[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 rfc5184                               
IRTF MobOpts RG                                               F. Teraoka
Internet-Draft                                                   K. Gogo
Intended status: Informational                                K. Mitsuya
Expires: March 25, 2007                                        R. Shibui
                                                               K. Mitani
                                                         KEIO University
                                                      September 21, 2006


          Unified L2 Abstractions for L3-Driven Fast Handover
               draft-irtf-mobopts-l2-abstractions-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on March 25, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).











Teraoka, et al.          Expires March 25, 2007                 [Page 1]


Internet-Draft               L2 Abstractions              September 2006


Abstract

   This draft proposes unified L2 abstractions for L3-driven fast
   handovers.  For efficient network communication, it is vital for a
   protocol layer to know or utilize other layer's information such as a
   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.  To
   solve the problem, this draft defines nine kinds of L2 abstractions
   in the form of "primitive" 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".





































Teraoka, et al.          Expires March 25, 2007                 [Page 2]


Internet-Draft               L2 Abstractions              September 2006


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6

   3.  Primitives for L2 Abstractions . . . . . . . . . . . . . . . .  7

   4.  Definitions of Primitives  . . . . . . . . . . . . . . . . . .  9
     4.1.  L2-LinkStatus (Type 1) . . . . . . . . . . . . . . . . . .  9
     4.2.  L2-PeerList (Type 1) . . . . . . . . . . . . . . . . . . .  9
     4.3.  L2-PeerFound (Type 2)  . . . . . . . . . . . . . . . . . .  9
     4.4.  L2-PeerLost (Type 2) . . . . . . . . . . . . . . . . . . .  9
     4.5.  L2-LinkUp (Type 2) . . . . . . . . . . . . . . . . . . . . 10
     4.6.  L2-LinkDown (Type 2) . . . . . . . . . . . . . . . . . . . 10
     4.7.  L2-LinkGoingDown (Type 2)  . . . . . . . . . . . . . . . . 10
     4.8.  L2-LinkConnect (Type 3)  . . . . . . . . . . . . . . . . . 10
     4.9.  L2-LinkDisconnect (Type 3) . . . . . . . . . . . . . . . . 10

   5.  Definitions of Static Parameters . . . . . . . . . . . . . . . 11
     5.1.  Network Interface ID . . . . . . . . . . . . . . . . . . . 11

   6.  Definitions of Dynamic Parameters  . . . . . . . . . . . . . . 12
     6.1.  Peer . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.2.  Condition  . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.3.  Peer List  . . . . . . . . . . . . . . . . . . . . . . . . 12
     6.4.  Enable/Disable . . . . . . . . . . . . . . . . . . . . . . 12
     6.5.  Ack/Error  . . . . . . . . . . . . . . . . . . . . . . . . 12

   7.  Architectural Considerations . . . . . . . . . . . . . . . . . 13

   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17

   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 18

   Appendix A.  Example Scenario  . . . . . . . . . . . . . . . . . . 19

   Appendix B.  Example Operation for FMIPv6  . . . . . . . . . . . . 21
     B.1.  Example Operation-1 for FMIPv6 . . . . . . . . . . . . . . 21
     B.2.  Example Operation-2 for FMIPv6 . . . . . . . . . . . . . . 23
     B.3.  Experiment . . . . . . . . . . . . . . . . . . . . . . . . 25

   Appendix C.  Example Mapping of Primitives and IEEE802.11  . . . . 27
     C.1.  L2-LinkStatus  . . . . . . . . . . . . . . . . . . . . . . 27
     C.2.  L2-PeerList  . . . . . . . . . . . . . . . . . . . . . . . 27
     C.3.  L2-PeerFound . . . . . . . . . . . . . . . . . . . . . . . 27
     C.4.  L2-PeerLost  . . . . . . . . . . . . . . . . . . . . . . . 28
     C.5.  L2-LinkUp  . . . . . . . . . . . . . . . . . . . . . . . . 28



Teraoka, et al.          Expires March 25, 2007                 [Page 3]


Internet-Draft               L2 Abstractions              September 2006


     C.6.  L2-LinkDown  . . . . . . . . . . . . . . . . . . . . . . . 28
     C.7.  L2-LinkGoingDown . . . . . . . . . . . . . . . . . . . . . 28
     C.8.  L2-LinkConnect . . . . . . . . . . . . . . . . . . . . . . 28
     C.9.  L2-LinkDisconnect  . . . . . . . . . . . . . . . . . . . . 29

   Appendix D.  Implementation and Evaluation of the Proposed
                Model . . . . . . . . . . . . . . . . . . . . . . . . 30

   Appendix E.  Changes from 01 . . . . . . . . . . . . . . . . . . . 32

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
   Intellectual Property and Copyright Statements . . . . . . . . . . 35







































Teraoka, et al.          Expires March 25, 2007                 [Page 4]


Internet-Draft               L2 Abstractions              September 2006


1.  Introduction

   In recent years, the execution environment around computers is not
   static and changes dynamically.  Especially, when a mobile node moves
   to a different network, its communication environment considerably
   changes.  For example, in the case of wireless communication,
   parameters such as radio strength largely changes depending on time
   or site.

   For efficient network communication, it is vital for a protocol layer
   to know or utilize other layer's control information.  There are
   several proposals for seamless handovers in IPv6 network such as Fast
   Handovers for Mobile IPv6 (FMIPv6) [1] and Hierarchical Mobile IPv6
   (HMIPv6) [2].  In FMIPv6, the network layer must know the indication
   of a handover from the link layer in advance to achieve seamless
   handovers.  However, control information exchange between protocol
   layers is not allowed because each protocol layer is designed
   independently.

   To solve the problem, this draft defines nine kinds of L2
   abstractions in the form of "primitive" 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".



























Teraoka, et al.          Expires March 25, 2007                 [Page 5]


Internet-Draft               L2 Abstractions              September 2006


2.  Terminology

   This document uses the following terms.


   L3-Driven Fast Handover

      The handover mechanism which is initiated by the network layer on
      a mobile node.  Since this mechanism allows the 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 of a
      handover procedure.


   Peer

      The attachment point of a mobile node. (e.g., An access point in
      IEEE 802.11 networks.)


   Primitive

      A unit of information which is sent from one layer to another.
      There are four classes of primitives: Request, Confirm, Indication
      and Response.

























Teraoka, et al.          Expires March 25, 2007                 [Page 6]


Internet-Draft               L2 Abstractions              September 2006


3.  Primitives for L2 Abstractions

   Each layer offers its services in the form of primitives.  There are
   four classes of primitives as shown in Figure 1: Request, Confirm,
   Indication, and Response.  The request is issued by the layer that
   wants to get the services or the information from another layer, and
   the confirm is the acknowledgment of the request.  The indication is
   the notification of the information to the layer that requested the
   service, and the response is the acknowledgment of the indication.
   In this architecture, a layer can evenly communicate with each other.


            ------------------------------------------------------
                      Request                    Response
                        ||      /\          /\      ||
            Layer N     ||      ||          ||      ||
            ------------||------||----------||------||------------
                        ||      ||          ||      ||
                        \/      ||          ||      \/
            Layer N-m        Confirm    Indication
            ------------------------------------------------------

                           Figure 1: Primitives


   The primitive consists of five fields: the protocol layer id to which
   this primitive should be sent, the protocol id to which protocol
   entity this primitive should be sent, the primitive class (i.e.,
   request, confirm, indication, or response), the primitive name, and
   parameters.

   There are three different usages of "Primitives":

   Type 1.  To provide L2 information to upper layers immediately

            A "Request" primitive is an acquisition request for L2
            information.  As a "Confirm" primitive, L2 information
            returns immediately.

   Type 2.  To notify upper layers of L2 events asynchronously

            "Request" and "Confirm" primitives are used just for
            registration.  When an event occurs, an "Indication"
            primitive is asynchronously delivered to an upper layer.







Teraoka, et al.          Expires March 25, 2007                 [Page 7]


Internet-Draft               L2 Abstractions              September 2006


   Type 3.  To control L2 actions from upper layers

            A "Request" primitive is a request for operation.  Ack or
            nack returns immediately as a "Confirm" primitive.















































Teraoka, et al.          Expires March 25, 2007                 [Page 8]


Internet-Draft               L2 Abstractions              September 2006


4.  Definitions of Primitives

   To obtain and exchange L2 information, the following Primitives are
   defined.

4.1.  L2-LinkStatus (Type 1)

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

4.2.  L2-PeerList (Type 1)

   The L2-PeerList.request primitive is sent to the link layer when an
   upper layer needs a list of the candidate peers.  The L2-
   PeerList.request primitive contains the "Network Interface ID"
   parameter.  In response, the L2-PeerList.confirm primitive returns
   with the "Network Interface ID" parameter and the "Peer List"
   parameter.  The "Peer List" parameter is a list of the candidate
   peers.

4.3.  L2-PeerFound (Type 2)

   The L2-PeerFound.indication primitive is asynchronously provided to
   an upper layer when new peers are detected.  This primitive carries
   the "Network Interface ID" parameter and the "Peer List" parameter.
   The "Peer List" parameter contains the information of new peers
   detected by the mobile node.  In order to use this notification, the
   registration process using the L2-PeerFound.request primitive and the
   L2-PeerFound.confirm primitive is needed in advance.  The L2-
   PeerFound.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-PeerFound.confirm primitive returns
   with the "Network Interface ID" parameter and the "Ack" parameter in
   response.

4.4.  L2-PeerLost (Type 2)

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



Teraoka, et al.          Expires March 25, 2007                 [Page 9]


Internet-Draft               L2 Abstractions              September 2006


   contains the information of the peers which disappeared from the
   candidates list.  The registration process using the L2-
   PeerLost.request primitive and the L2-PeerLost.confirm primitive is
   similar to the L2-PeerFound 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.  This primitive carries the
   "Network Interface ID" parameter and the "Peer" parameter.  The L2-
   LinkUp.request primitive contains the "Network Interface ID"
   parameter and the "Enable/Disable" parameter for registration.  When
   the registration succeeded, 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.  The registration
   processing is same as the L2-LinkUp primitive described above.

4.7.  L2-LinkGoingDown (Type 2)

   The L2-LinkGoingDown.indication primitive is asynchronously provided
   to an upper layer when an existing link is about to be disconnected.
   This notification contains two parameters: "Network Interface ID" and
   "Peer".  The "Peer" parameter indicates the attachment point at which
   the link quality is degrading.  In the registration processing, the
   L2-LinkGoingDown.request primitive carries the "Network Interface ID"
   parameter and the "Enable/Disable" parameter.

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 "Peer".
   This primitive carries the "Network Interface ID" parameter and the
   "Peer" parameter.  This operation begins after the link layer returns
   the L2-LinkConnect.confirm primitive with "Ack".

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
   "Peer".  This primitive carries the "Network Interface ID" parameter
   and the "Peer" parameter.  This operation begins after the link layer
   returns the L2-LinkDisconnect.confirm primitive with "Ack".





Teraoka, et al.          Expires March 25, 2007                [Page 10]


Internet-Draft               L2 Abstractions              September 2006


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 which indicates the kind of technology of the network
   interface (e.g., IEEE802.11a/b/g, 3GPP, etc.).  This parameter is
   required in all primitives.



































Teraoka, et al.          Expires March 25, 2007                [Page 11]


Internet-Draft               L2 Abstractions              September 2006


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.  Peer

   The "Peer" parameter uniquely identifies the peer.

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,
   NONE in descending order.

6.3.  Peer List

   The "Peer List" parameter consists of arbitrary couples of two sub-
   parameters: "Peer" and "Condition".  This parameter shows a list of
   peers and its condition.

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.











Teraoka, et al.          Expires March 25, 2007                [Page 12]


Internet-Draft               L2 Abstractions              September 2006


7.  Architectural Considerations

   The IAB document "Architectural Implications of Link Indications" [3]
   discusses the role and the issues of link indications within the
   Internet Architecture.  This section discusses the architectural
   considerations mentioned in Section 2 of the IAB document.


   [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, the
         Received Signal Strength Indicator (RSSI), the number of
         retransmissions and 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
         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 occurred.  The response is the reply to the indication.

         In our proposal about IEEE 802.11b, L2-LinkUp is defined as the
         status in which an association to the AP is established, and
         L2-LinkDown is defined as the status in which an association to
         the AP is not established.  L2-LinkGoingdown is generated when
         the link quality becomes below the predefined threshold.  Since



Teraoka, et al.          Expires March 25, 2007                [Page 13]


Internet-Draft               L2 Abstractions              September 2006


         the Received Signal Strength Indicator (RSSI) and the number of
         retransmissions are used to abstract and evaluate the link
         quality, L2-LinkGoingDown represents the link quality in both
         directions.  It should use an average of 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 largely 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-LinkGoingDown is notified.  The use of L2
         indications is related to parameter thresholds which trigger
         handover.  These thresholds vary based on the deployment
         scenario, and if not configured properly, could lead to
         misleading indications.


   [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 D uses
         the L2-LinkGoingDown indication as the trigger for starting
         handover.  L2-LinkGoingDown is indicated when the link quality
         goes down below the 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-LingGoingDown 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 is not



Teraoka, et al.          Expires March 25, 2007                [Page 14]


Internet-Draft               L2 Abstractions              September 2006


         directly affecting 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-LinkGoingDown
         indication to predict disconnection.  But L2-LinkGoingDown is
         not sometimes trusted because it is difficult to abstract the
         link quality.  Invalid L2-LinkGoingDown 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 an evaluation of the L3-driven handover
         mechanism is described in Appendix D.


   [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 to only the IP
         layer, race conditions between multiple layers never happen.


   [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.





Teraoka, et al.          Expires March 25, 2007                [Page 15]


Internet-Draft               L2 Abstractions              September 2006


         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, are more likely to be backward compatible, and are
         less likely to result in security vulnerabilities.


         Our proposal does not define exchange of link indications
         between nodes.



              ---------------------------------------------------------
              ----------===========     ----------===========
              |         |[        ]     |         |[        ]
              |   PE    |[   AE   ]     |   PE    |[   AE   ]
              |         |[        ]     |         |[        ]
              ----------===========     ----------===========
              Layer N     ||   /\                   ||   /\
              ------------||---||-------------------||---||------------
                   Request||   ||           Response||   ||
                          ||   ||                   ||   ||
                          ||   ||                   ||   ||
                          ||   ||Confirm            ||   ||Indication
              ------------||---||-------------------||---||------------
                          \/   ||                   \/   ||
              ----------===========     ----------===========
              |         |[        ]     |         |[        ]
              |   PE    |[   AE   ]     |   PE    |[   AE   ]
              |         |[        ]     |         |[        ]
              ----------===========     ----------===========
              Layer N-m
              ----------------------------------------------------------

                    Figure 2: AE and PE with Primitives






Teraoka, et al.          Expires March 25, 2007                [Page 16]


Internet-Draft               L2 Abstractions              September 2006


8.  Security Considerations

   The IAB document "Architectural Implications of Link Indications" [3]
   discusses the role and the issues of link indications within the
   Internet Architecture.  This section discusses the security
   considerations mentioned in Section 4 of the IAB document.


   [1]  Spoofing


        Our proposal is no more insecure than a particular link layer on
        which it is implemented.


   [2]  Indication validation


        Transportation of the link indications between nodes is not
        assumed, hence this consideration is out of scope in our
        proposal.


   [3]  Denial of service


        Our proposal is no more insecure than a particular link layer on
        which it is implemented.























Teraoka, et al.          Expires March 25, 2007                [Page 17]


Internet-Draft               L2 Abstractions              September 2006


9.  References

   [1]  Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068,
        July 2005.

   [2]  Soliman, H., Castelluccia, C., Malki, K., and L. Bellier,
        "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)",
        RFC 4140, August 2005.

   [3]  Aboda, B., "Architectural Implications of Link Indications",
        draft-iab-link-indications-05 (work in progress), July 2006.

   [4]  Ishiyama, M., Kunishi, M., 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.          Expires March 25, 2007                [Page 18]


Internet-Draft               L2 Abstractions              September 2006


Appendix A.  Example Scenario

   For example, the picture below shows L3-driven fast handover
   mechanism using the L2 triggers on MN.

                 L2                               L3
                  |                                |
                  |<----------LinkUP.req-----------|
                  |-----------LinkUP.cnf---------->|
                  |<-------LinkGoingDown.req-------|
                  |--------LinkGoingDown.cnf------>|
                  =                                =
                  |                                |
                 Low                               |
                Signal-----LinkGoingDown.ind------>|
                  |                                |
                  |<---------PeerList.req----------|
                  |----------PeerList.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, the L3 issues LinkUp.request to receive LinkUp.indication when
   the link becomes available.  The L3 also issues LinkGoingDown.request
   to receive LinkGoingDown.indication when the link quality goes down
   below the threshold.

   In the beginning of the L3-driven handover procedure, the L2 detects
   the radio signal strength is going down.  Then the L2 sends L2-
   LinkGoingDown.indication to the L3.  The L3 prepares for handover
   (e.g., CoA generation, DAD, ND cache creation, and routing table
   setting) and sends L2-PeerList.request to the L2 if the list of
   access points is needed.



Teraoka, et al.          Expires March 25, 2007                [Page 19]


Internet-Draft               L2 Abstractions              September 2006


   If the L3 decides to perform handover according to some rules, the L3
   sends L2-LinkConnect.request with some parameters about candidate
   access points to request L2 handover.  L2 handover begins after the
   L3 sends L2-LinkConnect.confirm to the L2.  When the L2 handover
   finished, the L2 sends L2-LinkUp.indication to notify the L3.
   Finally, the L3 performs handover (e.g., sending BU).

   One of the important features of L3-driven fast handover using
   Primitives is that the L3 handover preparation can be done during
   communication.  So, it can reduce disruption time during handover.









































Teraoka, et al.          Expires March 25, 2007                [Page 20]


Internet-Draft               L2 Abstractions              September 2006


Appendix B.  Example Operation for FMIPv6

   Here shows 2 scenarios of L3 driven fast handover for FMIPv6.
   Scenario 2 is differ from scenario 1 for the timing of sending some
   messages.

B.1.  Example Operation-1 for FMIPv6

   Figure 4 shows the predictive mode of FMIPv6 operation with L3-driven
   link switching mechanism.









































Teraoka, et al.          Expires March 25, 2007                [Page 21]


Internet-Draft               L2 Abstractions              September 2006


     MN-L2                            MN-L3        PAR-L3
       |                                |             |
      AP<---------PeerList.req----------|             |
     Scan---------PeerList.cnf--------->|             |
       |                                |---RtSolPr-->|
       |                                |<--PrRtAdv---|
       |---------PeerFound.ind--------->|             |
       |                                |---RtSolPr-->|
       |                                |<--PrRtAdv---|
       |                                |             |
       ~                                ~             ~
       |                                |             |
      Low                               |             |
     Signal-----LinkGoingDown.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


   When the MN establishes link connectivity to the PAR, it performs
   router discovery.  The MN sends RtSolPr message to the PAR to resolve
   the access point identifiers to the subnet router information.  To



Teraoka, et al.          Expires March 25, 2007                [Page 22]


Internet-Draft               L2 Abstractions              September 2006


   send RtSolPr, a MN discovers one or more access points by sending L2-
   PeerList.request to the link layer.  As a response to L2-
   PeerList.request, L2-PeerList.confirm returns with "Peer List"
   parameter which contains identifiers and conditions of nearby access
   points.  After initial AP discovery, L2-PeerFound.indication with
   "Peer List" is also sent from the link layer when one or more access
   points are discovered.

   When the link layer of the MN detects that radio signal strength is
   going down, it sends L2-LinkGoingDown.indication to the network
   layer.  Then, the MN sends the FBU message to the 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, the
   MN receives the FBack message and then immediately switches its link
   by L2-LinkConnect.request with the specific "Peer" 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.  The MN immediately sends the
   FNA message to the NAR.  The NAR will send tunneled and buffered
   packets to the MN.

B.2.  Example Operation-2 for FMIPv6

   Figure 5 shows the predictive mode of FMIPv6 operation with L3-driven
   link switching mechanism.
























Teraoka, et al.          Expires March 25, 2007                [Page 23]


Internet-Draft               L2 Abstractions              September 2006


     MN-L2                            MN-L3        PAR-L3
       |                                |             |
      AP<---------PeerList.req----------|             |
     Scan---------PeerList.cnf--------->|             |
       |                                |---RtSolPr-->|
       |                                |<--PrRtAdv---|
       |---------PeerFound.ind--------->|             |
       |                                |---RtSolPr-->|
       |                                |<--PrRtAdv---|
       |                                |             |
       ~                                ~             ~
       |                                |             |
      Low                               |             |
     Signal-----LinkGoingDown.ind------>|             |        NAR-L3
       |                                |-----FBU---->|           |
       |<-------LinkConnect.req---L3 Handover         |           |
   L2 Handover--LinkConnect.cnf-------->:             |           |
       |                                |             |----HI---->|
       |                                |             |<--HAck----|
       |                                |             |---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


   Unlike the scenario 1, the MN in scenario 2 sends LinkConnect.req
   from the network layer to the link layer after MN sends the FBU
   message.  As the MN sends the FBack message to both AR (not only the



Teraoka, et al.          Expires March 25, 2007                [Page 24]


Internet-Draft               L2 Abstractions              September 2006


   PAR but also the NAR), the MN can get the FBack message sent by the
   PAR through the NAR, and then it moves to the NAR.

B.3.  Experiment

   We implemented FMIPv6 and the proposed L2 primitives on FreeBSD-5.4.
   Figure 6 shows our test network.  The MN is connected to access
   routers by using IEEE802.11a wireless LAN.  The MN moves from the PAR
   to the 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.  Upon receiving L2-
   LinkGoingDown.indication, the L3 of the MN sends the FBU message and
   then receives the FBack message.  It took 20ms from the transmission
   of the FBU message and the reception of the FBack message.  After
   receiving the FBack message, the L3 of the MN issues L2-
   LinkConnect.request to the L2.  When L2 handover finishes, the L3
   receives L2-LinkUp.ind from the L2.  It took 1ms for an L2 handover.
   Next, the MN sends the FNA message to the NAR.  Upon receiving the
   FNA message, the NAR starts forwarding packets to the NM.  ICMP echo
   request packets were sent at 10ms intervals.  It was observed that no
   or 1 ICMP echo reply packet was lost during a handover.








Teraoka, et al.          Expires March 25, 2007                [Page 25]


Internet-Draft               L2 Abstractions              September 2006


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


                        Figure 7: Measured Results



























Teraoka, et al.          Expires March 25, 2007                [Page 26]


Internet-Draft               L2 Abstractions              September 2006


Appendix C.  Example Mapping of Primitives and IEEE802.11

   This section shows examples of the mapping between "Primitives" and
   IEEE802.11 parameters.

C.1.  L2-LinkStatus

   Most of 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 peer can be obtained by maintaining the transmission rate
   indication and the statistics of frame transmission at every time a
   frame is sent.  A link quality level can be updated by maintaining
   the following parameters and statistics at every time a frame is
   received: receive signal strength indication (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 threshold from
   software.  When the parameters cross the threshold, an interrupt is
   generated for the software.

C.2.  L2-PeerList

   In IEEE 802.11 networks, L2-PeerList returns the detected APs which
   quality level exceeds the specified threshold as peer candidates (by
   the "Peer List" parameter).  Therefore, the 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, the MN can
   transmit the probe request frame for access point discovery, if
   needed.

C.3.  L2-PeerFound

   In IEEE 802.11 networks, L2-PeerFound is notified when new peers
   which link quality level exceeds the specified threshold are detected
   by listening beacons or scanning APs.  If the received frame (mainly
   the beacon or the probe response) is not in the AP database described
   in Appendix C.2, then the link layer creates L2-PeerFound.indication.



Teraoka, et al.          Expires March 25, 2007                [Page 27]


Internet-Draft               L2 Abstractions              September 2006


   For example, if the threshold of link quality level specified by L2-
   PeerFound.request is GOOD, the L2-PeerFound.ind is made and sent to
   the upper layer when peer's link quality becomes stronger than to the
   level of GOOD.

C.4.  L2-PeerLost

   In IEEE 802.11 networks, L2-PeerLost is notified when an AP included
   in the list of candidate APs is got lost by listening beacons or
   scanning APs.  If the entry in the AP database described in
   Appendix C.2 expires, or link quality level goes under the threshold,
   then the link layer creates L2-PeerLost.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-PeerLost is BAD, L2-
   PeerLost.ind is made and sent to the upper layer when peer's link
   quality becomes weaker than the level of BAD.

C.5.  L2-LinkUp

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

C.6.  L2-LinkDown

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

C.7.  L2-LinkGoingDown

   In IEEE 802.11 networks, L2-LinkGoingDown is notified when the radio
   signal strength of the connected AP is going down and becomes under
   the specified threshold.

C.8.  L2-LinkConnect

   In IEEE802.11 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 BSSID or the SSID.  Also, the channel
   should be set appropriately at the same time by searching the



Teraoka, et al.          Expires March 25, 2007                [Page 28]


Internet-Draft               L2 Abstractions              September 2006


   database described in Appendix C.2.  To connect to the AP, the MN
   should be authenticated by the AP.  The MN sends the authentication
   message to the AP, and then the MN sends the association message to
   associate with the AP.

C.9.  L2-LinkDisconnect

   In IEEE802.11 networks, the MN sends the disassociation message to
   the 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.







































Teraoka, et al.          Expires March 25, 2007                [Page 29]


Internet-Draft               L2 Abstractions              September 2006


Appendix D.  Implementation and Evaluation of the Proposed Model

   This section describes an implementation of the proposed link
   indication architecture and its evaluation.

   An IEEE802.11a 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 the RSSI, the 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, the RSSI or
   the retransmission count is converted to the common indicator "link
   quality".

   L2-PeerList 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-PeerFound or L2-PeerLost is notified if the link quality went up
   or down beyond the thresholds when the abstract information is
   updated.  If the link quality of the current AP went down below the
   specific threshold, L2-LinkGoingDown 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 to know the device
   dependent information.

   In our outdoor testbed, there are eight ARs, each of which is located
   at a 80-100m interval.  The AP is collocated at the AR.  IEEE802.11a
   was used as the link layer.  The same wireless channel was used at
   all the APs.  Thus there are eight wireless IPv6 subnets in the
   testbed.  The mobile node in a car moved 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 DVTS was running on the mobile node and sent digital video
   data at about a 15Mbps data rate through the wireless IPv6 subnet to
   the correspondent node, which replayed received digital video data.
   In this environment, the L2 handover needed less than 1 msec and
   mobility protocol LIN6 [4] needed a few msec for location
   registration.  Thus, the total gap time due to the handover was 3-4



Teraoka, et al.          Expires March 25, 2007                [Page 30]


Internet-Draft               L2 Abstractions              September 2006


   msec.  In most case, there was no influence to the replayed pictures
   over handover.

















































Teraoka, et al.          Expires March 25, 2007                [Page 31]


Internet-Draft               L2 Abstractions              September 2006


Appendix E.  Changes from 01


      - References were updated.















































Teraoka, et al.          Expires March 25, 2007                [Page 32]


Internet-Draft               L2 Abstractions              September 2006


Authors' Addresses

   Fumio Teraoka
   Graduate School of Science and Technology, KEIO University
   3-14-1 Hiyoshi, Kohoku-ku
   Yokohama, Kanagawa  223-8522
   Japan

   Phone: 45-566-1425
   Email: tera@ics.keio.ac.jp
   URI:   http://www.tera.ics.keio.ac.jp/


   Kazutaka Gogo
   Faculty of Science and Technology, KEIO University
   3-14-1 Hiyoshi, Kohoku-ku
   Yokohama, Kanagawa  223-8522
   Japan

   Phone: 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_at_sfc.wide.ad.jp
   URI:


   Rie Shibui
   Graduate School of Science and Technology, KEIO University
   3-14-1 Hiyoshi, Kohoku-ku
   Yokohama, Kanagawa  223-8522
   Japan

   Phone: 45-566-1425
   Email: shibrie@tera.ics.keio.ac.jp
   URI:   http://www.tera.ics.keio.ac.jp/







Teraoka, et al.          Expires March 25, 2007                [Page 33]


Internet-Draft               L2 Abstractions              September 2006


   Koki Mitani
   Graduate School of Science and Technology, KEIO University
   3-14-1 Hiyoshi, Kohoku-ku
   Yokohama, Kanagawa  223-8522
   Japan

   Phone: 45-566-1425
   Email: koki@tera.ics.keio.ac.jp
   URI:   http://www.tera.ics.keio.ac.jp/










































Teraoka, et al.          Expires March 25, 2007                [Page 34]


Internet-Draft               L2 Abstractions              September 2006


Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   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
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


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
   http://www.ietf.org/ipr.

   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
   ietf-ipr@ietf.org.


Acknowledgment

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





Teraoka, et al.          Expires March 25, 2007                [Page 35]