GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5271

Network Working Group H. Yokota Request for Comments: 5271 KDDI Lab Category: Informational G. Dommety

                                                   Cisco Systems, Inc.
                                                             June 2008
          Mobile IPv6 Fast Handovers for 3G CDMA Networks

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Abstract

 Mobile IPv6 is designed to maintain its connectivity while moving
 from one network to another.  It is adopted in 3G CDMA networks as a
 way to maintain connectivity when the mobile node (MN) moves between
 access routers.  However, this handover procedure requires not only
 movement detection by the MN, but also the acquisition of a new
 Care-of Address and Mobile IPv6 registration with the new care-of
 address before the traffic can be sent or received in the target
 network.  During this period, packets destined for the mobile node
 may be lost, which may not be acceptable for a real-time application
 such as Voice over IP (VoIP) or video telephony.  This document
 specifies fast handover methods in the 3G CDMA networks in order to
 reduce latency and packet loss during handover.

Yokota & Dommety Informational [Page 1] RFC 5271 3G CDMA Fast Handover June 2008

Table of Contents

 1. Introduction ....................................................2
 2. Requirements Notation ...........................................3
 3. Terminology .....................................................3
 4. Network Reference Model for Mobile IPv6 over 3G CDMA Networks ...4
 5. Fast Handover Procedures ........................................6
    5.1. Predictive Fast Handover ...................................7
    5.2. Reactive Fast Handover ....................................12
    5.3. Considerations on the Link Indications ....................15
 6. Message Format .................................................15
    6.1. Handover Assist Information Option ........................15
    6.2. Mobile Node Identifier Option .............................16
    6.3. New Flag Extension to FBU Message .........................17
    6.4. New Flag Extension to PrRtAdv Message .....................17
 7. Security Considerations ........................................18
 8. IANA Considerations ............................................18
 9. Acknowledgements ...............................................19
 10. References ....................................................19
    10.1. Normative References .....................................19
    10.2. Informative References ...................................19

1. Introduction

 Mobile IPv6 [2] allows mobile nodes (MNs) to maintain persistent IP
 connectivity while the MN moves around in the IPv6 network.  It is
 adopted in 3G CDMA networks for handling host-based mobility
 management [12].  During handover, however, the mobile node (MN)
 needs to switch the radio link to obtain a new Care-of Address (CoA)
 and to re-register with the home agent (HA), which may cause a
 communication disruption.  This is not desirable for real-time
 applications such as VoIP and video telephony.  To reduce this
 disruption time or latency, a fast handover protocol for Mobile IPv6
 [3] is proposed.  RFC 4260 [7] further describes how this Mobile IPv6
 Fast Handover could be implemented on link layers conforming to the
 IEEE 802.11 suite of specifications.  However, 3G CDMA and IEEE
 802.11 networks are substantially different in the radio access, the
 representations of the network nodes or parameters, and the network
 attachment procedures; for example, the beacon scanning or New Access
 Router (NAR) discovery based on [Access Point Identifier, Access
 Router-info (AP-ID, AR-info)] tuples specified in RFC 4260 can not be
 directly applied to 3G CDMA networks.  This document therefore
 specifies how Mobile IPv6 fast handovers can be applied in the 3G
 CDMA networks.

Yokota & Dommety Informational [Page 2] RFC 5271 3G CDMA Fast Handover June 2008

2. Requirements Notation

 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 [1].

3. Terminology

 This document refers to [3] for Mobile IPv6 fast handover
 terminology.  Terms that first appear in this document are defined
 below:
 Access Network Identifier (ANID): An identifier that is used by the
    Packet Data Serving Node (PDSN) to determine whether the MN is
    being handed off from the access network that was not previously
    using this PDSN.  Anytime the MN crosses into a new region, which
    is defined by the ANID, it must re-register with that access
    network.  The ANID is further composed of the System ID (SID),
    Network ID (NID), and Packet Zone ID (PZID) and these values are
    administered by the operator.  The lengths of the SID, NID, and
    PZID are 2 octets, 2 octets, and 1 octet, respectively.  Thus,
    that of the ANID occupies 5 octets [11].
 Forward Pilot Channel:  A portion of the Forward Channel that carries
    the pilot.  The Forward Channel is a portion of the physical layer
    channels transmitted from the 3G CDMA access network to the MN.
    Further, several sets of pilots (e.g., the active set or neighbor
    set) are defined to determine when and where to handover.
 Home Link Prefix (HLP):  The prefix address assigned to the home link
    where the MN should send the binding update message.  This is also
    called Home Network Prefix (HNP) and one of the bootstrap
    parameters for the MN.
 International Mobile Subscriber Identity (IMSI):  The IMSI is a
    string of decimal digits, up to a maximum of 15 digits, that
    identifies a unique mobile terminal or mobile subscriber
    internationally.  The IMSI consists of three fields:  the Mobile
    Country Code (MCC), the Mobile Network Code (MNC), and the Mobile
    Subscriber Identification Number (MSIN).  An example of the IMSI
    is "440701234567890", where "440" is the MCC, "70" is the MNC, and
    "1234567890" is the MSIN.  The IMSI conforms to the ITU-T E.212
    numbering standard [6].  In this specification, IMSI is an ASCII
    string that consists of not more than 15 decimal digits (ASCII
    values between 30 and 39 hexadecimal), one character per IMSI
    digit.  The above example would therefore be encoded as "34 34 30
    37 30 31 32 33 34 35 36 37 38 39 30" in hexadecimal notation.

Yokota & Dommety Informational [Page 3] RFC 5271 3G CDMA Fast Handover June 2008

 Mobile Identity (MN ID):  An identifier of the Mobile Node that is
    used by the access network.  The value (e.g., IMSI) is unique
    within the operator's network.
 Packet Data Serving Node (PDSN):  An entity that routes MN originated
    or MN terminated packet data traffic.  A PDSN establishes,
    maintains, and terminates link-layer sessions to MNs.  A PDSN is
    the access router in the visited access provider network.
 Sector Address Identifier (SectorID):  A typical cell divides its
    coverage area into several sectors.  In 3G CDMA systems, each
    sector uses a different PN (Pseudo Noise) code offset and is
    associated with SectorID.  The SectorID is 128 bits long and can
    be represented in the IPv6 address format [8].

4. Network Reference Model for Mobile IPv6 over 3G CDMA Networks

 Figure 1 shows a simplified reference model of the Mobile IP enabled
 3G CDMA networks.  The home agent (HA) and Authentication,
 Authorization, and Accounting (AAA) server of the mobile node (MN)
 reside in the home IP network, and the MN roams within or between the
 access provider network(s).  Usually, the home IP network is not
 populated by the MNs, which are instead connected only to the access
 provider networks.  Prior to the Mobile IPv6 registration, the MN
 establishes a 3G CDMA access technology specific link-layer
 connection with the access router (AR).  When the MN moves from one
 AR to another, the link-layer connection is re-established, and a
 Mobile IPv6 handover is performed.  Those ARs reside in either the
 same or different access provider network(s).  The figure shows the
 situation, where the MN moves from the Previous Access Router (PAR)
 to the New Access Router (NAR) via the radio access network (RAN).

Yokota & Dommety Informational [Page 4] RFC 5271 3G CDMA Fast Handover June 2008

                        Home IP Network
                   +........................+
                   . +--------+  +--------+ .
                   . |   HA   |--|  AAA   | .
                   . +--------+  +--------+ .
                   +../......\..............+
                     /        \
               Access Provider Network(s)
        +.............+      +.............+
        . +---------+ .      . +---------+ .
        . |   PAR   | .      . |   NAR   | .
        . +---------+ .      . +---------+ .
        .      |:     .      .     :|      .
        .      |:L2link      L2link:|      .
        .      |:     .      .     :|      .
        . +----+:---+ .      . +---:+----+ .
        . |   RAN   | .      . |   RAN   | .
        . +----+:---+ .      . +---:+----+ .
        .      |:     .      .     :|      .
        .    +----+   .      .   +----+    .
        .    | MN |  --------->  | MN |    .
        .    +----+   .      .   +----+    .
        +.............+      +.............+
      Figure 1: Reference Model for Mobile IP
 In 3G CDMA networks, pilot channels transmitted by base stations
 allow the MN to obtain a rapid and accurate C/I (carrier to
 interference) estimate.  This estimate is based on measuring the
 strength of the Forward Pilot Channel or the pilot, which is
 associated with a sector of a base station (BS).  The MN searches for
 the pilots and maintains those with sufficient signal strength in the
 pilot sets.  The MN sends measurement results, which include the
 offsets of the PN code in use and the C/Is in the pilot sets, to
 provide the radio access network (RAN) with the estimate of sectors
 in its neighborhood.  There are several triggers for the MN to send
 those estimates, e.g., when the strength of a pilot in the pilot sets
 exceeds that of the current pilot, the MN sends the estimates to the
 access network.  As long as the sector to which the MN is going to
 move belongs to the same access network, the mobility within that
 access network is handled by the access-specific interfaces [10] and
 the link-layer connection between the MN and AR can be maintained
 without a re-establishment.  The MN can continually search for pilots
 without disrupting the data communication and a timely handover is
 assisted by the network.  If, however, the serving access network
 finds that the sector associated with the highest pilot strength
 belongs to a different AR, it attempts to close the connection with
 the MN.  The MN then attempts to get a new traffic channel assigned

Yokota & Dommety Informational [Page 5] RFC 5271 3G CDMA Fast Handover June 2008

 in the new access network, which is followed by establishing a new
 connection with the new AR.  This could cause a noticeable
 communication disruption and lead to a serious degradation of the
 user experience.  In order to minimize the service degradation,
 during the handover between ARs, an IP-level fast handover approach
 as defined in RFC 5268 needs to be involved.  If the air interface
 information can be used as a trigger for the handover between access
 routers, fast and smooth handover of Mobile IPv6 can be realized in
 3G CDMA networks.  The MN can continually search for pilots without
 disrupting the data communication and a timely handover is assisted
 by the network.
 To assist the handover of the MN to the new AR, various types of
 information can be considered: the pilot sets, which include the
 candidates of the target sectors or BSs, the cell information where
 the MN resides, the serving nodes in the radio access network, and
 the location of the MN, if available.  To identify the access network
 that the MN moves to or from, the Access Network Identifiers (ANID)
 or the subnet information can be used [9][10].  In this document, a
 collection of such information is called "handover assist
 information".  In 3G CDMA networks, the Link-Layer Address of the New
 Access Point (AP) defined in [3] may not be available.  If this is
 the case, the Handover Assist Information option defined in this
 document SHOULD be used instead.

5. Fast Handover Procedures

 There are two modes defined in [3] according to the time of sending
 the FBU (Fast Binding Update); one is called "predictive mode", where
 the MN sends the FBU and receives the FBAck (Fast Binding
 Acknowledgment) on the PAR's (Previous Access Router's) link and the
 other is called "reactive mode", where the MN sends the FBU from the
 NAR's (New Access Router's) link.  In the predictive mode, the time
 and place the MN hands off must be indicated sufficiently before the
 time it actually happens.  In cellular systems, since handovers are
 controlled by the network, the predictive mode is well applied.
 However, if the network is not configured to be able to identify the
 new AR, to which the MN is moving next, in a timely manner, the
 reactive mode is better applied.
 Section 2 of RFC 4907 [20] suggests architectural principles on the
 link indication and the effectiveness of the optimization.  The link
 indication of this document relies on 3G CDMA networks and the
 effectiveness of the optimization is attributed to RFC 5268.  The
 above principles are thus considered by the related specifications
 referenced in this document.

Yokota & Dommety Informational [Page 6] RFC 5271 3G CDMA Fast Handover June 2008

5.1. Predictive Fast Handover

 Figure 2 shows the predictive mode of MIPv6 fast handover operation.
 When the MN finds a sector or a BS whose pilot signal is sufficiently
 strong, it initiates handover according to the following sequence:
 (a)  A router solicitation for proxy router advertisement is sent to
      the PAR.  Handover assist information for the target 3G CDMA
      network is attached to this message.
 (b)  Based on the received handover assist information, the NAR is
      determined and a proxy router advertisement (PrRtAdv) containing
      the prefix of the NAR is sent back to the MN.  The MN also
      checks that the R flag is not set in the PrRtAdv message, which
      indicates the network supports the predictive fast handover mode
      (defined later).
 (c)  The MN creates an NCoA (new CoA) and sends the Fast Binding
      Update (FBU) with the NCoA to the PAR, which in turn sends the
      Handover Initiate (HI) to the NAR.
 (d)  The NAR sends the Handover Acknowledge (HAck) back to the PAR,
      which in turn sends the FBU acknowledgment (FBAck) to the MN.
 (e)  The PAR starts forwarding packets toward the NCoA and the NAR
      captures and buffers them.
 (f)  The link-layer connection associated with the PAR is closed and
      a new traffic channel is assigned in the new access network.
 (g)  The MN attaches to the new access network.  The attachment
      procedure is access technology specific and that for 3G CDMA
      network including the PPP transactions is described later.
 (h)  The MN sends the Unsolicited Neighbor Advertisement (UNA).
 (i)  The NAR starts delivering packets to the MN.
 (j)  The MN sends the Binding Update (BU) to the HA to update the
      Binding Cache Entry (BCE) with the NCoA, and the HA sends back
      the Binding Acknowledgment (BA) to the MN.

Yokota & Dommety Informational [Page 7] RFC 5271 3G CDMA Fast Handover June 2008

      MN            PAR             NAR            HA             AAA
      |    RtSolPr   |               |              |              |
 (a)  |------------->|               |              |              |
      |    PrRtAdv   |               |              |              |
 (b)  |<-------------|               |              |              |
      |      FBU     |      Hl       |              |              |
 (c)  |------------->|-------------->|              |              |
      |     FBack    |     HAck      |              |              |
 (d)  |<-------------|<--------------|              |              |
      |              |forward packets|              |              |
 (e)  |              |==============>|(buffering)   |              |
      |              |               |              |              |
 (f) handover        |               |              |              |
      |              |               |              |              |
     +--------------------------------------------------------------+
 (g) |                     Attachment procedure                     |
     +--------------------------------------------------------------+
      |             UNA              |              |              |
 (h)  |----------------------------->|              |              |
      |       deliver packets        |              |              |
 (i)  |<=============================|              |              |
      |              |        BU/BA  |              |              |
 (j)  |<------------------------------------------->|              |
      |              |               |              |              |
      Figure 2: MIPv6 Fast Handover Operation (Predictive Mode)
 It is assumed that the NAR can be identified by the PAR leveraging
 the handover assist information from the MN.  To perform the
 predictive mode, the MN MUST send the FBU before the connection with
 the current access network is closed.  If the MN fails to send the
 FBU before handover, it SHOULD fall back to the reactive mode.  Even
 if the MN successfully sends the FBU, its reception by the PAR may be
 delayed for various reasons such as congestion.  If the NAR receives
 the HI triggered by the delayed FBU after the reception of the UNA
 ((c) comes after (h)), then the NAR SHOULD send the HAck with
 handover not accepted and behave as the reactive mode.
 In (a), Router Solicitation for Proxy Advertisement (RtSolPr) is
 supposed to include the New Access Point and the MN Link-Layer
 Address (LLA) options (Option Code=1 and 2, respectively) according
 to [3].  The New AP-LLA option MAY be replaced by the handover assist
 information option in 3G CDMA networks.  As for the MN-LLA option, if
 the LLA for the MN is not available, 3G specific IDs such as IMSI[11]
 MAY be used.  If this is the case, the MN ID option defined in
 Section 6.2, which can support other types of IDs and a length that
 is not necessarily multiples of 8 octets, SHOULD be used instead of
 the MN-LLA option.

Yokota & Dommety Informational [Page 8] RFC 5271 3G CDMA Fast Handover June 2008

 In (b), PrRtAdv MUST include options for the IP address of the NAR,
 which may be the link-local address, and the prefix for the MN.  The
 PAR SHOULD be able to identify the NAR from the handover assist
 information provided by the MN.
 Figure 3 shows the call flow for the initial attachment in the 3G
 CDMA network [12].  After the traffic channel is assigned, the MN
 first establishes a link-layer connection between itself and the
 access router.  As a link-layer protocol, PPP is considered in this
 figure, and a PPP handshake is depicted as an example.  After a
 link-layer connection is established, the MN registers with the HA by
 sending a Binding Update message.  There are several parameters for
 using Mobile IPv6 such as the home address (HoA), the Care-of Address
 (CoA), the home agent address (HA), and the home link prefix (HLP).
 In [12], obtaining these values is called bootstrapping, and the
 bootstrapping information can be obtained during the link-layer
 establishment phase and/or the mobility binding phase [13].

Yokota & Dommety Informational [Page 9] RFC 5271 3G CDMA Fast Handover June 2008

            MN            PAR         NAR         HA          AAA
     /       |     (serving PDSN) (target PDSN)    |           |
     |       |        LCP  |           |           |           |
     | (1)   |<----------------------->|           |           |
     |       |        CHAP/PAP         | Access-Request/Accept |
     | (2)   |<----------------------->|<-------------|------->|
     |       |             |        +------+       |  |        |
     | (3)   |             |        |  HA  |<---------+        |
     |       |             |        +------+       |           |
     |+........................................+   |           |
     |.      |                         |       .   |           |
     |.      |    IPv6CP(IF-ID)        |       .   |           |
     |.(4)*  |<---------|------------->|       .   |           |
 (g)< .    +---------+  |  |           |       .   |           |
     |.(5)*| LL-addr |<-+  |           |       .   |           |
     |.    +---------+     |           |       .   |           |
     |.      |                         |       .   |           |
     |.      |       RA(prefix)        |       .   |           |
     |.(6)*  |<---------|--------------|       .   |           |
     |.    +-----+      |  |           |       .   |           |
     |.(7)*| CoA |<-----+  |           |       .   |           |
     |.    +-----+         |           |       .   |           |
     |+........................................+   |           |
     |       |      DHCPv6(HA)         |           |           |
     | (8)   |<---------------+------->|           |           |
     |     +-----+         |  |        |           |           |
     | (9) | HA  |<-----------+        |           |           |
     |     +-----+         |           |           |           |
     |       |             |           |           |           |
     \       |             |           |           |           |
        Figure 3: Attachment Procedure in 3G CDMA Network
 The procedure for the initial attachment is as follows:
 (g)    The link-layer connection establishment and the bootstrapping
        phase.
 (g-1)  The LCP (Link Control Protocol) configure-request/response
        messages are exchanged.
 (g-2)  User authentication (e.g., Challenge Handshake Authentication
        Protocol (CHAP) or Password Authentication Protocol (PAP)) is
        conducted.

Yokota & Dommety Informational [Page 10] RFC 5271 3G CDMA Fast Handover June 2008

 (g-3)  The static bootstrapping information is conveyed from the AAA
        and stored in the NAR (target PDSN).  The HoA and HLP can be
        dynamically assigned by the HA in the mobility binding phase.
        This step can be skipped in the handover case.
 (g-4)  Unique interface IDs are negotiated in IPv6 Control Protocol
        (IPv6CP).
 (g-5)  The MN configures its link-local address based on the obtained
        interface ID.
 (g-6)  A router advertisement containing the prefix is received by
        the MN.
 (g-7)  The MN configures its CoA based on the obtained prefix.
 (g-8)  DHCPv6 is used to obtain the static bootstrap information
        (e.g., the HA address).  This step is performed in the initial
        attachment and can be skipped once the MN obtains those
        parameters.
 (g-9)  The MN installs the bootstrap information for further
        procedures (e.g., the mobility binding).
 As is shown in Figure 3, it takes a considerable amount of time to
 establish a link-layer connection and almost all of the above
 sequences run every time the MN attaches to a new access network.  It
 is therefore beneficial if packets in transit to the MN are saved not
 only during the time period when the MN switches to the new radio
 channel but also during the time period when the MN establishes the
 link-layer connection.
 There are several ways to configure a unique IP address for the MN.
 If a globally unique prefix is assigned per link as introduced in
 [12], the MN can use any interface ID except that of the other peer
 (the AR to which the MN is attached) to create a unique IP address.
 If this is the case, however, the PAR cannot provide the MN with a
 correct prefix for the new network in the PrRtAdv since such a prefix
 is selected by the NAR and provided in the router advertisement.  The
 MN therefore configures a temporary NCoA with the prefix provided by
 the PAR and the correct NCoA MUST be assigned by the NAR.  Therefore,
 in 3G CDMA network, the PAR MUST send the HI with the S flag set when
 it receives the FBU from the MN at step (c) in Figure 2.

Yokota & Dommety Informational [Page 11] RFC 5271 3G CDMA Fast Handover June 2008

 The UNA is supposed to include the MN-LLA [3], but the point-to-point
 link-layer connection may be able to uniquely identify the MN.  The
 most required information by the UNA is the NCoA to check if there is
 a corresponding buffer.  Therefore, in (h), the function of the UNA
 can be realized in several ways:
 o  Since the establishment of the link-layer connection in (g)
    indicates readiness of data communication on the MN side, the NAR
    immediately checks if there is a buffer that has packets destined
    for the NCoA, which was configured at steps (c) - (d), and starts
    delivering, if any (substitution of UNA).
 o  The MN sends the UNA as defined in [3].  Instead of the MN-LLA in
    the LLA option, the MN ID MAY be included in the MN ID option
    (standard implementation of UNA).
 The primary benefit of the predictive fast handover mode is that the
 packets destined for the MN can be buffered at the NAR, and packet
 loss due to handover will be much lower than that of the normal MIPv6
 operation.  Regarding the bootstrapping, the following benefit can be
 obtained, too:
 o  Since the NCoA can be configured via the fast handover procedures,
    a router advertisement is not required.
 Therefore, the procedures (g-4) to (g-7) can be skipped from the
 standard MIPv6 operation in Figure 3.

5.2. Reactive Fast Handover

 When the network does not support the predictive fast handover mode,
 the reactive fast handover is applied.  In this document, a new flag
 is defined in PrRtAdv to inform the MN about the capability of the
 network (see Section 6.4).  To minimize packet loss in this
 situation, the PAR instead of the NAR can buffer packets for the MN
 until the MN regains connectivity with the NAR.  The NAR obtains the
 information of the PAR from the MN on the NAR's link and receives
 packets buffered at the PAR.  In this case, the PAR does not need to
 know the IP address of the NAR or the NCoA and just waits for the NAR
 to contact the PAR.  However, since the PAR needs to know when to
 buffer packets for the MN, the PAR obtains the timing of buffering
 from the MN via the FBU or the lower-layer signaling, e.g., an
 indication of the release of the connection with the MN.  Details of
 the procedure are as follows:
 (a)  A router solicitation for proxy router advertisement MAY be sent
      to the PAR.

Yokota & Dommety Informational [Page 12] RFC 5271 3G CDMA Fast Handover June 2008

 (b)  The proxy router advertisement MAY be sent to the MN.  If the
      information on the NAR is not available by the PAR, "0::0" MUST
      be used for the options related to the NAR (e.g., IP address of
      the NAR).
 (c)  The MN sends the FBU or the access network indicates the close
      of the connection with the MN by the lower-layer signaling.  If
      the MN cannot formulate the NCoA, "0::0", MUST be used for the
      NCoA in the FBU.  If the B flag is set in the FBU, the PAR
      SHOULD start buffering packets destined for the PCoA.
 (d)  The link-layer connection associated with the PAR is closed and
      a new traffic channel is assigned in the new access network.
 (e)  The MN attaches to the new access network.  This part is the
      same as described in Section 5.1 and illustrated in Figure 3.
 (f)  The MN sends the UNA to the NAR.
 (g)  The MN sends the Fast Binding Update (FBU) to the PAR via the
      NAR.
 (h)  The NAR forwards the FBU from the MN to the PAR.
 (i)  The PAR sends the Handover Initiate (HI) to the NAR with the
      Code set to 1.
 (j)  The NAR sends the Handover Acknowledge (HAck) back to the PAR.
 (k)  The PAR sends the FBAck to the NAR.
 (l)  If the PAR is buffering packets destined for the PCoA, it starts
      forwarding them as well as newly arriving ones to the NAR.
 (m)  The NAR delivers the packets to the MN.
 (n)  The MN sends the BU to the HA to update the BCE with the NCoA
      and the HA sends back the BA to the MN.

Yokota & Dommety Informational [Page 13] RFC 5271 3G CDMA Fast Handover June 2008

      MN            PAR             NAR             HA            AAA
      |   RtSolPr    |               |              |              |
 (a)  |------------->|               |              |              |
      |   PrRtAdv    |               |              |              |
 (b)  |<-------------|               |              |              |
      |     FBU      |               |              |              |
 (c)  |- - - - - - ->|(buffering)    |              |              |
      |              |               |              |              |
 (d) handover        |               |              |              |
      |              |               |              |              |
     +--------------------------------------------------------------+
 (e) |                    Attachment procedure                      |
     +--------------------------------------------------------------+
      |             UNA              |              |              |
 (f)  |----------------------------->|              |              |
      |             FBU              |              |              |
 (g)  |----------------------------->|              |              |
      |              |     FBU       |              |              |
 (h)  |              |<--------------|              |              |
      |              |      HI       |              |              |
 (i)  |              |-------------->|              |              |
      |              |     HAck      |              |              |
 (j)  |              |<--------------|              |              |
      |              |     FBack     |              |              |
 (k)  |              |-------------->|              |              |
      |              |forward packets|              |              |
 (l)  |              |==============>|              |              |
      |        deliver packets       |              |              |
 (m)  |<=============================|              |              |
      |              |        BU/BA  |              |              |
 (n)  |<------------------------------------------->|              |
      |              |               |              |              |
      Figure 4: MIPv6 Fast Handover Operation (Reactive Mode)
 To indicate the PAR to buffer packets destined for the PCoA, in step
 (c), a new flag 'B' is defined in the FBU.  When the PAR receives the
 FBU with this flag set, it SHOULD buffer packets for the MN.  The PAR
 MAY also start buffering packets for the MN based on lower layer
 signal during handover.  Since the packets are buffered at the PAR in
 this scenario, the UNA, which is received and processed by the NAR,
 can not be used to trigger to forward the buffered packets at the
 PAR.  In Figure 4, the HAck from the NAR is used as the trigger for
 the forwarding of any buffered packets.
 The handover indication from the lower layer of 3G CDMA system is
 reasonably reliable by the periodical reports from the MN; however,
 there are several situations where the target link is not available

Yokota & Dommety Informational [Page 14] RFC 5271 3G CDMA Fast Handover June 2008

 after the handover (step (d)) and the MN comes back to the PAR, or
 the MN is not able to move to the target link for some reason after
 the connection was closed.  If this is the case, the attachment
 procedure is performed on the previous link.  The packets buffered at
 the PAR SHOULD be delivered to the MN after the connection is
 re-established.

5.3. Considerations on the Link Indications

 This section discusses if the link indications assumed in this
 document meet the principles defined in Section 2 of RFC 4907[20],
 which suggests 11 architectural principles on the link indication and
 the effectiveness of the optimization.  This document relies on the
 3G CDMA network regarding the link indication, which is precisely
 specified by 3GPP2.  Therefore, principles (1) to (5), (7), (8), and
 (11), that is, "Model Validation", "Clear Definition", "Robustness",
 "Recovery from Invalid Indications", "Congestion Control",
 "Interoperability", "Race Condition", and "Transport of Link
 Indications" are considered by those specs.  Principle (6)
 "Effectiveness" mentions the effectiveness of the optimization.  This
 document bases its effectiveness on RFC 5268.  Therefore, this
 principle is dealt by that RFC.  Principle (9) "Metric Consistency"
 mentions inconsistencies between link and routing layer metrics.  The
 spec of this document does not change the routing metrics and
 multi-homing is not considered.  Finally, principle (10) "Layer
 Compression", mentions an overhead reduction scheme and
 interoperability.  This document does not deal with overhead
 reduction and therefore this principle does not apply.

6. Message Format

6.1. Handover Assist Information Option

 If the lower layer information of the new point of attachment is not
 represented as the link-layer address, the following option SHOULD be
 used.  The primary purpose of this option is to convey the handover
 assist information described in Section 4.
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Type       |    Length     |  Option-Code  |   HAI-Length  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                HAI-Value...
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Yokota & Dommety Informational [Page 15] RFC 5271 3G CDMA Fast Handover June 2008

 Type           29
 Length         The size of this option in 8 octets including the
                Type, Length, Option-Code, and HAI-Length (Handover
                Assist Information-Length) fields.
 Option-Code
                1: Access Network Identifier (AN ID)
                2: Sector ID
 HAI-Length     The size of the HAI-Value field in octets.
 HAI-Value      The value specified by the Option-Code.
 If those that received this message do not support this option, they
 SHOULD treat this option as opaque and MUST NOT drop it.
 Option-Code indicates the particular type of handover assist
 information.  Currently, two types of information are defined to
 assist the discovery of the NAR (see Section 3).
 Depending on the size of the HAI-Value field, appropriate padding
 MUST be used to ensure that the entire option size is a multiple of 8
 octets.  The HAI-Length is used to disambiguate the size of the
 HAI-Value.
 The handover assist information MAY replace the New Access Point
 Link-Layer Address in 3G CDMA networks.

6.2. Mobile Node Identifier Option

 This option is used to transfer the Identifier of the MN, which is
 not its link-layer address.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +---------------+---------------+---------------+---------------+
 |      Type     |     Length    |   Option-Code |  MN ID-Length |
 +---------------------------------------------------------------+
 |               MN ID ...
 +-----------------------------
 Type           30
 Length         The size of this option is in 8 octets including the
                Type, Length, and Option-Code.

Yokota & Dommety Informational [Page 16] RFC 5271 3G CDMA Fast Handover June 2008

 Option-Code
                1: NAI [4]
                2: IMSI (See Section 3)
 MN ID-Length   The length of the MN ID in octets.
 MN ID          MN ID value
 The MN ID MAY replace the MN Link-Layer Address in 3G CDMA networks.

6.3. New Flag Extension to FBU Message

 The MN MUST send the FBU to the PAR with the following new (B) flag
 set in the previous network to indicate the PAR to buffer packets
 destined for the PCoA.  The rest of the Binding Update message format
 remains the same as defined in [2] and with the additional (M), (R),
 and (P) flags as specified in [14], [15], and [16], respectively.
                                 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                 |          Sequence #           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |A|H|L|K|M|R|P|B|   Reserved    |            Lifetime           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 .                                                               .
 .                        Mobility options                       .
 .                                                               .
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 B flag:        If the 'B' flag is set, the PAR SHOULD start buffering
                the packets destined for the MN as specified in
                Section 5.2.

6.4. New Flag Extension to PrRtAdv Message

 A new flag 'R' is defined in the PrRtAdv to inform the MN about the
 fast handover mode that the network supports.
  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      Type     |      Code     |           Checksum            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Subtype    |R|  Reserved   |           Identifier          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    Options ...
 +-+-+-+-+-+-+-+-+-+-+-+-

Yokota & Dommety Informational [Page 17] RFC 5271 3G CDMA Fast Handover June 2008

 R flag:        If the 'R' flag is set, the network supports only the
                reactive handover mode.  Otherwise, the network
                supports both the predictive and reactive fast
                handover mode.

7. Security Considerations

 The security considerations for Mobile IPv6 fast handover are
 described in [3].  When a 3G CDMA network is considered, it can be
 assumed that the PAR and the NAR have a trust relationship and the
 links between them and those between the ARs and the MN are secured.
 The MN is authenticated every time it attaches to the new link;
 therefore, the AR can securely identify the MN.  Depending on the
 operator's policy, however, SEcure Neighbor Discovery (SEND) [18] and
 the shared handover key defined in [17] can also be applied.

8. IANA Considerations

 This document defines two new IPv6 Neighbor Discovery options that
 have been assigned from the same space as the IPv6 Neighbor Discovery
 Options defined in [19].
    29: Handover Assist Information Option (Section 6.1)
    30: Mobile Node Identifier Option (Section 6.2)
 This document creates two new registries for the Option-Code field in
 the Handover Assist Information Option and that in the Mobile Node
 Identifier Option.  The values for the Option-Code must be within the
 range 0-255.  New values for both registries can be allocated by
 Standards Action or IESG approval [5].
 The Option-Code values that have been assigned by IANA are as
 follows:
  Option-Code for Handover Assist Information Option
  Value Description                   Reference
  ----- ----------------------------  ----------
    0   Reserved
    1   ANID                          Section 6.1
    2   Sector ID                     Section 6.1

Yokota & Dommety Informational [Page 18] RFC 5271 3G CDMA Fast Handover June 2008

  Option-Code for Mobile Node Identifier Option
  Value Description                   Reference
  ----- ----------------------------  ----------
    0   Reserved
    1   NAI                           Section 6.2
    2   IMSI                          Section 6.2

9. Acknowledgements

 The authors would like to thank Kuntal Chowdhury, Ashutosh Dutta, Ved
 Kafle, and Vijay Devarapalli for providing feedback and support for
 this work.  The authors would also thank Sebastian Thalanany for
 3GPP2 expert review.

10. References

10.1. Normative References

 [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.
 [2]   Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
       IPv6", RFC 3775, June 2004.
 [3]   Koodli, R., Ed., "Mobile IPv6 Fast Handovers", RFC 5268, June
       2008.
 [4]   Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network
       Access Identifier", RFC 4282, December 2005.
 [5]   Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
       Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
 [6]   ITU-T Recommendation, "The international identification plan
       for mobile terminals and mobile users", ITU-T E.212, May 2004.

10.2. Informative References

 [7]   McCann, P., "Mobile IPv6 Fast Handovers for 802.11 Networks",
       RFC 4260, November 2005.
 [8]   3GPP2 TSG-C, "cdma2000 High Rate Packet Data Air Interface
       Specification", C.S0024-A v.2.0, July 2005.
 [9]   3GPP2 TSG-A, "3GPP2 Access Network Interfaces Interoperability
       Specification", A.S0001-A v.2.0, June 2001.

Yokota & Dommety Informational [Page 19] RFC 5271 3G CDMA Fast Handover June 2008

 [10]  3GPP2 TSG-A, "Interoperability Specification for High Rate
       Packet 1 2 Data (HRPD) Access Network Interfaces - Rev A.",
       A.S0007-A v.2.0, May 2003.
 [11]  3GPP2 TSG-A, "Interoperability Specification (IOS) for High
       Rate Packet Data (HRPD) Access Network Interfaces", 3GPP2
       A.S0008-0 v3.0, May 2003.
 [12]  3GPP2 TSG-X, "cdma2000 Wireless IP Network Standard: Simple IP
       and Mobile IP services", X.S0011-002-D v.1.0, February 2006.
 [13]  Devarapalli, V., Patel, A., Keung, K., and K. Chowdhury,
       "Mobile IPv6 Bootstrapping for the Authentication Option
       Protocol", Work in Progress, September 2007.
 [14]  Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,
       "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)", RFC
       4140, August 2005.
 [15]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
       "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
       January 2005.
 [16]  Gundavell, S., Ed., Leung, K., Devarapalli, V., Chowdhury, K.,
       and B. Patil, "Proxy Mobile IPv6", Work in Progress, February
       2008.
 [17]  Kempf, J., Ed. and R. Koodli, "Distributing a Symmetric FMIPv6
       Handover Key using SEND", RFC 5269, June 2008.
 [18]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, "SEcure
       Neighbor Discovery (SEND)", RFC 3971, March 2005.
 [19]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
       "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
       September 2007.
 [20]  Aboba, B., Ed., "Architectural Implications of Link
       Indications", RFC 4907, June 2007.

Yokota & Dommety Informational [Page 20] RFC 5271 3G CDMA Fast Handover June 2008

Authors' Addresses

 Hidetoshi Yokota
 KDDI Lab
 2-1-15 Ohara, Fujimino
 Saitama,  356-8502
 JP
 Phone: +81 49 278 7894
 Fax:   +81 49 278 7510
 EMail: yokota@kddilabs.jp
 Gopal Dommety
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA  95134
 US
 Phone: +1 408 525 1404
 EMail: gdommety@cisco.com

Yokota & Dommety Informational [Page 21] RFC 5271 3G CDMA Fast Handover June 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
 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, THE IETF TRUST 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.

Yokota & Dommety Informational [Page 22]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5271.txt · Last modified: 2008/06/18 19:24 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki