One document matched: draft-daniel-mip6-optimized-vertical-handover-00.txt



  MIP6 WG                                                S. Daniel Park 
  Internet Draft                                    Samsung Electronics 
  Expires: 30 July 2004                                    Eric Njedjou 
                                                     France Telecom R&D 
                                                      Nicolas Montavont 
                                                                  LSIIT 
                                                        31 January 2004 
   
   
   
             L2 Triggers Optimized Mobile IPv6 Vertical Handover: 
                            The 802.11/GPRS Example 
                                        
            <draft-daniel-mip6-optimized-vertical-handover-00.txt> 
   
   
  Status of this Memo 
      
     This document is an Internet-Draft and is in full conformance with 
     all provisions of Section 10 of RFC2026. 
      
     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. 
      
      
  Abstract 
     This document describes a mechanism that extends Mobile IPv6 
     protocol to smoothly manage handovers for Mobile Nodes equipped with 
     multiple interfaces and moving across different and heterogeneous 
     links. For this purpose, the document provides indications on how to 
     use the link events information to optimize L3 movement detection.  
      
      
      


   
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  Table of Contents 
      
     1.  Introduction...................................................3 
     2.  Conventions used in this document..............................4 
     3.  Terminology....................................................4 
     4.  Standard mobile IPv6 node behavior for movement detection and 
     handover...........................................................5 
        4.1  Limitation of the standard mechanism.......................5 
     5.  Layer 2 Triggers / Hints.......................................6 
        5.1  Introduction and Background................................6 
        5.2  Differences between L2 Triggers and L2 Hints...............7 
        5.3  Some Definitions...........................................7 
     6.  Link triggers/hints optimized mobile IPv6 vertical handover....8 
        6.1  How the l2 information should be utilized to enhance 
        movement detection and handover.................................8 
        6.1.1  Use of LINK-UP trigger...................................8 
        6.1.2  Use of the LINK-TYPE hint................................9 
        6.1.3  Use of LINK-DOWN trigger.................................9 
        6.2  Previously defined optimizations to movement detection....10 
     7.  Example of 802.11 / GPRS handover.............................10 
        7.1  GPRS and 802.11 coexistence...............................10 
        7.2  GPRS and 802.11 link triggers/hints.......................11 
        7.2.1  GPRS....................................................11 
        7.2.2  802.11..................................................12 
        7.2.3  LINK-TYPE indication....................................13 
        7.3  Mobile IPv6 node recommended behavior from 802.11 to GPRS.13 
        7.4  Mobile IPv6 node recommended behavior from GPRS to 802.11.14 
     8.  Security Considerations.......................................15 
     9.  References....................................................15 
        9.1  Normative References......................................15 
        9.2  Informative References....................................15 
      
   
   
   
   
   
   
   
   
   
   



   
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  1. Introduction 
      
     In order to provide sessions continuity for wireless users, Mobile 
     IPv6 protocol [MIPv6] is currently available. It is capable of 
     handling IP handovers between different subnets, in a transparent 
     way for higher-level connections. 
      
     Various solutions have been developed within the IETF to provide 
     signaling and handoff optimizations to [MIPv6], such as Hierarchical 
     Mobility ([HMIPv6]) and Fast Handoffs ([FMIPv6]). [FMIPv6] allows a 
     Mobile Node to anticipate its attachment with a prospective default 
     router (behind a new link), by helping to prepare the new IP 
     configuration in advance, in a way to enable the Mobile Node to send 
     and receive packets as soon as it attaches to the new link. [FMIPv6] 
     assumes that this new IP configuration is to be received through the 
     currently used network interface. 
      
     [FMIPv6] requires adding additional support to IPv6 implementation 
     in routers, which already deployed IPv6 infrastructure may not be 
     ready to afford. Still, today, mobile users require ubiquitous 
     Internet access, which implies being able to support smooth 
     handovers from one IP subnet to another each serving a radio 
     coverage of a different technology. 
      
     Mobile Nodes are more and more equipped with several interfaces of 
     different L2 technologies. As such they may be reachable through 
     multiple links at the same time or alternatively use each interface 
     depending on the network environment. It is then possible to totally 
     prepare, and more importantly, build the IP configuration to be used 
     on a new link, while still using the currently active care-of-
     address (built on another link). In this case, there may be no need 
     to use the RtSolPr/PrRtAdv exchange to learn the IP configuration to 
     be used on the new link as this can be directly done with the new 
     Access Router (AR) by using a second L2 interface connected to the 
     AP serving this new link. Therefore, the new IP configuration of the 
     target interface can be done without interfering the communication 
     on the currently used interface if it is still connected to the 
     network. For these reasons, [FMPv6] may not be useful for vertical 
     handover, when the new IP configuration can be done before of the 
     actual vertical handover. 
      
     Nevertheless, the handover still needs to be made smoothly. And, In 
     order to optimally achieve a MIPv6 vertical handoff, the generic, 
     link-layer independent movement detection mechanism as described in 


   
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     [MIPv6] appears not sufficient. Effectively, it concentrates on 
     detecting Layer3 movement while timely knowledge of L2 events might 
     be beneficial to assist in seamless operations. 
      
     In this document, we describe a link-layer triggers optimized 
     movement detection process for Mobile IPv6 protocol. For this 
     purpose, we briefly describe the standard [MIPv6] movement detection 
     process and exhibit its limits. We then introduce the link triggers 
     and hints, before describing the enhanced movement detection 
     algorithm. We further apply the optimization to the GPRS/802.11 
     Mobile IPv6 handover case after having identified the link 
     triggers/hints to be used for both technologies. 
      
      
  2. Conventions used in this document 
      
     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 [RFC 2119]. 
      
      
  3. Terminology 
      
     Access Point (AP)  
     An Access Point is a layer 2 device that is connected to the wired 
     Network and offers the wireless link connection to the MN. 
      
     Access Router (AR)  
     A router residing on the edge of an Access Network and connected to 
     one or more APs. An AR offers IP connectivity to Mobile Nodes. 
      
     GGSN 
     Gateway GPRS Support Node. A router between the GPRS network and an 
     external network (i.e, the Internet). The GGSN is an example of an 
     Access Network Gateway. 
      
     GPRS 
     General Packet Radio Service. Packet-switched data  
     transmission service on top of the GSM network. 
      
     Layer 2 Handoff (L2 Handoff)  
     A process of terminating existing link layer connectivity and 
     obtaining new one. This handoff alone is transparent to the routing 
     at the IP layer. 


   
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     Layer 3 Handoff (L3 Handoff) 
     A process of terminating existing network layer connectivity and 
     obtaining new one. 
      
     Mobile Node (MN) 
     A host or router that changes its point of attachment from one 
     network or subnet to another 
      
      
  4. Standard mobile IPv6 node behavior for movement detection and 
     handover 
      
     Section 11.5 of [MIPv6] describes a generic movement detection 
     process, that uses the absence of due Router Advertisements (RAs) 
     and Neighbor Unreachability Detection (NUD) to detect when the 
     default router is no longer reachable. This triggers Router 
     Discovery, initiated by the sending of RAs, to learn about the 
     presence of a candidate new default router. After discovering new 
     routers, the mobile node performs DAD for link-local address, 
     selects a new router, performs prefix discovery for that router to 
     form a new care-of address and, as a consequence, performs the 
     binding update and route optimization. 
      
      
  4.1 Limitation of the standard mechanism 
      
     The only use of L3 information in [MIPv6] movement detection 
     algorithm has the following consequences; 
      
     1. A Mobile Node is not able to detect that its default router is no 
        longer reachable unless 
      
        - The RA Advertisement interval expires without the MN receiving 
          any other advertisement. 
      
        - It has packets to send 
         
     2. Moreover, a Mobile Node is not able to detect that it has lost 
     attachment to its default router even with such hints as the 
     reception of a new RA with a new prefix. Effectively, the reception 
     of a new RA advertising a new prefix does not determine a lost of L3 
     connectivity as there might be multiple routers sharing the link. 
      


   
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     3. A Mobile Node has to wait until it receives a RA to acquire 
     knowledge of the presence of a new router. Still, for the purpose of 
     achieving smooth handovers from one IP subnet to another, it might 
     be unaffordable for some time-constrained applications to realize 
     that reachability with the default router has been lost, long after 
     it really had. It may be unaffordable as well for such applications 
     to wait for received RAs before discovering new routers and form a 
     new care-of address. 
      
     To quickly detect any L3 movement (i.e loss of attachment with 
     default router and discovery of new router), link-layer indication 
     might be precious. However current Mobile IPv6 protocol [MIPv6] does 
     not indicate how to make use of these L2 indications , well kown as 
     triggers, but consider it as an item for further studies. The two 
     next sections are an attempt to address this well known deficiency 
     to [MIPv6]. 
      
      
  5. Layer 2 Triggers / Hints 
      
  5.1 Introduction and Background 
      
     L2 triggers were introduced in the IETF terminology a long time ago. 
     In [manyfloks], the concept of L2 triggers was defined to optimize 
     IP handovers between access points belonging to different subnets. 
     In this context, five L2 triggers were proposed: two messages in 
     reaction to a L2 handover/connection establishment (Link up and Link 
     Down) and three messages that are issued before a L2 handover occurs 
     (Source Trigger, Target Trigger or Mobile Trigger). These pre-
     handover messages were designed to help L3 operations because they 
     allowed the anticipation of potential movements. The Fast Handoffs 
     specification, [FMIPv6], which proposes extension to Standard Mobile 
     IP to support smooth handover, describes a message exchange between 
     the MN and its old and new ARs to enhance movement operation. The 
     mechanism is based on an anticipation of movement where the MN is 
     supposed to discover close APs. The way the MN discovers its 
     neighboring APs is not defined in the document. Moreover, the 
     documents says that L2 triggering can be used for anticipation and 
     start of the Fast Handover mechanism, but as of today no general L2 
     trigger specification exists. 
      
     [802.11fh] details how to perform a MIPv6 fast handover over IEEE 
     802.11 networks. The feasability of the anticipation in IEEE 802.11 



   
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     networks is studied and a specific L2 trigger to IEEE 802.11 is 
     proposed.  
     It is also to be noted that the use of L2 information by the IP 
     layer was discussed in MANET Working Group for ad-hoc devices. L2 
     triggering and L2 parameters were identified as being capable of 
     enhancing the routing protocol in an ad-hoc environment; If a node 
     has different choices to compute its next hop, the intensity of 
     signal between itself and its neighbors could be considered in the 
     choice of the next hop. 
      
     More recently, a new Working Group has been setting up, called 
     Detecting Network Attachment (DNA), which aims is to determine the 
     operations needed to faster discover the IPv6 subnet a MN is to 
     connect to. In this context, the information to be extracted from L2 
     for use by L3 has been discussed in [L2Hint] and [Parameters]. The 
     goal of this work in progress is to provide a catalog of L2 triggers 
     and L2 hints available at the link layer. We can expect that this 
     catalog will lead to a generic abstraction of the L2 technologies 
     that can be used by the IP layer for different purposes: IP 
     attachment detection, handover optimization, anticipation of 
     movement, etc. Such an abstraction will consist in events and states 
     of the L2, as well as L2 parameters. An abstraction aims at defining 
     optimized L3 operations over any L2 technologies, independently from 
     these technologies. 
      
      
  5.2 Differences between L2 Triggers and L2 Hints 
      
     In the specification of L2-L3 interaction, a distinction is made 
     between L2 Triggers and L2 Hints; a L2 Trigger is an event that 
     occured at the Link Layer that is forwarded to the upper layer 
     (Layer 3). This event can help the Layer 3 to instantaneously react 
     by initiating an L3 operation (such as to trigger a L3 handover). 
      
     A L2 Hint is an information that can be optionally transported with 
     a L2 trigger and that can help the Layer 3 enhance triggered 
     operations. Therefore, it is a supplementary information transported 
     with the L2 Trigger that even help to make L3 link discovery faster. 
      
      
  5.3 Some Definitions 
      




   
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     LINK-UP trigger: This event corresponds to the establishment of a 
     new L2 link, which allows IP communication over it. This is 
     typically a new full connection between the MN and an AP. 
      
     LINK-DOWN trigger: This event corresponds to a L2 Link that has been 
     broken down. This typically happens when a current connection 
     between the MN and an AP has been terminated. The interface which 
     generates this trigger can not be used for communication until a 
     connection with an AP is made (LINK UP). 
      
     LINK-TYPE hint: The type of the technology from which the trigger 
     was generated, e.g., GPRS or WLAN. 
      
      
  6. Link triggers/hints optimized mobile IPv6 vertical handover 
      
  6.1 How the l2 information should be utilized to enhance movement 
      detection and handover 
      
     In this section, we try to show how information extracted from lower 
     layer protocols, namely triggers and hints, can provide better 
     performance for the movement detection algorithm. The gain in 
     performance is not measured here but could be the subject of other 
     documents. 
      
      
  6.1.1 Use of LINK-UP trigger 
      
     When a LINK-UP indication is received from L2, the Mobile Node 
     immediately sends a Router Solicitation message (rather than waiting 
     for any Router Advertisement message to be received). On some types 
     of links, routers could be configured in a way to avoid sending 
     unsolicited Router Solicitation messages or to sending them at a 
     frequency not adapted to mobility demands. Waiting for RAs in such 
     cases could be really prejudicial for the performance of Mobile IPv6. 
     It is to be noted that the random time advised by RFC 2461 between 0 
     and MAX_ROUTER_SOLICITATION_DELAY before sending any RS can be 
     avoided for optimization purposes, as it is accepted that Mobile 
     Nodes constraints render it essential the need to have the shortest 
     possible router discovery time. 
     The LINK UP indication should be accompanied by a LINK-TYPE 
     indication. The use of the LINK-TYPE parameter is explained later in 
     this section. 



   
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     The Mobile Node then processes the RA received as response to the RS, 
     builds a table where it associates the RA information on the new 
     link with the LINK-TYPE parameter, then performs DAD, Prefix 
     Discovery, IP address auto-configuration, care-of-address 
     construction as usual. 
      
      
  6.1.2 Use of the LINK-TYPE hint 
      
     A Mobile Node should send at least one RS each time it discovers a 
     new link. In doing so, when at least two RAs have been received on 
     different links, and care-of-addresses have been correspondingly 
     built, the Mobile Node can use the LINK-TYPE indication associated 
     to each RA (thus to each Care-of-address) in the selection of the 
     primary care-of address as described in [MIPv6]. In such a way, the 
     Mobile Node would be able to choose to have its primary care-of-
     address on one link offering as an example, better characteristics 
     with respect to bandwidth and latency, than any other link available. 
      
     This is why it makes sense to immediately proceed to sending a 
     Router Solicitation when a LINK-UP indication is received, as the 
     link features deducted from the LINK-TYPE hint can lead to the 
     preference of the newly discovered link for the choice of the 
     primary care-of-address. It is to be reminded that the intent here 
     is not to specify how the care-of-address should be selected but 
     rather to indicate elements that can help this selection. 
      
      
  6.1.3 Use of LINK-DOWN trigger  
      
     When a LINK-DOWN indication is received from L2 the Mobile Node 
     should immediately invalidate the care-of-address associated with 
     the link in question, this in accordance with [MIPv6], re-select a 
     new primary care-of-address if available, or wait for the next LINK-
     UP indication to proceed to active Router Discovery again. 
     This avoid loosing the time corresponding to the delay experienced 
     in waiting for the Mobile Node to realize that it is no more 
     receiving any RA added to the delay for performing any IP 
     connectivity check as NUD. 
      
     If the Mobile Node was already engaged in a NUD check, upon 
     reception of a LINK-DOWN indication for the link associated with the 
     router the check has been initiated for, the check can be 



   
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     immediately aborted as the result of NUD can be anticipated by the 
     information that the link is lost. 
      
      
  6.2 Previously defined optimizations to movement detection 
      
     A couple of Mobile IPv6 movement detection optimisations schemes 
     have been suggested within the IETF: [FastRA] and [LinkID] seek to 
     reduce the time taken to perform Router Discovery but from a layer 3 
     perspective. As for [FRD], it makes use of Layer 2 information to 
     accelerate the process of Router Discovery but requires 
     modifications to L2 technologies and especially Access Points. 
      
      
  7. Example of 802.11 / GPRS handover 
      
  7.1 GPRS and 802.11 coexistence 
      
     The increasing popularity of IEEE 802.11-based WLANs, which are 
     deployed in such areas as Hot Spots, combined to the recent advent 
     of 2.5G wide-area wireless networks such as GPRS, has created the 
     need to judiciously make use of these two wireless IP access 
     technologies by taking advantage of their complementarity for moving 
     users. 
     While it is indicated to let the l2 handle the horizontal handover 
     where there is no need of configuration change at IP layer as it is 
     the case in most 802.11b and GPRS deployment scenarios, such 
     vertical handoffs as GPRS to WLAN or vice-versa would quite often 
     require a change of subnet. And from most views, Mobile IP looks an 
     appropriate candidate to help perform this specific inter-technology 
     handoff. 
     Based on the link triggers and hints we've specified in the 
     precedent section for each of the aforementioned technologies, we 
     hereafter apply the optimized Mobile IPv6 movement detection process 
     presented in section 3 to the GPRS/WLAN handoff case. 
      
      
      
      
      
      
      
      
      


   
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         ------- 
        /        \  
       | Internet +-------------------------------------+ 
        \        /                                      | 
         ---+--- \                                      | 
            |     \                                     | 
            |      +------------+                       | 
            |                   |                       | 
         +--+--+            +---+--+                 +--+--+ 
         | AR1 |            | GGSN |                 | AR2 | 
         +--+--+            +---+--+                 +--+--+ 
            |                   |                       | 
            |                    \   GPRS               | 
            |                     \                     | 
            |                      \                    | 
          +-+--+       +----+     +-+--+             +--+-+ 
          | AP |.......| AP |     |SGSN|             | AP | 
          +----+       +----+ *   +----+           * +----+ 
            .             .    *      .           *     . 
             .           .      *      .         *       . 
              .         .       *       .        *        .  
            +----+              *      +----+    *      +----+ 
            | MN |============> * ===> | MN | ====>     | MN | 
            +----+   movement   *      +----+    *      +----+ 
                               *                  * 
           802.11 coverage    *                     * 802.11 coverage 
                            *                         * 
           * * * * * * * * *                           * * * * * * 
      
     Fig. Movement scenario of a MN between GPRS and 802.11 coverage 
      
      
  7.2 GPRS and 802.11 link triggers/hints 
      
     We identify the link triggers/hints to be used for each technology. 
      
      
  7.2.1 GPRS 
      
     LINK-UP indication 
      
     A MN that wants to establish IP level connections through its GPRS 
     interface should first request the GPRS network to settle the 
     necessary soft state mechanism (GPRS tunneling Protocol) between the 


   
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     GPRS AP (SGSN) it is attached to and the AR (GGSN) corresponding to 
     the type of network it is requesting connection for (Intranet, 
     Internet). This routing mechanism between the SGSN and the GGSN 
     enable the forwarding of IP packets between the MN and external data 
     networks as the Internet or an Intranet (via the GGSN). The process 
     by which this is made possible is designated as a PDP Context 
     activation. It corresponds to the IP configuration process. 
      
     A PDP Context is considered activated on the MT side as soon as an 
     "Activate PDP Context Accept" message has been received from the 
     SGSN. As such, the reception of this message can be considered as a 
     LINK-UP indication for the MN GPRS/UMTS interface. 
      
      
     LINK-DOWN indication 
      
     The GPRS network can initiate a PDP context deactivation at any time. 
     A "Deactivate PDP Context Request" message is then sent by the SGSN 
     (GPRS AP). The reception of this message is an indication that the 
     IP configuration of the MN's GPRS interface is about to be deleted 
     by the network. 
     As such, the reception of the message can be considered as a LINK-
     DOWN trigger for the GPRS/UMTS interface 
      
      
  7.2.2 802.11 
      
     LINK-UP indication 
      
     In order to have an IP level connection through an IEEE 802.11 
     network, a MN must be associated with an Access Point. The last 
     messages exchanged between the MN and a target Access Point to 
     establish a connection is a (Re)Association Response sent from the 
     Access Point to the MN. This message indicates to the MN the status 
     of the association (accepted or rejected). If the association is 
     accepted, then the MN can usually start to send and receive IP 
     packets through the Access Point. 
      
     But, if the MN is connecting to an Access Point which uses enhanced 
     security mechanisms as defined in [IEEE 802.11i] (MN enters a Robust 
     Security Network), the reception of the (Re)Association Response is 
     not the relevant trigger that informs that IP packets can be 
     exchanged. In a Robust Security Network, an IEEE 802.1x port is used 
     on each station (Access Point and MN) to filter packets: while a 


   
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     mutual authentication of both the Access Point and the MN is not 
     done, all data packets are discarded. Instead, EAP packets are used 
     to transport authentication. Upon the reception of an "EAP-accept" 
     message with a successful status, the data packets are authorized to 
     use the association between the access point and the MN. 
      
     To summarize this section, in a non-secure 802.11 network, a 
     successful (re)association response can be taken as a Link-Up 
     trigger while in 802.1x, it is the EAP-accept message which is taken 
     as a Link-Up trigger. 
      
      
     LINK-DOWN indication  
      
     To allow IP packets exchange with a MN using an IEEE 802.11 
     interface, the MN has to be authenticated and associated with an AP. 
     As soon as the MN is no more authenticated or associated to an AP, 
     IP connectivity is broken. Upon the reception of "Disassociation" 
     message, the MN is considered disconnected and then has no more IP 
     connectivity through the AP. Therefore, the "Disassociation" message 
     is to be considered as a Link-Down trigger. 
      
     It has to be noted that a Disassociation message is not required to 
     be sent each time a MN disassociates from an AP. In IEEE 802.11, if 
     a MN measures a poor signal with its current AP, it can 
     disassociates by itself and no messages are sent. 
      
      
  7.2.3 LINK-TYPE indication 
      
     The LINK-TYPE indication would generally not be directly provided by 
     the L2. Each implementation of the L2 messages extraction will have 
     to figure out how it is able to fetch the information. 
      
      
  7.3 Mobile IPv6 node recommended behavior from 802.11 to GPRS 
      
     Here the Mobile Node steps outside of the 802.11b Access Point radio 
     range it is attached to. It is assumed that no other in-range 
     802.11b AP is present to offer connectivity. 
     At some time in the movement, a "disassociation" beacon will be 
     received by the host, triggering the MN to immediately invalidate 
     the care-of-address associated with the 802.11b interface, and 
     select the care-of-address associated to GPRS as its primary then 


   
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     register it to its Home Agent. This assumes that the GPRS interface 
     was still up. 
     Note that power consumption considerations on Mobile Terminals as 
     laptops and PDAs can dictate the need for deactivation of all 
     interfaces but the one associated to the primary care-of-address. In 
     such a case, smooth handoff operation require exploiting any hint 
     from 802.11b layer that the MN will soon be de-associated. Reception 
     of such a hint then anticipates the build-up of the PDP context that 
     will be necessary to establish the GPRS care-of-address (A "Activate 
     PDP context Request" message is sent to the SGSN): once the 
     "Activate PDP context Accept" message is received from the network, 
     the MN sends a RS to the IPv6 GGSN to receive router prefix 
     information and form new care-of-address. DAD can be avoided here as 
     the shared link concept utilized in such networks as 802.11b is not 
     valid in 3GPP networks where every MN holds a "private" link-layer 
     connectivity with the AP (i.e unknown to other MNs that are GPRS-
     connected to the same AP). The GPRS IPv6 address is then selected as 
     primary and registered to the HA. It may happen that the 802.11b 
     link get down before all the previous process is performed. Still, 
     it is better to anticipate the loss of 802.11 link connection as 
     this results in reduced packets loss. 
      
      
  7.4 Mobile IPv6 node recommended behavior from GPRS to 802.11 
      
     This step represents the Mobile Node arriving inside a 802.11 
     network. Start of this step is indicated on the Mobile Node by the 
     reception of an "association" or "EAP-accept" message, coming from 
     the nearest in-range Access Point. This triggers the sending by the 
     MN of a Router Solicitation message to check router presence on the 
     newly discovered 802.11 link and receive prefix information in order 
     to build care-of-address after performing Duplicate Address 
     Detection. Next, the registration process with the Home Agent is 
     completed. 
      
     For smooth handoff operation, [MIPv6] does not preclude the use of a 
     still valid previous primary care-of-address for the reception of 
     packets after registering a new primary care-of-address to the HA. 
     Therefore, the Mobile Node can keep its GPRS interface and 
     associated care-of-address active for an additional period of time 
     that will have to be tuned according to such criteria as the GPRS 
     link latency. Effectively, the latency encountered on such links can 
     cause the packets sent before the new care-of-address was registered 
     to arrive with delay. 


   
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  8. Security Considerations 
      
     Implementations of the L2 triggers extraction should guarantee that 
     the information received at the IP layer is originated from the MN 
     L2 stack rather than sent by a malicious node.  
      
      
  9. References 
      
  9.1 Normative References 
      
     [RFC2119]   S. Bradner, "Key words for use in RFCs to Indicate 
                 Requirement Levels", BCP 14, RFC 2119, March 1997 
      
     [MIPv6]     D. Johnson, C. Perkins, J. Arkko.  Mobility Support in 
                 IPv6. Internet Draft (work in progress), July 2003. 
      
     [WLAN]      "Wireless LAN Medium Access Control (MAC) and Physical 
                 Layer (PHY) Specifications", ANSI/IEEE Std 802.11, 1999 
                 Edition. 
      
     [GPRS]      3GPP TS 03.60 (release 1998) "Digital cellular 
                 telecommunications system (Phase 2+); General Packet 
                 Radio Service (GPRS) Service description; Stage 2", 
                 version 7.9.0 
     [REQ]       M. Wasserman, Ed. "Recommendations for IPv6 in Third 
                 Generation Partnership Project (3GPP) Standards", RFC 
                 3314, September 2002 
      
     [802.11i]   IEEE Sd 802.11i/D7.0, Medium Access Control (MAC) 
                 Security Enhancements, October 2003. 
      
     [802.11fh]  Peter J. McCann, Mobile IPv6 Fast Handover for 802.11 
                 networks, draft-mccan-mobile-802.11fh-01.txt, expired in 
                 May 2003. 
      
      
  9.2 Informative References 
      
     [MoveDetect]G. Delay, J. Choi, "Movement Detection Optimization in 
                 Mobile IPv6", Internet Draft, May 2003. 
      


   
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     [FASTRA]    M. Khalil, J. Kempf, B. Pentland. "IPv6 Fast Router  
                 Advertisement (FastRA) ", Internet Draft (work in 
                 progress), October 2002. 
      
     [LINKID]    B. Pentland, G Daley, J Choi. "Router Advertisement Link 
                 Identification for Mobile IPv6 Movement Detection", 
                 Internet Draft (work in progress), May 2003 
      
     [FRD]       J. Choi, D. Shin. "Fast Router Discovery with RA         
                 Caching in AP", Internet Draft (work in progress), Feb 
                 2003. 
      
     [manyfolks] A. Yegin, D. Funato, K. El Malki, Y. Gwon, J. Kempf, 
                 M. Pettersson, P.Roberts, H. Soliman, A. Takeshita, 
                 "Supporting Optimized Handover for IP Mobility - 
                 Requirements for Underlying Systems", draft-manyfolks-
                 l2-mobilereq-02.txt, expired December 2002. 
      
     [fmipv6]    R. Koodli et al, "Fast Handovers for Mobile IPv6", 
                 draft-ietf-mipshop-fast-mipv6-00.txt, October 2003. 
      
     [Link Hints]Alper Yegin, E. Njedjou, S. Veerepalli, N. Montavont, 
                 T. Noel, "Link-layer Hints for Detecting Network 
                 Attachments", draft-yegin-dna-l2-hints-00.txt, November 
                 2003. 
      
     [Parameter] P. Bertin, T. Noel, N. Montavont, "Parameters for Link 
                 Hints", draft-bertin-hints-params-00.txt, September 2003. 
      
      
  Acknowledgements 
      
     Leave your name 
      
      
      
      
      
      
      
      
      
      
   


   
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  Authors' Addresses 
      
     Soohong Daniel Park 
     Samsung Electronics 
     416, Maetan-3dong, Youngtong-gu, Suwon 
     Korea 
     Phone: +82 31 200 4508 
     Email: soohong.park@samsung.com 
      
     Eric Njedjou 
     France Telecom R&D 
     4, Rue du Clos Courtel BP 91226 
     35512 Cesson-S‰vign‰ 
     Fr&nce 
     Phone: +33 299124202 
     Email: eric.njedjou@francetelecom.com 
     URL: http://perso.rd.francetelecom.fr 
      
     Nicolas Montavont 
     LSIIT Universit‰ Louis Pasteur 
     Pole API, bureau C430 
     Boulevard Sebastien Brant 
     Illkirch 67400 
     FranceT 
     Phone: (33) 390244587 
     Email:montavont@dpt-info.u-strasbg.fr 
     URL: www-r2.u-strasbg.fr/~montavont 
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      


   
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