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rfc:rfc5184

Network Working Group F. Teraoka Request for Comments: 5184 K. Gogo Category: Experimental K. Mitsuya

                                                             R. Shibui
                                                             K. Mitani
                                                       KEIO University
                                                              May 2008
                 Unified Layer 2 (L2) Abstractions
               for Layer 3 (L3)-Driven Fast Handover

Status of This Memo

 This memo defines an Experimental Protocol for the Internet
 community.  It does not specify an Internet standard of any kind.
 Discussion and suggestions for improvement are requested.
 Distribution of this memo is unlimited.

IESG Note

 This document is not an IETF Internet Standard.  It represents the
 consensus of the MOBOPTS Research Group of the Internet Research Task
 Force.  It may be considered for standardization by the IETF in the
 future.

Abstract

 This document proposes unified Layer 2 (L2) abstractions for Layer 3
 (L3)-driven fast handovers.  For efficient network communication, it
 is vital for a protocol layer to know or utilize other layers'
 information, such as the form of L2 triggers.  However, each protocol
 layer is basically designed independently.  Since each protocol layer
 is also implemented independently in current operating systems, it is
 very hard to exchange control information between protocol layers.
 This document defines nine kinds of L2 abstractions in the form of
 "primitives" to achieve fast handovers in the network layer as a
 means of solving the problem.  This mechanism is called "L3-driven
 fast handovers" because the network layer initiates L2 and L3
 handovers by using the primitives.  This document is a product of the
 IP Mobility Optimizations (MobOpts) Research Group.

Teraoka, et al. Experimental [Page 1] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

Table of Contents

 1. Introduction ....................................................3
 2. Terminology .....................................................3
 3. Primitives for L2 Abstractions ..................................4
 4. Definitions of Primitives .......................................6
    4.1. L2-LinkStatus (Type 1) .....................................6
    4.2. L2-PoAList (Type 1) ........................................6
    4.3. L2-PoAFound (Type 2) .......................................6
    4.4. L2-PoALost (Type 2) ........................................6
    4.5. L2-LinkUp (Type 2) .........................................7
    4.6. L2-LinkDown (Type 2) .......................................7
    4.7. L2-LinkStatusChanged (Type 2) ..............................7
    4.8. L2-LinkConnect (Type 3) ....................................7
    4.9. L2-LinkDisconnect (Type 3) .................................8
 5. Definitions of Static Parameters ................................8
    5.1. Network Interface ID .......................................8
 6. Definitions of Dynamic Parameters ...............................8
    6.1. PoA (Point of Attachment) ..................................8
    6.2. Condition ..................................................8
    6.3. PoA List ...................................................9
    6.4. Enable/Disable .............................................9
    6.5. Ack/Error ..................................................9
 7. Architectural Considerations ....................................9
 8. Security Considerations ........................................13
 9. Acknowledgements ...............................................14
 10. References ....................................................14
    10.1. Normative References .....................................14
    10.2. Informative References ...................................14
 Appendix A.  Example Scenario  ....................................16
 Appendix B.  Example Operation for FMIPv6  ........................17
   B.1.  Example Operation-1 for FMIPv6 ............................18
   B.2.  Example Operation-2 for FMIPv6 ............................20
   B.3.  Experiment ................................................21
 Appendix C.  Example Mapping between L2 Primitives and
              Primitives in IEEE 802.11 and IEEE 802.16e  ..........22
 Appendix D.  Example Mapping of Primitives and IEEE 802.11  .......24
   D.1.  L2-LinkStatus  ............................................24
   D.2.  L2-PoAList ................................................24
   D.3.  L2-PoAFound  ..............................................24
   D.4.  L2-PoALost ................................................25
   D.5.  L2-LinkUp  ................................................25
   D.6.  L2-LinkDown  ..............................................25
   D.7.  L2-LinkStatusChanged ......................................25
   D.8.  L2-LinkConnect ............................................26
   D.9.  L2-LinkDisconnect  ........................................26
 Appendix E.  Implementation and Evaluation of the Proposed
              Model ................................................26

Teraoka, et al. Experimental [Page 2] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

1. Introduction

 Recent years have witnessed the rapid proliferation of wireless
 networks as well as mobile devices accessing them.  Unlike wired
 network environments, wireless networks are characterized by
 dynamically changing radio conditions, connectivity, and available
 bandwidth.  For efficient network communication, it is vital for a
 protocol layer to know or utilize other layers' control information.
 Mobile IPv4 [2] and Mobile IPv6 [3] have been standardized to support
 communication with mobile nodes.  There are several proposals for
 seamless handovers in IPv6 networks, such as Fast Handovers for
 Mobile IPv6 (FMIPv6) [4] and Hierarchical Mobile IPv6 (HMIPv6) [5].
 In FMIPv6, the network layer must know in advance the indication of a
 handover from the link layer to achieve seamless handovers.  However,
 control information exchange between protocol layers is typically not
 available because each protocol layer is designed independently.
 To solve the problem, this document defines nine kinds of L2
 abstractions in the form of "primitives" to achieve fast handovers in
 the network layer.  This mechanism is called "L3-driven fast
 handovers" because the network layer initiates L2 and L3 handovers by
 using the primitives.
 IEEE 802.21 [6] also defines several services that make use of L2
 information.  For the sake of ease of implementation and deployment,
 the primitives defined in this document make use of only the
 information available in the mobile node, while IEEE 802.21 [6]
 introduces the information server in the network to provide the
 mobile node with network-related information, such as a global
 network map.
 This document represents the consensus of the MobOpts Research Group.
 It has been reviewed by Research Group members active in the specific
 area of work.

2. Terminology

 This document uses the following terms:
 L3-Driven Fast Handover
    The handover mechanism that is initiated by the network layer on a
    mobile node.  Since this mechanism allows handover preparation in
    L3 before the start of an L2 handover on the mobile node, it can
    reduce packet loss during a handover.  The L3-driven fast handover
    mechanism requires L2 information as a trigger for a handover
    procedure.

Teraoka, et al. Experimental [Page 3] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 PoA
    The point of attachment of a mobile node (e.g., an access point in
    IEEE 802.11 networks [7]).
 Primitive
    A unit of information that is sent from one layer to another.
    There are four classes of primitives: Request, Confirm,
    Indication, and Response.  One or more classes of a primitive are
    exchanged, depending on the type of primitive.
 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 [1].

3. Primitives for L2 Abstractions

 Each layer offers its services in the form of primitives.  Four
 classes of primitives are defined, as shown in Figure 1.  Request is
 issued by the layer that wants to get the services or information
 from another layer, and Confirm is the acknowledgment of the request.
 Indication is the notification of the information to the layer that
 requested the service, and Response is the acknowledgment of the
 indication.  In this architecture, communication between layers is
 symmetrical.
  1. ———————— —————————–

Request Response

                ||      /\             /\      ||
    Layer N     ||      ||             ||      ||
    ------------||------||---   -------||------||------------
                ||      ||             ||      ||
                \/      ||             ||      \/
    Layer N-m        Confirm       Indication
    -------------------------   -----------------------------
    Figure 1: Interaction Model between Layers
 The primitive consists of five fields: protocol layer ID, protocol
 ID, primitive class (Request, Response, Indication, or Confirm),
 primitive name, and parameters.  The protocol layer ID specifies to
 which layer this primitive should be sent, e.g., Layer 2 or Layer 3.
 The protocol ID specifies to which protocol entity this primitive
 should be sent, e.g., IEEE 802.11 [7] or IEEE 802.3 [8].

Teraoka, et al. Experimental [Page 4] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 For unified L2 abstractions for L3-driven fast handovers, three
 different usages of primitives are defined, as described below:
 Type 1.  To provide L2 information to upper layers immediately
    This type of primitive is used to provide the L2 information to
    upper layers immediately.  The Request and Confirm classes of
    primitives MUST be exchanged for the interaction.  The Request
    primitive is for an acquisition request for the L2 information.
    The Confirm primitive is for the answer.
 Type 2.  To notify upper layers of L2 events asynchronously
    This type of primitive is used to notify upper layers of L2 events
    asynchronously.  The Request, Confirm, and Indication classes of
    primitive MUST be exchanged, and the Response class MAY be
    exchanged for the interaction.  The Request and Confirm primitives
    are used just for registration.  When an event occurs, the
    Indication primitive is asynchronously delivered to the upper
    layer.
 Type 3.  To control L2 actions from upper layers
    This type of primitive is used to control L2 actions from upper
    layers.  The Request and Confirm classes of primitives MUST be
    exchanged for the interaction.  The Request primitive is a request
    for operation.  Ack or Nack returns immediately as the Confirm
    primitive.
 A protocol entity can register primitives anytime by exchanging the
 Request and Confirm messages that include the fields defined above.
 When the registered event occurs, the Indication and Response
 messages are exchanged as well.
 The way to exchange a message between protocol entities is beyond the
 scope of this document.  Any information-exchange method between
 layers, such as the work in [10], can be used.
 The timing for sending an Indication primitive is also beyond the
 scope of this document.  For example, a layer 2 event is generated
 when layer 2 status has been changed, and this depends upon how
 scanning algorithms, for example, are implemented.

Teraoka, et al. Experimental [Page 5] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

4. Definitions of Primitives

 To obtain and exchange L2 information, the following primitives are
 defined.  Appendix C shows example mapping between the L2 primitives
 and the primitives in IEEE 802.11 [7] and IEEE 802.16e [9].

4.1. L2-LinkStatus (Type 1)

 The L2-LinkStatus.request primitive is sent to the link layer when an
 upper layer requires the current information of a link.  The
 L2-LinkStatus.request primitive contains the "Network Interface ID"
 parameter (see Section 5.1).  In response, the L2-LinkStatus.confirm
 primitive returns.  The L2-LinkStatus.confirm primitive contains
 three parameters: "Network Interface ID", "PoA", and "Condition".
 "PoA" and "Condition" indicate the current status of the link between
 the mobile node and a PoA.

4.2. L2-PoAList (Type 1)

 The L2-PoAList.request primitive is sent to the link layer when an
 upper layer requires a list of the candidate PoAs.  The
 L2-PoAList.request primitive contains the "Network Interface ID"
 parameter.  In response, the L2-PoAList.confirm primitive returns the
 "Network Interface ID" parameter and the "PoA List" parameter.  The
 "PoA List" parameter is a list of the candidate PoAs.

4.3. L2-PoAFound (Type 2)

 The L2-PoAFound.indication primitive is asynchronously provided to an
 upper layer when new PoAs are detected.  This primitive carries the
 "Network Interface ID" parameter and the "PoA List" parameter.  The
 "PoA List" parameter contains information on new PoAs detected by the
 mobile node.  In order to use this notification, the registration
 process using the L2-PoAFound.request primitive and the
 L2-PoAFound.confirm primitive is needed in advance.  The
 L2-PoAFound.request primitive has two parameters: "Network Interface
 ID" and "Enable/Disable".  The "Enable/Disable" parameter shows
 whether this notification function is turned on.  When this
 registration succeeds, the L2-PoAFound.confirm primitive returns with
 the "Network Interface ID" parameter and the "Ack" parameter in
 response.

4.4. L2-PoALost (Type 2)

 The L2-PoALost.indication primitive is asynchronously provided to an
 upper layer when a PoA included in the list of candidate PoAs
 disappears.  This primitive carries the "Network Interface ID"
 parameter and the "PoA List" parameter.  The "PoA List" parameter

Teraoka, et al. Experimental [Page 6] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 contains information on the PoAs that disappeared from the list of
 candidates.  The registration process using the L2-PoALost.request
 primitive and the L2-PoALost.confirm primitive is similar to the
 L2-PoAFound primitive described above.

4.5. L2-LinkUp (Type 2)

 The L2-LinkUp.indication primitive is asynchronously provided to an
 upper layer when a new link is connected and IP packets can be
 transmitted through the new link.  As described in RFC 4957 [12],
 what "link is connected" means depends on link types.  For example,
 in case of the infrastructure mode in IEEE 802.11 [7] (WiFi), this
 primitive is provided when an association to an access point is
 established.  This primitive carries the "Network Interface ID"
 parameter and the "PoA" parameter.  The L2-LinkUp.request primitive
 contains the "Network Interface ID" parameter and the
 "Enable/Disable" parameter for registration.  When the registration
 succeeds, the L2-LinkUp.confirm primitive with the "Network Interface
 ID" parameter and the "Ack" parameter returns.

4.6. L2-LinkDown (Type 2)

 The L2-LinkDown.indication primitive is asynchronously provided to an
 upper layer when an existing link is disconnected and IP packets
 cannot be transmitted through the link.  The registration processing
 is the same as the L2-LinkUp primitive described above.

4.7. L2-LinkStatusChanged (Type 2)

 The L2-LinkStatusChanged.indication primitive is asynchronously
 provided to an upper layer when the status of a link has changed.
 This notification contains three parameters: "Network Interface ID",
 "PoA", and "Condition".  The "PoA" parameter indicates the attachment
 point at which the link quality changed.  In the registration
 processing, the L2-LinkStatusChanged.request primitive carries the
 "Network Interface ID" parameter, the "Enable/Disable" parameter, and
 the "Condition" parameter.  "Condition" indicates the event type and
 the threshold for the Indication.

4.8. L2-LinkConnect (Type 3)

 The L2-LinkConnect.request primitive is sent to the link layer when
 an upper layer has to establish a new link to the specific "PoA".
 This primitive carries the "Network Interface ID" parameter and the
 "PoA" parameter.  This operation begins after the link layer returns
 the L2-LinkConnect.confirm primitive with "Ack".

Teraoka, et al. Experimental [Page 7] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

4.9. L2-LinkDisconnect (Type 3)

 The L2-LinkDisconnect.request primitive is sent to the link layer
 when an upper layer has to tear down an existing link to the specific
 "PoA".  This primitive carries the "Network Interface ID" parameter
 and the "PoA" parameter.  This operation begins after the link layer
 returns the L2-LinkDisconnect.confirm primitive with "Ack".

5. Definitions of Static Parameters

 This section lists static parameters.  Once the values of static
 parameters are configured, they basically remain unchanged during
 communication.  The following parameters are transferred as a part of
 primitives.

5.1. Network Interface ID

 The "Network Interface ID" parameter uniquely identifies the network
 interface in the node.  The syntax of the identifier is
 implementation-specific (e.g., name, index, or unique address
 assigned to each interface).  This parameter also contains the
 network interface type that indicates the kind of technology of the
 network interface (e.g., IEEE 802.11a/b/g [7], Third Generation
 Partnership Project (3GPP), etc.).  This parameter is required in all
 primitives.

6. Definitions of Dynamic Parameters

 This section lists dynamic parameters.  The values of dynamic
 parameters change frequently during communication.  The following
 parameters are transferred as a part of primitives.

6.1. PoA (Point of Attachment)

 The "PoA" parameter uniquely identifies the PoA.

6.2. Condition

 The "Condition" parameter consists of the following sub-parameters:
 available bandwidth and link quality level.  These sub-parameters are
 the abstracted information that indicates the current quality of
 service.  The abstraction algorithms of sub-parameters depend on
 hardware devices and software implementation.  The useful range of
 link quality is divided into five levels: EXCELLENT, GOOD, FAIR, BAD,
 and NONE, in descending order.  The quality levels of an L2 device

Teraoka, et al. Experimental [Page 8] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 are independent of those of other devices.  However, making decisions
 based on these metrics is error prone and not guaranteed to result in
 an optimal choice of links.  An example of the thresholds among the
 five levels in IEEE 802.11 [7] is described in Appendix E.

6.3. PoA List

 The "PoA List" parameter consists of arbitrary couples of two
 sub-parameters: "PoA" and "Condition".  This parameter shows a list
 of PoAs and their conditions.

6.4. Enable/Disable

 The "Enable/Disable" flag is used for turning event notification on/
 off.  When an upper layer needs notifications, the Request primitive
 with "Enable" is sent to the link layer as registration.  When an
 upper layer needs no more notifications, the Request primitive with
 "Disable" is sent.

6.5. Ack/Error

 When an upper layer requests some notifications, the link layer
 receives and confirms this Request.  If the Request is valid, the
 Confirm primitive with "Ack" is sent to the upper layer.  If it is
 invalid, the Confirm with "Error" is sent to the upper layer.

7. Architectural Considerations

 RFC 4907 [11] discusses the role and the issues of link indications
 within the Internet Architecture.  This section discusses the
 architectural considerations mentioned in Section 2 of RFC 4907.
 1.    Proposals should avoid use of simplified link models in
       circumstances where they do not apply.
       The information in each layer should be abstracted before it is
       sent to another layer.  For example, in IEEE 802.11 [7], the
       Received Signal Strength Indicator (RSSI), the number of
       retransmissions, and the existence of association between the
       mobile node and the access point are used so that the link
       layer indications can adjust themselves to various environments
       or situations.  The thresholds needed for some link indications
       are defined from empirical study.
       In the conventional protocol-layering model, the Protocol
       Entity (PE) is defined as the entity that processes a specific
       protocol.  Our proposal introduced the Abstract Entity (AE) to

Teraoka, et al. Experimental [Page 9] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

       achieve link independency of the link indications.  An AE and a
       PE make a pair.  An AE abstracts the PE-dependent information
       to the PE-independent information.
       Figure 2 shows AEs and PEs using primitives.
 2.    Link indications should be clearly defined, so that it is
       understood when they are generated on different link layers.
       To make the link information/indications clear, our proposal
       defines the 4 types of primitives: Request/Confirm and
       Indication/Response, as described in Section 3.  The Request is
       used to obtain the information of another layer.  The Confirm
       is the reply to the request and it includes the requested
       information.  The Indication is generated when a particular
       event occurs.  The Response is the reply to the indication.
       In our proposal on IEEE 802.11b [7], L2-LinkUp is defined as
       the status in which an association to the Access Point (AP) is
       established, and L2-LinkDown is defined as the status in which
       an association to the AP is not established.
       L2-LinkStatusChanged is generated when the link quality goes
       below the predefined threshold.  Since the Received Signal
       Strength Indicator (RSSI) and the number of retransmissions are
       used to abstract and evaluate the link quality, L2-
       LinkStatusChanged represents the link quality in both
       directions.  It should use an average of the RSSI or the number
       of retransmissions damped for one second or more to cope with
       transient link conditions.
 3.    Proposals must demonstrate robustness against misleading
       indications.
       Since RSSI changes significantly even when the mobile node
       stands still according to the measurements in our experiments,
       our proposal uses the RSSI, the number of retransmissions, and
       the existence of an association to calculate the link status,
       as described above.  In our experiments, there were some
       "ping-pong" handovers between two APs.  Such ping-pong
       handovers could be reduced by detecting the most suitable AP by
       L2-LinkStatus when L2-LinkStatusChanged is notified.  The use
       of L2 indications is related to parameter thresholds that
       trigger handover.  These thresholds vary based on the
       deployment scenario and, if not configured properly, could lead
       to misleading indications.

Teraoka, et al. Experimental [Page 10] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 4.    Upper layers should utilize a timely recovery step so as to
       limit the potential damage from link indications determined to
       be invalid after they have been acted on.
       The proposed L3-driven handover described in Appendix E uses
       the L2-LinkStatusChanged indication as the trigger for starting
       handover.  L2-LinkStatusChanged is indicated when the link
       quality goes below a specific threshold.  This indication is
       not canceled even if the link quality goes up soon.  As
       described above, L2-LinkStatus can be used to detect the most
       suitable AP.  The IP layer can cancel a handover if it finds
       that the current AP is the most suitable one by using
       L2-LinkStatus when L2-LinkStatusChanged is notified.
 5.    Proposals must demonstrate that effective congestion control is
       maintained.
       Since this mechanism is coupled to the IP layer, and not
       directly to the transport layer, the proposed mechanism does
       not directly affect congestion control.
 6.    Proposals must demonstrate the effectiveness of proposed
       optimizations.
       In IPv6 mobility, the L3-driven handover mechanism using link
       indications can dramatically reduce gap time due to handover.
       The L3-driven handover mechanism needs the L2-LinkStatusChanged
       indication to predict disconnection.  But L2-LinkStatusChanged
       is not trusted sometimes because it is difficult to abstract
       the link quality.  Invalid L2-LinkStatusChanged may cause
       redundant handover.  A handover mechanism using only L2-LinkUp/
       L2-LinkDown can also reduce gap time modestly.  An example of
       an implementation and evaluation of the L3-driven handover
       mechanism is described in Appendix E.
 7.    Link indications should not be required by upper layers in
       order to maintain link independence.
       Our proposal does not require any modifications to the
       transport and upper layers.
 8.    Proposals should avoid race conditions, which can occur where
       link indications are utilized directly by multiple layers of
       the stack.
       Since our proposal defines the link indications only to the IP
       layer, race conditions between multiple layers never occur.

Teraoka, et al. Experimental [Page 11] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 9.    Proposals should avoid inconsistencies between link and routing
       layer metrics.
       Our proposal does not deal with routing metrics.
 10.   Overhead reduction schemes must avoid compromising
       interoperability and introducing link-layer dependencies into
       the Internet and transport layers.
       As described above, the link indications in our proposal are
       abstracted to the information independent of link types to
       reduce the gap time due to a handover, and the ordinary host
       can execute handover without using the link indications defined
       in our proposal.
 11.   Proposals advocating the transport of link indications beyond
       the local host need to carefully consider the layering,
       security, and transport implications.  In general, implicit
       signals are preferred to explicit transport of link indications
       since they add no new packets in times of network distress,
       operate more reliably in the presence of middle boxes, such as
       NA(P)Ts (Network Address (Port) Translations), are more likely
       to be backward compatible, and are less likely to result in
       security vulnerabilities.
       Our proposal does not define the exchange of link indications
       between nodes.

Teraoka, et al. Experimental [Page 12] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

  1. ——————————————————–
  2. ———=========== ———-===========

| |[ ] | |[ ]

    |   PE    |[   AE   ]     |   PE    |[   AE   ]
    |         |[        ]     |         |[        ]
    ----------===========     ----------===========
    Layer N     ||   /\                   ||   /\
    ------------||---||-------------------||---||------------
         Request||   ||           Response||   ||
                ||   ||                   ||   ||
                ||   ||                   ||   ||
                ||   ||Confirm            ||   ||Indication
    ------------||---||-------------------||---||------------
                \/   ||                   \/   ||
    ----------===========     ----------===========
    |         |[        ]     |         |[        ]
    |   PE    |[   AE   ]     |   PE    |[   AE   ]
    |         |[        ]     |         |[        ]
    ----------===========     ----------===========
    Layer N-m
    ---------------------------------------------------------
    Figure 2: AE and PE with Primitives

8. Security Considerations

 RFC 4907 [11] discusses the role and issues of link indications
 within the Internet Architecture.  This section discusses the
 security considerations mentioned in Section 4 of RFC 4907.
 1.  Spoofing
       The proposed primitives suffer from spoofed link-layer control
       frames.  For example, if a malicious access point is set up and
       spoofed beacon frames are transmitted, L2-PoAFound.indication
       is generated in the mobile node.  As a result, the mobile node
       may establish an association with the malicious access point by
       an L2-LinkConnect.request.
 2.  Indication validation
       Transportation of the link indications between nodes is not
       assumed; hence, this consideration is beyond the scope of our
       proposal.

Teraoka, et al. Experimental [Page 13] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 3.  Denial of service
       Since this proposal does not change link-layer protocols, no
       more insecurity is added to a particular link-layer protocol.
       However, the proposed primitives suffer from denial-of-service
       attacks by spoofed link-layer frames.  For example, L2-
       PoAFound.indication and L2-PoALost.indication may frequently be
       generated alternately if a malicious access point frequently
       transmits control frames that indicate strong RSSI and weak
       RSSI alternately.

9. Acknowledgements

 The authors gratefully acknowledge the contributions of Jukka Manner,
 Christian Vogt, and John Levine for their review.

10. References

10.1. Normative References

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

10.2. Informative References

 [2]  Perkins, C., Ed., "IP Mobility Support for IPv4", RFC 3344,
      August 2002.
 [3]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
      IPv6", RFC 3775, June 2004.
 [4]  Koodli, R., Ed., "Fast Handovers for Mobile IPv6", RFC 4068,
      July 2005.
 [5]  Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,
      "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
      4140, August 2005.
 [6]  "Draft IEEE Standard for Local and Metropolitan Area Networks:
      Media Independent Handover Services", IEEE P802.21/D02.00,
      September 2006.
 [7]  IEEE, "802.11-2007 IEEE Standard for LAN/MAN - Specific
      requirements Part 11: Wireless LAN Medium Access Control (MAC)
      and Physical Layer (PHY) Specifications", 2007.

Teraoka, et al. Experimental [Page 14] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 [8]  IEEE, "802.3, 2000 EDITION ISO/IEC 8802-3:2000 (E) Information
      Technology - LAN/MAN - Part 3: Carrier Sense Multiple Access
      with Collision Detection (CSMA/CD) Access Method and Physical
      Layer Specifications", 2000.
 [9]  IEEE, "802.16e-2005 & 802.16/COR1 Part 16: Amendment for
      Physical & Medium Access Control Layers for Combined Fixed &
      Mobile Operation", 2006.
 [10] Gogo, K., Shibu, R., and F. Teraoka, "An L3-Driven Fast Handover
      Mechanism in IPv6 Mobility", In Proc. of International Symposium
      on Applications and the Internet (SAINT2006) Workshop in IPv6,
      February 2006.
 [11] Aboba, B., Ed., "Architectural Implications of Link
      Indications", RFC 4907, June 2007.
 [12] Krishnan, S., Ed., Montavont, N., Njedjou, E., Veerepalli, S.,
      and A. Yegin, Ed., "Link-Layer Event Notifications for Detecting
      Network Attachments", RFC 4957, August 2007.
 [13] Ishiyama, M., Kunishi, M., Uehara, K., Esaki, H., and F.
      Teraoka, "LINA: A New Approach to Mobility Support in Wide Area
      Networks", IEICE Transactions on Communication vol. E84-B, no.
      8, pp. 2076-2086, August 2001.

Teraoka, et al. Experimental [Page 15] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

Appendix A. Example Scenario

 For example, the picture below shows L3-driven fast handover
 mechanism using the L2 triggers on a mobile node (MN).
        L2                               L3
         |                                |
         |<----------LinkUP.req-----------|
         |-----------LinkUP.cnf---------->|
         |<-----LinkStatusChanged.req-----|
         |------LinkStatusChanged.cnf---->|
         =                                =
         |                                |
        Low                               |
       Signal---LinkStatusChanged.ind---->|
         |                                |
         |<----------PoAList.req----------|
         |-----------PoAList.cnf------>Handover
         |                            Preparation
         |<-------LinkConnect.req---------|
     L2 Handover--LinkConnect.cnf-------->:
         :                                :
         :                                :
         finish---------LinkUp.ind----->L3 Handover
         |                             finish
         |                                |
      L2: Link Layer on MN
      L3: Network Layer on MN
     req: Request
     cnf: Confirm
     ind: Indication
    Figure 3: L3-Driven Fast Handover Mechanism
 First, L3 issues LinkUp.request to receive LinkUp.indication when the
 link becomes available.  L3 also issues LinkStatusChanged.request to
 receive LinkStatusChanged.indication when the link quality goes below
 the threshold.
 In the beginning of the L3-driven handover procedure, L2 detects that
 the radio signal strength is going down.  Then, L2 sends
 L2-LinkStatusChanged.indication to L3.  L3 prepares for handover
 (e.g., Care-of Address (CoA) generation, Duplicate Address Detection
 (DAD), Neighbor Discovery (ND) cache creation, and routing table
 setting) and sends L2-PoAList.request to L2 if the list of access
 points is needed.

Teraoka, et al. Experimental [Page 16] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 If L3 decides to perform handover according to some rules, L3 sends
 L2-LinkConnect.request with some parameters about candidate access
 points to request L2 handover.  L2 handover begins after L2 sends
 L2-LinkConnect.confirm to L3.  When the L2 handover finishes, L2
 sends L2-LinkUp.indication to notify L3.  Finally, L3 performs
 handover (e.g., sending a Binding Update (BU)).
 One of the important features of L3-driven fast handover using
 primitives is that L3 handover preparation can be done during
 communication.  So, it can reduce disruption time during handover.

Appendix B. Example Operation for FMIPv6

 There are two scenarios of L3-driven fast handover for FMIPv6.
 Scenario 2 is different from scenario 1 for the timing of sending
 some messages.

Teraoka, et al. Experimental [Page 17] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

B.1. Example Operation-1 for FMIPv6

 Figure 4 shows the predictive mode of FMIPv6 operation with an
 L3-driven link-switching mechanism.
    MN-L2                            MN-L3        PAR-L3
      |                                |             |
     AP<----------PoAList.req----------|             |
    Scan----------PoAList.cnf--------->|             |
      |                                |---RtSolPr-->|
      |                                |<--PrRtAdv---|
      |----------PoAFound.ind--------->|             |
      |                                |---RtSolPr-->|
      |                                |<--PrRtAdv---|
      |                                |             |
      ~                                ~             ~
      |                                |             |
     Low                               |             |
    Signal---LinkStatusChanged.ind---->|             |        NAR-L3
      |                                |-----FBU---->|           |
      |                                |             |----HI---->|
      |                                |             |<--HAck----|
      |                                |<----FBack---|           |
      |<-------LinkConnect.req---L3 Handover         |           |
  L2 Handover--LinkConnect.cnf-------->:                         |
      :                                :                         |
      :                                :                         |
   finish---------LinkUp.ind---------->:                         |
      |                                :-----------FNA---------->|
      |                             finish<======packets=========|
      |                                |                         |
 MN-L2   : Link Layer on Mobile Node
 MN-L3   : Network Layer on Mobile Node
 PAR-L3  : Network Layer on Previous Access Router
 NAR-L3  : Network Layer on New Access Router
 req     : Request
 cnf     : Confirm
 ind     : Indication
 RtSolPr : Router Solicitation for Proxy
 PrRtAdv : Proxy Router Advertisement
 FBU     : Fast Binding Update
 FBack   : Fast Binding Acknowledgment
 FNA     : Fast Neighbor Advertisement
 HI      : Handover Initiate
 HAck    : Handover Acknowledge
 Figure 4: L3-Driven Fast Handover Mechanism with FMIPv6 Scenario 1

Teraoka, et al. Experimental [Page 18] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 When MN establishes link connectivity to PAR, it performs router
 discovery.  MN sends an RtSolPr message to PAR to resolve the access
 point identifiers to the subnet router information.  To send RtSolPr,
 MN discovers one or more access points by sending L2-PoAList.request
 to the link layer.  As a response to L2-PoAList.request,
 L2-PoAList.confirm returns with "PoA List" parameter that contains
 identifiers and conditions of nearby access points.  After initial AP
 discovery, L2-PoAFound.indication with "PoA List" is also sent from
 the link layer when one or more access points are discovered.
 When the link layer of MN detects that radio signal strength is
 dropping, it sends L2-LinkStatusChanged.indication to the network
 layer.  Then, MN sends the FBU message to PAR as the beginning of the
 L3 handover procedure.  The NCoA required for the FBU message is
 determined according to the MN's policy database and the received
 PrRtAdv message.  As a response to the FBU message, MN receives the
 FBack message and then immediately switches its link by
 L2-LinkConnect.request with the specific "PoA" parameter.  The
 handover policy of the MN is outside the scope of this document.
 After L2 handover, the link layer of the MN sends
 L2-LinkUp.indication to the network layer.  MN immediately sends the
 FNA message to the New Access Router (NAR).  The NAR will send
 tunneled and buffered packets to MN.

Teraoka, et al. Experimental [Page 19] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

B.2. Example Operation-2 for FMIPv6

 Figure 5 shows the predictive mode of FMIPv6 operation with an
 L3-driven link-switching mechanism.
    MN-L2                            MN-L3        PAR-L3
      |                                |             |
     AP<----------PoAList.req----------|             |
    Scan----------PoAList.cnf--------->|             |
      |                                |---RtSolPr-->|
      |                                |<--PrRtAdv---|
      |----------PoAFound.ind--------->|             |
      |                                |---RtSolPr-->|
      |                                |<--PrRtAdv---|
      |                                |             |
      ~                                ~             ~
      |                                |             |
     Low                               |             |
    Signal---LinkStatusChanged.ind---->|             |        NAR-L3
      |                                |-----FBU---->|           |
      |<-------LinkConnect.req---L3 Handover         |           |
  L2 Handover--LinkConnect.cnf-------->:             |           |
      |                                |             |----HI---->|
      |                                |             |<--HAck----|
      |                                |     <-FBack-|---FBack-->|
      |                                |<----FBack---------------|
      :                                :                         |
   finish---------LinkUp.ind---------->:                         |
      |                                :-----------FNA---------->|
      |                             finish<======packets=========|
      |                                |                         |
 MN-L2   : Link Layer on Mobile Node
 MN-L3   : Network Layer on Mobile Node
 PAR-L3  : Network Layer on Previous Access Router
 NAR-L3  : Network Layer on New Access Router
 req     : Request
 cnf     : Confirm
 ind     : Indication
 RtSolPr : Router Solicitation for Proxy
 PrRtAdv : Proxy Router Advertisement
 FBU     : Fast Binding Update
 FBack   : Fast Binding Acknowledgment
 FNA     : Fast Neighbor Advertisement
 HI      : Handover Initiate
 HAck    : Handover Acknowledge
 Figure 5: L3-Driven Fast Handover Mechanism with FMIPv6 Scenario 2

Teraoka, et al. Experimental [Page 20] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 Unlike scenario 1, MN in scenario 2 sends LinkConnect.req from the
 network layer to the link layer after MN sends the FBU message.  As
 PAR sends the FBack messages not only to PAR's subnet but also to
 NAR's subnet, MN can get the FBack message sent by PAR through NAR,
 and then it moves to NAR.

B.3. Experiment

 We implemented FMIPv6 and the proposed L2 primitives on FreeBSD-5.4.
 Figure 6 shows our test network.  MN is connected to access routers
 by using IEEE802.11a wireless LAN.  MN moves from PAR to NAR.
                |
             +--+---+
             |Router|
             +--+---+
                |                                 100BaseTX
    ---+--------+---------+---------+---------+------------
       |                  |         |         |
    +--+--+            +--+--+   +--+--+   +--+--+
    | PAR |            | NAR |   | HA  |   | CN  |
    +-----+            +-----+   +-----+   +-----+
       |                  |
        IEEE802.11a        IEEE802.11a         PAR, NAR: nexcom EBC
       |Channel 7         |Channel7            MN: ThinkPad X31
                                               OS: FreeBSD-5.4
       |                  |                        KAME/SHISA/TARZAN
    +-----+            +-----+
    | MN  |  ------->  | MN  |
    +-----+            +-----+
    Figure 6: Test Network
 Scenario 1 was used in this experiment since it was more stable than
 scenario 2.  Upon receiving L2-LinkStatusChanged.indication, L3 of MN
 sent the FBU message and then received the FBack message.  It took
 20ms from the transmission of the FBU message to the reception of the
 FBack message.  After receiving the FBack message, L3 of MN issued
 L2-LinkConnect.request to L2.  When L2 handover finished, L3 received
 L2-LinkUp.indication from L2.  It took 1ms for an L2 handover.  Next,
 MN sent the FNA message to NAR.  Upon receiving the FNA message, NAR
 started forwarding packets to NM.  ICMP echo request packets were
 sent at 10ms intervals.  It was observed that zero or one ICMP echo
 reply packet was lost during a handover.

Teraoka, et al. Experimental [Page 21] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

                MN                PAR                NAR
                |                  |                  |
                |----- RtSolPr --->|                  |
                |<---- PrRtAdv ----|                  |
                |                  |                  |
          +---  |------ FBU ------>|                  |
          |     |                  |------- HI ------>|
      20ms|     |                  |                  |
          |     |                  |<----- HAck ------|
          |     |                  |                  |
          +---  |<-------------- FBack -------------->|
                |                  |                  |
          +-- disconnect           |                  |
          |  1ms|                  |                  |
          |   connect              |                  |
    8-10ms|     |                  |                  |
          |  7ms|                  |                  |
          |     |                  |                  |
          |     +----- FNA -------------------------->|
          +--   |<------------------------ deliver packets
                |                  |                  |
                 Figure 7: Measured Results

Appendix C. Example Mapping between L2 Primitives and the Primitives in

           IEEE 802.11 and IEEE 802.16e
 This section shows example mapping between the L2 primitives and the
 primitives in IEEE 802.11 [7] and IEEE 802.16e [9] in Table 1.

Teraoka, et al. Experimental [Page 22] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

    +-------------------+----------------------+------------------+
    | L2 Primitive      | IEEE802.11           | IEEE802.16e      |
    +-------------------+----------------------+------------------+
    | L2-LinkStatus     | PMD_RSSI             | Available        |
    |                   |                      |                  |
    |                   | PMD_RATE             |                  |
    |                   |                      |                  |
    | L2-PoAList        | MLME-SCAN            | M_ScanScheduling |
    |                   |                      |                  |
    |                   |                      | M_Scanning       |
    |                   |                      |                  |
    | L2-PoAFound       | MLME-SCAN            | M_Neighbor       |
    |                   |                      |                  |
    |                   |                      | M_Scanning       |
    |                   |                      |                  |
    | L2-PoALost        | MLME-SCAN            | M_Neighbor       |
    |                   |                      |                  |
    |                   |                      | M_Scanning       |
    |                   |                      |                  |
    | L2-LinkUp         | MLME-ASSOCIATE       | M_Registration   |
    |                   |                      |                  |
    |                   | MLME-AUTHENTICATE    |                  |
    |                   |                      |                  |
    | L2-LinkDown       | MLME-DEASSOCIATE     | M_Ranging        |
    |                   |                      |                  |
    |                   | MLME-DISAUTHENTICATE |                  |
    |                   |                      |                  |
    | L2-StatusChanged  | PMD_RSSI             | M_Ranging        |
    |                   |                      |                  |
    |                   |                      | M_ScanReport     |
    |                   |                      |                  |
    |                   |                      | M_Scanning       |
    |                   |                      |                  |
    | L2-LinkConnect    | MLME-JOIN            | M_MACHandover    |
    |                   |                      |                  |
    |                   | MLME-ASSOCIATE       | M_HOIND          |
    |                   |                      |                  |
    |                   | MLME-REASSOCIATE     |                  |
    |                   |                      |                  |
    |                   | MLME-AUTHENTICATE    |                  |
    |                   |                      |                  |
    | L2-LinkDisconnect | MLME-DISASSOCIATE    | M_Management     |
    |                   |                      |                  |
    |                   | MLME-DEASSOCIATE     | (Deregistration) |
    +-------------------+----------------------+------------------+
    Table 1: Mapping between L2 Primitives and the Primitives in
             IEEE 802.11 and IEEE 802.16e

Teraoka, et al. Experimental [Page 23] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

Appendix D. Example Mapping of Primitives and IEEE 802.11

 This section shows examples of the mapping between primitives and
 IEEE 802.11 [7] parameters.

D.1. L2-LinkStatus

 Most parameters of L2-LinkStatus are related to the configuration of
 network-interface hardware.  The operating system and the
 device-driver module can easily collect such information.  However,
 to create the "Condition" parameter, the MN should maintain
 statistics and parameters related to the current wireless
 environment.
 There are two sub-parameters of the "Condition" parameter: available
 bandwidth and link quality level.  The available bandwidth of the
 current PoA can be obtained by maintaining the transmission rate
 indication and the statistics of frame transmission every time a
 frame is sent.  A link quality level can be updated by maintaining
 the following parameters and statistics every time a frame is
 received: Received Signal Strength Indicator (RSSI), transmission/
 reception rate indication, transmit/receive latency, bit-error rate,
 frame-error rate, and noise level.  Link quality level is divided
 into five levels: EXCELLENT, GOOD, FAIR, BAD, and NONE, in descending
 order.  Some parameters can be managed by setting thresholds from
 software.  When the parameters cross the threshold, an interrupt is
 generated for the software.

D.2. L2-PoAList

 In IEEE 802.11 networks, L2-PoAList returns the detected APs whose
 quality level exceeds the specified threshold for PoA candidates (by
 the "PoA List" parameter).  Therefore, an MN should always maintain
 the database of available access points according to reception of
 beacon frame, probe response frame, and all frames.  This AP database
 is managed in consideration of time, number of frames, and signal
 strength.  There are some kinds of network-interface hardware that
 can notify events to operating system only when the desired event
 occurs by setting a threshold from software.  Moreover, MN can
 transmit the probe request frame for access point discovery, if
 needed.

D.3. L2-PoAFound

 In IEEE 802.11 networks, L2-PoAFound is notified when new PoAs whose
 link quality level exceeds the specified threshold are detected by
 listening beacons or scanning APs.  If the received frame (mainly the

Teraoka, et al. Experimental [Page 24] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 beacon or the probe response) is not in the AP database described in
 Appendix D.2, then the link layer creates L2-PoAFound.indication.
 For example, if the threshold of link quality level specified by
 L2-PoAFound.request is GOOD, L2-PoAFound.indication is created and
 sent to the upper layer when PoA's link quality becomes better than
 GOOD.

D.4. L2-PoALost

 In IEEE 802.11 networks, L2-PoALost is notified when an AP included
 in the list of candidate APs is lost by listening beacons or scanning
 APs.  If the entry in the AP database described in Appendix D.2
 expires, or link quality level goes under the threshold, then the
 link layer creates L2-PoALost.indication.  To calculate the link
 quality level, the signal strength of the received frame (mainly the
 beacon or the probe response) can be used.  For example, if the
 threshold of the link quality specified by L2-PoALost is BAD,
 L2-PoALost.indication is created and sent to the upper layer when
 PoA's link quality becomes worse than BAD.

D.5. L2-LinkUp

 In IEEE 802.11 networks, L2-LinkUp is notified when association or
 reassociation event occurs.  When such an event occurs, MN receives
 the association response frame or the reassociation response frame.
 Immediately after receiving it, the link layer creates
 L2-LinkUp.indication.

D.6. L2-LinkDown

 In IEEE 802.11 networks, L2-LinkDown is notified when a
 disassociation event occurs or when no beacon is received during a
 certain time.  When such an event occurs, MN sends the disassociation
 frame to AP, or the entry of the specific AP is deleted from the AP
 database described in Appendix D.2.  By detecting such events, the
 link layer creates an L2-LinkDown.indication.

D.7. L2-LinkStatusChanged

 In IEEE 802.11 networks, L2-LinkStatusChanged is notified when the
 radio signal strength of the connected AP drops below the specified
 threshold.

Teraoka, et al. Experimental [Page 25] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

D.8. L2-LinkConnect

 In IEEE 802.11 networks, each AP is identified by the BSSID and the
 service set of several APs is identified by the SSID.  When
 L2-LinkConnect is used to connect a specific AP or a service set, the
 link layer should set the Basic Service Set Identifier (BSSID) or the
 Service Set Identifier (SSID).  Also, the channel should be set
 appropriately at the same time by searching the database described in
 Appendix D.2.  To connect to AP, MN should be authenticated by AP.
 MN sends the authentication message to AP, and then MN sends the
 association message to associate with AP.

D.9. L2-LinkDisconnect

 In IEEE 802.11 networks, MN sends the disassociation message to AP
 for disconnection.  When L2-LinkDisconnect is used for disconnection
 from the current AP, the link layer should send the disassociation
 message to the appropriate AP, and stop data transmission.

Appendix E. Implementation and Evaluation of the Proposed Model

 This section describes an implementation of the proposed link
 indication architecture and its evaluation.
 An IEEE 802.11a wireless LAN device driver was modified to provide
 abstract link-layer information in the form of primitives defined in
 Section 4.  The modified driver has two AP lists.  One contains the
 device-dependent information such as RSSI, retransmission count,
 various AP parameters, and various statistics.  The device-dependent
 information, except for the AP parameters, is updated whenever the
 device receives a frame.  If the received frame is the management
 frame, the AP parameters are also updated according to the parameters
 in the frame.
 Another AP list contains the abstract information.  The abstract
 information is updated periodically by using the device-dependent
 information.  In the abstraction processing, for example, RSSI or the
 retransmission count is converted to the common indicator "link
 quality".  In our outdoor testbed described below, the thresholds of
 the RSSI value between the link quality levels were defined as
 follows:
 o  EXCELLENT -- 34 -- GOOD
 o  GOOD -- 27 -- FAIR
 o  FIAR -- 22 -- BAD

Teraoka, et al. Experimental [Page 26] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 o  BAD -- 15 -- NONE
 L2-PoAList and L2-LinkStatus were implemented by using only the
 abstract information.  Thus, the upper layers can use information of
 the current AP and the adjacent APs without depending on the devices.
 L2-PoAFound or L2-PoALost is notified if the link quality rises or
 falls beyond the thresholds when the abstract information is updated.
 If the link quality of the current AP goes below the specific
 threshold, L2-LinkStatusChanged is notified.  L2-LinkUp or
 L2-LinkDown is notified when an association with an AP is established
 or destroyed.  To realize L2-LinkConnect and L2-LinkDisconnect,
 functions to connect or disconnect to the specified AP were
 implemented.  In these functions, since only abstract information is
 needed to specify the AP, other layers need not know the
 device-dependent information.
 In our outdoor testbed, there are eight Access Routers (ARs) located
 at 80-100m intervals.  AP is collocated at AR.  IEEE 802.11a was used
 as the link layer.  The same wireless channel was used at all APs.
 Thus, there are eight wireless IPv6 subnets in the testbed.  The
 mobile node was in a car moving at a speed of 30-40 km/h.  When link
 quality of the current AP goes down, the mobile node executes
 L3-driven handover, described in Appendix A.  An application called
 Digital Video Transport System (DVTS) was running on the mobile node
 and sent digital video data at a data rate of about 15Mbps through
 the wireless IPv6 subnet to the correspondent node, which replayed
 received digital video data.  In this environment, the L2 handover
 required less than 1 msec, and the mobility protocol Location
 Independent Networking in IPv6 (LIN6) [13] required a few msecs for
 location registration.  Thus, the total gap time due to the handover
 was 3-4 msec.  In most cases, there was no effect on the replayed
 pictures due to handover.

Authors' Addresses

 Fumio Teraoka
 Faculty of Science and Technology, KEIO University
 3-14-1 Hiyoshi, Kohoku-ku
 Yokohama, Kanagawa  223-8522
 Japan
 Phone: +81-45-566-1425
 EMail: tera@ics.keio.ac.jp
 URI:   http://www.tera.ics.keio.ac.jp/

Teraoka, et al. Experimental [Page 27] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

 Kazutaka Gogo
 Graduate School of Science and Technology, KEIO University
 3-14-1 Hiyoshi, Kohoku-ku
 Yokohama, Kanagawa  223-8522
 Japan
 Phone: +81-45-566-1425
 EMail: gogo@tera.ics.keio.ac.jp
 URI:   http://www.tera.ics.keio.ac.jp/
 Koshiro Mitsuya
 Jun Murai Lab, Shonan Fujisawa Campus, KEIO University
 5322 Endo
 Fujisawa, Kanagawa  252-8520
 Japan
 Phone: +81-466-49-1100
 EMail: mitsuya@sfc.wide.ad.jp
 Rie Shibui
 Graduate School of Science and Technology, KEIO University
 3-14-1 Hiyoshi, Kohoku-ku
 Yokohama, Kanagawa  223-8522
 Japan
 Phone: +81-45-566-1425
 EMail: shibrie@tera.ics.keio.ac.jp
 URI:   http://www.tera.ics.keio.ac.jp/
 Koki Mitani
 Graduate School of Science and Technology, KEIO University
 3-14-1 Hiyoshi, Kohoku-ku
 Yokohama, Kanagawa  223-8522
 Japan
 Phone: +81-45-566-1425
 EMail: koki@tera.ics.keio.ac.jp
 URI:   http://www.tera.ics.keio.ac.jp/

Teraoka, et al. Experimental [Page 28] RFC 5184 L2 Abstractions for L3-Driven Fast Handover May 2008

Full Copyright Statement

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 contained in BCP 78 and at http://www.rfc-editor.org/copyright.html,
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Teraoka, et al. Experimental [Page 29]

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