Network Working Group C. Liu Internet-Draft Q. Sun Intended status: Informational J. Wu Expires: January 24, 2015 Tsinghua University July 23, 2014 Dynamic IPv4 Provisioning for Lightweight 4over6 draft-liu-softwire-lw4over6-dhcp-deployment-04 Abstract Lightweight 4over6 [I-D.ietf-softwire-lw4over6] is an IPv4 over IPv6 hub and spoke mechanism that provides overlay IPv4 services in an IPv6-only access network. Provisioning IPv4 addresses and port set to customers is the core function of Lightweight 4over6 control plane. [I-D.ietf-softwire-lw4over6] illustrates how to use DHCPv6 for deterministic IPv4 provisioning. This document discusses how to provision IPv4 parameters by using dynamic IPv4 provisioning protocols such as DHCPv4 over DHCPv6 [I-D.ietf-dhc-dhcpv4-over-dhcpv6]. This document describes a dynamic IPv4 provisioning mode for Lightweight 4over6 that uses DHCPv4 over DHCPv6 [I-D.ietf-dhc-dhcpv4-over-dhcpv6] for IPv4 address provisioning. 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 January 24, 2015. Copyright Notice Copyright (c) 2014 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 Liu, et al. Expires January 24, 2015 [Page 1] Internet-Draft lw4over6 dynamic provisioning July 2014 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Advantage of Dynamic IPv4 Provisioning . . . . . . . . . . . 3 4. Using DHCPv4 over DHCPv6 for Lw4over6 Provisioning . . . . . 4 4.1. IP Addressing . . . . . . . . . . . . . . . . . . . . . . 4 4.2. DHCPv6 Configuration . . . . . . . . . . . . . . . . . . 4 4.3. DHCPv4 over DHCPv6 Function . . . . . . . . . . . . . . . 4 4.4. Port Set Consideration . . . . . . . . . . . . . . . . . 5 4.5. lwAFTR Binding Table Maintenance . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Lightweight 4over6 [I-D.ietf-softwire-lw4over6] provides IPv4 access over IPv6 network in hub-and-spoke softwire architecture. In Lightweight 4over6, each Lightweight B4 (lwB4) is assigned with a port-restricted public IPv4 address or a full public IPv4 address to be used for IPv4 communication. Provisioning IPv4 address, port set and other IPv4 parameters to lwB4 is the core function of the Lightweight 4over6 control plane. It can be achieved by several protocols, such as DHCPv6 [RFC3315] [I-D.ietf-softwire-map-dhcp], DHCPv4 over DHCPv6 [I-D.ietf-dhc-dhcpv4-over-dhcpv6] , and PCP [RFC6887]. [I-D.ietf-softwire-lw4over6] illustrates how to use DHCPv6 for deterministic IPv4 provisioning. The IPv4 address and port set id (PSID) are carried in DHCPv6 options defined in [I-D.ietf-softwire-map-dhcp]. However, the deterministic IPv4 provisioning adds some restrictions for addressing and deployment: the IPv4 address's life time needs to be bound to the IPv6 lease time; the IPv4 address and PSID need to be embedded into clients' /128 IPv6 address so the client can not use arbitrary /128 IPv6 Liu, et al. Expires January 24, 2015 [Page 2] Internet-Draft lw4over6 dynamic provisioning July 2014 address as tunnel source address; a customer network that is provisioned with a unique IPv6 prefix can only build one tunnel instance. Thus This document describes how to deploy Lightweight 4over6 using DHCPv4 over DHCPv6 for dynamic IPv4 address provisioning. Since pure DHCPv4 is unable to directly work in native IPv6 network, DHCPv4 over DHCPv6 [I-D.ietf-dhc-dhcpv4-over-dhcpv6] is proposed to support DHCPv4 functionality in IPv6 network by transporting DHCPv4 messages over DHCPv6 message. [I-D.ietf-dhc-dynamic-shared-v4allocation] describes how to allocate port set to clients using DHCPv4 over DHCPv6. [I-D.fsc-softwire-dhcp4o6-saddr-opt] defines options for lwB4 to report its IPv6 tunnel source address to the server. This document does not define a new provisioning method, but describes how these existing specifications are organized to support IPv4 provisioning for Lightweight 4over6. 2. Terminology Terminology defined in [I-D.ietf-dhc-dhcpv4-over-dhcpv6] and [I-D.ietf-softwire-lw4over6] is used extensively in this document. 3. Advantage of Dynamic IPv4 Provisioning [I-D.ietf-softwire-lw4over6] describes the behavior of lwB4 and lwAFTR using DHCPv6 as provisioning protocol. It is based on a pre- determined binding relationship between IPv6 prefix and IPv4 address + PSID. With dynamic IPv4 provisioning, there is no restriction on how the lwB4's IPv6 address is generated. Since in the DHCPv4 over DHCPv6 process the lwB4 is able to tell the server which IPv6 address it intends to use, the lwB4 can run SLAAC, DHCPv6 or other mechanism to achieve and generate its IPv6 address that is used for IPv6 tunnel source address. It is different from the deterministic provisioning mode that IPv4 address are pre-binded to IPv6 prefix and multiple lwB4s sourced behind the same IPv4 prefix can not be supported, and generally lwB4 can not run SLAAC to generate its IPv6 address for tunnel. From the IPv4 address life time view, dynamic IPv4 provisioning allows IPv4 address to have a independent IPv4 life time. This is helpful that the in some case the IPv4 provisioning server may not be able to know the lwB4's IPv6 address life time. It may be because that the IPv4 provisioning server may not also be the IPv6 provisioning server for the lwB4, or even the lwB4's IPv6 address does not have a life time at all, thus to bound the IPv4 address life time to IPv6 address life time may cause a waste of IPv4 addresses that the provisioning server is unable to recycle IPv4 address. The dynamic provisioning schema is suitable for operators that has Liu, et al. Expires January 24, 2015 [Page 3] Internet-Draft lw4over6 dynamic provisioning July 2014 restricted IPv4 address recourses. 4. Using DHCPv4 over DHCPv6 for Lw4over6 Provisioning This section describes how DHCPv4 over DHCPv6 is used for Lightweight 4over6 configuration. In the remaining of this section, "lwB4" without explicitly written as "stateless lwB4" will refer to stateful lwB4 that runs DHCPv4 over DHCPv6 for dynamic IPv4 provisioning. 4.1. IP Addressing Before starting DHCPv4 over DHCPv6 to achieve IPv4 configuration, lwB4 MUST be configured with an IPv6 address. There's no restrictions on how IPv6 address is provisioned. The configured IPv6 address is used for IPv6 tunneling and DHCPv4 over DHCPv6 process. The address that lwB4 chooses MUST be routable to the lwAFTR and DHCP 4o6 server, e.g. a link-local address must not be used. The softwire provider is free to provide any IPv4 address for a lwB4. There's no restrictions on IPv6/IPv4 addressing, e.g. scattered IPv4 addresses can be used, and there's no need for embedding IPv4 address/PSID into IPv6 address. 4.2. DHCPv6 Configuration Before stateful lwB4 runs DHCPv4 over DHCPv6 to acquire IPv4 address and port set, lwB4 MUST run DHCPv6 to achieve the DHCP 4o6 server's IPv6 address. The DHCPv6 server provides the DHCP 4o6 server's IPv6 address by OPTION_DHCP4_O_DHCP6_SERVER as defined in [I-D.ietf-dhc-dhcpv4-over-dhcpv6]. A stateful lwB4 may also be compatible with [I-D.ietf-softwire-map- dhcp] and thus will require both OPTION_DHCP4_O_DHCP6_SERVER and OPTION_S46_CONT_LW. The DHCPv6 server decides whether supply OPTION_S46_CONT_LW and OPTION_S46_V4V6BIND directly or indicate the client to run DHCPv4 over DHCPv6 by supplying OPTION_DHCP4_O_DHCP6_SERVER according to its policy. The lwB4 should implement a local logic to decide which one it prefers. The strategy of how to decide preferences between the provisioning modes is out of the scope of the document. 4.3. DHCPv4 over DHCPv6 Function The DHCPv4 over DHCPv6 function in lwB4 is disabled by default, and enabled by OPTION_DHCP4_O_DHCP6_SERVER in DHCPv6 server's response. Once enabled, lwB4 runs stateful DHCPv4 over DHCPv6 to acquire IPv4 address and port set. lwB4 provides one of its IPv6 address as IPv6 tunnel source address to the DHCP 4o6 server, and get the lwAFTR's Liu, et al. Expires January 24, 2015 [Page 4] Internet-Draft lw4over6 dynamic provisioning July 2014 tunnel address through DHCPv4 over DHCPv6. The DHCPv4 over DHCPv6 message flow is described in section 4 of [I-D.fsc-softwire-dhcp4o6-saddr-opt] and MUST be followed. 4.4. Port Set Consideration lwB4 gets its PSID through DHCPv4 over DHCPv6 along with its IPv4 address. [I-D.ietf-dhc-dynamic-shared-v4allocation] describes how to provision PSID to lwB4 through DHCPv4 over DHCPv6. When sending a DHCPDISCOVER over DHCPv6 message, lwB4 MUST include OPTION_V4_PORTPARAMS in the Parameter Request List. If the server decides to reply a port-restricted address, it MUST reply OPTION_V4_PORTPARAMS to lwB4. if the server decides to reply a full IPv4 address, it SHOULD NOT reply OPTION_V4_PORTPARAMS in the response. When lwB4 receives DHCPv4 over DHCPv6 response without OPTION_V4_PORTPARAMS, it configures itself with the full IPv4 address as regular DHCPv4 client does. When lwB4 receives a shared IPv4 address, the address is used for NAPT and MUST NOT be used to identify the lwB4. 4.5. lwAFTR Binding Table Maintenance lwAFTR maintains its binding table as per section 6.1 of [I-D.ietf-softwire-lw4over6]. Unless the binding table is fixed and pre-determined, it is synchronized with DHCPv4 over DHCPv6 process. The following DHCPv4 over DHCPv6 messages triggers binding table modification: o DHCPACK: Generated by DHCP server, triggers lwAFTR to add a new entry or modify an existing entry. o DHCPRELEASE: Generated by lwB4, triggers lwAFTR to delete an existing entry. When lwAFTR receives a DHCPACK event, it looks up the binding table using the lwB4's IPv4 address and PSID. If there is an existing entry found, the lwAFTR updates the lifetime and IPv6 address field of the entry; otherwise the lwAFTR creates a new entry accordingly. When lwAFTR receives a DHCPRELEASE event, it looks up the binding table using the lwB4's IPv6 address, IPv4 address and PSID. The lwAFTR deletes the entry either by removing it from the binding table or mark the lifetime field to an invalid value (e.g. 0). There are two cases on how lwAFTR interacts with the DHCP server. When lwAFTR is located on the IPv4 provisioning path (typically co- located with DHCP server), it listens all DHCPv4 over DHCPv6 messages and updates the bindings through valid messages. When lwAFTR is out Liu, et al. Expires January 24, 2015 [Page 5] Internet-Draft lw4over6 dynamic provisioning July 2014 of the provisioning path, the DHCP server informs the lwAFTR about the binding updates. There are several ways to support this function, e.g. by NETCONF. A standardized data model may be needed, but it's out of the scope of this document. 5. Security Considerations Security considerations in [I-D.ietf-softwire-lw4over6] and [I-D.ietf-dhc-dhcpv4-over-dhcpv6] should be considered. The DHCP message triggered binding table maintenance may be used by an attacker to send faked DHCP messages to lwAFTR. The operator network should deploy [RFC2827] to prevent this kind of attack. 6. IANA Considerations This document does not include an IANA request. 7. References 7.1. Normative References [I-D.fsc-softwire-dhcp4o6-saddr-opt] Farrer, I., Sun, Q., and Y. Cui, "DHCPv4 over DHCPv6 Source Address Option", draft-fsc-softwire-dhcp4o6-saddr- opt-00 (work in progress), July 2014. [I-D.ietf-dhc-dhcpv4-over-dhcpv6] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I. Farrer, "DHCPv4 over DHCPv6 Transport", draft-ietf-dhc- dhcpv4-over-dhcpv6-09 (work in progress), June 2014. [I-D.ietf-dhc-dynamic-shared-v4allocation] Cui, Y., Qiong, Q., Farrer, I., Lee, Y., Sun, Q., and M. Boucadair, "Dynamic Allocation of Shared IPv4 Addresses", draft-ietf-dhc-dynamic-shared-v4allocation-01 (work in progress), July 2014. [I-D.ietf-softwire-lw4over6] Cui, Y., Qiong, Q., Boucadair, M., Tsou, T., Lee, Y., and I. Farrer, "Lightweight 4over6: An Extension to the DS- Lite Architecture", draft-ietf-softwire-lw4over6-10 (work in progress), June 2014. [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. Liu, et al. Expires January 24, 2015 [Page 6] Internet-Draft lw4over6 dynamic provisioning July 2014 7.2. Informative References [I-D.ietf-softwire-map-dhcp] Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec, W., Bao, C., leaf.yeh.sdo@gmail.com, l., and X. Deng, "DHCPv6 Options for configuration of Softwire Address and Port Mapped Clients", draft-ietf-softwire-map-dhcp-07 (work in progress), March 2014. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, April 2013. Authors' Addresses Cong Liu Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-6278-5822 Email: gnocuil@gmail.com Qi Sun Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-6278-5822 Email: sunqi@csnet1.cs.tsinghua.edu.cn Jianping Wu Tsinghua University Department of Computer Science, Tsinghua University Beijing 100084 P.R.China Phone: +86-10-6278-5983 Email: jianping@cernet.edu.cn Liu, et al. Expires January 24, 2015 [Page 7]