Network Working Group                                   Y. Ohba (Editor)
Internet-Draft                                                   Toshiba
Expires: March 9, 2008                                 September 6, 2007

                EAP Pre-authentication Problem Statement

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-

   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

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on March 9, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).


   EAP pre-authentication is defined as the utilization of EAP to pre-
   establish EAP keying material on an authenticator prior to arrival of
   the peer at the access network managed by that authenticator.  This
   draft discusses EAP pre-authentication problems in details.

Ohba (Editor)             Expires March 9, 2008                 [Page 1]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

Table of Contents

   1.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Specification of Requirements  . . . . . . . . . . . . . .  4
   3.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Usage Scenarios  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Direct Pre-authentication  . . . . . . . . . . . . . . . .  7
     4.2.  Indirect Pre-authentication  . . . . . . . . . . . . . . .  8
   5.  Architectural Considerations . . . . . . . . . . . . . . . . .  9
     5.1.  Authenticator Discovery  . . . . . . . . . . . . . . . . .  9
     5.2.  Context Binding  . . . . . . . . . . . . . . . . . . . . .  9
   6.  AAA Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 12
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Performance Requirements  . . . . . . . . . . . . . . 14
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
   Intellectual Property and Copyright Statements . . . . . . . . . . 16

Ohba (Editor)             Expires March 9, 2008                 [Page 2]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

1.  Contributors

   The following people contributed to this document.

        Yoshihiro Ohba (

        Ashutosh Dutta (

        Srinivas Sreemanthula (

        Alper E. Yegin (

        Madjid Nakhjiri (

        Mahalingam Mani (

2.  Introduction

   When a mobile during an active communication session moves from one
   access network to another access network and changes its point of
   attachment it is subjected to disruption in the continuity of service
   because of the associated handover operation.  During the handover
   process, when the mobile changes its point-of-attachment in the
   network, it may change its subnet or administrative domain it is
   connected to.  We provide in Appendix A some performance requirement
   that are needed to support an interactive real-time communication
   such as VoIP and thus can serve as the guidelines for handover

   Handover often requires authorization for acquisition or modification
   of resources assigned to a mobile and the authorization needs
   interaction with a central authority in a domain.  In many cases an
   authorization procedure during a handover procedure follows an
   authentication procedure that also requires interaction with a
   central authority in a domain.  The delay introduced due to such an
   authentication and authorization procedure adds to the handover
   latency and consequently affects the ongoing multimedia sessions.
   The authentication and authorization procedure may include EAP
   authentication [RFC3748] where an AAA server may be involved in EAP
   messaging during the handover.  Depending upon the type of
   architecture, in some cases the AAA signals traverse all the way to
   the AAA server in the home domain of the mobile as well before the
   network service is granted to the mobile in the new network.

   Real-time communication and interactive traffic such as VoIP is very
   sensitive to the delay.  Thus it is desirable that interactions
   between the mobile and AAA servers must be avoided or be reduced

Ohba (Editor)             Expires March 9, 2008                 [Page 3]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   during the handover.

   This draft discusses EAP pre-authentication problems in details where
   EAP pre-authentication is defined as the utilization of EAP to pre-
   establish EAP keying material on an authenticator prior to arrival of
   the peer at the access network managed by that authenticator.

2.1.  Specification of Requirements

   In this document, several words are used to signify the requirements
   of the specification.  These words are often capitalized.  The key
   "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document
   are to be interpreted as described in [RFC2119].

3.  Problem Statement

   Basic mechanism of handover is a three-step procedure involving i)
   discovery of potential points of attachment and their authenticators,
   ii) network selection procedure to determine the appropriate
   candidate network point of attachment and iii) handover or setting up
   of L2 and L3 connectivity to the target network point of attachment.
   Currently, security mechanisms for authentication and authorization
   is performed as part of the third step directly with the target
   network.  For example, in basic IEEE 802.11b based wireless networks,
   the security mechanism involves performing a new IEEE 802.1X message
   exchange with the authenticator in the target AP (Access Point) to
   initiate an EAP exchange to the authentication server [WPA].
   Following a successful authentication, a four-way handshake with the
   wireless station derives a new set of the session keys for use in
   data communications.  Unless PMK (Pairwise Master Key) is not cached
   in the target AP, this mechanism is same as the initial setup to the
   AP with no particular optimizations for the handover scenario.  The
   handover latency introduced by this security mechanism has proven to
   be larger than what is acceptable for some handover scenarios.
   Hence, improvement in the handover latency performance due to
   security procedures is a necessary objective for such scenarios.

   For example, if a mobile only requires 250 ms for "fast reconnect"
   then if it is moving at 60 mph (87 feet/second), then the mobile will
   have moved roughly 22 feet during the EAP authentication process.
   This is larger than the average coverage overlap of a wireless LAN

   There is relevant work undertaken by various standards organizations.
   But these efforts are scoped to a specific access technology.  IEEE
   802.11f has defined context transfer between APs.  IEEE 802.11i

Ohba (Editor)             Expires March 9, 2008                 [Page 4]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   defines a pre-authentication mechanism for use in 802.11 variant
   wireless networks.  This mechanism allows mobile devices to pre-
   authenticate using EAP to one or more candidate authenticators over
   the wired medium, by way of the serving authenticator.  Presently,
   IEEE 802.11r WG has been working to define Fast BSS transition
   mechanisms involving a definition of key management hierarchy and
   setup of session keys before the re-association to the target AP.
   These mechanisms, as indicated before, are defined for IEEE 802.11
   technologies and are only applicable within a certain access domain
   and fall short when it comes to inter-access technology handovers.
   They also require L2 (e.g., Ethernet) connectivity for transfer of
   encapsulated signaling to a candidate or the target AP.  Especially,
   a solution is needed to enable EAP pre-authentication in IEEE 802.11
   to work even if the station and AP are not members of the same VLAN.

   As various flavors of wireless technologies are increasingly
   available, there is a growing demand for seamless inter-access
   technology mobility and handovers.  This is particularly beneficial
   in the presence of high bandwidth wireless technologies (e.g., IEEE
   802.11a/b/g) with only hotspot like coverages while the overlay
   licensed wireless/cellular coverages are expensive and relatively
   lower bandwidth.  There is a strong motivation to allow seamless
   inter-technology handovers for all kinds of data communications.
   Hence, the security optimization mechanisms for better handover
   performance must be looked at from the IP level so as to make it a
   common method over different access technologies.

   Solutions for inter-authenticator mobility security optimizations can
   be largely seen as security context transfer, handover keying or EAP
   pre-authentication.  Security context transfer involves transfer of
   reusable key context in the new point of attachment.  However, the
   recent AAA key management requirement [RFC4962] does not recommend
   horizontal context transfer of reusable key context because of domino
   effect in which a compromise of an authenticator will lead to a
   compromise of another authenticator.  Nakhjiri et al
   [I-D.nakhjiri-aaa-hokey-ps] discusses handover keying.  Handover
   keying uses an existing EAP-generated key for deriving a key to be
   used for a candidate authenticator in order to reduce the handover
   delay, which eliminates the need for running EAP for each inter-
   authenticator handover.  On the other hand, there are certain cases
   where an EAP-generated key does not exist or is not usable for
   handover keying at the time of handover and an EAP run is not
   avoidable to generate a key for the candidate authenticator.  One
   case is an inter-domain handover without any trust relationship
   between domains.  Another case is a handover to an existing
   technology that does not support handover keying.

   EAP pre-authentication discussed in this document is mainly to deal

Ohba (Editor)             Expires March 9, 2008                 [Page 5]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   with an environment where the mobile device and candidate
   authenticators are not in the same subnet or of the same link-layer
   technology.  Such use of EAP pre-authentication would enable the
   mobile device to authenticate and setup keys prior to connecting to
   one of the candidate authenticators.

   This framework has general applicability to various deployment
   scenarios in which proactive signaling can take effect.  In other
   words, applicability of EAP pre-authentication is limited to the
   scenarios where candidate authenticators can be easily discovered, an
   accurate prediction of movement can be easily made.  Also the
   effectiveness of EAP pre-authentication may be less significant for
   particular inter-technology handover scenarios where simultaneous use
   of multiple technologies is not a major concern or where there is
   sufficient radio-coverage overlap among different technologies.

   Note that EAP pre-authentication problem for intra-technology intra-
   subnet handover could be solved by each link-layer and is thus out of
   the scope of this document while a general solution developed at IETF
   can be used for intra-technology and intra-subnet scenarios as well.

   In EAP pre-authentication, AAA authentication and authorization for a
   candidate authenticator is performed while application sessions are
   in progress via the serving network.  The goal of EAP pre-
   authentication is to avoid AAA signaling for EAP when or soon after
   the device moves.  There are several AAA issues related to EAP pre-
   authentication.  The pre-authentication AAA issues are described in
   Section 6.

   Figure 1 shows the functional elements that are related to EAP pre-

     +------+         +-------------+     +------+
     |Mobile|---------|   Serving   |    /        \
     | Node |         |Authenticator|---/          \
     +------+         +-------------+  /            \
        .                             /              \    +----------+
        . Move                       +    Internet    +---|AAA Server|
        .                             \              /    +----------+
        v             +-------------+  \            /
                      |  Candidate  |---\          /
                      |Authenticator|    \        /
                      +-------------+     +------+

           Figure 1: EAP Pre-authentication Functional Elements

   A mobile node is attached to the serving access network.  Before the
   mobile node performs handover from the serving access network to a

Ohba (Editor)             Expires March 9, 2008                 [Page 6]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   candidate access network, it performs EAP pre-authentication with a
   candidate authenticator, an authenticator in the candidate access
   network, via the serving access network.  The mobile node may perform
   EAP pre-authentication with one or more candidate authenticators.  It
   is assumed that each authenticator has an IP address when
   authenticators are on different IP links.  It is assumed that there
   is at least one candidate authenticator in each candidate access
   network while the serving access network may or may not have a
   serving authenticator.  The serving and candidate access networks may
   use different link-layer technologies.

   Each authenticator has the functionality of EAP authenticator which
   is either standalone EAP authenticator or pass-through EAP
   authenticator.  When an authenticator acts as a standalone EAP
   authenticator, it also has the functionality of EAP server.  On the
   other hand, when an authenticator acts as a pass-through EAP
   authenticator, it communicates with EAP server typically implemented
   on a AAA server using a AAA protocol such as RADIUS and Diameter.

   If the candidate authenticator is of an existing link-layer
   technology that uses an MSK (Master Session Key)
   [I-D.ietf-eap-keying] for generating lower-layer ciphering keys, EAP
   pre-authentication is used for proactively generating the MSK for the
   candidate authenticator.

4.  Usage Scenarios

   There are two scenarios on how EAP pre-authentication signaling can
   happen among a mobile node, a serving authenticator, a candidate
   authenticator and a AAA server, depending on how the serving
   authenticator is involved in the EAP pre-authentication signaling.

4.1.  Direct Pre-authentication

   Direct pre-authentication signaling is shown in Figure 2.

    Mobile             Serving              Candidate             AAA
     Node           Authenticator         Authenticator          Server
     (MN)                (SA)                 (CA)
      |                   |                    |                   |
      |                   |                    |                   |
      |       MN-CA Signaling (L2 or L3)       |       AAA         |
      |                   |                    |                   |
      |                   |                    |                   |

                    Figure 2: Direct Pre-authentication

Ohba (Editor)             Expires March 9, 2008                 [Page 7]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   In this type of pre-authentication, the serving authenticator
   forwards the EAP pre-authentication traffic as it would any other
   data traffic or there may be no serving authenticator at all in the
   serving access network.

   [I-D.ietf-pana-preauth] is identified as a protocol to realize direct

4.2.  Indirect Pre-authentication

   Indirect pre-authentication signaling is shown in Figure 3.

    Mobile             Serving              Candidate             AAA
     Node            Authenticator        Authenticator          Server
     (MN)                (SA)                 (CA)
      |                   |                    |                   |
      |                   |                    |                   |
      |   MN-SA Signaling |   SA-CA Signaling  |       AAA         |
      |    (L2 or L3)     |        (L3)        |                   |
      |                   |                    |                   |
      |                   |                    |                   |

                   Figure 3: Indirect Pre-authentication

   With indirect pre-authentication, the serving authenticator is
   involved in EAP pre-authentication signaling.  Indirect pre-
   authentication is needed if the MN cannot discover the CA's IP
   address or if IP communication is not allowed between the candidate
   authenticator and unauthorized nodes for security reasons.

   Indirect pre-authentication signaling is spliced into mobile node to
   serving authenticator signaling (MN-SA signaling) and serving
   authenticator to candidate authenticator signaling (SA-CA signaling).

   SA-CA signaling is performed over L3.

   MN-SA signaling is performed over L2 or L3.

   The role of the serving authenticator in indirect pre-authentication
   is to forward EAP pre-authentication signaling between the mobile
   node and the candidate authenticator and not to act as an EAP
   authenticator, while it acts as an EAP authenticator for normal
   authentication signaling.  This is illustrated in Figure 4.

Ohba (Editor)             Expires March 9, 2008                 [Page 8]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

        Mobile                   Serving                   Candidate
         Node                  Authenticator             Authenticator
         (MN)                     (SA)                       (CA)

     +-----------+                                       +-----------+
     |           |<- - - - - - - - - - - - - - - - - - ->|           |
     | EAP Peer  |    +-----------------------------+    | EAP Auth- |
     |           |    |Pre-authentication Forwarding|    | enticator |
     +-----------+    +-----------+-----+-----------+    +-----------+
     | MN-SA     |    | MN-SA     |     | SA-CA     |    | SA-CA     |
     | Signaling |<-->| Signaling |     | Signaling |<-->| Signaling |
     | Layer     |    | Layer     |     | Layer     |    | Layer     |
     +-----------+    +-----------+     +-----------+    +-----------+

           Figure 4: Indirect Pre-authentication Layering Model

5.  Architectural Considerations

   There are two architectural issues relating to pre-authentication,
   i.e., authenticator discovery and context binding.

5.1.  Authenticator Discovery

   In general, pre-authentication requires an address of a candidate
   authenticator to be discovered either by a mobile node or by a
   serving authenticator prior to handover.  An authenticator discovery
   protocol is typically defined as a separated protocol from a pre-
   authentication protocol as described below.

   When a candidate authenticator uses link-layer EAP transport for both
   normal authentication and pre-authentication, a mechanism for
   candidate authenticator discovery is typically defined in each link-
   layer technology.  For other cases, a mechanism for discovering an IP
   address of a candidate authenticator is needed.  For example, IEEE
   802.21 Information Service (IS) [802.21] provides a link-layer
   independent mechanism for obtaining neighboring network information
   by defining a set of Information Elements (IEs), where one of the IEs
   is defined to contain an IP address of a point of attachment.  IEEE
   802.21 IS queries for such an IE may be used as a method for
   discovering an IP address of a candidate authenticator.

5.2.  Context Binding

   When a candidate authenticator uses different EAP transport protocols
   for normal authentication and pre-authentication, a mechanisms is
   needed to bind link-layer independent context carried over pre-
   authentication signaling to the link-layer specific context of the

Ohba (Editor)             Expires March 9, 2008                 [Page 9]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   link to be established between the mobile node and the candidate
   authenticator.  The link-layer independent context includes the
   identities of the peer and authenticator as well as the MSK.  The
   link-layer specific context includes link-layer addresses of the
   mobile node and the candidate authenticator.

   There are two possible approaches to address the context binding
   issue.  The first approach is based on communicating the lower-layer
   context as opaque data via pre-authentication signaling and perform
   the link-layer specific secure association procedure after handover.
   The second approach is based on use of normal EAP authentication
   after handover with using the same link-layer independent context for
   both pre-authentication and normal authentication and then perform
   the link-layer specific secure association procedure.

6.  AAA Issues

   Most of the AAA documentations today do not distinguish between a
   full authentication and a pre-authentication and this creates a set
   of open issues:

   Pre-authentication authorization:   Many users may not be allowed to
      have more than one logon session at the time.  This means, when
      such users actively engage in an active session (as a result of a
      previously valid authentication), they will not be able to perform
      pre-authentication.  The AAA server currently has no way of
      distinguishing between a full authentication request and a pre-
      authentication request.

   Pre-authentication life time:   Currently AAA protocols define
      attributes (AVPs) carrying life time information for a full
      authentication session.  Even when a user profile and the AAA
      server support pre-authentication function, after the pre-
      authentication of a peer is complete, since the pre-authentication
      may be accompanied with a pre-authorization, the pre-
      authentication is typically valid only for a short amount of time.
      It is currently not possible for a AAA server to indicate to the
      AAA client or a peer what the life time of the pre- authenticated
      session is.  In other words, it is not clear to the peer or the
      NAS, when the pre-authentication will expire.

   Pre-authentication retries:   It is typically expected that shortly
      following the pre-authentication process, the mobile entity moves
      to the new point of attachment and converts the pre-authentication
      state to a full authentication state (the procedure for which is
      not the topic of this particular subsection).  However, if the
      peer has yet not moved to the new location and realizes that the

Ohba (Editor)             Expires March 9, 2008                [Page 10]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

      pre-authentication is expiring, it may perform another pre-
      authentication.  In order to avoid unlimited number of pre-
      authentication tries, it is quite possible that the network policy
      sets a limit on the maximum number of pre-authentication attempts.

   Completion of network attachment:   Once the peer has successfully
      attached to the new point of attachment, it needs to convert its
      authentication state from pre-authenticated to fully attached and
      authorized.  There may need to be a mechanism within the AAA
      protocol to provide this indication to the AAA server.

   Session Resumption:   In case the peer ping pongs between a network
      N1 with which it has a full authentication state to another
      network N2 and then back to N1, it should possible to simply
      convert the full authentication state to a pre-authenticated
      state.  The problems around handling session life time and keying
      material caching needs to be dealt with.

   Multiple candidate authenticators:   There may be situations where
      the mobile node may need to make a selection between a number of
      candidate attachment points.  In such cases it is desirable for
      the mobile to perform pre-authentication with multiple
      authenticators.  In such cases the AAA server may need to be aware
      of the situation.

   Roaming support:   In case the pre-authentication is being performed
      through a serving network that is foreign to the MN's home AAA
      server, the AAA server needs to obtain the information about the
      serving network in addition to the information about the candidate
      network, so that the AAA server can make authorization decisions
      accordingly, e.g., depending on the authorization policy, the home
      AAA server may not allow pre-authentication via a particular
      serving network.

   Inter-technology support:   Current specifications on pre-
      authentication mostly deal with homogeneous 802.11 networks.  The
      AAA attributes such as Calling-Station-ID [I-D.aboba-radext-wlan]
      may need to be expanded to cover other access technologies.
      Furthermore, heterogeneous handovers may require a change of the
      MN identifier as part of the handover.  Investigation on the best
      type of identifiers for MNs that support multiple access
      technologies is required.

   Network controlled handovers:   It is becoming quite common for the
      network operators to maintain the control over the handovers for
      various reasons including load balancing and performance.  Hence
      the network may need to direct the MN to perform pre-
      authentication to a set of candidate authenticators in an

Ohba (Editor)             Expires March 9, 2008                [Page 11]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

      anticipation for a handover.  The AAA protocol extensions for
      carrying out such procedures needs to be provided.

7.  Security Considerations

   Since pre-authentication described in this document needs to work
   across multiple authenticators, any solution for this problem needs
   considerations on the following security threats.

   First, a possible resource consumption denial of service attack where
   an attacker that is not on the same IP link as the mobile node or the
   candidate authenticator may send unprotected pre-authentication
   messages to the mobile node or the candidate authenticator to let the
   legitimate mobile node and candidate authenticator spend their
   computational and bandwidth resources.

   Second, consideration for the Channel Binding problem described in
   [I-D.ietf-eap-keying] is needed as lack of Channel Binding may enable
   an authenticator to impersonate another authenticator or communicate
   incorrect information via out-of-band mechanisms (such as via a AAA
   or lower layer protocol) [RFC3748].  It should be noted that it would
   be easier to launch such an impersonation attack for pre-
   authentication than normal authentication because an attacker does
   not need to be physically on the same link as the legitimate peer to
   send a pre-authentication trigger to the peer.  A simple solution
   would be to let the peer always initiate EAP pre-authentication and
   not allow EAP pre-authentication initiation from authenticator side.

8.  IANA Considerations

   This document has no actions for IANA.

9.  Acknowledgments

   The authors would like to thank Bernard Aboba and Jari Arkko for
   their valuable input.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

Ohba (Editor)             Expires March 9, 2008                [Page 12]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, "Extensible Authentication Protocol (EAP)",
              RFC 3748, June 2004.

   [RFC4962]  Housley, R. and B. Aboba, "Guidance for Authentication,
              Authorization, and Accounting (AAA) Key Management",
              BCP 132, RFC 4962, July 2007.

              Aboba, B., "Extensible Authentication Protocol (EAP) Key
              Management Framework", draft-ietf-eap-keying-18 (work in
              progress), February 2007.

              Ohba, Y., "Pre-authentication Support for PANA",
              draft-ietf-pana-preauth-01 (work in progress), March 2006.

10.2.  Informative References

              Nakhjiri, M., "AAA based Keying for Wireless Handovers:
              Problem Statement", draft-nakhjiri-aaa-hokey-ps-03 (work
              in progress), June 2006.

              Malinen, J. and B. Aboba, "RADIUS Attributes for IEEE 802
              Networks", draft-aboba-radext-wlan-06 (work in progress),
              July 2007.

   [802.21]   IEEE, "Draft Standard for Local and Metropolitan Area
              Networks: Media Independent Handover Services", LAN MAN
              Standards Committee of the IEEE Computer Society 2007.

   [ITU]      ITU-T, "General Characteristics of International Telephone
              Connections and International Telephone Circuits: One-Way
              Transmission Time", ITU-T Recommendation G.114 1998.

   [ETSI]     ETSI, "Telecommunications and Internet Protocol
              Harmonization Over Networks (TIPHON) Release 3: End-to-end
              Quality of Service in TIPHON systems; Part 1: General
              aspects of Quality of Service.", ETSI TR 101 329-6 V2.1.1.

   [WPA]      The Wi-Fi Alliance, "WPA (Wi-Fi Protected Access)", Wi-
              Fi WPA v3.1, 2004.

Ohba (Editor)             Expires March 9, 2008                [Page 13]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

Appendix A.  Performance Requirements

   In order to provide the desirable quality of service for interactive
   VoIP and streaming traffic during handoff, one needs to limit the
   value of end-to-end delay, jitter and packet loss to a certain
   threshold level.  ITU-T and ITU-R standards define the acceptable
   values for these parameters.  For example for one-way delay, ITU-T
   G.114 [ITU] recommends 150 ms as the upper limit for most of the
   applications, and 400 ms as generally unacceptable delay.  One way
   delay tolerance for video conferencing is in the range of 200 to 300
   ms.  Also if an out-of-order packet is received after a certain
   threshold, it is considered lost.  The performance requirement will
   vary based on the type of application and its characteristics such as
   delay tolerance and loss tolerance limit.  Interactive traffic such
   as VoIP and streaming traffic will have different tolerance for delay
   and packet loss.  For example, according to ETSI TR 101 [ETSI] a
   normal voice conversation can tolerate up to 2% packet loss.
   Similarly there are other factors such as Transmission Rating Factor
   (R) standardized within ITU-T G.107, End to End delay (one way mouth-
   to-ear) and call blocking ratio that determine the QoS metrics.  An R
   value of 50 is considered to be poor and a value of 90 can be
   considered as the best that provides most user satisfaction.  As an
   example, a class B QoS which is equivalent to cellular telephony has
   a R factor that is greater than 70, E2E delay of less than 150 ms and
   call blocking ratio which is less than or equal to 0.15.  Class A QoS
   that is the highest and is equivalent to fixed phone quality has an R
   value that is more than 80 and an end-to-end delay that is less than
   100 ms.  Similarly, 3GPP TS23.107 defines 4 application classes:
   conversational, streaming, interactive and background each with
   different set of end-to-end delay and QoS requirement.  The streaming
   class has the tolerable packet (SDU) error rates ranging from 0.1 to
   0.00001 and the transfer delay of less than 300ms.  In short, the
   delay and packet loss tolerance value will depend upon the type of
   application and different standard bodies and vendors provide
   different specification for each type of application and thus any
   optimized handoff mechanism will need to take these values into

   It is desirable to support a heterogeneous handover that is agnostic
   to link-layer technologies in an optimized and secure fashion without
   incurring unreasonable complexity while providing seamless handover
   experience to the user.  As a mobile goes through a handover process,
   it is subjected to handover delay because of the rebinding of
   properties at several layers of the protocol stack, such as layer 2,
   layer 3 and application layer.  There are several common properties
   that contribute to the re-establishment or modification of these
   layers during handover.  These properties can mostly be attributed to
   things such as access characteristics (e.g., bandwidth, channel

Ohba (Editor)             Expires March 9, 2008                [Page 14]

Internet-Draft  EAP Pre-authentication Problem Statement  September 2007

   characteristics, channel scan, access point association), access
   mechanism (e.g., CDMA, CSMA/CA, TDMA), configuration of layer 3
   parameters such as IP address acquisition, re-authentication, re-
   authorization, rebinding of security association at all layers,
   binding update etc.  Although each of the components during the
   handover process that contributes to the handover delay needs to be
   optimized, we focus our discussion on optimizing the delay due to
   authentication and authorization.

Author's Address

   Yoshihiro Ohba
   Toshiba America Research, Inc.
   1 Telcordia Drive
   Piscataway, NJ  08854

   Phone: +1 732 699 5365

Ohba (Editor)             Expires March 9, 2008                [Page 15]

Internet-Draft  EAP Pre-authentication Problem Statement  September 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.

   This document and the information contained herein are provided on an

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at


   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).

Ohba (Editor)             Expires March 9, 2008                [Page 16]