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Internet Engineering Task Force                                J. Manner
INTERNET DRAFT                                                   M. Kojo
Expires, 8 January 2002                           University of Helsinki
                                                      Charles E. Perkins
                                                   Nokia Research Center
                                                               T. Suihko
                                              VTT Information Technology
                                                              P. Eardley
                                                               D. Wisely
                                                         British Telecom
                                                              R. Hancock
                                             Siemens/Roke Manor Research
                                                       N. Georganopoulos
8 July 2001                                        King's College London

                      Mobility Related Terminology
                   draft-manner-seamoby-terms-02.txt


Status of This Memo

   This document is a submission by the seamoby Working Group of the
   Internet Engineering Task Force (IETF).  Comments should be submitted
   to the seamoby@diameter.org mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

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

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


Abstract

   There is a need for common definitions of terminology for protocols
   related to IP mobility.  This document is intended for use by
   the Seamoby working group, especially in Seamoby WG documents and






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   discussions.  It is hoped that the same terminology can be found
   useful within the manet and mobile-ip working groups.

                                Contents


Status of This Memo                                                    i

Abstract                                                               i

 1. Introduction                                                       1

 2. General Terms                                                      1

 3. Network Components                                                 7

 4. Handover Terminology                                              10
     4.1. Scope of Handover . . . . . . . . . . . . . . . . . . . .   11
     4.2. Handover Control  . . . . . . . . . . . . . . . . . . . .   13
     4.3. Simultaneous connectivity to Access Routers . . . . . . .   14
     4.4. Performance and Functional Aspects  . . . . . . . . . . .   14
     4.5. Micro Diversity, Macro Diversity, and IP Diversity  . . .   16
     4.6. Paging, and Mobile Node States and Modes  . . . . . . . .   16
     4.7. Context Transfer Terminology  . . . . . . . . . . . . . .   18
     4.8. User, Personal and Host Mobility  . . . . . . . . . . . .   18

 5. Specific Terminology for Mobile Ad-Hoc Networking                 19

 6. Acknowledgement                                                   20

Author's Addresses                                                    23

 A. Examples                                                          24
     A.1. Mobility  . . . . . . . . . . . . . . . . . . . . . . . .   25
     A.2. Handovers . . . . . . . . . . . . . . . . . . . . . . . .   26
     A.3. Diversity combining . . . . . . . . . . . . . . . . . . .   27
     A.4. Miscellaneous . . . . . . . . . . . . . . . . . . . . . .   27

 B. Index of Terms                                                    28

Full Copyright Statement                                              28











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1. Introduction

   This document presents terminology to be used for documents and
   discussions within the Seamoby Working Group.  Other working groups
   may also take advantage of this terminology in order to create a
   common terminology for the area of mobility.

   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.

   New to this version of the draft are extensions of the terminology
   to cover Mobile Ad-Hoc Networking (MANET). A separate subsection
   has been added to include terminology specific to work in the MANET
   working group.  It is hoped that concepts useful for other working
   groups concerned with mobile networking (e.g., manet and mobile-ip)
   can be specified using the same or compatible terminology.

   The terminology in this draft is divided into several sections.
   First, there is a list of terms for general use, followed by some
   terms specific for handovers, and finally some terms used within the
   manet working group.


2. General Terms

      Bandwidth

         The total capacity of a link to carry information (typically
         bits).

      Bandwidth Utilization

         The actual amount of information delivered over a link,
         expressed as a percent of the available bandwidth on that link.







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      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.

      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 can communicate only when they have uncontested
         access to the medium, so that there will be no interference.

      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 style of routing protocol 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 equal 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.





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      Forwarding node

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

      Home Address

         An IP address that is assigned for an extended period of time
         to a mobile node.  It remains unchanged regardless of where the
         node is attached to the Internet [10].

      Interface

         A node's attachment to a link.

            DISCUSSION: If an interface can hide two different
            links from the IP layer, should this say "...  to one
            link.  In addition, special interfaces can map more than
            one different link to a single interface (eg.  GSM and
            GPRS)."

      IP access address

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

      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.

         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 access network.  This may involve allocating a channel, or



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         other local wireless resources, possibly including a minimum
         level of service or bandwidth.

      Link State

         A style of routing protocol in which every node within the
         network is expected to maintain information about every link
         within the network topology.

      Link-level Acknowledgement

         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 acknowledgements are often used as part of 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.

      Mobility Factor

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

      Mobility Security Association

         A collection of security contexts, between a pair IP nodes,
         each of which is configured to be applied to mobility-related



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         protocol messages exchanged between them.  Mobility security
         associations MAY be stored separately from the node's IPsec
         Security Policy Database (SPD).

      Neighbor

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

            How shall we say 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.

      Prefix

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

      Route 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 route 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.

      Security Context

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

      Security Parameter Index (SPI)

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

      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 of all the 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.

      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.

      Topology

         A network can be viewed abstractly as a "graph" whose
         "topology" at any point in time is defined by set of "points"
         connected by (possibly directed) "edges."





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      Triggered Update

         An unsolicited route update transmitted by an router along a
         path to a destination.


3. Network Components

   Figure 1 presents a reference architecture which illustrates the
   presented network components which will be defined in this section.
   The figure presents two examples of possible access network (AN)
   topologies.

   We intend to define the concept of the Access Network (AN) which
   supports enhanced mobility.  It is possible that to support
   routing and QoS for mobile nodes, existing routing protocols (i.e.,
   OSPF or other standard IGPs) 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 capability.  We can
   distinguish three types of Access Network components:  Access
   Routers (AR) which handle the last hop to the mobile; 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/ANG/ANR.

      Mobile Node (MN)

         An IP node capable of changing its point of attachment to the
         network.  A Mobile Node may have routing functionality.

      Mobile Host (MH)

         A mobile node that is an end host and not a router.

      Access Link (AL)

         A link between a Mobile Node and an Access Router.  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. The wireless device may be co-located
         with the Mobile Node.







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                    ---        ------                    -------  |
      ---   | <-->  | | -------| AR | -------------------|     |  |
      | |--[]       ---       /------           \       /| ANG |--|
      ---            AP      /                   \     / |     |  |
       MN                   /                     \   /  -------  |
   (+wireless       ___    /                       \ /            |
      device)       | |----                         X             |
                    ---                            / \            |
                     AP                           /   \           |
                                                 /     \ -------  |
                    ---       ------            /       \|     |  |
                    | |-------| AR |---------------------| ANG |--|
                    ---       ------                     |     |  |
                     AP                                  -------  |
                                                                  |
                         Access Network (AN) 1                    |
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  -| -
                         Access Network (AN) 2                    |
                                                                  |
                                                                  |
                    ---        ------                    -------  |
      ---   |<-->   | | -------| AR | -------------------|     |  |
      | |--[]       ---       /------                   /| ANG |--|
      ---            AP      /                         / |     |  |
       MN                   /                         /  -------  |
   (+wireless       ___    /                         /            |
      device)       | |----                         /             |
                    ---                            /              |
                     AP                           /               |
                                                 /                |
                    ---       ------            /                 |
                    | |-------| AR |------------                  |
                    --- \     ------          /                   |
                     AP  \                   /                    |
                          \                 /                     |
                    ---    \  ------       /                      |
                    | |-------| AR |-------                       |
                    ---       ------                              |
                     AP                                           |


                Figure 1: Reference Network Architecture



      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



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         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.

      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.  An Access Router and an Access Network
         Gateway may be the same physical node.  The Access Network
         Gateway looks to the other IP networks like a standard IP
         router.

      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
         Mobile Host.  This is usually the point of departure for the
         Mobile Node as it makes its way towards a new Access Router



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         (then 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.

      Old Access Router (OAR)

         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.

      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.  Same as OAR.

      Candidate Access Router (CAR)

         An Access Router to which the Mobile Node may move next.  A
         handover scheme may support several Candidate Access Routers.


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 of [4].


4.1. Scope of Handover

      I think the definitions of horizontal vs.  vertical handover
      need work before they can be useful; they have been widely
      used to mean something different than is shown here.

      Layer 2 Handover

         When a MN changes APs (or some other aspect of the radio
         channel) connected to the same AR's interface then a layer 2
         handover occurs.  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 IP layer's network interface
         to the mobile.  This causes routing changes internal to the AR.
         The IP address by which the MN is reachable does not change.

      Intra-AN Handover

         When the MN changes ARs inside the same AN then this handover
         occurs.  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.  The
         IP address by which the MN is reachable does not change.  Note
         that the ANG may change for only some of the MN's data flows.

      Inter-AN Handover

         When the MN moves to a new AN then this handover occurs.  This
         requires some sort of host mobility across 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.



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      Intra-technology Handover

         A handover between equipment of the same technology.

      Inter-technology Handover

         A handover between equipment of different technologies.

      Horizontal Handover

         A handover in which the MN's access router does not change
         (from the IP point of view).  A horizontal handover is
         typically also an intra-technology handover but it can be an
         inter-technology handover if the layer 2 device attached to
         the MN can perform a layer 2 handover between two different
         technologies without changing the network interface seen by the
         IP layer.

      Macro mobility

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

      Vertical Handover

         A handover in which the MN's access router changes.  A vertical
         handover is typically an inter-technology handover but it may
         also be an intra- technology handover if the MN has several
         network interfaces of the same type.  That is, after the
         handover, the IP layer communicates with the AN through a
         different network interface.

   The different handover types defined in this section and in section
   4.1 have no direct relationship.  In particular, a MN can do an
   intra-AN handover of any of the types defined above.





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   Note that the horizontal and vertical handovers are not tied to a
   change in the link layer technology.  They define whether, after
   a handover, the IP packet flow goes through the same (horizontal
   handover) or a different (vertical handover) network interface.
   These two handovers do not define whether the AR changes as a result
   of a handover.


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 (MCHO)

         the MN has the primary control over the handover process.

      Network-controlled Handover (NCHO)

         the network has the primary control over the handover process.

   A handover may also be 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 no assistance is provided by the MN or the AR to
         each other.




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

      Backward handover

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

      Forward 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 signalling can be
         done in advance of the MN getting connected to the new AR, e.g.
         building a temporary tunnel from the old AR to the new AR.

      Unplanned handover

         a reactive (unexpected) handover, where no signalling is done
         in advance of the MN's move of the OAR to the new AR.

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


4.3. Simultaneous connectivity to Access Routers

      Make-before-break (MBB)

         During a MBB handover the MN can communicate simultaneously
         with the old and new AR. This should not be confused with "soft
         handover" which relies on macro diversity.

      Break-before-make (BBM)

         During a BBM handover the MN cannot communicate simultaneously
         with the old and the new AR.


4.4. Performance and Functional Aspects

      Handover Latency

         Handover latency is the time difference between when a MN is
         last able to send and/or receive an IP packet by way of the



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         OAR, until when 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 delay, 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.  See [7] for more discussion on the
         topic.

      Throughput

         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
         and protocol overhead from the data packets.

      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.





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      Exposed terminal problem

         The problem whereby a transmitting node prevents


4.5. Micro Diversity, Macro Diversity, and IP Diversity

   Certain air interfaces (e.g.  UTRAN 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.

      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

         the splitting and combining of packets at the IP level.


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'.



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   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 AL 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 MH's Paging
                    Area, but the MH has no SAR and so packets cannot
                    be delivered to the MH without the AN initiating
                    paging.

      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 traffic to the mobile during
                    listening periods.

      Inactive State
                    the MH is in neither the Active nor Dormant State.
                    The host is no longer listening for any packets, not
                    even periodically, and not sending packets.  The
                    host 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.

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

      Paging

         a procedure initiated by the Access Network to move an Idle
         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.



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      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 Idle 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 protocol used on a
         paging channel is usually dictated by the radio link protocol,
         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 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.

   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.


4.7. Context Transfer Terminology

   context, config, state, feature, microflow, context transfer.


4.8. User, Personal and Host Mobility

   Different sorts of mobility management may be required of a mobile
   system.  We can differentiate between user, personal and host
   mobility.




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      User mobility

         refers to the ability of a user to access services from
         different physical hosts.  This usually means, the user has
         an account on these different hosts or that a host does not
         restrict users from using the host to access services.

      Personal mobility

         complements user mobility with the ability to track the user's
         location and provide the user's current location to allow
         sessions to be initiated by and towards the user by anyone on
         any other network.  Personal mobility is also concerned with
         enabling associated security, billing and service subscription
         authorization made between administrative domains.

            Is this distinction really needed for [seamoby]?!

            It needs to be much crisper anyway, and I can't figure
            out how.

      Host mobility

         refers to the function of allowing a mobile host to change
         its point of attachment to the network, without interrupting
         IP packet delivery to/from that host.  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 idle modes of operation, depending
         on whether the host 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'.


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
         propogation of routing information.







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      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.

      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. Acknowledgement

   Part of this work has been performed in the framework of the IST
   project IST-1999-10050 BRAIN, which is partly funded by the European
   Union.  The authors would like to acknowledge the contributions of
   their colleagues from Siemens AG, British Telecommunications PLC,



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   Agora Systems S.A., Ericsson Radio Systems AB, France Telecom R&D,
   INRIA, King's College London, Nokia Corporation, NTT DoCoMo, Sony
   International (Europe) GmbH, and T-Nova Deutsche Telekom Innovations-
   gesellschaft GmbH.

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


References

    [1] D. Blair, A. Tweedly, M. Thomas, J. Trostle, and
        M. Ramalho.  Realtime Mobile IPv6 Framework (work in
        progress).  Internet Draft, Internet Engineering Task Force.
        draft-blair-rt-mobileipv6-seamoby-00.txt, November 2000.

    [2] P. Calhoun, G. Montenegro, and C. Perkins.  Mobile IP
        Regionalized Tunnel Management (work in progress).  Internet
        Draft, Internet Engineering Task Force, November 1998.

    [3] S. Deering and R. Hinden.  Internet Protocol, Version 6 (IPv6)
        Specification.  Request for Comments (Draft Standard) 2460,
        Internet Engineering Task Force, December 1998.

    [4] George Tsirtzis (ed.).  Fast Handovers for Mobile IPv6 (work
        in progress).  draft-ietf-mobileip-fast-mipv6-01.txt, February
        2001.

    [5] Yavatkar et al.  A Framework for Policy-based Admission Control.
        Request for Comments 2753, Internet Engineering Task Force,
        January 2000.

    [6] J. Kempf, P. McCann, and P. Roberts.  IP Mobility and the CDMA
        Radio Access Network:  Applicability Statement for Soft Handoff
        (work in progress).  Internet Draft, Internet Engineering Task
        Force.  draft-kempf-cdma-appl-00.txt, July 2000.

    [7] O.H. et al. Levkowetz.  Problem Description:  Reasons
        For Doing Context Transfers Between Nodes in an IP Access
        Network.  Internet Draft, Internet Engineering Task Force.
        draft-ietf-seamoby-context-transfer-problem-stat-00.txt,
        February 2001.

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

    [9] C. Perkins.  IP Mobility Support.  Request for Comments
        (Proposed Standard) 2002, Internet Engineering Task Force,
        October 1996.



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   [10] R. Ramjee, T. La Porta, S. Thuel, K. Varadhan, and
        L. Salgarelli.  IP micro-mobility support using HAWAII (work in
        progress).  Internet Draft, Internet Engineering Task Force,
        June 1999.
















































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Author's Addresses

   Questions about this document may be directed to:

   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)


A. Examples

   This appendix provides examples for the terminology presented.



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A.1. Mobility

   Host mobility is logically independent of user mobility, although in
   real networks, at least the address management functions are often
   required to initially attach the host to the network.  In addition,
   if the network wishes to determine whether access is authorized (and
   if so, who to charge for it), then this may be tied to the identity
   of the user of the terminal.

   An example of user mobility would be a campus network, where a
   student can log into the campus network from several workstations and
   still retrieve files, emails, and other services automatically.

   Personal mobility support typically amounts to the maintenance and
   update of some sort of address mapping database, such as a SIP server
   or DNS server; it is also possible for the personal mobility support
   function to take a part in forwarding control messages between end
   user and correspondent rather than simply acting as a database.  SIP
   is a protocol for session initiation in IP networks.  It includes
   registration procedures which partially support personal mobility
   (namely, the ability for the network to route a session towards a
   user at a local IP address).

   Personal mobility has been defined in [8] as "the ability of
   end users to originate and receive calls and access subscribed
   telecommunication services on any terminal in any location, and the
   ability of the network to identify end users as they move.  Personal
   mobility is based on the use of a unique personal identity (i.e.,
   personal number)."

   Roaming, in its original (GSM) sense, is the ability of a user to
   connect to the networks owned by operators other than the one having
   a direct formal relationship with the user.  More recently (e.g.,
   in data networks and UMTS) it also refers providing user-customized
   services in foreign networks (e.g., QoS profiles for specific
   applications).

   HAWAII, Cellular IP, Regional Registration and EMA are examples of
   micro mobility schemes, with the assumption that Mobile IP is used
   for macro mobility.

   WLAN technologies such as IEEE 802.11 typically support aspects of

   user and host mobility in a minimal way.  User mobility procedures
   (for access control and so on) are defined only over the air
   interface (and the way these are handled within the network is not
   further defined).





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   PLMNs (GSM/UMTS) typically have extensive support for both user
   and host mobility.  Complete sets of protocols (both over the air
   and on the network side) are provided for user mobility, including
   customized service provision.  Handover for host mobility is also
   supported, both within access networks, and also within the GSM/UMTS
   core network for mobility between access networks of the same
   operator.

      Citations needed for UMTS, UTRAN, W-CDMA, etc.


A.2. Handovers

   A hard handover is required where a MN is not able to receive or send
   traffic from/to two APs simultaneously.  In order to move the traffic
   channel from the old to the new access point the MN abruptly changes
   the frequency/timeslot/code on which it is transmitting and listening
   to new values associated with a new access point.

      Need definition for hard handover.  Probably related to MBB.

      Need definition for "context-aware" handover.

      Need definition for "node B".  Replace by "basestation"
      here...

   A good example of hard handover is GSM where the mobile listens for
   new base stations, reports back to the network the signal strength
   and identity of the new base station(s) heard.  When the old base
   station decides that a handover is required it instructs the new
   base station to set up resources and, when confirmed, instructs the
   mobile to switch to a new frequency and time slot.  This sort of hand
   over is called hard, mobile assisted, network initiated and backward
   (meaning that the old base station is responsible for handling the
   change-over).

   In a TDMA system, such as GSM, the hard hand over is delayed until
   the mobile has moved well within the coverage of the new base
   station.  If the handover threshold was set to the point where the
   new base station signal exceeded the old then there would be a very
   large number of handovers as the mobile moved through the region
   between the cells and radio signals fluctuated, this would create
   a large signalling traffic.  To avoid this a large hysteresis is
   set, i.e.  the new base station must be (say) 10dB stronger for
   handover to occur.  If the same was done in W-CDMA then the mobile
   would be transmitting a powerful signal to the old base station and
   creating interference for other users, since in CDMA everyone else's
   transmissions are seen as noise, thus reducing capacity.  To avoid
   this soft handover is used, giving an estimated doubling in capacity.



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   Support for soft handover (in a single mode terminal) is
   characteristic of radio interfaces which also require macro diversity
   for interference limitation but the two concepts are logically
   independent.

   A good example of soft handover is the UTRAN FDD mode.  W-CDMA
   is particularly suited to soft handover because of the design
   of the receivers and transmitters:  typically a rake receiver
   will be used to overcome the multi-path fading of the wide-band
   channel.  Rake receivers have a number of so-called fingers, each
   effectively separate detectors, that are tuned to the same signal
   (e.g.  spreading code) but delayed by different times.  When the
   delay times are correctly adjusted and the various components
   properly combined (this is micro diversity combining) the effect of
   multi-path fading is removed.  The rake receiver can also be used to
   detect signals from different transmitters by tuning the fingers to
   different spreading codes.  Soft handover is used in UTRAN FDD mode
   to also increase capacity.

   Every handover can be seen as a context-aware Handover.  In PLMNs the
   context to be fulfilled is that the new AP can accommodate the new
   mobile, for example, the new GSM cell can serve the incoming phone.
   Lately, the notion of Context-aware Handovers has been enlarged
   by, for example, QoS-aware handovers, meaning that the handover is
   governed by the need to support the QoS-context of the moving mobile
   in order to keep the service level assured to the user of the MN.


A.3. Diversity combining

   In the case of UMTS it is radio frames that are duplicated at some
   point in the network (the serving RNC) and sent to a number of
   basestations and, possibly via other (drift) RNCs.  The combining
   that takes place at the serving RNC in the uplink direction is
   typically based on some simple quality comparison of the various
   received frames, which implies that the various copies of these
   frames must contain identical upper layer information.  The serving
   RNC also has to do buffering data frames to take account of the
   differing time of flight from each basestation to the RNC.


A.4. Miscellaneous

   In a GPRS/UMTS system the Access Network Gateway node could be
   the GGSN component.  The ANG can provide support for mobility of
   hosts, admission control, policy enforcement, and Foreign Agent
   functionality [9].





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   When presenting a mobile network topology, APs and ARs are usually
   pictured as separate components (see Figure 1.  This is the case with
   GSM/GPRS/UMTS presentations, for example.  From the IP point of view
   APs are not directly visible.  An AP should only be seen from the
   MN's or AR's IP layer as a link (interface) connecting MNs to the AR.

   When the mobile moves through the network, depending on the mobility
   mechanism, the OAR will forward packets destined to the old MNs
   address to the SAR which currently serves the MN. At the same time
   the handover mechanism may be studying CARs to find the best NAR
   where the MN will be handed next.


B. Index of Terms

   <TBA when terminology finalized>


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