Mobility Related Terminology
draft-ietf-seamoby-mobility-terminology-06

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
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 all provisions of Section 10 of RFC2026.
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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
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 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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