Internet Engineering Task Force J. Manner (ed.) Internet-Draft M. Kojo (ed.) Expires:
May,September, 2003 University of Helsinki November, 2002March, 2003 Mobility Related Terminology <draft-ietf-seamoby-mobility-terminology-01.txt><draft-ietf-seamoby-mobility-terminology-02.txt> Status of this Memo This document is a working group document of the Seamoby Working Group. 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. This Internet-Draft will expire in May,September, 2003. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract There is a need for common definitions of terminology in the work to be done around IP mobility. This memo defines terms for mobility related terminology. It is intended as a living document for use by the Seamoby Working Group in Seamoby drafts and in WG discussions, but not limited in scope to the terms needed by the Seamoby Working Group. Other working groups dealing with mobility may take advantage of this terminology. Changes from -01 - Added security terminology - Miscellaneous small refinements of definitions Changes from -00 - Added definition for Routing Proxy - Added basic terminology about mobile networks - Added Link-Layer Trigger from FMIPv6 - Edited the CAR terminology section - Added definitions for MPR, CoA, BU - Changed the definition of Home Address - Added a mobile network into Figure 1 - Edited the Network Components section TODO's The draft-irtf-mm-taxonomy-00.txt (expired) includes several good additional candidate definitions, eg.: o Mobility identities o Transports o Others? We also need someone to write the Security Terminology section.Table of Contents 1 Introduction ................................................. 2 2 General Terms ................................................ 3 3 Mobile Access Network Components .............................Networks and Mobile Networks ................... 8 4 Handover Terminology ......................................... 1112 4.1 Scope of Handover .......................................... 12 4.2 Handover Control ........................................... 1314 4.3 Simultaneous connectivity to Access Routers ................ 1415 4.4 Performance and Functional Aspects ......................... 15 4.5 Micro Diversity, Macro Diversity, and IP Diversity ......... 16 4.6 Paging, and Mobile Node States and Modes ................... 17 4.7 Context Transfer ........................................... 1819 4.8 Candidate Access Router Discovery .......................... 19 4.9 User, Personal and Host Mobility ........................... 1920 5 Specific Terminology for Mobile Ad-Hoc Networking ............ 21 6 Mobile Networks .............................................. 22 7Security-related Terminology ................................. 22 87 Security Considerations ...................................... 23 98 Contributors ................................................. 23 109 Acknowledgement ............................................. 23 11.............................................. 24 10 References .................................................. 23 1224 11 Author's Addresses .......................................... 25 1326 12 Appendix A - Examples ....................................... 27 1428 13 Appendix B - Index of Terms ................................. 2930 1. Introduction This document presents terminology to be used for documents and discussions within the Seamoby Working Group. Other mobility related working groups could like 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. 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. 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. Among the multiple care-of addresses that a mobile node may have at any given time (e.g., with different subnet prefixes), the one registered with the mobile node's home agent is called its "primary" care-of address . 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. Forwarding node A node which performs the function of forwarding datagrams from one of its neighbors to another. Home Address 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 . Interface A node's 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 accesslocal 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. 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 accesslocal 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 L2 that informs L3 of the detailed events involved in handover sequencing at L2. L2 triggers are not specific to any particular L2, but rather represent generalizations of L2 information available from a wide variety of L2 protocols . 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. 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 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. 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. Route Activation The process of putting a route into use after it has been determined. Routing Proxy A node that routes packets by overlays, eg. 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. 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." Triggered Update An unsolicited route update transmitted by an router along a path to a destination. 3. Mobile Access Network ComponentsNetworks and Mobile Networks In order to support host mobility a set of nodes towards the network edge oftenmay need to have specific functions. Such a set of nodes form a mobile access network that may or may not be part of the global Internet. The Figure 1 presents two examples of such access network (AN)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 (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, 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/ANG/ANR. 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). A more thorough discussion on 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 MANETs. --- ------ ------- | --- | <--> | | -------| AR | -------------------| | | | |-- --- /------ \ /| ANG |--| --- AP / \ / | | | MNMH / \ / ------- | (+wireless ___ / ------- | device) | |---- | ANR | | --- ------- | AP / \ | / \ ------- | --- ------ / \| | | | |-------| AR |---------------------| ANG |--| --- ------ | | | AP ------- | | Access Network (AN) 1 | - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -| Access Network (AN) 2 | | | --- ------ ------- | --- |<--> | | -------| AR | -------------------| | | | |-- --- /------ /| ANG |--| --- AP / / | | | MNMH / / ------- | (+wireless ___ / / | device) | |---- / | --- / | AP / | / | --- ------ ------- | --- | I<--> | |-------| AR |---------| ANR | | | |--| ------ --- \ ------ ------- | --- |--| MR | AP \ / | MNN | ------ \ / | | --- \ ------ / | --- | | |-------| AR |------- | | |--| --- ------ | --- | AP | MNN Figure 1: Reference Network Architecture Mobile Node (MN) An IP node capable of changing its point of attachment to the network. A Mobile Node may or may not have routingforwarding functionality. Mobile Host (MH) A mobile node that is an end host and not a router. Access Link (AL)A last-hop link between aMobile Nodehost is capable of sending and an Access Router. Thatreceiving packets, that is, being a facilitysource or medium over which an Access Point and thedestination of traffic, but not a forwarder of it. Mobile Node can communicate at the link layer, i.e., the layer immediately below IP. Access Point (AP)Network An Access Point isentire network, moving as a layer 2 deviceunit, which dynamically changes its point of attachment to the Internet and thus its reachability in the topology. The mobile network is connected to the global Internet via one or more Access Routers and offersmobile router(s). The internal configuration of the wirelessmobile network is assumed to be relatively stable with respect to the MR and is not a matter of concern. Mobile Router (MR) A router which is capable of changing its point of attachment to IP networks, moving from one link to another link. A mobile router is capable of forwarding packets between two or more interfaces, and possibly running a dynamic routing protocol modifying the state by which to do packet forwarding. Mobile Network Node (MNN) Any node (host or router) located within a mobile network, either permanently or temporarily. A Mobile Network Node may be a Mobile Router. Access Link (AL) A last-hop 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. 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. 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. 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.  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 (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 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. 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 . 4.1. Scope of Handover Note: the definitions of horizontal and vertical handover are different than the ones commonly used today. These definitions try to look at the handover from the IP layer's point of view; the IP layer works with network interfaces, rather than specific technologies used by those interfaces. 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 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 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. 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 ) to the MN. 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 mobile node's network interface does not change (from the IP point of view); the MN communicates with the access networkrouter via the same network interface before and after the handover. A horizontal handover is typically also an intra- technology handover but it can be an inter-technology handover if the MN can do a layer 2 handover between two different technologies without changing the network interface seen by the IP layer. Vertical Handover In a vertical handover the mobile node's network interface to the Access Networkaccess network 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 Access Networkaccess network 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. 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 where no assistance is provided by the MN or the AR to each other. 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 OAR, until when the MN is able to send and/or receive an IP packet through the NAR. Adapted from . 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  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. Exposed terminal problem The problem whereby a transmitting node prevents another node from transmitting although it could have safely transmitted to anyone else but that node. 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 . 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 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. 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 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. 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. 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 mobile host from scratch. Feature context The collection of information representing the context for a given feature. The full context associated with a mobile host 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 mobile host. Initially establishing routing-related services usually requires a protocol exchange with the mobile host. 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 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 to. 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. 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. 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. 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'. Two subcategories of "Host mobility" can be identified: 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 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. 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 itself 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 propogation 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. 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. Mobile NetworksSecurity-related Terminology This section presents a few basic terms about mobile networks. A more thorough discussion onincludes terminology commonly used around mobile networks can be found in the working group documentsand wireless networking. Only a mobility-related subset of the NEMO Working Group . Mobile Network Anentire network, moving as a unit,security terminology is presented. Authorization-enabling extension An authentication which dynamically changes its point of attachmentmakes a (registration) message acceptable to the Internet and thus its reachability in the topology. The mobile network is connected toultimate recipient of the global Internet via one or more mobile router(s). The internal configuration of the mobile network is assumed to be relatively stable with respect to the MR and is not a matter of concern. Mobile Router (MR) A router which is capable of changing its point of attachment to IP networks, moving from one link to another link. A mobile router is capable of forwarding packets between two or more interfaces, and possibly running a dynamic routing protocol modifying the state by which to do packet forwarding. Mobile Network Node (MNN) Any host or router located within the mobile network, either permanently or temporarily. A Mobile Network Node may be a Mobile Router. 7. Security-related Terminology <This section will include terminology commonly used around mobile and wireless networking. Only a subset of the entire security terminology is actually needed.> The following were in the previous versions of this document:registration message. An authorization-enabling extension must contain an SPI . Mobility Security Association A collection of security contexts, between a pair IP nodes, eachof nodes, which is configured tomay 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 MAYmay be stored separately from the node's IPsec Security Policy Database (SPD).(SPD) . Registration Key A key used as the basis of a 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 . 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. 8.Stale challenge Any challenge that has been used by the mobile node in a Registration Request message and processed by the Foreign Agent by relaying or generating The Foreign Agent may not be able to keep records for all previously used challenges . Unknown challenge Any challenge from a particular mobile node that the foreign agent has no record of having put either into one of its recent Agent Advertisements or into a registration reply message to that mobile node . Unused challenge A challenge that has not been already accepted by the Foreign Agent challenge in a corresponding Registration Reply message -- i.e., a challenge that is neither unknown nor previously used . The Mobile IPv6 specification includes more security terminology related to MIPv6 bindings [RFC3xxx]. 7. Security Considerations This document presents only terminology. There are no security issues in this document. 9.8. 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. 10.9. Acknowledgement 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. The authors would like to acknowledge the help of their colleagues in preparing this document. Some definitions of terminology have been adapted from , , , , , , , ,  and . 11.10. References  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.  P. Calhoun, G. Montenegro, and C. Perkins. Mobile IP Regionalized Tunnel Management (work in progress). Internet Draft, Internet Engineering Task Force, November 1998.  S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6) Specification. Request for Comments (Draft Standard) 2460, Internet Engineering Task Force, December 1998.  G. Dommety (ed.). Fast Handovers for Mobile IPv6 (work in progress). draft-ietf-mobileip-fast-mipv6-05.txt, September, 2002.  Yavatkar et al. A Framework for Policy-based Admission Control. Request for Comments 2753, Internet Engineering Task Force, January 2000.  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, draft-kempf-cdma-appl-00.txt, July 2000.  J. Kempf (ed.). Problem Description: Reasons For Doing Context Transfers Between Nodes in an IP Access Network. RFC 3374, Internet Engineering Task Force, September, 2002.  R. Pandya. Emerging Mobile and Personal Communication Systems. IEEE Communications Magazine, 33:44--52, June 1995.  C. Perkins. IP Mobility Support. Request for Comments (Proposed Standard) 2002, Internet Engineering Task Force, October 1996.  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.  D. Trossen, G. Krishnamurthi, H. Chaskar, J. Kempf, "Issues in candidate access router discovery for seamless IP-level handoffs. Internet Draft (work in progress), draft-ietf-seamoby-cardiscovery-issues-04.txt, October 2002.  David B. Johnson, Charles E. Perkins, Jari Arkko, "Mobility Support in IPv6". Internet Draft, draft-ietf-mobileip-ipv6-18.txt (work in progress), June 2002.  Thierry Ernst and Hong-Yon Lach, "Network Mobility Support Terminology". Internet Draft, draft-ernst-monet-terminology-01.txt (work in progress), July 2002. 12. Charles Perkins (ed.), "IP Mobility Support for IPv4". Request for Comments 3344, August 2002.  Charles Perkins, Pat Calhoun, Jayshree Bharatia, "Mobile IPv4 Challenge/Response Extensions (revised)". Internet Draft, December, 2002 (draft-ietf-mobileip-rfc3012bis-04.txt).  Charles Perkins, Pat Calhoun, "AAA Registration Keys for Mobile IP". Internet Draft, October 2002, (draft-ietf-mobileip-aaa-key-10.txt). 11. 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: email@example.com 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: firstname.lastname@example.org Charles E. Perkins Communications Systems Lab Nokia Research Center 313 Fairchild Drive Mountain View, California 94043 USA Phone: +1-650 625-2986 E-Mail: email@example.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: firstname.lastname@example.org Phil Eardley BTexaCT Adastral Park Martlesham Ipswich IP5 3RE United Kingdom Voice: +44-1473-645938 Fax: +44-1473-646885 E-Mail: email@example.com Dave Wisely BTexaCT Adastral Park Martlesham Ipswich IP5 3RE United Kingdom Voice: +44-1473-643848 Fax: +44-1473-646885 E-Mail: firstname.lastname@example.org Robert Hancock Roke Manor Research Ltd Romsey, Hants, SO51 0ZN United Kingdom Voice: +44-1794-833601 Fax: +44-1794-833434 E-Mail: email@example.com Nikos Georganopoulos King's College London Strand London WC2R 2LS United Kingdom Voice: +44-20-78482889 Fax: +44-20-78482664 E-Mail: firstname.lastname@example.org) 13.12. Appendix A - Examples This appendix provides examples for the terminology presented. 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  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). 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. 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. Thus, the handover is a break-before-make handover. 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. 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 . 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. 14.13. Appendix B - Index of Terms <TBA when terminology finalized> Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. 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