Network Working Group M. Nakhjiri, Ed. Internet-Draft Huawei USA Intended status: Informational K. Chowdhury Expires: January 21, 2008 Starent Networks A. Lior Bridgewater Systems K. Leung Cisco Systems July 20, 2007 Mobile IPv4 RADIUS requirements draft-ietf-mip4-radius-requirements-04.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 21, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document provides an applicability statement as well as a scope definition for specifying RADIUS extensions to support Mobile IPv4. The goal is to allow specification of RADIUS attributes to assist the Nakhjiri, et al. Expires January 21, 2008 [Page 1] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 Mobile IPv4 signaling procedures. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . . . 4 3.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Non-Goals . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Security considerations . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Nakhjiri, et al. Expires January 21, 2008 [Page 2] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 1. Introduction To kick start the Mobile IPv4 [RFC3344] processing of its packets by Mobile IP agents, a mobile node (MN) needs to be able to acquire a pair of home and care of addresses (HoA and CoA, respectively), find a willing agent to act as a Home Agent, HA, for the MN and perform a registration process with the HA. The registration process consists of an exchange of a registration request and reply message between the MN and the HA. The specification in [RFC3344] allows an MN to start the registration process prior to having acquired its home address or the address of its HA. Acquiring those parameters by the MN is typically part of a process referred to as bootstrapping. Successful processing of registration requests, and replies among other things depends on successful creation and verification of a number of authentication extensions developed specifically to protect the integrity and security of the registration requests and replies and the entities processing them, i.e. MN, HA and some times, foreign agents, FA [RFC3344]. Creation as well as verification of these extensions requires existence of trust relationships and shared keys between MN and each of the mobility agents. However, creation of these trust relationships, typically referred to as mobility security associations, MSA, is considered outside scope of the base Mobile IPv4 specification defined in [RFC3344]. It is desired to avoid the scalability issues arising from creating static security associations between an MN and all possible mobility agents. Thus it is preferred to establish the associations dynamically using the pre- existing relationship between the MN and the AAA server. To allow for utilization of an existing AAA infrastructure in the bootstrapping of the Mobile IPv4 parameters and security relationships, the Mobile IPv4 working group has developed extensions to allow the MN to authenticate to the home AAA server [RFC4721] and to request assistance from the AAA server in creation of security associations [RFC3957] with the mobility agents, all based on the pre-established trust relationship between the MN and its home AAA server. However, utilization of the AAA infrastructure for Mobile IPv4 purposes, involves both Mobile IP and AAA signaling, where the interaction between the MN and the mobility agents (HA and FA) is based on Mobile IP signaling, while the signaling beyond the mobility agents to the AAA server is based on AAA protocols. Around the same time, when the specification was being developed, the AAA community was in the process of designing Diameter as a successor to RADIUS. Thus, the Mobile IP group developed a set of guidelines and requirements specifically from Mobile IP standpoint [RFC2977] for such a successor. These requirements, led to development of an Nakhjiri, et al. Expires January 21, 2008 [Page 3] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 specification for use of Diameter in Mobile IPv4 bootstrapping [RFC4004], while the requirement document is essentially standardized [RFC2977] after standardization of RADIUS [RFC2865] Thus it is obvious that RADIUS does not and cannot meet all the requirements listed In [RFC2977] without undergoing an extensive design change and thus no RADIUS attributes have been standardized for Mobile IP support thus far. However, in the absence of IETF standardized RADIUS attributes for support of MIPv4, different wireless SDOs have taken the path of developing VSAs for dynamic bootstrapping of Mobile IPv4 registration procedure. The use of different VSAs and different RADIUS procedures for the same purpose of Mobile IPv4 bootstrapping at different SDOs will cause a lack interoperability between these wireless standards, potentially hindering mobility across these wireless networks. To respond to the described issue, it is desired to standardize a set of RADIUS attributes within IETF to allow a consistent and interoperable interaction with RADIUS based AAA infrastructure during the Mobile IPv4 Registration procedure. The bootstrapping attributes can include configuration parameters as well as material used for provisioning security of Mobile IPv4 messaging (authentication) as defined by [RFC4721] and [RFC3957]. Given that RADIUS as it stands today cannot meet all the requirements in [RFC2977], the purpose of this requirement is to define a set of goals and nongoals specifically defined for RADIUS when it comes to assisting mobile nodes and mobility agents in bootstrapping Mobile IPv4 operation. 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 RFC 2119 [RFC2119]. 3. Goals and Non-Goals Since this document serves as requirement specification for RADIUS extensions supporting Mobile IPv4 interaction with RADIUS infrastructure, the goals and non-goals refer to only those RADIUS extensions that are required for support of Mobile IPv4. Nakhjiri, et al. Expires January 21, 2008 [Page 4] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 3.1. Goals The scope of the work is to standardize RADIUS attributes and to define the procedure by which the Mobile IPv4 agents, e.g. Home agent (HA) and Foreign Agent (FA) map the Mobile IP registration message fields into the proposed RADIUS attributes and vice versa. o It is required of the RADIUS servers to be able to understand and process the attributes to be defined for Mobile IPv4 support and to perform verification of authentication extensions specified in [RFC4721]. RADIUS proxies are expected to be able to forward messages including the Mobile IPv4 related attributes as they would with any other RADIUS messages and attributes. o All RADIUS work MUST be backward compatible with existing RADIUS RFCs, including RFCs as follows: [RFC2865], [RFC2866], [RFC2867], [RFC2868], [RFC2869], [RFC3576], [RFC3579], and [RFC3580]. o It is also required of the Mobile IP agents (FA and HA) to operate as RADIUS clients (NASes in context of [RFC2865]) when translating RADIUS signaling into Mobile IP signaling and vice versa. Details on the behavior of Mobile IP agents as RADIUS clients are to be provided by the solution draft describing the RADIUS extensions for Mobile IP support. 3.2. Non-Goals The scope of this work is to only standardize RADIUS attributes and to define the procedure by which the Mobile IPv4 agents, e.g. Home agent (HA) and Foreign Agent (FA) map the Mobile IP registration message fields into the proposed RADIUS attributes and vice versa. It is not the intention to extend the functionality of existing RADIUS servers or protocol. More specifically, the following are NON-GOALS: o Enhancing RADIUS Security: Creating new security properties for RADIUS, such as creating key transport capabilities is not the goal. No new security mechanisms are to be defined for the transport of RADIUS Access Requests in relation to support of Mobile IPv4 bootstrapping. Existing RADIUS authentication procedures, e.g. Message-Authenticator (80) described in [RFC2869], are used. The security considerations for use of RADIUS in bootstrapping Mobile IPv4 are described in a later section of this document. o Enhancing RADIUS transport reliability: Transport properties of RADIUS remain intact. No new reliability mechanisms are defined in the transport of such Access Requests. o Extending RADIUS message set: RADIUS extensions for bootstrapping Mobile IPv4 are not to define new RADIUS messages. Diameter Mobile IP application [RFC4004] has defined new command codes for support of Mobile IP signaling, depending on whether Diameter server is dealing with a Mobile IP HA or an FA. RADIUS currently Nakhjiri, et al. Expires January 21, 2008 [Page 5] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 does not have any messages that correspond to these Diameter commands. Instead, RADIUS extensions for Mobile IPv4 bootstrapping need to provide proposals for new RADIUS attributes that facilitates Diameter-RADIUS messaging translation without defining any new RADIUS messaging. At the same time, the RADIUS extensions for Mobile IPv4 need to re-use Diameter AVPs to the fullest extent possible. o RFC2977 compatibility: Extending RADIUS in a way that fulfills the full list of requirements in [RFC2977] will not be attempted. 4. Attributes A specification of the RADIUS extensions for Mobile IPv4 needs to describe the full set of attributes required for RADIUS-Mobile IP interaction. While some of the attributes may already be standardized, others will require standardization and IANA type assignments. 5. IANA Considerations This requirement document does not allocate any numbers, so there are no IANA considerations. On the other hand, solution documentations for RADIUS support of Mobile IPv4 will likely introduce new RADIUS attributes. Thus those documents will need new attribute type numbers assigned by IANA. 6. Security considerations Enhancing security properties of RADIUS are a specific non-goal for the RADIUS extensions providing support for Mobile IP. Also, as this is a requirement document and not a solution specification document, no new security considerations aside from those that already exist for RADIUS are noted. As such, the existing RADIUS security considerations described previously apply, and no additional security considerations are added here. For instance, the assumption in RADIUS is that intermediary nodes are trusted, while at the same time there is a concern on using AAA protocols that use hop by hop security to distribute keys. Use of hop by hop security for key distribution can be in conflict with some of the requirements stated in [housley-aaa-key-mgmt], such as the requirement on binding a key to its context and the requirement on limitation of the key scope. The former for instance states that a key Must be bound to the parties that are expected to have access to the keying material, while the latter implies that parties that do not require access to a key to perform their role MUST not have access to the key. Both of Nakhjiri, et al. Expires January 21, 2008 [Page 6] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 these requirements rule against trusting intermediary nodes and proxies with distribution of keys. Due to lack of end to end security mechanisms for RADIUS, imposing a MUST requirement for not trusting proxies is not possible. RADIUS extension working group is in the process of specifying procedures for wrapping key materials within RADIUS attributes. For the time being, support of Mobile IP within RADIUS may need to be based on trust of intermediaries, despite the security considerations described. When it comes to protecting attributes in Access Request, [RFC2868] section 3.5 provides a mechanism for encrypting RADIUS attributes, such as passwords. There is also work under progress for specifying wrapping of sensitive attributes, such as key material within RADIUS Access Accept messages. This work is currently considered as part of RADIUS crypto-agility extensions and when completed can be used in the process of distributing sensitive attributes, such as keying material from RADIUS servers. It is also possible to protect RADIUS transactions using IPsec (e.g. as in RFC3579). 7. Acknowledgements The authors would like to thank Alan DeKok for review and feedback, Pete McCann and Jari Arkko for diligent shepherding of this document. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [RFC2865] Rigney, C., "Remote Authentication Dial In User Service", June 2000. [RFC2866] Rigney, C., "RADIUS Accounting", June 2000. [RFC2867] Zorn, G., "Remote Accounting Modification for Tunnel Protocol Support", June 2000. [RFC2977] Glass, S. and Perkins, "Mobile IP Authentication, Authorization, and Accounting Requirements", October 2000. [RFC3344] Perkins, C., "IP Mobility Support", August 2002. Nakhjiri, et al. Expires January 21, 2008 [Page 7] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 [RFC3957] Perkins, C. and P. Calhoun, "AAA Registration Keys for Mobile IP", March 2005. [RFC4004] Calhoun, P. and C. Perkins, "Diameter Mobile IP application", May 2004. [RFC4721] Perkins, C. and P. Calhoun, "Mobile IP Challenge/Response Extensions (Revised)", January 2007. [housley-aaa-key-mgmt] Housley, R., "Guidance for AAA key management", draft-housley-aaa-key-mgmt-09 (work in progress). 8.2. Informative References [RFC2868] Zorn, G., "RADIUS Attributes for Tunnel Protocol Support", June 2000. [RFC2869] Rigney, C., "RADIUS Extensions", June 2000. [RFC3576] Chiba, M., "Dynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)", July 2003. [RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial In User Service) Support For Extensible Authentication Protocol (EAP)", September 2003. [RFC3580] Cogdon, P., "IEEE 802.1X Remote Authentication Dial In User Service (RADIUS) Usage Guidelines", September 2003. Authors' Addresses Madjid Nakhjiri (editor) Huawei USA Email: mnakhjiri@huawei.com Kuntal Chowdhury Starent Networks Email: kchowdhury@starentnetworks.com Nakhjiri, et al. Expires January 21, 2008 [Page 8] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 Avi Lior Bridgewater Systems Email: avi@bridgewatersystems.com Kent Leung Cisco Systems 170 West Tasman Drive San Jose, CA 95134 US Email: kleung@cisco.com Nakhjiri, et al. Expires January 21, 2008 [Page 9] Internet-Draft Mobile IP4 RADIUS Requirements July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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