator or CGN. 0 is the highest. When receiving multiple options, user chooses a primary softwire concentrator among them based on the preference. The others are backup softwire concentrators. The service provider assigns different preference of each softwire concentrator to support traffic engineering. Tunnel Type Tunnel type which users connect to softwire concentrators or CGN. 1 for L2TPv2, 2 for L2TPv3, 3 for GRE, 4 for IP in IP, 5 for IPsec. Protocol Type This designates IPv4 or IPv6 packet encapsulated in tunnel, of the types defined in [IANA-ET] as ETHER TYPEs. Sub Options An optional, variable length field is used to carry other information, such as GRE Key. Guo & Jiang Expires January 8, 2010 [Page 6] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 3. Security Considerations The mechanisms based on DHCPv6 are all vulnerable by man-in-middle attacks. Proper use of DHCPv6 autoconfiguration facilities [RFC3315], such as AUTH option or Secure DHCP [SDHCP] can prevent these threats, provided that a configuration token is known to both the client and the server. 4. IANA Considerations IANA is requested to allocate one DHCPv4 SCD Option code TBD1 and one DHCPv6 Option code TBD2. This document defines three new name spaces: - DHCPv4 SCD Option SC Types - DHCPv6 SCD Option SC Types - Tunnel Types 4.1. DHCPv4 SCD Option SC Types Section 2.1 defines the following SC Types, which should be assigned by IANA for use within DHCPv4 SCD Option. IANA set up a registry for "DHCPv4 SCD Option SC Types". This is a registry of one-octet values (0-255), to be assigned on a first-come, first-served basis. The initial assignments are as follows: Softwire Concentrator / CGN Name Type -------------------------------- ----- Softwire concentrator 0 Incremental CGN 1 Port-range PRR 2 4.2. DHCPv6 SCD Option SC Types Section 2.2 defines the following SC Types, which should be assigned by IANA for use within DHCPv6 SCD Option. IANA set up a registry for "DHCPv6 SCD Option SC Types". This is a registry of one-octet values (0-255), to be assigned on a first-come, first-served basis. The initial assignments are as follows: Softwire Concentrator / CGN Name Type -------------------------------- ----- Softwire concentrator 0 DSlite CGN 1 Port-range PRR 2 Guo & Jiang Expires January 8, 2010 [Page 7] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 4.3. Tunnel Types Section 2.1 & 2.2 defines the following Tunnel Types, which should assigned by IANA for use within DHCPv4 & DHCPv6 SCD Option. IANA set up a registry for "Tunnel Types for DHCP SCD Option". This is a registry of one-octet values (0-255), to be assigned on a first-come, first-served basis. The initial assignments are as follows: Tunnel Name Type --------------- ----- Reserved 0 L2TPv2 1 L2TPv3 2 GRE 3 IP in IP 4 IPsec 5 5. Acknowledgments The authors would like to thank Wei Cao for been involved in the early requirement identification. 6. References 6.1. Normative References [RFC2131] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC3315] R. Droms, et al., "Dynamic Host Configure Protocol for IPv6", RFC3315, July 2003. [RFC5512] P. Mohapatra, E. and Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC 5512, April 2009. [RFC5571] B. Storer, et al., "Softwire Hub & Spoke Deployment Framework with L2TPv2", RFC 5571, June 2009. 6.2. Informative References [RFC4925] X. Li, S. Dawkins, D. Ward, and A. Durand, "Softwire Problem Statement", RFC 4925, July 2007. Guo & Jiang Expires January 8, 2010 [Page 8] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 [Ds-lite CGN] A. Durand, R. Droms, B. Haberman, and J. Woodyatt, "Dual-stack lite broadband deployments post IPv4 exhaustion", draft-ietf-softwire-dual-stack-lite-00, work in progress, March 2009. [Incremental CGN] S. Jiang, D. Guo, and B. Carpenter, "An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition" draft-jiang- v6ops-incremental-cgn-00, work in progress, May 2009 [Port-range] B. Storer, et al., "IPv4 Connectivity Access in the Context of IPv4 Address Exhaustion", draft-boucadair-port- range-01.txt, work in progress, January 2009. [PR-v6] M. Boucadair, et al., "Flexible IPv6 Migration Scenarios in the Context of IPv4 Address Shortage", draft-boucadair- behave-ipv6-portrange-01, work in progress, March 2009. [IANA-ET] "Ether Types", http://www.iana.org/assignments/ethernet- numbers. [SDHCP] S. Jiang and S. Shen, "Secure DHCPv6 Using CGAs", draft- jiang-dhc-secure-dhcpv6-01.txt, work in progress, January 2009. Guo & Jiang Expires January 8, 2010 [Page 9] Internet-Draft draft-guo-softwire-sc-discovery-01 July 2009 Author's Addresses Dayong Guo Huawei Technologies Co., Ltd KuiKe Building, No.9 Xinxi Rd., Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085 P.R. China Phone: 86-10-82836077 Email: guoseu@huawei.com Sheng Jiang Huawei Technologies Co., Ltd KuiKe Building, No.9 Xinxi Rd., Shang-Di Information Industry Base, Hai-Dian District, Beijing 100085 P.R. China Phone: 86-10-82836081 Email: shengjiang@huawei.com Guo & Jiang Expires January 8, 2010 [Page 10]