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INTERNET-DRAFT                                         J. Manner, Editor
draft-ietf-seamoby-mobility-terminology-06.txt           M. Kojo, Editor
Category: Informational                                   February, 2004
Expires: August, 2004


                      Mobility Related Terminology


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
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Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.



Abstract

   There is a need for common definitions of terminology in the work to
   be done around IP mobility. This document defines terms for mobility
   related terminology. The document originated out of work done in the
   Seamoby Working Group but has broader applicability for terminology
   used in IETF-wide discourse on technology for mobility and IP
   networks. Other working groups dealing with mobility may want to take
   advantage of this terminology.










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Table of Contents

   1 Introduction .................................................    2
   2 General Terms ................................................    3
   3 Mobile Access Networks and Mobile Networks ...................    9
   4 Handover Terminology .........................................   13
   4.1 Scope of Handover ..........................................   14
   4.2 Handover Control ...........................................   15
   4.3 Simultaneous connectivity to Access Routers ................   17
   4.4 Performance and Functional Aspects .........................   17
   4.5 Micro Diversity, Macro Diversity, and IP Diversity .........   18
   4.6 Paging, and Mobile Node States and Modes ...................   19
   4.7 Context Transfer ...........................................   21
   4.8 Candidate Access Router Discovery ..........................   21
   4.9 Types of Mobility ..........................................   22
   5 Specific Terminology for Mobile Ad-Hoc Networking ............   23
   6 Security-related Terminology .................................   24
   7 Security Considerations ......................................   25
   8 Contributors .................................................   25
   9 Acknowledgments ..............................................   25
   10 Informative References ......................................   26
   11 Authors' Addresses ..........................................   27
   12 Appendix A - Index of Terms .................................   29


1.  Introduction

   This document presents terminology to be used for documents and
   discussions within the Seamoby Working Group. Other mobility related
   working groups could take advantage of this terminology, in order to
   create a common terminology for the area of mobility in IP networks.
   These groups would include MIP, MANET, ROHC and NEMO.

   Some terms and their definitions that are not directly related to the
   IP world are included for the purpose of harmonizing the terminology.
   For example, 'Access Point' and 'base station' refer to the same
   component, from the point of view of IP, but 'Access Router' has a
   very different meaning.  The presented terminology may also, it is
   hoped, be adequate to cover mobile ad-hoc networks.

   The proposed terminology is not meant to assert any new terminology.
   Rather the authors would welcome discussion on more exact definitions
   as well as missing or unnecessary terms.  This work is a
   collaborative enterprise between people from many different
   engineering backgrounds and so already presents a first step in
   harmonizing the terminology.

   The terminology in this draft is divided into several sections.
   First, there is a list of terms for general use and mobile access
   networks followed by terms related to handovers, and finally some
   terms used within the MANET and NEMO working group.




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2.  General Terms

     Bandwidth

       The total width of the frequency band available to or used by a
       communications channel. Usually measured in Hertz (Hz). The
       bandwidth of a channel limits the available channel capacity.

     Bandwidth utilization

       The actual rate of information transfer achieved over a link,
       expressed as a percentage of the theoretical maximum channel
       capacity on that link, according to Shannon's Law.

     Beacon

       A control message broadcast by a node (especially, a base
       station) informing all the other nodes in its neighborhood of the
       continuing presence of the broadcasting node, possibly along with
       additional status or configuration information.

     Binding Update (BU)

       A message indicating a mobile node's current mobility binding,
       and in particular its care-of address.

     Care-of-Address (CoA)

       An IP address associated with a mobile node while visiting a
       foreign link; the subnet prefix of this IP address is a foreign
       subnet prefix. A packet addressed to the mobile node which
       arrives at the mobile node's home network when the mobile node is
       away from home and has registered a Care-of Address will be
       forwarded to that address by the Home Agent in the home network.

     Channel

       A subdivision of the physical medium allowing possibly shared
       independent uses of the medium.  Channels may be made available
       by subdividing the medium into distinct time slots, or distinct
       spectral bands, or decorrelated coding sequences.

     Channel access protocol

       A protocol for mediating access to, and possibly allocation of,
       the various channels available within the physical communications
       medium.  Nodes participating in the channel access protocol agree
       to communicate only when they have uncontested access to one of
       the channels, so that there will be no interference.

     Channel capacity

       The total capacity of a link to carry information (typically
       bits) per unit time. With a given bandwidth, the theoretical

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       maximum channel capacity is given by Shannon's Law. The actual
       channel capacity of a channel is determined by the channel
       bandwidth, the coding system used, and the signal to noise ratio.

     Control message

       Information passed between two or more network nodes for
       maintaining protocol state, which may be unrelated to any
       specific application.

     Distance vector

       A characteristic of some routing protocols in which, for each
       desired destination, a node maintains information about the
       distance to that destination, and a vector (next hop) towards
       that destination.

     Fairness

       A property of channel access protocols whereby a medium is made
       fairly available to all eligible nodes on the link.  Fairness
       does not strictly imply equality, especially in cases where nodes
       are given link access according to unequal priority or
       classification.

     Flooding

       The process of delivering data or control messages to every node
       within the network under consideration.

     Foreign subnet prefix

       A bit string that consists of some number of initial bits of an
       IP address which identifies a node's foreign link within the
       Internet topology.

     Forwarding node

       A node which performs the function of forwarding datagrams from
       one of its neighbors to another.

     Home Address (HoA)

       An IP address assigned to a mobile node, used as the permanent
       address of the mobile node.  This address is within the mobile
       node's home link.  Standard IP routing mechanisms will deliver
       packets destined for a mobile node's home address to its home
       link [11].

     Home Agent (HA)

       A router on a mobile node's home link with which the mobile node
       has registered its current care-of address. While the mobile node
       is away from home, the home agent intercepts packets on the home

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       link destined to the mobile node's home address, encapsulates
       them, and tunnels them to the mobile node's registered care-of
       address.

     Home subnet prefix

       A bit string that consists of some number of initial bits of an
       IP address which identifies a node's home link within the
       Internet topology (i.e. the IP subnet prefix corresponding to the
       mobile node's home address, as defined in [11]).

     Interface

       A node's point of attachment to a link.

     IP access address

       An IP address (often dynamically allocated) which a node uses to
       designate its current point of attachment to the local network.
       The IP access address is typically to be distinguished from the
       mobile node's home address; in fact, while visiting a foreign
       network the former may be considered unsuitable for use as an
       end-point address by any but the most short-lived applications.
       Instead, the IP access address is typically used as the care-of
       address of the node.

     Link

       A communication facility or physical medium that can sustain data
       communications between multiple network nodes, such as an
       Ethernet (simple or bridged). A link is the layer immediately
       below IP. In a layered network stack model, the Link Layer (Layer
       2) is normally below the Network (IP) Layer (Layer 3), and above
       the Physical Layer (Layer 1).

     Asymmetric link

       A link with transmission characteristics which are different
       depending upon the relative position or design characteristics of
       the transmitter and the receiver of data on the link.  For
       instance, the range of one transmitter may be much higher than
       the range of another transmitter on the same medium.

     Link establishment

       The process of establishing a link between the mobile node and
       the local network.  This may involve allocating a channel, or
       other local wireless resources, possibly including a minimum
       level of service or bandwidth.

     Link-layer trigger (L2 Trigger)

       Information from the link layer that informs the network layer of
       the detailed events involved in handover sequencing at the link

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       layer. L2 triggers are not specific to any particular link layer,
       but rather represent generalizations of link layer information
       available from a wide variety of link layer protocols [4].

     Link state

       A characterization of some routing protocols in which every node
       within the network is expected to maintain information about
       every link within the network topology.

     Link-level acknowledgment

       A protocol strategy, typically employed over wireless media,
       requiring neighbors to acknowledge receipt of packets (typically
       unicast only) from the transmitter. Such strategies aim to avoid
       packet loss or delay resulting from lack of, or unwanted
       characteristics of, higher level protocols. Link-layer
       acknowledgments are often used as part of Automatic Repeat-
       Request (ARQ) algorithms for increasing link reliability.

     Local broadcast

       The delivery of data to every node within range of the
       transmitter.

     Loop-free

       A property of routing protocols whereby the path taken by a data
       packet from source to destination never transits the same
       intermediate node twice before arrival at the destination.

     Medium Access Protocol (MAC)

       A protocol for mediating access to, and possibly allocation of,
       the physical communications medium.  Nodes participating in the
       medium access protocol can communicate only when they have
       uncontested access to the medium, so that there will be no
       interference.  When the physical medium is a radio channel, the
       MAC is the same as the Channel Access Protocol.

     Mobile network prefix

       A bit string that consists of some number of initial bits of an
       IP address which identifies the entire mobile network within the
       Internet topology. All nodes in a mobile network necessarily have
       an address containing this prefix.

     Mobility factor

       The relative frequency of node movement, compared to the
       frequency of application initiation.




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     Multipoint relay (MPR)

       A node which is selected by its one-hop neighbor to re-transmit
       all broadcast messages that it receives. The message must be new
       and the time-to-live field of the message must be greater than
       one.  Multipoint relaying is a technique to reduce the number of
       redundant re-transmissions while diffusing a broadcast message in
       the network.

     Neighbor

       A "neighbor" is any other node to which data may be propagated
       directly over the communications medium without relying on the
       assistance of any other forwarding node.

     Neighborhood

       All the nodes which can receive data on the same link from one
       node whenever it transmits data.

     Next hop

       A neighbor which has been selected to forward packets along the
       way to a particular destination.

     Payload

       The actual data within a packet, not including network protocol
       headers which were not inserted by an application. Note that
       payloads are different between layers:  user data is the payload
       of TCP, which are the payload of IP, which three are the payload
       of link layer protocols etc. Thus, it is important to identify
       the scope when talking about payloads.

     Prefix

       A bit string that consists of some number of initial bits of an
       address.

     Routing table

       The table where forwarding nodes keep information (including next
       hop) for various destinations.

     Route entry

       An entry for a specific destination (unicast or multicast) in the
       routing table.

     Route establishment

       The process of determining a route between a source and a
       destination.


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     Route activation

       The process of putting a route into use after it has been
       determined.

     Routing proxy

       A node that routes packets by overlays, e.g.. by tunneling,
       between communicating partners. The Home Agent and Foreign Agent
       are examples of routing proxies, in that they receive packets
       destined for the mobile node and tunnel them to the current
       address of the mobile node.

     Shannon's Law

       A statement defining the theoretical maximum rate at which error-
       free digits can be transmitted over a bandwidth-limited channel
       in the presence of noise. No practical error correction coding
       system exists that can closely approach the theoretical
       performance limit given by Shannon's law.

     Signal strength

       The detectable power of the signal carrying the data bits, as
       seen by the receiver of the signal.

     Source route

       A source route from node A to node B is an ordered list of IP
       addresses, starting with the IP address of node A and ending with
       the IP address of the node B. Between A and B, the source route
       includes an ordered list intermediate hops between A and B, as
       well as the interface index of the interface through which the
       packet should be transmitted to reach the next hop. The list of
       intermediate hops might not include all visited nodes, some hops
       might be omitted for a reason or another.

     Spatial re-use

       Simultaneous use of channels with identical or close physical
       characteristics, but located spatially far enough apart to avoid
       interference (i.e., co-channel interference)

     System-wide broadcast

       Same as flooding, but used in contrast to local broadcast.

     Subnet

       A subnet is a logical group of connected network nodes. In IP
       networks, nodes in a subnet share a common network mask (in IPV4)
       or a network prefix (in IPv6).



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     Topology (Network Topology)

       The interconnection structure of a network: which nodes are
       directly connected to each other, and through which links they
       are connected.  Some simple topologies have been given names,
       such as for instance 'bus topology', 'mesh topology', 'ring
       topology', 'star topology' and 'tree topology'.

     Triggered update

       A solicited route update transmitted by a router along a path to
       a destination.


3.  Mobile Access Networks and Mobile Networks

   In order to support host mobility a set of nodes towards the network
   edge may need to have specific functions. Such a set of nodes forms a
   mobile access network that may or may not be part of the global
   Internet. Figure 1 presents two examples of such access network
   topologies. The figure depicts a reference architecture which
   illustrates an IP network with components defined in this section.

   We intend to define the concept of the Access Network (AN) which may
   also support enhanced mobility. It is possible that to support
   routing and QoS for mobile nodes, existing routing protocols (e.g.,
   Open Shortest Path First (OSPF) [16]) may not be appropriate to
   maintain forwarding information for these mobile nodes as they change
   their points of attachment to the Access Network. These new functions
   are implemented in routers with additional capabilities. We can
   distinguish three types of Access Network components: Access Routers
   (AR) which handle the last hop to the mobile, typically over a
   wireless link; Access Network Gateways (ANG) which form the boundary
   on the fixed network side and shield the fixed network from the
   specialized routing protocols; and (optionally) other internal Access
   Network Routers which may also be needed in some cases to support the
   protocols. The Access Network consists of the equipment needed to
   support this specialized routing, i.e. AR or ANG. AR and ANG may be
   the same physical nodes.

   In addition, we present a few basic terms on mobile networks, that
   is, mobile network, mobile router (MR), and mobile network node
   (MNN). More terminology for discussing mobile networks can be found
   in [15]. A more thorough discussion of mobile networks can be found
   in the working group documents of the NEMO Working Group.

   Note: this reference architecture is not well suited for people
   dealing with Mobile Ad-hoc Networks (MANET).







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                                                                    |
                                                                    |
                      ---        ------                    -------  |
         ---  | <-->  | | -------| AR | -------------------|     |  |
         | |--[]      ---        /------          \       /| ANG |--|
         ---            AP      /                  \     / |     |  |
          MH                   /                    \   /  -------  |
    (with wireless     ___    /                    -------          |
         device)       | |----                     | ANR |          |
                       ---                         -------          |
                        AP                          /   \           |
                                                   /     \ -------  |
                      ---       ------            /       \|     |  |
                      | |-------| AR |---------------------| ANG |--|
                      ---       ------                     |     |  |
                       AP                                  -------  |
                                                                    |
                           Access Network (AN) 1                    |
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  -|
                           Access Network (AN) 2                    |
                                                                    |
                                                                    |
                      ---        ------                    -------  |
        ---  | <-->   | | -------| AR | -------------------|     |  |
        | |--[]       ---       /------                   /| ANG |--|
        ---            AP      /                         / |     |  |
         MH                   /                         /  -------  |
    (with wireless    ___    /                         /            |
        device)       | |----                         /             |
                      ---                            /              |
                       AP                           /               |
                                                   /                |
        |            ---       ------         -------               |
    --- |       | <->| |-------| AR |---------| ANR |               |
    | |-|      []    ---  \    ------         -------               |
    --- |  -----|     AP   \                  /                     |
    MNN |--i MR e           \                /                      |
        |  ------    ---     \ ------       /                       |
    --- | (with      | |-------| AR |-------                        |
    | |-| wireless   ---       ------                               |
    --- |  device)    AP                                            |
    MNN                                 'i': MR ingress interface   |
                                        'e': MR egress interface    |
                                                                    |

                 Figure 1: Reference Network Architecture









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     Mobile Node (MN)

       An IP node capable of changing its point of attachment to the
       network. A Mobile Node may either be a Mobile Host (no forwarding
       functionality) or a Mobile Router (forwarding functionality).

     Mobile Host (MH)

       A mobile node that is an end host and not a router. A Mobile Host
       is capable of sending and receiving packets, that is, being a
       source or destination of traffic, but not a forwarder of it.

     Fixed Node (FN)

       A node, either a host or a router, unable to change its point of
       attachment to the network and its IP address without breaking
       open sessions.

     Mobile network

       An entire network, moving as a unit, which dynamically changes
       its point of attachment to the Internet and thus its reachability
       in the topology. The mobile network is composed of one or more
       IP-subnets and is connected to the global Internet via one or
       more Mobile Routers (MR). The internal configuration of the
       mobile network is assumed to be relatively stable with respect to
       the MR.

     Mobile Router (MR)

       A router capable of changing its point of attachment to the
       network, moving from one link to another link. The MR is capable
       of forwarding packets between two or more interfaces, and
       possibly running a dynamic routing protocol modifying the state
       by which it does packet forwarding.

       A MR acting as a gateway between an entire mobile network and the
       rest of the Internet has one or more egress interface(s)  and one
       or more ingress interface(s). Packets forwarded upstream to the
       rest of the Internet are transmitted through one of the MR's
       egress interface; packets forwarded downstream to the mobile
       network are transmitted through one of the MR's ingress
       interface.

       Ingress interface

         The interface of a MR attached to a link inside the mobile
         network.

       Egress interface

         The interface of a MR attached to the home link if the MR is at
         home, or attached to a foreign link if the MR is in a foreign
         network.

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     Mobile Network Node (MNN)

       Any node (host or router) located within a mobile network, either
       permanently or temporarily. A Mobile Network Node may either be a
       mobile node or a fixed node.

     Access Link (AL)

       A last-hop link between a Mobile Node and an Access Point.  That
       is, a facility or medium over which an Access Point and the
       Mobile Node can communicate at the link layer, i.e., the layer
       immediately below IP.

     Access Point (AP)

       An Access Point is a layer 2 device which is connected to one or
       more Access Routers and offers the wireless link connection to
       the Mobile Node.  Access Points are sometimes called base
       stations or access point transceivers.  An Access Point may be a
       separate entity or co-located with an Access Router.

     Radio Cell

       The geographical area within which an Access Point provides radio
       coverage, i.e.  where radio communication between a Mobile Node
       and the specific Access Point is possible.

     Access Network Router (ANR)

       An IP router in the Access Network. An Access Network Router may
       include Access Network specific functionalities, for example,
       related to mobility and/or QoS. This is to distinguish between
       ordinary routers and routers that have Access Network-related
       special functionality. An ANR is neither an AR nor an ANG.

     Access Router (AR)

       An Access Network Router residing on the edge of an Access
       Network and connected to one or more Access Points.  The Access
       Points may be of different technology.  An Access Router offers
       IP connectivity to Mobile Nodes, acting as a default router to
       the Mobile Nodes it is currently serving.  The Access Router may
       include intelligence beyond a simple forwarding service offered
       by ordinary IP routers.

     Access Network Gateway (ANG)

       An Access Network Router that separates an Access Network from
       other IP networks, much in the same way as an ordinary gateway
       router. The Access Network Gateway looks to the other IP networks
       like a standard IP router. In a small network, an ANG may also
       offer the services of an AR, namely offer the IP connectivity to
       the mobile nodes.


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     Access Network (AN)

       An IP network which includes one or more Access Network Routers.

     Administrative Domain (AD)

       A collection of networks under the same administrative control
       and grouped together for administrative purposes [5].

     Serving Access Router (SAR)

       The Access Router currently offering the connectivity to the MN.
       This is usually the point of departure for the MN as it makes its
       way towards a new Access Router (at which time the Serving Access
       Router takes the role of the Old Access Router). There may be
       several Serving Access Routers serving the Mobile Node at the
       same time.

     New Access Router (NAR)

       The Access Router that offers connectivity to the Mobile Node
       after a handover.

     Previous Access Router (PAR)

       An Access Router that offered connectivity to the Mobile Node
       prior to a handover.  This is the Serving Access Router that will
       cease or has ceased to offer connectivity to the Mobile Node.

     Candidate Access Router (CAR)

       An Access Router to which the Mobile Node may do a handoff.


4.  Handover Terminology

   These terms refer to different perspectives and approaches to
   supporting different aspects of mobility.  Distinctions can be made
   according to the scope, range overlap, performance characteristics,
   diversity characteristics, state transitions, mobility types, and
   control modes of handover techniques.

     Roaming

       An operator-based term involving formal agreements between
       operators that allows a mobile to get connectivity from a foreign
       network.  Roaming (a particular aspect of user mobility)
       includes, for example, the functionality by which users can
       communicate their identity to the local AN so that inter-AN
       agreements can be activated and service and applications in the
       MN's home network can be made available to the user locally.




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     Handover (also known as handoff)

       The process by which an active MN (in the Active State, see
       section 4.6) changes its point of attachment to the network, or
       when such a change is attempted. The access network may provide
       features to minimize the interruption to sessions in progress.

       There are different types of handover classified according to
       different aspects involved in the handover.  Some of this
       terminology follows the description in [4].


4.1.  Scope of Handover

     Layer 2 handover

       A handover where the MN changes APs (or some other aspect of the
       radio channel) connected to the same AR's interface. This type of
       handover is transparent to the routing at the IP layer (or it
       appears simply as a link layer reconfiguration without any
       mobility implications).

     Intra-AR handover

       A handover which changes the AR's network interface to the
       mobile.  That is, the Serving AR remains the same but routing
       changes internal to the AR take place.

     Intra-AN handover

       A handover where the MN changes ARs inside the same AN. Such a
       handover is not necessarily visible outside the AN. In case the
       ANG serving the MN changes, this handover is seen outside the AN
       due to a change in the routing paths. Note that the ANG may
       change for only some of the MN's data flows.

     Inter-AN handover

       A handover where the MN moves to a new AN. This requires some
       sort of host mobility ANs, which typically is be provided by the
       external IP core. Note that this would have to involve the
       assignment of a new IP access address (e.g., a new care-of
       address [9]) to the MN.

     Intra-technology handover

       A handover between equipment of the same technology.

     Inter-technology handover

       A handover between equipment of different technologies.




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     Horizontal handover

       This involves MNs moving between access points of the same type
       (in terms of coverage, data rate and mobility), such as, UMTS to
       UMTS, or WLAN to WLAN.

     Vertical handover

       This involves MNs moving between access points of different type,
       such as, UMTS to WLAN.


   Note that the difference between a horizontal and vertical handover
   is vague. For example, a handover from an AP with 802.11b WLAN link
   to an AP with 802.11g WLAN link may be considered as either a
   vertical or a horizontal handover, depending on an individual's point
   of view.

   Note also that the IP layer sees network interfaces and IP addresses,
   rather than specific technologies used by those interfaces.  Thus,
   horizontal and vertical handovers may or may not be noticed at the IP
   layer. Usually a handover can be noticed if the IP address assigned
   to the interface changes, the network interface itself changes (which
   can also change the IP address), or there is a link outage, for
   example, when the mobile node moves out of coverage for a while. For
   example, in a GPRS network a horizontal handover happens usually
   unnoticed by the IP layer. Similarly, a WLAN horizontal handover may
   be noticed if the IP address of the interface changes. On the other
   hand, vertical handovers often change the network interface and are,
   therefore, noticed on the IP layer. Still, some specific network
   cards may be able to switch between access technologies (e.g. GPRS to
   UMTS) without changing the network interface. Moreover, either of the
   two handovers may or may not result in changing the AR. For example,
   an AR could control WLAN and Bluetooth access points, and the mobile
   node could do horizontal and vertical handovers under the same AR
   without changing its IP address or even the network interface.


4.2.  Handover Control

   A handover must be one of the following two types (a):

     Mobile-initiated handover

       The MN is the one that makes the initial decision to initiate the
       handover.

     Network-initiated handover

       The network makes the initial decision to initiate the handover.

   A handover is also one of the following two types (b):

     Mobile-controlled handover

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       The MN has the primary control over the handover process.

     Network-controlled handover

       The network has the primary control over the handover process.

   A handover decision usually involves some sort of measurements about
   when and where to handover to. Therefore, a handover is also either
   of these three types (c):

     Mobile-assisted handover

       Information and measurement from the MN are used by the AR to
       decide on the execution of a handover.

     Network-assisted handover

       A handover where the AN collects information that can be used by
       the MN in a handover decision.

     Unassisted handover

       A handover where no assistance is provided by the MN or the AR to
       each other.

   Note that it is possible that the MN and the AR both do measurements
   and decide on the handover.

   A handover is also one of the following two types (d):

     Push handover

       A handover either initiated by the PAR, or where the MN initiates
       a handover via the PAR.

     Pull handover

       A handover either initiated by the NAR, or where the MN initiates
       a handover via the NAR.

   The handover is also either proactive or reactive (e):

     Planned handover

       A proactive (expected) handover where some signaling can be done
       in advance of the MN getting connected to the new AR, e.g.
       building a temporary tunnel from the previous AR to the new AR.

     Unplanned handover

       A reactive (unexpected) handover where no signaling is done in
       advance of the MN's move of the previous AR to the new AR.



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   The five handover types (a-e) are mostly independent, and every
   handover should be classifiable according to each of these types.


4.3.  Simultaneous connectivity to Access Routers

     Make-before-break (MBB)

       During a MBB handover the MN makes the new connection before the
       old one is broken. Thus, the MN can communicate simultaneously
       with the old and new AR during the handover. This should not be
       confused with "soft handover" which relies on macro diversity,
       described in Section 4.5.

     Break-before-make (BBM)

       During a BBM handover the MN breaks the old connection before the
       new connection is made. Thus the MN cannot communicate
       simultaneously with the old and the new AR.


4.4.  Performance and Functional Aspects

     Handover latency

       Handover latency is the difference between the time a MN is last
       able to send and/or receive an IP packet by way of the PAR, and
       the time the MN is able to send and/or receive an IP packet
       through the NAR.  Adapted from [4].

     Smooth handover

       A handover that aims primarily to minimize packet loss, with no
       explicit concern for additional delays in packet forwarding.

     Fast handover

       A handover that aims primarily to minimize handover latency, with
       no explicit interest in packet loss.

     Seamless handover

       A handover in which there is no change in service capability,
       security, or quality. In practice, some degradation in service is
       to be expected.  The definition of a seamless handover in the
       practical case should be that other protocols, applications, or
       end users do not detect any change in service capability,
       security or quality, which would have a bearing on their (normal)
       operation. As a consequence, what would be a seamless handover
       for one less demanding application might not be seamless for
       another more demanding application. See [7] for more discussion
       on the topic.

     Throughput

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       The amount of data from a source to a destination processed by
       the protocol for which throughput is to be measured for instance,
       IP, TCP, or the MAC protocol.  The throughput differs between
       protocol layers.

     Goodput

       The total bandwidth used, less the volume of control messages,
       protocol overhead from the data packets, and packets dropped due
       to CRC errors.

     Pathloss

       A reduction in signal strength caused by traversing the physical
       medium constituting the link.

     Hidden-terminal problem

       The problem whereby a transmitting node can fail in its attempt
       to transmit data because of destructive interference which is
       only detectable at the receiving node, not the transmitting node.

     Exposed terminal problem

       The problem whereby a transmitting node A prevents another node B
       from transmitting, although node B could have safely transmitted
       to anyone else but the transmitting node A.


4.5.  Micro Diversity, Macro Diversity, and IP Diversity

   Certain air interfaces (e.g.  the Universal Mobile Telephone System
   (UMTS) Terrestrial Radio Access Network (UTRAN) running in Frequency
   Division Duplex (FDD) mode)  require or at least support macro
   diversity combining.  Essentially, this refers to the fact that a
   single MN is able to send and receive over two independent radio
   channels ('diversity branches') at the same time; the information
   received over different branches is compared and that from the better
   branch passed to the upper layers.  This can be used both to improve
   overall performance, and to provide a seamless type of handover at
   layer 2, since a new branch can be added before the old is deleted.
   See also [6].

   It is necessary to differentiate between combining/diversity that
   occurs at the physical and radio link layers, where the relevant unit
   of data is the radio frame, and that which occurs at layer 3, the
   network layer, where what is considered is the IP packet itself.

   In the following definitions micro- and macro diversity refer to
   protocol layers below the network layer, and IP diversity refers to
   the network layer.




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     Micro diversity

       for example, two antennas on the same transmitter send the same
       signal to a receiver over a slightly different path to overcome
       fading.

     Macro diversity

       Duplicating or combining actions taking place over multiple APs,
       possibly attached to different ARs.  This may require support
       from the network layer to move the radio frames between the base
       stations and a central combining point.

     IP diversity

       Refers to the process of duplicating IP packets and sending them
       to the receiver through more than one point of attachment. This
       is semantically allowed by IP because it does not guarantee
       packet uniqueness, and higher level protocols are assumed to
       eliminate duplicates whenever that is important for the
       application.


4.6.  Paging, and Mobile Node States and Modes

   Mobile systems may employ the use of MN states in order to operate
   more efficiently without degrading the performance of the system. The
   term 'mode' is also common and means the same as 'state'.

   A MN is always in one of the following three states:

     Active state

       When the AN knows the MN's SAR and the MN can send and receive IP
       packets. The access link may not be active, but the radio layer
       is able to establish one without assistance from the network
       layer. The MN has an IP address assigned.

     Dormant state

       A state in which the mobile restricts its ability to receive
       normal IP traffic by reducing its monitoring of radio channels.
       The AN knows the MN's Paging Area, but the MN has no SAR and so
       packets cannot be delivered to the MN without the AN initiating
       paging. Often also called Idle state.

     Time-slotted dormant mode

       A dormant mode implementation in which the mobile alternates
       between periods of not listening for any radio traffic and
       listening for traffic. Time-slotted dormant mode implementations
       are typically synchronized with the network so the network can
       deliver paging messages to the mobile during listening periods.


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     Inactive state

       the MN is in neither the Active nor Dormant State. The MN is no
       longer listening for any packets, not even periodically, and not
       sending packets.  The MN may be in a powered off state, it may
       have shut down all interfaces to drastically conserve power, or
       it may be out of range of a radio access point.  The MN does not
       necessarily have an IP access address from the AN.


   Note: in fact, as well as the MN being in one of these three states,
   the AN also stores which state it believes the MN is in. Normally
   these are consistent; the definitions above assume so.

   Here are some additional definitions for paging, taking into account
   the above state definitions.

     Paging

       A procedure initiated by the Access Network to move a Dormant MN
       into the Active State.  As a result of paging, the MN establishes
       a SAR and the IP routes are set up.

     Location updating

       A procedure initiated by the MN, by which it informs the AN that
       it has moved into a new paging area.

     Paging area

       A part of the Access Network, typically containing a number of
       ARs/APs, which corresponds to some geographical area.  The AN
       keeps and updates a list of all the Dormant MNs present in the
       area.  If the MN is within the radio coverage of the area it will
       be able to receive paging messages sent within that Paging Area.

     Paging area registrations

       Signaling from a dormant mode mobile node to the network, by
       which it establishes its presence in a new paging area.  Paging
       Area Registrations thus enable the network to maintain a rough
       idea of where the mobile is located.

     Paging channel

       A radio channel dedicated to signaling dormant mode mobiles for
       paging purposes. By current practice, the paging channel carries
       only control traffic necessary for the radio link, although some
       paging protocols have provision for carrying arbitrary traffic
       (and thus could potentially be used to carry IP).

     Traffic channel

       The radio channel on which IP traffic to an active mobile is

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       typically sent.  This channel is used by a mobile that is
       actively sending and receiving IP traffic, and is not
       continuously active in a dormant mode mobile.  For some radio
       link protocols, this may be the only channel available.


4.7.  Context Transfer

     Context

       The information on the current state of a routing-related service
       required to re-establish the routing-related service on a new
       subnet without having to perform the entire protocol exchange
       with the MN from scratch.

     Feature context

       The collection of information representing the context for a
       given feature. The full context associated with a MN is the
       collection of one or more feature contexts.

     Context transfer

       The movement of context from one router or other network entity
       to another as a means of re-establishing routing related services
       on a new subnet or collection of subnets.

     Routing-related service

       A modification to the default routing treatment of packets to and
       from the MN. Initially establishing routing-related services
       usually requires a protocol exchange with the MN. An example of a
       routing-related service is header compression. The service may
       also be indirectly related to routing, for example, security.
       Security may not affect the forwarding decision of all
       intermediate routers, but a packet may be dropped if it fails a
       security check (can't be encrypted, authentication failed, etc.).
       Dropping the packet is basically a routing decision.


4.8.  Candidate Access Router Discovery

     Capability of an AR

       A characteristic of the service offered by an AR that may be of
       interest to an MN when the AR is being considered as a handoff
       candidate.

     Candidate AR (CAR)

       An AR to which MN has a choice of performing IP-level handoff.
       This means that MN has the right radio interface to connect to an
       AP that is served by this AR, as well as the coverage of this AR
       overlaps with that of the AR to which MN is currently attached.

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     Target AR (TAR)

       An AR with which the procedures for the MN's IP-level handoff are
       initiated. TAR is selected after running a TAR Selection
       Algorithm that takes into account the capabilities of CARs,
       preferences of MN and any local policies.


4.9.  Types of Mobility

   We can differentiate between host and network mobility, and various
   types of network mobility. Terminology related more to applications
   such as the Session Initiation Protocol, such as personal mobility,
   is out of scope for this document.

     Host mobility support

       Refers to the function of allowing a mobile node to change its
       point of attachment to the network, without interrupting IP
       packet delivery to/from that node.  There may be different sub-
       functions depending on what the current level of service is being
       provided; in particular, support for host mobility usually
       implies active and dormant modes of operation, depending on
       whether the node has any current sessions or not.  Access Network
       procedures are required to keep track of the current point of
       attachment of all the MNs or establish it at will. Accurate
       location and routing procedures are required in order to maintain
       the integrity of the communication.  Host mobility is often
       called 'terminal mobility'.

     Network mobility support

       Refers to the function of allowing an entire network to change
       its point of attachment to the Internet, and, thus, its
       reachability in the topology, without interrupting IP packet
       delivery to/from that mobile network.

   Two subcategories of mobility can be identified within both host
   mobility and network mobility:

     Global mobility

       Same as Macro mobility.

     Local mobility

       Same as Micro mobility.

     Macro mobility

       Mobility over a large area. This includes mobility support and
       associated address registration procedures that are needed when a
       MN moves between IP domains. Inter-AN handovers typically involve
       macro-mobility protocols. Mobile-IP can be seen as a means to

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       provide macro mobility.

     Micro mobility

       Mobility over a small area.  Usually this means mobility within
       an IP domain with an emphasis on support for active mode using
       handover, although it may include idle mode procedures also.
       Micro-mobility protocols exploit the locality of movement by
       confining movement related changes and signaling to the access
       network.

     Local mobility management

       Local mobility management (LMM) is a generic term for protocols
       dealing with IP mobility management confined within the access
       network. LMM messages are not routed outside the access network,
       although a handover may trigger Mobile IP messages to be sent to
       correspondent nodes and home agents.


5.  Specific Terminology for Mobile Ad-Hoc Networking

     Cluster

       A group of nodes located within close physical proximity,
       typically all within range of one another, which can be grouped
       together for the purpose of limiting the production and
       propagation of routing information.

     Cluster head

       A cluster head is a node (often elected in the cluster formation
       process) that has complete knowledge about group membership and
       link state information in the cluster.  Each cluster should have
       one and only one cluster head.

     Cluster member

       All nodes within a cluster EXCEPT the cluster head are called
       members of that cluster.

     Convergence

       The process of approaching a state of equilibrium in which all
       nodes in the network agree on a consistent collection of state
       about the topology of the network, and in which no further
       control messages are needed to establish the consistency of the
       network topology.

     Convergence time

       The time which is required for a network to reach convergence
       after an event (typically, the movement of a mobile node) which
       changes the network topology.

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     Laydown

       The relative physical location of the nodes within the ad hoc
       network.

     Pathloss matrix

       A matrix of coefficients describing the pathloss between any two
       nodes in an ad hoc network.  When the links are asymmetric, the
       matrix is also asymmetric.

     Scenario

       The tuple <laydown, pathloss matrix, mobility factor, traffic>
       characterizing a class of ad hoc networks.


6.  Security-related Terminology

   This section includes terminology commonly used around mobile and
   wireless networking. Only a mobility-related subset of the entire
   security terminology is presented.

     Authorization-enabling extension

       An authentication which makes a (registration) message acceptable
       to the ultimate recipient of the registration message. An
       authorization-enabling extension must contain an SPI (see below)
       [12].

     Mobility security association

       A collection of security contexts, between a pair of nodes, which
       may be applied to mobility-related protocol messages exchanged
       between them. In Mobile IP, each context indicates an
       authentication algorithm and mode, a secret (a shared key, or
       appropriate public/private key pair), and a style of replay
       protection in use.  Mobility security associations may be stored
       separately from the node's IPsec Security Policy Database (SPD)
       [12].

     Registration key

       A key used in the Mobility Security Association between a mobile
       node and a foreign agent. A registration key is typically only
       used once or a very few times, and only for the purposes of
       verifying a small volume of Authentication data [14].

     Security context

       A security context between two nodes defines the manner in which
       two nodes choose to mutually authenticate each other, and
       indicates an authentication algorithm and mode.


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     Security Parameter Index (SPI)

       An index identifying a security context between a pair of routers
       among the contexts available in the mobility security
       association.


   The Mobile IPv6 specification includes more security terminology
   related to MIPv6 bindings [11]. Terminology about the MIP
   challenge/response mechanism can be found in [13].


7.  Security Considerations

   This document presents only terminology. There are no security issues
   in this document.


8.  Contributors

   This draft was initially based on the work of

   o Tapio Suihko, VTT Information Technology, Finland
   o Phil Eardley and Dave Wisely, BT, UK
   o Robert Hancock, Siemens/Roke Manor Research, UK,
   o Nikos Georganopoulos, King's College London
   o Markku Kojo and Jukka Manner, University of Helsinki, Finland.

   Since revision -02 of the document draft-manner-seamoby-terms-02.txt,
   Charles Perkins has given as input terminology related to ad-hoc
   networks.

   Thierry Ernst has provided the terminology for discussing mobile
   networks.

   Henrik Levkowetz did a final check of the definitions in revision -05
   and suggested a number of changes.


9.  Acknowledgments

   This work has been partially performed in the framework of the IST
   project IST-2000-28584 MIND, which is partly funded by the European
   Union. Some of the authors would like to acknowledge the help of
   their colleagues in preparing this document.

   Randy Presuhn did a very thorough and helpful review of the -02
   version of the terminology.

   Some definitions of terminology have been adapted from [1], [7], [3],
   [2], [4], [9], [10], [11] and [12].




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10.  Informative References

     [1] Blair, D., Tweedly, A., Thomas, M., Trostle, J. and
         Ramalho, M., "Realtime Mobile IPv6 Framework", Work in
         Progress.

     [2] Calhoun, P., Montenegro, G. and Perkins, C., "Mobile IP
         Regionalized Tunnel Management", Work in Progress.

     [3] Deering, S. and Hinden, R., "Internet Protocol, Version 6
         (IPv6) Specification". RFC 2460, December 1998.

     [4] Dommety, G. (ed.), "Fast Handovers for Mobile IPv6", Work in
         Progress.

     [5] Yavatkar, R., Pendarakis, D. and Guerin, R., "A Framework for
         Policy-based Admission Control". RFC 2753, January 2000.

     [6] Kempf, J., McCann, P. and Roberts, P., "IP Mobility and the
         CDMA Radio Access Network:  Applicability Statement for Soft
         Handoff", Work in Progress.

     [7] Kempf, J. (ed.), "Problem Description:  Reasons For Doing
         Context Transfers Between Nodes in an IP Access Network".
         RFC 3374, September 2002.

     [8] Pandya, R., "Emerging Mobile and Personal Communication
         Systems". IEEE Communications Magazine, 33:44--52, June 1995.

     [9] Ramjee, R., La Porta, T., Thuel, S., Varadhan, K. and
         Salgarelli, L., "IP micro-mobility support using HAWAII", Work
         in Progress.

    [10] Trossen, D., Krishnamurthi, G., Chaskar, H. and Kempf, J.,
         "Issues in candidate access router discovery for seamless
         IP-level handoffs", Work in Progress.

    [11] Johnson, D., Perkins, D. and Arkko, J., "Mobility
         Support in IPv6", Work in Progress.

    [12] Perkins, C. (ed.), "IP Mobility Support for IPv4". RFC 3344,
         August 2002.

    [13] Perkins, C., Calhoun, P. and Bharatia, J., "Mobile
         IPv4 Challenge/Response Extensions (revised)", Work in
         Progress.

    [14] Perkins, C. and Calhoun, P., "AAA Registration Keys for Mobile
         IP", Work in Progress.

    [15] Ernst, T.  and Lach, H., "Network Mobility Support
         Terminology", Work in Progress.

    [16] Moy, J., OSPF Version 2. RFC 2328, April 1998.

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11.  Authors' Addresses

      Jukka Manner
      Department of Computer Science
      University of Helsinki
      P.O. Box 26 (Teollisuuskatu 23)
      FIN-00014 HELSINKI
      Finland

      Voice:  +358-9-191-44210
      Fax:    +358-9-191-44441
      E-Mail: jmanner@cs.helsinki.fi


      Markku Kojo
      Department of Computer Science
      University of Helsinki
      P.O. Box 26 (Teollisuuskatu 23)
      FIN-00014 HELSINKI
      Finland

      Voice:  +358-9-191-44179
      Fax:    +358-9-191-44441
      E-Mail: kojo@cs.helsinki.fi


      Charles E. Perkins
      Communications Systems Lab
      Nokia Research Center
      313 Fairchild Drive
      Mountain View, California 94043
      USA
      Phone:  +1-650 625-2986
      E-Mail:  charliep@iprg.nokia.com
      Fax:  +1 650 625-2502


      Tapio Suihko
      VTT Information Technology
      P.O. Box 1203
      FIN-02044 VTT
      Finland

      Voice:  +358-9-456-6078
      Fax:    +358-9-456-7028
      E-Mail: tapio.suihko@vtt.fi









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      Phil Eardley
      BTexaCT
      Adastral Park
      Martlesham
      Ipswich IP5 3RE
      United Kingdom

      Voice:  +44-1473-645938
      Fax:    +44-1473-646885
      E-Mail: philip.eardley@bt.com


      Dave Wisely
      BTexaCT
      Adastral Park
      Martlesham
      Ipswich IP5 3RE
      United Kingdom

      Voice:  +44-1473-643848
      Fax:    +44-1473-646885
      E-Mail: dave.wisely@bt.com


      Robert Hancock
      Roke Manor Research Ltd
      Romsey, Hants, SO51 0ZN
      United Kingdom

      Voice:  +44-1794-833601
      Fax:    +44-1794-833434
      E-Mail: robert.hancock@roke.co.uk


      Nikos Georganopoulos
      King's College London
      Strand
      London WC2R 2LS
      United Kingdom

      Voice:  +44-20-78482889
      Fax:    +44-20-78482664
      E-Mail: nikolaos.georganopoulos@kcl.ac.uk












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12.  Appendix A - Index of Terms

   AD ............................................................. 13
   AL ............................................................. 12
   AN ............................................................. 13
   ANG ............................................................ 12
   ANR ............................................................ 12
   AP ............................................................. 12
   AR ............................................................. 12
   Access Link .................................................... 12
   Access Network ................................................. 13
   Access Network Gateway ......................................... 12
   Access Network Router .......................................... 12
   Access Point ................................................... 12
   Access Router .................................................. 12
   Active state ................................................... 19
   Administrative Domain .......................................... 13
   Asymmetric link ................................................. 5
   Authorization-enabling extension ............................... 24
   BBM ............................................................ 17
   BU .............................................................. 3
   Bandwidth ....................................................... 3
   Bandwidth utilization ........................................... 3
   Beacon .......................................................... 3
   Binding Update .................................................. 3
   Break-before-make .............................................. 17
   CAR ............................................................ 13
   CAR ............................................................ 21
   Candidate AR ................................................... 21
   Candidate Access Router ........................................ 13
   Capability of an AR ............................................ 21
   Care-of-Address ................................................. 3
   Channel ......................................................... 3
   Channel access protocol ......................................... 3
   Channel capacity ................................................ 3
   Cluster ........................................................ 23
   Cluster head ................................................... 23
   Cluster member ................................................. 23
   CoA ............................................................. 3
   Context ........................................................ 21
   Context transfer ............................................... 21
   Control message ................................................. 4
   Convergence .................................................... 23
   Convergence time ............................................... 23
   Distance vector ................................................. 4
   Dormant state .................................................. 19
   Egress interface ............................................... 11
   Exposed terminal problem ....................................... 18
   FN ............................................................. 11
   Fairness ........................................................ 4
   Fast handover .................................................. 17
   Feature context ................................................ 21
   Fixed Node ..................................................... 11
   Flooding ........................................................ 4

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   Foreign subnet prefix ........................................... 4
   Forwarding node ................................................. 4
   Global mobility ................................................ 22
   Goodput ........................................................ 18
   HA .............................................................. 4
   Handoff ........................................................ 14
   Handover ....................................................... 14
   Handover latency ............................................... 17
   Hidden-terminal problem ........................................ 18
   HoA ............................................................. 4
   Home Address .................................................... 4
   Home Agent ...................................................... 4
   Home subnet prefix .............................................. 5
   Horizontal Handover ............................................ 15
   Host mobility support .......................................... 22
   IP access address ............................................... 5
   IP diversity ................................................... 19
   Inactive state ................................................. 19
   Ingress interface .............................................. 11
   Inter-AN handover .............................................. 14
   Inter-technology handover ...................................... 14
   Interface ....................................................... 5
   Intra-AN handover .............................................. 14
   Intra-AR handover .............................................. 14
   Intra-technology handover ...................................... 14
   L2 Trigger ...................................................... 5
   Laydown ........................................................ 24
   Layer 2 handover ............................................... 14
   Link ............................................................ 5
   Link establishment .............................................. 5
   Link state ...................................................... 6
   Link-layer trigger .............................................. 5
   Link-level acknowledgment ....................................... 6
   Local broadcast ................................................. 6
   Local mobility ................................................. 22
   Local mobility management ...................................... 23
   Location updating .............................................. 20
   Loop-free ....................................................... 6
   MAC ............................................................. 6
   MBB ............................................................ 17
   MH ............................................................. 11
   MN ............................................................. 11
   MNN ............................................................ 12
   MPR ............................................................. 7
   MR ............................................................. 11
   Macro diversity ................................................ 19
   Macro mobility ................................................. 22
   Make-before-break .............................................. 17
   Medium Access Protocol .......................................... 6
   Micro diversity ................................................ 18
   Micro mobility ................................................. 23
   Mobile Host .................................................... 11
   Mobile Network Node ............................................ 12
   Mobile Node .................................................... 11

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   Mobile Router .................................................. 11
   Mobile network ................................................. 11
   Mobile network prefix ........................................... 6
   Mobile-assisted handover ....................................... 16
   Mobile-controlled handover ..................................... 15
   Mobile-initiated handover ...................................... 15
   Mobility factor ................................................. 6
   Mobility security association .................................. 24
   Multipoint relay ................................................ 7
   NAR ............................................................ 13
   Neighbor ........................................................ 7
   Neighborhood .................................................... 7
   Network mobility support ....................................... 22
   Network-assisted handover ...................................... 16
   Network-controlled handover .................................... 15
   Network-initiated handover ..................................... 15
   New Access Router .............................................. 13
   Next hop ........................................................ 7
   PAR ............................................................ 13
   Paging ......................................................... 20
   Paging area .................................................... 20
   Paging area registrations ...................................... 20
   Paging channel ................................................. 20
   Pathloss ....................................................... 18
   Pathloss matrix ................................................ 24
   Payload ......................................................... 7
   Planned handover ............................................... 16
   Prefix .......................................................... 7
   Previous Access Router ......................................... 13
   Pull handover .................................................. 16
   Push handover .................................................. 16
   Radio Cell ..................................................... 12
   Registration key ............................................... 24
   Roaming ........................................................ 13
   Route activation ................................................ 8
   Route entry ..................................................... 7
   Route establishment ............................................. 7
   Route table ..................................................... 7
   Routing proxy ................................................... 8
   Routing-related service ........................................ 21
   SAR ............................................................ 13
   SPI ............................................................ 25
   Scenario ....................................................... 24
   Seamless handover .............................................. 17
   Security Parameter Index ....................................... 25
   Security context ............................................... 24
   Serving Access Router .......................................... 13
   Shannon's Law ................................................... 8
   Signal strength ................................................. 8
   Smooth handover ................................................ 17
   Source route .................................................... 8
   Spatial re-use .................................................. 8
   Subnet .......................................................... 8
   System-wide broadcast ........................................... 8

Manner et al                Expires July 2004                  [Page 31]

Internet-Draft        Mobility Related Terminology         February 2004

   TAR ............................................................ 21
   Target AR ...................................................... 21
   Throughput ..................................................... 17
   Time-slotted dormant mode ...................................... 19
   Topology ........................................................ 9
   Traffic channel ................................................ 20
   Triggered update ................................................ 9
   Unassisted handover ............................................ 16
   Unplanned handover ............................................. 16
   Vertical Handover .............................................. 15


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Manner et al                Expires July 2004                  [Page 32]


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