Network Working Group Dayong Guo Internet Draft Sheng Jiang (Editor) Intended status: Standards Track Huawei Technologies Co., Ltd Expires: April 28, 2012 R. Despres RD-IPtech R. Maglione Telecom Italia October 26, 2011 RADIUS Attribute for 6rd draft-ietf-softwire-6rd-radius-attrib-04.txt 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 28, 2012. 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. Jiang, et al. Expires April 28, 2012 [Page 1] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 Abstract IPv6 Rapid Deployment (6rd) is one of the most popular methods to provide both IPv4 and IPv6 connectivity services simultaneously during the IPv4/IPv6 co-existing period. The Dynamic Host Configuration Protocol (DHCP) 6rd option has been defined to configure 6rd Customer Edge (CE). However, in many networks, the configuration information may be stored in Authentication Authorization and Accounting (AAA) servers while user configuration is mainly from Broadband Network Gateway (BNG) through DHC protocol. This document defines a Remote Authentication Dial In User Service (RADIUS) attribute that carries 6rd configuration information from AAA server to BNG. Table of Contents 1. Introduction ................................................ 3 2. Terminology ................................................. 3 3. IPv6 6rd Configuration with RADIUS .......................... 3 4. Attributes .................................................. 5 4.1. IPv6-6rd-Configuration Attribute ....................... 5 4.2. Table of attributes .................................... 8 5. Diameter Considerations ..................................... 8 6. Security Considerations ..................................... 8 7. IANA Considerations ......................................... 9 8. Acknowledgments ............................................. 9 9. References .................................................. 9 9.1. Normative References ................................... 9 9.2. Informative References ................................ 10 Jiang, et al. Expires April 28, 2012 [Page 2] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 1. Introduction Recently providers start to deploy IPv6 and consider how to transit to IPv6. IPv6 Rapid Deployment (6rd) [RFC5969] is one of the most popular methods to provide both IPv4 and IPv6 connectivity services simultaneously during the IPv4/IPv6 co-existing period. 6rd is used to provide IPv6 connectivity service through legacy IPv4-only infrastructure. 6rd adopt Dynamic Host Configuration Protocol (DHCP) as auto-configuring protocol. The 6rd Customer Edge (CE) extends DHCP option to discover 6rd border relay and to configure IPv6 prefix and address. In many networks, user configuration information may be managed by AAA servers, together with user Authentication, Authorization, and Accounting (AAA). Current AAA servers communicate using the Remote Authentication Dial In User Service (RADIUS) [RFC2865] protocol. In a fixed line broadband network, the Broadband Network Gateways (BNGs) act as the access gateway of users. The BNGs are assumed to embed a DHCP server function that allows them to locally handle any DHCP requests issued by hosts. Since the 6rd configuration information is stored in AAA servers and user configuration is mainly through DHC protocol between BNGs and hosts. New RADIUS attributes are needed to propagate the information from AAA servers to BNGs. 2. Terminology 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 [RFC2119]. The terms 6rd CE and 6rd Border Relay are defined in [RFC5969]. 3. IPv6 6rd Configuration with RADIUS The below Figure 1 illustrates how the RADIUS protocol and DHCP cooperate to provide 6rd CE with 6rd configuration information. Jiang, et al. Expires April 28, 2012 [Page 3] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 6rd CE BNG AAA Server | | | |-------DHCPDISCOVER------>| | | |--Access-Request(6rd Attr)-->| | | | | |<--Access-Accept(6rd Attr)---| |<-------DHCPOFFER---------| | | | | |--------DHCPREQUEST------>| | | (6rd Option) | | |<--------DHCPACK----------| | | (6rd option) | | | | | DHCP RADIUS Figure 1: the cooperation between DHCP and RADIUS BNGs act as a client of RADIUS and as a DHCP server for DHC protocol. First, a BNG receives a DHCPDISCOVER from the 6rd CE. It initiates the BNG to request correspondent user authentication relevant from an AAA server using RADIUS protocol. A 6rd configuration request may be also sent in the same message. If the user authentication is approved by the AAA server, an Access-Accept message is acknowledged with the IPv6-6rd-Configuration Attribute, defined in the next Section. After the BNG responds to the user with an Advertise message, the user requests for a 6rd Option. Then, the BNG can reply the user using DHCP protocol. In the abovementioned scenario, the Access-Request packet contains a Service-Type attribute with the value Authorize Only (17), thus according to [RFC5080] the Access-Request packet MUST contain a State attribute. Figure 2 describes another scenario, in which the authentication operation is not coupled with DHCP. In the authentication stage, the BNG obtains the 6rd configuration information from the AAA server through RADIUS protocol. When the user requests the 6rd Option, the BNG replies with a 6rd option in DHCPACK. Jiang, et al. Expires April 28, 2012 [Page 4] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 6rd CE BNG AAA Server | | | | |--Access-Request(6rd Attr)-->| | | | | |<--Access-Accept(6rd Attr)---| | | | |--------DHCPREQUEST------>| | | (6rd Option) | | |<---------DHCPACK---------| | | (6rd option) | | | | | DHCP RADIUS Figure 2: the cooperation between DHCP and RADIUS After receiving the IPv6-6rd-Configuration Attribute in the initial Access-Accept, the BNG MUST store the received 6rd configuration parameters locally. When the 6rd Customer Edge sends a DHCP Request message to request an extension of the lifetimes for the assigned address, the BNG does not have to initiate a new Access-Request towards the AAA server to request the 6rd configuration parameters. The BNG retrieves the previously stored 6rd configuration parameters and use them in its reply. If the DHCP server to which the DHCP Request message was sent at time T1 has not responded, the DHCP client enters the REBINDING state and attempts to contact any server. In this scenario the BNG receiving the DHCP message MUST initiate a new Access-Request towards the AAA server. The BNG MAY include the IPv6-6rd-Configuration Attribute in its Access-Request. If the BNG does not receive the IPv6-6rd- Configuration Attribute in the Access-Accept it MAY fallback to a pre-configured default 6rd configuration, if any. If the BNG does not have any pre-configured default 6rd configuration or if the BNG receives an Access-Reject, the tunnel cannot be established. 4. Attributes This section defines IPv6-6rd-Configuration Attribute which is used in the 6rd scenario. The attribute design follows [RFC6158]. 4.1. IPv6-6rd-Configuration Attribute The IPv6-6rd-Configuration Attribute is structured as follows (The specification requires that multiple IPv4 addresses are associated strongly with one IPv6 prefix. Given that RADIUS currently has no recommended way of grouping multiple attributes, the below design appears to be a reasonable compromise.): Jiang, et al. Expires April 28, 2012 [Page 5] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | SubType | SubLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4MaskLen | SubType | SubLen | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 6rdPrefixLen | | +-+-+-+-+-+-+-+-+ + | | + + | 6rdPrefix | + + | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | SubType | SubLen |6rdBRIPv4Address| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 6rdBRIPv4Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type TBD Length 25 + n*6 (the length of the entire attribute in octets; n stands the number of BR IPv4 addresses, minimum n is 1). SubType 1 (SubType number, for the IPv4 Mask Length suboption) SubLen 3 (the length of the IPv4 Mask Length suboption) IPv4MaskLen The number of high-order bits that are identical across all CE IPv4 addresses within a given 6rd domain. This may be any value between 0 and 32. Any value greater than 32 is invalid. SubType 2 (SubType number, for the 6rd prefix suboption) Jiang, et al. Expires April 28, 2012 [Page 6] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 SubLen 20 (the length of the 6rd prefix suboption) Reserved Set to be all 0 for now. Reserved for the future use. To be compatible with other IPv6 prefix attributes in the Radius Protocol. 6rdPrefixLen The IPv6 Prefix length of the Service Provider's 6rd IPv6 prefix in number of bits. The 6rdPrefixLen MUST be less than or equal to 128. 6rdPrefix The Service Provider's 6rd IPv6 prefix represented as a 16 octet IPv6 address. The bits after the 6rdPrefixlen number of bits in the prefix SHOULD be set to zero. SubType 3 (SubType number, for the 6rd Border Relay IPv4 address suboption) SubLen 6 (the length of the 6rd Border Relay IPv4 address suboption) 6rdBRIPv4Address One or more IPv4 addresses of the 6rd Border Relay(s) for a given 6rd domain. The maximum RADIUS Attribute length of 255 octets results in a limit of 58 IPv4 addresses. The IPv6-6rd-Configuration Attribute MAY be used in Access-Request packets as a hint to the RADIUS server; for example if the BNG is pre-configured with a default 6rd configuration, these parameters MAY be inserted in the attribute. The RADIUS server MAY ignore the hint sent by the BNG and it MAY assign different 6rd parameters. If the BNG includes the IPv6-6rd-Configuration Attribute, but the AAA server does not recognize it, this attribute MUST be ignored by the AAA Server. Jiang, et al. Expires April 28, 2012 [Page 7] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 If the BNG does not receive IPv6-6rd-Configuration Attribute in the Access-Accept it MAY fallback to a pre-configured default 6rd configuration, if any. If the BNG does not have any pre-configured default 6rd configuration, the 6rd tunnel can not be established. If the BNG is pre-provisioned with a default 6rd configuration and the 6rd configuration received in Access-Accept is different from the configured default, then the 6rd configuration received in the Access-Accept message MUST be used for the session. If the BNG cannot support the received 6rd configuration for any reason, the tunnel SHOULD NOT be established. 4.2. Table of attributes The following table provides a guide to which attributes may be found in which kinds of packets, and in what quantity. Request Accept Reject Challenge Accounting # Attribute Request 0-1 0-1 0 0 0-1 TBD IPv6-6rd- Configuration The following table defines the meaning of the above table entries. 0 This attribute MUST NOT be present in packet. 0+ Zero or more instances of this attribute MAY be present in packet. 0-1 Zero or one instance of this attribute MAY be present in packet. 1 Exactly one instance of this attribute MUST be present in packet. 5. Diameter Considerations This attribute is usable within either RADIUS or Diameter [RFC3588]. Since the Attributes defined in this document will be allocated from the standard RADIUS type space, no special handling is required by Diameter entities. 6. Security Considerations In 6rd scenarios, the RADIUS protocol is run over IPv4. Known security vulnerabilities of the RADIUS protocol are discussed in RFC 2607 [RFC2607], RFC 2865 [RFC2865], and RFC 2869 [RFC2869]. Use of IPsec [RFC4301] for providing security when RADIUS is carried in IPv6 is discussed in RFC 3162 [RFC3162]. Jiang, et al. Expires April 28, 2012 [Page 8] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 Security considerations for the Diameter protocol are discussed in RFC 3588 [RFC3588]. 7. IANA Considerations This document requires the assignment of one new RADIUS Attribute Types in the "Radius Types" registry (currently located at http://www.iana.org/assignments/radius-types for the following attributes: o IPv6-6rd-Configuration IANA should allocate the number from the standard RADIUS Attributes space using the "IETF Review" policy [RFC5226]. 8. Acknowledgments The authors would like to thank Maglione Roberta, Alan DeKok, for valuable comments. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. [RFC3162] Aboba, B., Zorn, G., and D. Mitton, "RADIUS and IPv6", RFC 3162, August 2001. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J., Arkko, "Diameter Base Protocol", RFC 3588, September 2003. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC5080] Nelson, D. and DeKok A., "Common Remote Authentication Dial In User Service (RADIUS) Implementation Issues and Suggested Fixes", RFC 5080, December 2007. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, May 2008. Jiang, et al. Expires April 28, 2012 [Page 9] Internet-Draft draft-ietf-softwire-6rd-radius-attrib-04 October 2011 [RFC5969] Townsley, M. and O. Troan, "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) -- Protocol Specification", RFC5969, August 2010. [RFC6158] DeKok, A. and G. Weber, "RADIUS Design Guidelines", RFC 6158, March 2011. 9.2. Informative References [RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy Implementation in Roaming", RFC 2607, June 1999. [RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RADIUS Extensions", RFC 2869, June 2000. Author's Addresses Dayong Guo Huawei Technologies Co., Ltd Q14 Huawei Campus, 156 BeiQi Road, ZhongGuan Cun, Hai-Dian District, Beijing 100085 P.R. China Email: guoseu@huawei.com Sheng Jiang (Editor) Huawei Technologies Co., Ltd Q14 Huawei Campus, 156 BeiQi Road, ZhongGuan Cun, Hai-Dian District, Beijing 100085 P.R. China Email: jiangsheng@huawei.com Remi Despres RD-IPtech 3 rue du President Wilson Levallois, France Email: remi.despres@free.fr Roberta Maglione Telecom Italia Via Reiss Romoli 274 Torino 10148 Italy Email: roberta.maglione@telecomitalia.it Jiang, et al. Expires April 28, 2012 [Page 10]