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INFORMATIONAL
Internet Engineering Task Force (IETF)                      G. Zorn, Ed.Request for Comments: 6697                                   Network ZenCategory: Informational                                            Q. WuISSN: 2070-1721                                                T. Taylor                                                                  Huawei                                                                  Y. Nir                                                             Check Point                                                               K. Hoeper                                                Motorola Solutions, Inc.                                                              S. Decugis                                                           INSIDE Secure                                                               July 2012Handover Keying (HOKEY) Architecture DesignAbstract   The Handover Keying (HOKEY) Working Group seeks to minimize handover   delay due to authentication when a peer moves from one point of   attachment to another.  Work has progressed on two different   approaches to reduce handover delay: early authentication (so that   authentication does not need to be performed during handover), and   reuse of cryptographic material generated during an initial   authentication to save time during re-authentication.  A basic   assumption is that the mobile host or "peer" is initially   authenticated using the Extensible Authentication Protocol (EAP),   executed between the peer and an EAP server as defined inRFC 3748.   This document defines the HOKEY architecture.  Specifically, it   describes design objectives, the functional environment within which   handover keying operates, the functions to be performed by the HOKEY   architecture itself, and the assignment of those functions to   architectural components.  It goes on to illustrate the operation of   the architecture within various deployment scenarios that are   described more fully in other documents produced by the HOKEY Working   Group.Zorn, et al.                  Informational                     [Page 1]

RFC 6697                HOKEY Architecture Design              July 2012Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6697.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Zorn, et al.                  Informational                     [Page 2]

RFC 6697                HOKEY Architecture Design              July 2012Table of Contents1. Introduction ....................................................32. Terminology .....................................................63. Design Goals ....................................................63.1. Reducing Signaling Overhead ................................73.1.1. Minimized Communications with Home Servers ..........73.1.2. Minimized User Interaction for Authentication .......73.2. Integrated Local Domain Name (LDN) Discovery ...............73.3. Fault-Tolerant Re-Authentication ...........................83.4. Improved Deployment Scalability ............................84. Required Functionality ..........................................84.1. Authentication Subsystem Functional Overview ...............84.2. Pre-Authentication Function (Direct or Indirect) ...........94.3. EAP Re-Authentication Function .............................94.4. EAP Authentication Function ...............................104.5. Authenticated Anticipatory Keying (AAK) Function ..........104.6. Management of EAP-Based Handover Keys .....................105. Components of the HOKEY Architecture ...........................115.1. Functions of the Peer .....................................125.2. Functions of the Serving Authenticator ....................135.3. Functions of the Candidate Authenticator ..................145.4. Functions of the EAP Server ...............................155.5. Functions of the ER Server ................................166. Usage Scenarios ................................................166.1. Simple Re-Authentication ..................................166.2. Intra-Domain Handover .....................................176.3. Inter-Domain Handover .....................................176.4. Inter-Technology Handover .................................177. AAA Considerations .............................................177.1. Authorization .............................................177.2. Transport Aspect ..........................................188. Security Considerations ........................................189. Acknowledgments ................................................1810. References ....................................................1810.1. Normative References .....................................1810.2. Informative References ...................................191.  Introduction   The Extensible Authentication Protocol (EAP) [RFC3748] is an   authentication framework that supports different types of   authentication methods.  Originally designed for dial-up connections,   EAP is now commonly used for authentication in a variety of access   networks.Zorn, et al.                  Informational                     [Page 3]

RFC 6697                HOKEY Architecture Design              July 2012   When a host (or "peer", the term used from this point onward) changes   its point of attachment to the network, it must be re-authenticated.   If a full EAP authentication must be repeated, several message round   trips between the peer and the home EAP server may be involved.  The   resulting delay will result in degradation -- or, in the worst case,   loss of any service session in progress -- if communication is   suspended while re-authentication is carried out.  The delay is worse   if the new point of attachment is in a visited network rather than   the peer's home network because of the extra procedural steps   involved as well as the probable increase in round-trip time.   Clancy, et al. [RFC5169] describe this problem more fully and   establish design goals for solutions to reduce re-authentication   delay for transfers within a single administrative domain.  They also   suggest a number of ways to achieve a solution:   o  specification of a method-independent, efficient re-authentication      protocol based upon EAP;   o  reuse of keying material from the initial EAP authentication;   o  deployment of re-authentication servers local to the peer to      reduce round-trip delay; and   o  specification of the additional protocol needed to allow the EAP      server to pass authentication information to the local      re-authentication servers.   Salowey, et al. [RFC5295] tackle the problem of the reuse of keying   material by specifying how to derive a hierarchy of cryptographically   independent purpose-specific keys from the results of the original   EAP authentication, while Cao, et al. [RFC6696] specify a method-   independent re-authentication protocol (the EAP Re-authentication   Protocol (ERP)) applicable to two specific deployment scenarios:   o  where the peer's home EAP server also performs re-authentication;      and   o  where a local re-authentication server exists but is co-located      with an Authentication, Authorization, and Accounting (AAA) proxy      within the domain.   Other work provides further pieces of the solution or insight into   the problem.  For the purpose of this memo, Hoeper, et al. [RFC5749]   provide an abstract mechanism for distribution of keying material   from the EAP server to re-authentication servers.  Ohba,   et al. [RFC5836] contrast the EAP Re-authentication (ER) strategy   provided by ERP with an alternative strategy called "earlyZorn, et al.                  Informational                     [Page 4]

RFC 6697                HOKEY Architecture Design              July 2012   authentication".RFC 5836 defines EAP early authentication as the   use of EAP by a mobile peer to establish authenticated keying   material on a target attachment point prior to its arrival.  Hence,   the goal of EAP early authentication is to complete all EAP-related   communications, including AAA signaling, in preparation for the   handover, before the mobile device actually moves.  Early   authentication includes direct and indirect pre-authentication as   well as Authenticated Anticipatory Keying (AAK).  All three early   authentication mechanisms provide means to securely establish   authenticated keying material on a Candidate Attachment Point (CAP)   while still being connected to the Serving Attachment Point (SAP) but   vary in their respective system assumptions and communication paths.   In particular, direct pre-authentication assumes that clients are   capable of discovering CAPs and all communications are routed through   the SAP.  On the other hand, indirect pre-authentication assumes an   existing relationship between the SAP and CAP, whereas the discovery   and selection of CAPs is outside the scope of AAK.  Furthermore, both   direct and indirect pre-authentication require a full EAP execution   to occur before the handover of the peer takes place, while AAK   techniques (like ERP [RFC6696]) use keys derived from the initial EAP   authentication.   Both EAP re-authentication and early authentication enable faster   inter-authenticator handovers.  However, it is currently unclear how   the necessary handover infrastructure can be deployed and integrated   into existing EAP infrastructures.  In particular, previous work has   not described how ER servers that act as endpoints in the   re-authentication process should be integrated into local and home   domain networks.  Furthermore, how EAP infrastructure can support the   timely triggering of early authentications and aid with the selection   of CAPs is currently unspecified.   This document proposes a general HOKEY architecture and demonstrates   how it can be adapted to different deployment scenarios.  To begin   with,Section 3 recalls the design objectives for the HOKEY   architecture.Section 4 reviews the functions that must be supported   within the architecture.Section 5 describes the components of the   HOKEY architecture.Section 6 describes the different deployment   scenarios that the HOKEY Working Group has addressed and the   information flows that must occur within those scenarios, by   reference to the documents summarized above where possible and   otherwise within this document itself.  Finally,Section 7 provides   an analysis of how AAA protocols can be applied in the HOKEY   architecture.Zorn, et al.                  Informational                     [Page 5]

RFC 6697                HOKEY Architecture Design              July 20122.  Terminology   This document reuses terms defined inSection 2 of Ohba,   et al. [RFC5836] andSection 2 of Cao, et al. [RFC6696].  In   addition, it defines the following:   DS-rRK      Domain-Specific re-authentication Root Key.   pMSK      pre-established Master Session Key.   EAP Early Authentication      The use of EAP by a mobile peer to establish authenticated keying      material on a target attachment point prior to its arrival; see      Ohba, et al. [RFC5836].   ER Key Management      An instantiation of the mechanism described in Hoeper,      et al. [RFC5749] for creating and delivering root keys from an EAP      server to an ER server.   EAP Re-authentication (ER)      The use of keying material derived from an initial EAP      authentication to enable single-round-trip re-authentication of a      mobile peer.  For a detailed description of the keying material,      seeSection 4 of Cao, et al. [RFC6696].   ER Server      A component of the HOKEY architecture that terminates the EAP      re-authentication exchange with the peer.3.  Design Goals   This section investigates the design goals for the HOKEY   architecture.  These include reducing the signaling overhead for   re-authentication and early authentication, integrating local domain   name discovery, enabling fault-tolerant re-authentication, and   improving deployment scalability.  These goals supplement those   discussed inSection 4 of RFC 5169.  Note that the identification and   selection of CAPs is not a goal of the architecture, since those   operations are generally specific to the lower layer in use.Zorn, et al.                  Informational                     [Page 6]

RFC 6697                HOKEY Architecture Design              July 20123.1.  Reducing Signaling Overhead3.1.1.  Minimized Communications with Home Servers   ERP [RFC6696] requires only one round trip; however, this round trip   may require communication between a peer and its home ER and/or home   AAA server in explicit bootstrapping and communication between local   servers and the home server in implicit bootstrapping even if the   peer is currently attached to a visited (local) network.  As a   result, even this one round trip may introduce long delays because   the home ER and home AAA servers may be distant from the peer and the   network to which it is attached.  To lower signaling overhead,   communication with the home ER server and home AAA server should be   minimized.  Ideally, a peer should only need to communicate with   local servers and other local entities.3.1.2.  Minimized User Interaction for Authentication   When the peer is initially attached to the network or moves between   heterogeneous networks, full EAP authentication between the peer and   EAP server occurs and user interaction may be needed, e.g., a dialog   to prompt the user for credentials.  To reduce latency, user   interaction for authentication at each handover should be minimized.   Ideally, user involvement should take place only during initial   authentication and subsequent re-authentication should occur   transparently.3.2.  Integrated Local Domain Name (LDN) Discovery   ERP bootstrapping must occur before (implicit) or during (explicit) a   handover to transport the necessary keys to the local ER server   involved.  Implicit bootstrapping is preferable because it does not   require communication with the home ER server during handover, but it   requires that the peer know the domain name of the ER server before   the subsequent local ERP exchange happens in order to derive the   necessary re-authentication keying material.  ERP [RFC6696] does not   specify such a domain name discovery mechanism and suggests that the   peer may learn the domain name through the EAP-Initiate/Re-auth-Start   message or via lower-layer announcements.  However, domain name   discovery happens after the implicit bootstrapping completes, which   may introduce extra latency.  To allow more efficient handovers, a   HOKEY architecture should support an efficient domain name discovery   mechanism (for example, see Zorn, Wu & Wang [RFC6440]) and allow its   integration with ERP implicit bootstrapping.  Even in the case of   explicit bootstrapping, LDN discovery should be optimized such that   it does not require contacting the home AAA server, as is currently   the case.Zorn, et al.                  Informational                     [Page 7]

RFC 6697                HOKEY Architecture Design              July 20123.3.  Fault-Tolerant Re-Authentication   If all authentication services depend upon a remote server, a network   partition can result in the denial of service to valid users.   However, if for example an ER server exists in the local network,   previously authenticated users can re-authenticate even though a link   to the home or main authentication server doesn't exist.3.4.  Improved Deployment Scalability   To provide better deployment scalability, there should be no   requirement for the co-location of entities providing handover keying   services (e.g., ER servers) and AAA servers or proxies.  Separation   of these entities may cause problems with routing but allows greater   flexibility in deployment and implementation.4.  Required Functionality4.1.  Authentication Subsystem Functional Overview   The operation of the authentication subsystem provided by HOKEY also   depends on the availability of a number of discovery functions:   o  discovery of CAPs by the peer, by the SAP, or by some other      entity;   o  discovery of the authentication services supported at a given CAP;   o  discovery of the required server in the home domain when a CAP is      not in the same domain as the SAP, or no local server is      available;   o  peer discovery of the LDN when EAP re-authentication is used with      a local server.   It is assumed that these functions are provided by the environment   within which the authentication subsystem operates and are outside   the scope of the authentication subsystem itself.  LDN discovery is a   possible exception.   The major functions comprising the authentication subsystem and their   interdependencies are discussed in greater detail below.   o  When AAA is invoked to authorize network access, it uses one of      two services offered by the authentication subsystem: full EAP      authentication or EAP re-authentication.  Note that although AAA      may perform authentication directly in some cases, when EAP isZorn, et al.                  Informational                     [Page 8]

RFC 6697                HOKEY Architecture Design              July 2012      utilized AAA functions only as a transport for EAP messages and      the encryption keys (if any) resulting from successful EAP      authentication.   o  Pre-authentication triggers AAA network access authorization at      each CAP, which in turn causes full EAP authentication to be      invoked.   o  EAP re-authentication invokes ER key management at the time of      authentication to create and distribute keying material to ER      servers.   o  AAK relies on ER key management to establish keying material on      ER/AAK servers but uses an extension to ER key management to      derive and establish keying material on candidate authenticators.      AAK uses an extension to EAP re-authentication to communicate with      ER/AAK servers.   EAP authentication, EAP re-authentication, and handover key   distribution depend on the routing and secure transport service   provided by AAA.  Discovery functions and the function of   authentication and authorization of network entities (access points,   ER servers) are not shown.  As stated above, these are external to   the authentication subsystem.4.2.  Pre-Authentication Function (Direct or Indirect)   The pre-authentication function is responsible for discovery of CAPs   and completion of network access authentication and authorization at   each CAP in advance of handover.  The operation of this function is   described in general terms in Ohba, et al. [RFC5836].  No document is   yet available to describe the implementation of pre-authentication in   terms of specific protocols; pre-authentication support for the   Protocol for Carrying Authentication for Network Access (PANA)   [RFC5873] could be part of the solution.4.3.  EAP Re-Authentication Function   The EAP re-authentication function is responsible for authenticating   the peer at a specific access point using keying material derived   from a prior full EAP authentication.RFC 5169 [RFC5169] provides   the design objectives for an implementation of this function.  ERP   [RFC6696] describes a protocol to implement EAP re-authentication.Zorn, et al.                  Informational                     [Page 9]

RFC 6697                HOKEY Architecture Design              July 20124.4.  EAP Authentication Function   The EAP authentication function is responsible for authenticating the   peer at a specific access point using a full EAP exchange.  Aboba,   et al. [RFC3748] define the associated protocol, while Ohba,   et al. [RFC5836] describe the use of EAP as part of   pre-authentication.  Note that the HOKEY Working Group has not   specified the non-AAA protocol required to transport EAP frames over   IP that is shown in Figures 3 and 5 of Ohba, et al. [RFC5836],   although PANA [RFC5873] is a candidate.4.5.  Authenticated Anticipatory Keying (AAK) Function   The AAK function is responsible for pre-placing keying material   derived from an initial full EAP authentication on CAPs.  The   operation is carried out in two steps: ER key management (with   trigger not currently specified) places root keys derived from   initial EAP authentication onto an ER/AAK server associated with the   peer.  When requested by the peer, the ER/AAK server derives and   pushes predefined master session keys to one or more CAPs.  The   operation of the AAK function is described in very general terms in   Ohba, et al. [RFC5836].  A protocol specification exists (see Cao,   et al. [RFC6630]).4.6.  Management of EAP-Based Handover Keys   Handover key management consists of EAP method-independent key   derivation and distribution and comprises the following specific   functions:   o  handover key derivation   o  handover key distribution   The derivation of handover keys is specified in Salowey,   et al. [RFC5295], and AAA-based key distribution is specified in   Hoeper, Nakhjiri & Ohba [RFC5749].Zorn, et al.                  Informational                    [Page 10]

RFC 6697                HOKEY Architecture Design              July 20125.  Components of the HOKEY Architecture   This section describes the components of the HOKEY architecture in   terms of the functions they perform.  The components cooperate as   described in this section to carry out the functions described in the   previous section.Section 6 describes the different deployment   scenarios that are possible using these functions.   The components of the HOKEY architecture are as follows:   o  the peer;   o  the authenticator, which is a part of the SAP and CAPs;   o  the EAP server;   o  the ER server; and   o  the ER/AAK server [RFC6630], either in the home domain or local to      the authenticator.Zorn, et al.                  Informational                    [Page 11]

RFC 6697                HOKEY Architecture Design              July 20125.1.  Functions of the Peer   The peer participates in the functions described inSection 4, as   shown in Table 1.   +--------------------+----------------------------------------------+   | Function           | Peer Role                                    |   +--------------------+----------------------------------------------+   | EAP authentication | Determines that full EAP authentication is   |   |                    | needed based on context (e.g., initial       |   |                    | authentication), prompting from the          |   |                    | authenticator, or discovery that only EAP    |   |                    | authentication is supported.  Participates   |   |                    | in the EAP exchange with the EAP server.     |   | -                  | -                                            |   | Direct             | Discovers CAPs.  Initiates                   |   | pre-authentication | pre-authentication with each, followed by    |   |                    | EAP authentication as above, but using IP    |   |                    | rather than L2 transport for the EAP frames. |   | -                  | -                                            |   | Indirect           | Enters into a full EAP exchange when         |   | pre-authentication | triggered, using either L2 or L3 transport   |   |                    | for the frames.                              |   | -                  | -                                            |   | EAP                | Determines that EAP re-authentication is     |   | re-authentication  | possible based on discovery or authenticator |   |                    | prompting.  Participates in ERP exchange     |   |                    | with the ER server.                          |   | -                  | -                                            |   | AAK                | Determines that AAK is possible based on     |   |                    | discovery or serving authenticator           |   |                    | prompting.  Discovers CAPs.  Participates in |   |                    | ERP/AAK exchange, requesting distribution of |   |                    | keying material to the CAPs.                 |   | -                  | -                                            |   | ER key management  | No role.                                     |   +--------------------+----------------------------------------------+                      Table 1: Functions of the PeerZorn, et al.                  Informational                    [Page 12]

RFC 6697                HOKEY Architecture Design              July 20125.2.  Functions of the Serving Authenticator   The serving authenticator participates in the functions described inSection 4, as shown in Table 2.   +--------------------+----------------------------------------------+   | Function           | Serving Authenticator Role                   |   +--------------------+----------------------------------------------+   | EAP authentication | No role.                                     |   | -                  | -                                            |   | Direct             | No role.                                     |   | pre-authentication |                                              |   | -                  | -                                            |   | Indirect           | Discovers CAPs.  Initiates an EAP exchange   |   | pre-authentication | between the peer and the EAP server through  |   |                    | each candidate authenticator.  Mediates      |   |                    | between L2 transport of EAP frames on the    |   |                    | peer side and a non-AAA protocol over IP     |   |                    | toward the CAP.                              |   | -                  | -                                            |   | EAP                | No role.                                     |   | re-authentication  |                                              |   | -                  | -                                            |   | AAK                | Mediates between L2 transport of AAK frames  |   |                    | on the peer side and AAA transport toward    |   |                    | the ER/AAK server.                           |   | -                  | -                                            |   | ER key management  | No role.                                     |   +--------------------+----------------------------------------------+              Table 2: Functions of the Serving AuthenticatorZorn, et al.                  Informational                    [Page 13]

RFC 6697                HOKEY Architecture Design              July 20125.3.  Functions of the Candidate Authenticator   The candidate authenticator participates in the functions described   inSection 4, as shown in Table 3.   +--------------------+----------------------------------------------+   | Function           | Candidate Authenticator Role                 |   +--------------------+----------------------------------------------+   | EAP authentication | Invokes AAA network access authentication    |   |                    | and authorization upon handover/initial      |   |                    | attachment.  Mediates between L2 transport   |   |                    | of EAP frames on the peer link and AAA       |   |                    | transport toward the EAP server.             |   | -                  | -                                            |   | Direct             | Invokes AAA network access authentication    |   | pre-authentication | and authorization when the peer initiates    |   |                    | authentication.  Mediates between non-AAA L3 |   |                    | transport of EAP frames on the peer side and |   |                    | AAA transport toward the EAP server.         |   | -                  | -                                            |   | Indirect           | Same as direct pre-authentication, except    |   | pre-authentication | that it communicates with the serving        |   |                    | authenticator rather than the peer.          |   | -                  | -                                            |   | EAP                | Invokes AAA network access authentication    |   | re-authentication  | and authorization upon handover.  Discovers  |   |                    | or is configured with the address of the ER  |   |                    | server.  Mediates between L2 transport of    |   |                    | ERP frames on the peer side and AAA          |   |                    | transport toward the ER server.              |   | -                  | -                                            |   | AAK                | Receives and saves the pMSK.                 |   | -                  | -                                            |   | ER key management  | No role.                                     |   +--------------------+----------------------------------------------+             Table 3: Functions of the Candidate AuthenticatorZorn, et al.                  Informational                    [Page 14]

RFC 6697                HOKEY Architecture Design              July 20125.4.  Functions of the EAP Server   The EAP server participates in the functions described inSection 4,   as shown in Table 4.   +--------------------+----------------------------------------------+   | Function           | EAP Server Role                              |   +--------------------+----------------------------------------------+   | EAP authentication | Terminates EAP signaling between it and the  |   |                    | peer via the candidate authenticator.        |   |                    | Determines whether network access            |   |                    | authentication succeeds or fails.  Provides  |   |                    | the MSK to the authenticator (via AAA).      |   | -                  | -                                            |   | Direct             | Same as for EAP authentication.              |   | pre-authentication |                                              |   | -                  | -                                            |   | Indirect           | Same as for EAP authentication.              |   | pre-authentication |                                              |   | -                  | -                                            |   | EAP                | Provides an rRK or DS-rRK to the ER server   |   | re-authentication  | (via AAA).                                   |   | -                  | -                                            |   | AAK                | Same as for EAP re-authentication.           |   | -                  | -                                            |   | ER key management  | Creates an rRK or DS-rRK and distributes it  |   |                    | to the ER server requesting the information. |   +--------------------+----------------------------------------------+                   Table 4: Functions of the EAP ServerZorn, et al.                  Informational                    [Page 15]

RFC 6697                HOKEY Architecture Design              July 20125.5.  Functions of the ER Server   The ER server participates in the functions described inSection 4,   as shown in Table 5.   +--------------------+----------------------------------------------+   | Function           | ER Server Role                               |   +--------------------+----------------------------------------------+   | EAP authentication | No role.                                     |   | -                  | -                                            |   | Direct             | No role.                                     |   | pre-authentication |                                              |   | -                  | -                                            |   | Indirect           | No role.                                     |   | pre-authentication |                                              |   | -                  | -                                            |   | EAP                | Acquires an rRK or DS-rRK as applicable when |   | re-authentication  | necessary.  Terminates ERP signaling between |   |                    | it and the peer via the candidate            |   |                    | authenticator.  Determines whether network   |   |                    | access authentication succeeds or fails.     |   |                    | Provides an MSK to the authenticator.        |   | -                  | -                                            |   | AAK                | Acquires an rRK or DS-rRK as applicable when |   |                    | necessary.  Derives pMSKs and passes them to |   |                    | the CAPs.                                    |   | -                  | -                                            |   | ER key management  | Receives and saves an rRK or DS-rRK as       |   |                    | applicable.                                  |   +--------------------+----------------------------------------------+                    Table 5: Functions of the ER Server6.  Usage Scenarios   Depending upon whether a change in a domain or access technology is   involved, we have the following usage scenarios.6.1.  Simple Re-Authentication   The peer remains stationary and re-authenticates to the original   access point.  Note that in this case, the SAP takes the role of the   CAP in the discussion above.Zorn, et al.                  Informational                    [Page 16]

RFC 6697                HOKEY Architecture Design              July 20126.2.  Intra-Domain Handover   The peer moves between two authenticators in the same domain.  In   this scenario, the peer communicates with the ER server via the ER   authenticator within the same network.6.3.  Inter-Domain Handover   The peer moves between two different domains.  In this scenario, the   peer communicates with more than one ER server via one or two   different ER authenticators.  One ER server is located in the current   network as the peer, and one is located in the previous network from   which the peer moves.  Another ER server is located in the home   network to which the peer belongs.6.4.  Inter-Technology Handover   The peer moves between two heterogeneous networks.  In this scenario,   the peer needs to support at least two access technologies.  The   coverage of two access technologies usually is overlapped during   handover.  In this case, only authentication corresponding to   intra-domain handover is required; i.e., the peer can communicate   with the same local ER server to complete authentication and obtain   keying material corresponding to the peer.7.  AAA Considerations   This section provides an analysis of how the AAA protocol can be   applied in the HOKEY architecture in accordance withSection 4.1   ("Authentication Subsystem Functional Overview").7.1.  Authorization   Authorization is a major issue in deployments.  Wherever the peer   moves around, the home AAA server provides authorization for the peer   during its handover.  However, it is unnecessary to couple   authorization with authentication at every handover, since   authorization is only needed when the peer is initially attached to   the network or moves between two different AAA domains.  The EAP key   management document [RFC5247] discusses several vulnerabilities that   are common to handover mechanisms.  One important issue arises from   the way that the authorization decisions might be handled at the AAA   server during network access authentication.  For example, if AAA   proxies are involved, they may also influence authorization   decisions.  Furthermore, the reasons for choosing a particular   decision are not communicated to the AAA clients.  In fact, the AAA   client only knows the final authorization result.  Another issue   relates to session management.  In some circumstances, when the peerZorn, et al.                  Informational                    [Page 17]

RFC 6697                HOKEY Architecture Design              July 2012   moves from one authenticator to another, the peer may be   authenticated by the different authenticator during a period of time,   and the authenticator to which the peer is currently attached needs   to create a new AAA user session; however, the AAA server should not   view these handoffs as different sessions.  Otherwise, this may   affect user experience and also cause accounting or logging issues.   For example, session ID creation, in most cases, is done by each   authenticator to which the peer attaches.  In this sense, the new   authenticator acting as AAA client needs to create a new AAA user   session from scratch, which forces its corresponding AAA server to   terminate the existing user session with the previous authenticator   and set up a new user session with the new authenticator.  This may   complicate the setup and maintenance of the AAA user session.7.2.  Transport Aspect   The existing AAA protocols can be used to carry EAP and ERP messages   between the AAA server and AAA clients.  AAA transport of ERP   messages is specified in Hoeper, Nakhjiri & Ohba [RFC5749] and   Bournelle, et al. [DIAMETER-ERP].  AAA transport of EAP messages is   specified in [RFC4072].  Key transport also can be performed through   a AAA protocol.  Zorn, Wu & Cakulev [DIAMETER-AVP] specify a set of   Attribute-Value Pairs (AVPs) providing native Diameter support of   cryptographic key delivery.8.  Security Considerations   This document does not introduce any new security vulnerabilities.9.  Acknowledgments   The authors would like to thank Mark Jones, Zhen Cao, Semyon   Mizikovsky, Stephen Farrell, Ondrej Sury, Richard Barnes, Jari Arkko,   and Lionel Morand for their reviews and comments.10.  References10.1.  Normative References   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.              Levkowetz, Ed., "Extensible Authentication Protocol              (EAP)",RFC 3748, June 2004.   [RFC5169]  Clancy, T., Nakhjiri, M., Narayanan, V., and L. Dondeti,              "Handover Key Management and Re-Authentication Problem              Statement",RFC 5169, March 2008.Zorn, et al.                  Informational                    [Page 18]

RFC 6697                HOKEY Architecture Design              July 2012   [RFC5836]  Ohba, Y., Ed., Wu, Q., Ed., and G. Zorn, Ed., "Extensible              Authentication Protocol (EAP) Early Authentication Problem              Statement",RFC 5836, April 2010.   [RFC6696]  Cao, Z., He, B., Shi, Y., Wu, Q., Ed., and G. Zorn, Ed.,              "EAP Extensions for the EAP Re-authentication Protocol              (ERP)",RFC 6696, July 2012.10.2.  Informative References   [DIAMETER-AVP]              Zorn, G., Wu, Q., and V. Cakulev, "Diameter Attribute-              Value Pairs for Cryptographic Key Transport", Work              in Progress, August 2011.   [DIAMETER-ERP]              Bournelle, J., Morand, L., Decugis, S., Wu, Q., and G.              Zorn, "Diameter Support for the EAP Re-authentication              Protocol (ERP)", Work in Progress, June 2012.   [RFC4072]  Eronen, P., Ed., Hiller, T., and G. Zorn, "Diameter              Extensible Authentication Protocol (EAP) Application",RFC 4072, August 2005.   [RFC5247]  Aboba, B., Simon, D., and P. Eronen, "Extensible              Authentication Protocol (EAP) Key Management Framework",RFC 5247, August 2008.   [RFC5295]  Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri,              "Specification for the Derivation of Root Keys from an              Extended Master Session Key (EMSK)",RFC 5295,              August 2008.   [RFC5749]  Hoeper, K., Ed., Nakhjiri, M., and Y. Ohba, Ed.,              "Distribution of EAP-Based Keys for Handover and              Re-Authentication",RFC 5749, March 2010.   [RFC5873]  Ohba, Y. and A. Yegin, "Pre-Authentication Support for the              Protocol for Carrying Authentication for Network Access              (PANA)",RFC 5873, May 2010.   [RFC6440]  Zorn, G., Wu, Q., and Y. Wang, "The EAP Re-authentication              Protocol (ERP) Local Domain Name DHCPv6 Option",RFC 6440,              December 2011.   [RFC6630]  Cao, Z., Deng, H., Wu, Q., and G. Zorn, Ed., "EAP              Re-authentication Protocol Extensions for Authenticated              Anticipatory Keying (ERP/AAK)",RFC 6630, June 2012.Zorn, et al.                  Informational                    [Page 19]

RFC 6697                HOKEY Architecture Design              July 2012Authors' Addresses   Glen Zorn (editor)   Network Zen   227/358 Thanon Sanphawut   Bang Na, Bangkok  10260   Thailand   Phone: +66 (0) 909 201060   EMail: glenzorn@gmail.com   Qin Wu   Huawei Technologies Co., Ltd.   101 Software Avenue, Yuhua District   Nanjing, JiangSu  210012   China   Phone: +86-25-84565892   EMail: bill.wu@huawei.com   Tom Taylor   Huawei Technologies Co., Ltd.   Ottawa, Ontario   Canada   EMail: tom.taylor.stds@gmail.com   Yoav Nir   Check Point   5 Hasolelim St.   Tel Aviv  67897   Israel   EMail: ynir@checkpoint.com   Katrin Hoeper   Motorola Solutions, Inc.   1301 E. Algonquin Road   Schaumburg, IL  60196   USA   EMail: khoeper@motorolasolutions.com>   Sebastien Decugis   INSIDE Secure   41 Parc Club du Golf   Aix-en-Provence  13856   France   Phone: +33 (0)4 42 39 63 00   EMail: sdecugis@freediameter.netZorn, et al.                  Informational                    [Page 20]

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