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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 2460 (ref. '3') (Obsoleted by RFC 8200) -- Obsolete informational reference (is this intentional?): RFC 3344 (ref. '12') (Obsoleted by RFC 5944) Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Internet Engineering Task Force J. Manner (ed.) 2 Internet-Draft M. Kojo (ed.) 3 Expires: May, 2004 University of Helsinki 4 November, 2003 6 Mobility Related Terminology 7 9 Status of this Memo 11 This document is a working group document of the Seamoby Working 12 Group. 14 Distribution of this memo is unlimited. 16 This document is an Internet-Draft and is in full conformance with 17 all provisions of Section 10 of RFC2026. Internet-Drafts are working 18 documents of the Internet Engineering Task Force (IETF), its areas, 19 and its working groups. Note that other groups may also distribute 20 working documents as Internet-Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire in May, 2004. 35 Copyright Notice 37 Copyright (C) The Internet Society (2000). All Rights Reserved. 39 Abstract 41 There is a need for common definitions of terminology in the work to 42 be done around IP mobility. This memo defines terms for mobility 43 related terminology. It is intended as a living document for use by 44 the Seamoby Working Group in Seamoby drafts and in WG discussions, 45 but not limited in scope to the terms needed by the Seamoby Working 46 Group. Other working groups dealing with mobility may take advantage 47 of this terminology. 49 Table of Contents 51 1 Introduction ................................................. 2 52 2 General Terms ................................................ 3 53 3 Mobile Access Networks and Mobile Networks ................... 8 54 4 Handover Terminology ......................................... 13 55 4.1 Scope of Handover .......................................... 14 56 4.2 Handover Control ........................................... 15 57 4.3 Simultaneous connectivity to Access Routers ................ 17 58 4.4 Performance and Functional Aspects ......................... 17 59 4.5 Micro Diversity, Macro Diversity, and IP Diversity ......... 18 60 4.6 Paging, and Mobile Node States and Modes ................... 19 61 4.7 Context Transfer ........................................... 21 62 4.8 Candidate Access Router Discovery .......................... 21 63 4.9 Types of Mobility .......................................... 22 64 5 Specific Terminology for Mobile Ad-Hoc Networking ............ 23 65 6 Security-related Terminology ................................. 24 66 7 Security Considerations ...................................... 25 67 8 Contributors ................................................. 25 68 9 Change log ................................................... 26 69 10 Acknowledgement ............................................. 26 70 11 Informative References ...................................... 27 71 12 Authors' Addresses .......................................... 28 72 13 Appendix A - Examples ....................................... 30 73 14 Appendix B - Index of Terms ................................. 33 75 1. Introduction 77 This document presents terminology to be used for documents and 78 discussions within the Seamoby Working Group. Other mobility related 79 working groups could take advantage of this terminology, in order to 80 create a common terminology for the area of mobility in IP networks. 81 These groups would include MIP, MANET, ROHC and NEMO. 83 Some terms and their definitions that are not directly related to the 84 IP world are included for the purpose of harmonizing the terminology. 85 For example, 'Access Point' and 'base station' refer to the same 86 component, from the point of view of IP, but 'Access Router' has a 87 very different meaning. The presented terminology may also, it is 88 hoped, be adequate to cover mobile ad-hoc networks. 90 The proposed terminology is not meant to assert any new terminology. 91 Rather the authors would welcome discussion on more exact definitions 92 as well as missing or unnecessary terms. This work is a 93 collaborative enterprise between people from many different 94 engineering backgrounds and so already presents a first step in 95 harmonizing the terminology. 97 The terminology in this draft is divided into several sections. 98 First, there is a list of terms for general use and mobile access 99 networks followed by terms related to handovers, and finally some 100 terms used within the MANET and NEMO working group. 102 2. General Terms 104 Bandwidth 106 The total capacity of a link to carry information (typically 107 bits) per unit time. 109 Bandwidth utilization 111 The actual rate of information transfer achieved over a link, 112 expressed as a percent of the available bandwidth on that link. 114 Beacon 116 A control message broadcast by a node (especially, a base 117 station) informing all the other nodes in its neighborhood of the 118 continuing presence of the broadcasting node, possibly along with 119 additional status or configuration information. 121 Binding Update (BU) 123 A message indicating a mobile node's current mobility binding, 124 and in particular its care-of address. 126 Care-of-Address (CoA) 128 An IP address associated with a mobile node while visiting a 129 foreign link; the subnet prefix of this IP address is a foreign 130 subnet prefix. Among the multiple care-of addresses that a 131 mobile node may have at any given time (e.g., with different 132 subnet prefixes), the one registered with the mobile node's home 133 agent is called its "primary" care-of address [11]. 135 Channel 137 A subdivision of the physical medium allowing possibly shared 138 independent uses of the medium. Channels may be made available 139 by subdividing the medium into distinct time slots, or distinct 140 spectral bands, or decorrelated coding sequences. 142 Channel access protocol 144 A protocol for mediating access to, and possibly allocation of, 145 the various channels available within the physical communications 146 medium. Nodes participating in the channel access protocol agree 147 to communicate only when they have uncontested access to one of 148 the channels, so that there will be no interference. 150 Control message 152 Information passed between two or more network nodes for 153 maintaining protocol state, which may be unrelated to any 154 specific application. 156 Distance vector 158 A style of routing protocol in which, for each desired 159 destination, a node maintains information about the distance to 160 that destination, and a vector (next hop) towards that 161 destination. 163 Fairness 165 A property of channel access protocols whereby a medium is made 166 fairly available to all eligible nodes on the link. Fairness 167 does not strictly imply equality, especially in cases where nodes 168 are given link access according to unequal priority or 169 classification. 171 Flooding 173 The process of delivering data or control messages to every node 174 within the network under consideration. 176 Foreign subnet prefix 178 A bit string that consists of some number of initial bits of an 179 IP address which identifies a node's foreign link within the 180 Internet topology. 182 Forwarding node 184 A node which performs the function of forwarding datagrams from 185 one of its neighbors to another. 187 Home Address (HoA) 189 An IP address assigned to a mobile node, used as the permanent 190 address of the mobile node. This address is within the mobile 191 node's home link. Standard IP routing mechanisms will deliver 192 packets destined for a mobile node's home address to its home 193 link [11]. 195 Home subnet prefix 197 A bit string that consists of some number of initial bits of an 198 IP address which identifies a node's home link within the 199 Internet topology (i.e. the IP subnet prefix corresponding to the 200 mobile node's home address, as defined in [11]). 202 Interface 204 A node's attachment to a link. 206 IP access address 208 An IP address (often dynamically allocated) which a node uses to 209 designate its current point of attachment to the local network. 211 The IP access address is typically to be distinguished from the 212 mobile node's home address; in fact, while visiting a foreign 213 network the former may be considered unsuitable for use as an 214 end-point address by any but the most short-lived applications. 215 Instead, the IP access address is typically used as the care-of 216 address of the node. 218 Link 220 A communication facility or physical medium that can sustain data 221 communications between multiple network nodes, such as an 222 Ethernet (simple or bridged). A link is the layer immediately 223 below IP. In IP networks, a link usually connects two IP-based 224 nodes, for example, a mobile node and an access router (see below 225 the term "access link"). 227 Asymmetric link 229 A link with transmission characteristics which are different 230 depending upon the relative position or design characteristics of 231 the transmitter and the receiver of data on the link. For 232 instance, the range of one transmitter may be much higher than 233 the range of another transmitter on the same medium. 235 Link establishment 237 The process of establishing a link between the mobile node and 238 the local network. This may involve allocating a channel, or 239 other local wireless resources, possibly including a minimum 240 level of service or bandwidth. 242 Link-layer trigger (L2 Trigger) 244 Information from L2 that informs L3 of the detailed events 245 involved in handover sequencing at L2. L2 triggers are not 246 specific to any particular L2, but rather represent 247 generalizations of L2 information available from a wide variety 248 of L2 protocols [4]. 250 Link state 252 A style of routing protocol in which every node within the 253 network is expected to maintain information about every link 254 within the network topology. 256 Link-level acknowledgement 258 A protocol strategy, typically employed over wireless media, 259 requiring neighbors to acknowledge receipt of packets (typically 260 unicast only) from the transmitter. Such strategies aim to avoid 261 packet loss or delay resulting from lack of, or unwanted 262 characteristics of, higher level protocols. 264 Link-layer acknowledgements are often used as part of ARQ 265 algorithms for increasing link reliability. 267 Local broadcast 269 The delivery of data to every node within range of the 270 transmitter. 272 Loop-free 274 A property of routing protocols whereby the path taken by a data 275 packet from source to destination never transits the same 276 intermediate node twice before arrival at the destination. 278 Medium Access Protocol (MAC) 280 A protocol for mediating access to, and possibly allocation of, 281 the physical communications medium. Nodes participating in the 282 medium access protocol can communicate only when they have 283 uncontested access to the medium, so that there will be no 284 interference. When the physical medium is a radio channel, the 285 MAC is the same as the Channel Access Protocol. 287 Mobile network prefix 289 A bit string that consists of some number of initial bits of an 290 IP address which identifies the entire mobile network within the 291 Internet topology. All nodes in a mobile network necessarily have 292 an address named after this prefix. 294 Mobility factor 296 The relative frequency of node movement, compared to the 297 frequency of application initiation. 299 Multipoint relay (MPR) 301 A node which is selected by its one-hop neighbor to re-transmit 302 all broadcast messages that it receives. The message must be new 303 and the time-to-live field of the message must be greater than 304 one. Multipoint relaying is a technique to reduce the number of 305 redundant re-transmissions while diffusing a broadcast message in 306 the network. 308 Neighbor 310 A "neighbor" is any other node to which data may be propagated 311 directly over the communications medium without relying the 312 assistance of any other forwarding node. 314 Neighborhood 316 All the nodes which can receive data on the same link from one 317 node whenever it transmits data. 319 Next hop 321 A neighbor which has been selected to forward packets along the 322 way to a particular destination. 324 Payload 326 The actual data within a packet, not including network protocol 327 headers which were not inserted by an application. Note that 328 payloads are different between layers: user data is the payload 329 of TCP, which are the payload of IP, which three are the payload 330 of link layer protocols etc. Thus, it is important to identify 331 the scope when talking about payloads. 333 Prefix 335 A bit string that consists of some number of initial bits of an 336 address. 338 Route table 340 The table where forwarding nodes keep information (including next 341 hop) for various destinations. 343 Route entry 345 An entry for a specific destination (unicast or multicast) in the 346 route table. 348 Route establishment 350 The process of determining a route between a source and a 351 destination. 353 Route activation 355 The process of putting a route into use after it has been 356 determined. 358 Routing proxy 360 A node that routes packets by overlays, eg. by tunneling, between 361 communicating partners. The Home Agent and Foreign Agent are 362 examples of routing proxies, in that they receive packets 363 destined for the mobile node and tunnel them to the current 364 address of the mobile node. 366 Signal strength 368 The detectable power of the signal carrying the data bits, as 369 seen by the receiver of the signal. 371 Source route 373 A source route from node A to node B is an ordered list of IP 374 addresses, starting with the IP address of node A and ending with 375 the IP address of the node B. Between A and B, the source route 376 includes an ordered list intermediate hops between A and B, as 377 well as the interface index of the interface through which the 378 packet should be transmitted to reach the next hop. The list of 379 intermediate hops might not include all visited nodes, some hops 380 might be omitted for a reason or another. 382 Spatial re-use 384 Simultaneous use of channels with identical or close physical 385 characteristics, but located spatially far enough apart to avoid 386 interference (i.e., co-channel interference) 388 System-wide broadcast 390 Same as flooding, but used in contrast to local broadcast. 392 Subnet 394 A subnet is a logical group of connected network nodes. In IP 395 networks, nodes in a subnet share a common network mask (in IPV4) 396 or a network prefix (in IPv6). 398 Topology 400 A network can be viewed abstractly as a "graph" whose "topology" 401 at any point in time is defined by set of "points" connected by 402 (possibly directed) "edges." 404 Triggered update 406 An unsolicited route update transmitted by an router along a path 407 to a destination. 409 3. Mobile Access Networks and Mobile Networks 411 In order to support host mobility a set of nodes towards the network 412 edge may need to have specific functions. Such a set of nodes forms a 413 mobile access network that may or may not be part of the global 414 Internet. Figure 1 presents two examples of such access network 415 topologies. The figure depicts a reference architecture which 416 illustrates an IP network with components defined in this section. 418 We intend to define the concept of the Access Network (AN) which may 419 also support enhanced mobility. It is possible that to support 420 routing and QoS for mobile nodes, existing routing protocols (e.g., 421 OSPF or other standard IGPs) may not be appropriate to maintain 422 forwarding information for these mobile nodes as they change their 423 points of attachment to the Access Network. These new functions are 424 implemented in routers with additional capability. We can distinguish 425 three types of Access Network components: Access Routers (AR) which 426 handle the last hop to the mobile, typically over a wireless link; 427 Access Network Gateways (ANG) which form the boundary on the fixed 428 network side and shield the fixed network from the specialized 429 routing protocols; and (optionally) other internal Access Network 430 Routers which may also be needed in some cases to support the 431 protocols. The Access Network consists of the equipment needed to 432 support this specialized routing, i.e. AR or ANG. AR and ANG may be 433 the same physical nodes. 435 In addition, we present a few basic terms on mobile networks, that 436 is, mobile network, mobile router (MR), and mobile network node 437 (MNN). More terminology for discussing mobile networks can be found 438 in [15]. A more thorough discussion on mobile networks can be found 439 in the working group documents of the NEMO Working Group. 441 Note: this reference architecture is not well suited for people 442 dealing with MANETs. 444 | 445 --- ------ ------- | 446 --- | <--> | | -------| AR | -------------------| | | 447 | |--[] --- /------ \ /| ANG |--| 448 --- AP / \ / | | | 449 MH / \ / ------- | 450 (+wireless ___ / ------- | 451 device) | |---- | ANR | | 452 --- ------- | 453 AP / \ | 454 / \ ------- | 455 --- ------ / \| | | 456 | |-------| AR |---------------------| ANG |--| 457 --- ------ | | | 458 AP ------- | 459 | 460 Access Network (AN) 1 | 461 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -| 462 Access Network (AN) 2 | 463 | 464 | 465 --- ------ ------- | 466 --- | <--> | | -------| AR | -------------------| | | 467 | |--[] --- /------ /| ANG |--| 468 --- AP / / | | | 469 MH / / ------- | 470 (+wireless ___ / / | 471 device) | |---- / | 472 --- / | 473 AP / | 474 / | 475 | ------ --- ------ ------- | 476 --- |- i MR e <->| |-------| AR |---------| ANR | | 477 | |--| ------ --- \ ------ ------- | 478 --- | AP \ / | 479 MNN | \ / | 480 | --- \ ------ / | 481 --- | | |-------| AR |------- | 482 | |--| --- ------ | 483 --- | AP | 484 MNN 'i': MR ingress interface | 485 'e': MR egress interface | 486 | 488 Figure 1: Reference Network Architecture 490 Mobile Node (MN) 492 An IP node capable of changing its point of attachment to the 493 network. A Mobile Node may either be a Mobile Host (no forwarding 494 functionality) or a Mobile Router (forwarding functionality). 496 Mobile Host (MH) 498 A mobile node that is an end host and not a router. A Mobile Host 499 is capable of sending and receiving packets, that is, being a 500 source or destination of traffic, but not a forwarder of it. 502 Fixed Node (FN) 504 A node, either a host or a router, unable to change its point of 505 attachment to the network and its IP address without breaking 506 open sessions. 508 Mobile network 510 An entire network, moving as a unit, which dynamically changes 511 its point of attachment to the Internet and thus its reachability 512 in the topology. The mobile network is composed by one or more 513 IP-subnets and is connected to the global Internet via one or 514 more Mobile Routers (MR). The internal configuration of the 515 mobile network is assumed to be relatively stable with respect to 516 the MR. 518 Mobile Router (MR) 520 A router capable of changing its point of attachment to the 521 network, moving from one link to another link. The MR is capable 522 of forwarding packets between two or more interfaces, and 523 possibly running a dynamic routing protocol modifying the state 524 by which to do packet forwarding. 526 A MR acting as a gateway between an entire mobile network and the 527 rest of the Internet has one or more egress interface(s) and one 528 or more ingress interface(s). Packets forwarded upstream to the 529 rest of the Internet are transmitted through one of the MR's 530 egress interface; packets forwarded downstream to the mobile 531 network are transmitted through one of the MR's ingress 532 interface. 534 Ingress interface 536 The interface of a MR attached to a link inside the mobile 537 network. 539 Egress interface 541 The interface of a MR attached to the home link if the MR is at 542 home, or attached to a foreign link if the MR is in a foreign 543 network. 545 Mobile Network Node (MNN) 547 Any node (host or router) located within a mobile network, either 548 permanently or temporarily. A Mobile Network Node may either be a 549 mobile node or a fixed node. 551 Access Link (AL) 553 A last-hop link between a Mobile Node and an Access Point. That 554 is, a facility or medium over which an Access Point and the 555 Mobile Node can communicate at the link layer, i.e., the layer 556 immediately below IP. 558 Access Point (AP) 560 An Access Point is a layer 2 device which is connected to one or 561 more Access Routers and offers the wireless link connection to 562 the Mobile Node. Access Points are sometimes called base 563 stations or access point transceivers. An Access Point may be a 564 separate entity or co-located with an Access Router. 566 Radio Cell 568 The geographical area within which an Access Point provides radio 569 coverage, i.e. where radio communication between a Mobile Node 570 and the specific Access Point is possible. 572 Access Network Router (ANR) 574 An IP router in the Access Network. An Access Network Router may 575 include Access Network specific functionalities, for example, 576 related to mobility and/or QoS. This is to distinguish between 577 ordinary routers and routers that have Access Network-related 578 special functionality. 580 Access Router (AR) 582 An Access Network Router residing on the edge of an Access 583 Network and connected to one or more Access Points. The Access 584 Points may be of different technology. An Access Router offers 585 IP connectivity to Mobile Nodes, acting as a default router to 586 the Mobile Nodes it is currently serving. The Access Router may 587 include intelligence beyond a simple forwarding service offered 588 by ordinary IP routers. 590 Access Network Gateway (ANG) 592 An Access Network Router that separates an Access Network from 593 other IP networks, much in the same way as an ordinary gateway 594 router. The Access Network Gateway looks to the other IP networks 595 like a standard IP router. 597 Access Network (AN) 599 An IP network which includes one or more Access Network Routers. 601 Administrative Domain (AD) 603 A collection of networks under the same administrative control 604 and grouped together for administrative purposes [5]. 606 Serving Access Router (SAR) 608 The Access Router currently offering the connectivity to the MN. 609 This is usually the point of departure for the MN as it makes its 610 way towards a new Access Router (then Serving Access Router takes 611 the role of the Old Access Router). There may be several Serving 612 Access Routers serving the Mobile Node at the same time. 614 Old Access Router (OAR) 616 An Access Router that offered connectivity to the Mobile Node 617 prior to a handover. This is the Serving Access Router that will 618 cease or has ceased to offer connectivity to the Mobile Node. 620 New Access Router (NAR) 622 The Access Router that offers connectivity to the Mobile Node 623 after a handover. 625 Previous Access Router (PAR) 627 An Access Router that offered connectivity to the Mobile Node 628 prior to a handover. This is the Serving Access Router that will 629 cease or has ceased to offer connectivity to the Mobile Node. 630 Same as OAR. 632 Candidate Access Router (CAR) 634 An Access Router to which the Mobile Node may do a handoff. 636 4. Handover Terminology 638 These terms refer to different perspectives and approaches to 639 supporting different aspects of mobility. Distinctions can be made 640 according to the scope, range overlap, performance characteristics, 641 diversity characteristics, state transitions, mobility types, and 642 control modes of handover techniques. 644 Roaming 646 An operator-based term involving formal agreements between 647 operators that allows a mobile to get connectivity from a foreign 648 network. Roaming (a particular aspect of user mobility) 649 includes, for example, the functionality by which users can 650 communicate their identity to the local AN so that inter-AN 651 agreements can be activated and service and applications in the 652 MN's home network can be made available to the user locally. 654 Handover 656 (also known as handoff) the process by which an active MN (in the 657 Active State, see section 4.6) changes its point of attachment to 658 the network, or when such a change is attempted. The access 659 network may provide features to minimize the interruption to 660 sessions in progress. 662 There are different types of handover classified according to 663 different aspects involved in the handover. Some of this 664 terminology follows the description of [4]. 666 4.1. Scope of Handover 668 Note that the definitions of horizontal and vertical handover are 669 different than the ones commonly used today. These definitions try to 670 look at the handover from the IP layer's point of view; the IP layer 671 works with network interfaces, rather than specific technologies used 672 by those interfaces. 674 Layer 2 handover 676 A handover where the MN changes APs (or some other aspect of the 677 radio channel) connected to the same AR's interface. This type of 678 handover is transparent to the routing at the IP layer (or it 679 appears simply as a link layer reconfiguration without any 680 mobility implications). 682 Intra-AR handover 684 A handover which changes the AR's network interface to the 685 mobile. That is, the Serving AR remains the same but routing 686 changes internal to the AR take place. 688 Intra-AN handover 690 A handover where the MN changes ARs inside the same AN. Such a 691 handover is not necessarily visible outside the AN. In case the 692 ANG serving the MN changes, this handover is seen outside the AN 693 due to a change in the routing paths. Note that the ANG may 694 change for only some of the MN's data flows. 696 Inter-AN handover 698 A handover where the MN moves to a new AN. This requires some 699 sort of host mobility across ANs, which typically is be provided 700 by the external IP core. Note that this would have to involve the 701 assignment of a new IP access address (e.g., a new care-of 702 address [9]) to the MN. 704 Intra-technology handover 706 A handover between equipment of the same technology. 708 Inter-technology handover 710 A handover between equipment of different technologies. 712 Horizontal handover 714 A handover in which the mobile node's network interface does not 715 change (from the IP point of view); the MN communicates with the 716 access router via the same network interface before and after the 717 handover. A horizontal handover is typically also an intra- 718 technology handover but it can be an inter-technology handover if 719 the MN can do a layer 2 handover between two different 720 technologies without changing the network interface seen by the 721 IP layer. 723 Vertical handover 725 A handover in which the mobile node's network interface to the 726 access network changes. A vertical handover is typically an 727 inter-technology handover but it may also be an intra- technology 728 handover if the MN has several network interfaces of the same 729 type. That is, after the handover, the IP layer communicates with 730 the access network through a different network interface. 732 The different handover types defined in this section and in section 733 4.1 have no direct relationship. In particular, a MN can do an 734 intra-AN handover of any of the types defined above. 736 Note that the horizontal and vertical handovers are not tied to a 737 change in the link layer technology. They define whether, after a 738 handover, the IP packet flow goes through the same (horizontal 739 handover) or a different (vertical handover) network interface. 740 These two handovers do not define whether the AR changes as a result 741 of a handover. 743 4.2. Handover Control 745 A handover must be one of the following two types (a): 747 Mobile-initiated handover 749 the MN is the one that makes the initial decision to initiate the 750 handover. 752 Network-initiated handover 754 the network makes the initial decision to initiate the handover. 756 A handover is also one of the following two types (b): 758 Mobile-controlled handover 760 the MN has the primary control over the handover process. 762 Network-controlled handover 764 the network has the primary control over the handover process. 766 A handover is also either of these three types (c): 768 Mobile-assisted handover 770 information and measurement from the MN are used by the AR to 771 decide on the execution of a handover. 773 Network-assisted handover 775 a handover where the AN collects information that can be used by 776 the MN in a handover decision. 778 Unassisted handover 780 a handover where no assistance is provided by the MN or the AR to 781 each other. 783 Note that it is possible that the MN and the AR both do 784 measurements and decide on the handover. 786 A handover is also one of the following two types (d): 788 Backward handover 790 a handover either initiated by the OAR, or where the MN initiates 791 a handover via the OAR. 793 Forward handover 795 a handover either initiated by the NAR, or where the MN initiates 796 a handover via the NAR. 798 The handover is also either proactive or reactive (e): 800 Planned handover 802 a proactive (expected) handover where some signalling can be done 803 in advance of the MN getting connected to the new AR, e.g. 804 building a temporary tunnel from the old AR to the new AR. 806 Unplanned handover 808 a reactive (unexpected) handover, where no signalling is done in 809 advance of the MN's move of the OAR to the new AR. 811 The five handover types (a-e) are mostly independent, and every 812 handover should be classiable according to each of these types. 814 4.3. Simultaneous connectivity to Access Routers 816 Make-before-break (MBB) 818 During a MBB handover the MN can communicate simultaneously with 819 the old and new AR. This should not be confused with "soft 820 handover" which relies on macro diversity. 822 Break-before-make (BBM) 824 During a BBM handover the MN cannot communicate simultaneously 825 with the old and the new AR. 827 4.4. Performance and Functional Aspects 829 Handover latency 831 Handover latency is the time difference between when a MN is last 832 able to send and/or receive an IP packet by way of the OAR, until 833 when the MN is able to send and/or receive an IP packet through 834 the NAR. Adapted from [4]. 836 Smooth handover 838 A handover that aims primarily to minimize packet loss, with no 839 explicit concern for additional delays in packet forwarding. 841 Fast handover 843 A handover that aims primarily to minimize delay, with no 844 explicit interest in packet loss. 846 Seamless handover 848 A handover in which there is no change in service capability, 849 security, or quality. In practice, some degradation in service 850 is to be expected. The definition of a seamless handover in the 851 practical case should be that other protocols, applications, or 852 end users do not detect any change in service capability, 853 security or quality, which would have a bearing on their (normal) 854 operation. See [7] for more discussion on the topic. 856 Throughput 858 The amount of data from a source to a destination processed by 859 the protocol for which throughput is to be measured for instance, 860 IP, TCP, or the MAC protocol. The throughput differs between 861 protocol layers. 863 Goodput 865 The total bandwidth used, less the volume of control messages, 866 protocol overhead from the data packets, and packets dropped due 867 to CRC errors. 869 Pathloss 871 A reduction in signal strength caused by traversing the physical 872 medium constituting the link. 874 Hidden-terminal problem 876 The problem whereby a transmitting node can fail in its attempt 877 to transmit data because of destructive interference which is 878 only detectable at the receiving node, not the transmitting node. 880 Exposed terminal problem 882 The problem whereby a transmitting node prevents another node 883 from transmitting although it could have safely transmitted to 884 anyone else but that node. 886 4.5. Micro Diversity, Macro Diversity, and IP Diversity 888 Certain air interfaces (e.g. the Universal Mobile Telephone System 889 (UMTS) Terrestial Radio Access Network (UTRAN) running in Frequency 890 Division Duplex (FDD) mode) require or at least support macro 891 diversity combining. Essentially, this refers to the fact that a 892 single MN is able to send and receive over two independent radio 893 channels ('diversity branches') at the same time; the information 894 received over different branches is compared and that from the better 895 branch passed to the upper layers. This can be used both to improve 896 overall performance, and to provide a seamless type of handover at 897 layer 2, since a new branch can be added before the old is deleted. 898 See also [6]. 900 It is necessary to differentiate between combining/diversity that 901 occurs at the physical and radio link layers, where the relevant unit 902 of data is the radio frame, and that which occurs at layer 3, the 903 network layer, where what is considered is the IP packet itself. 905 In the following definitions micro- and macro diversity refer to 906 protocol layers below the network layer, and IP diversity refers to 907 the network layer. 909 Micro diversity 911 for example, two antennas on the same transmitter send the same 912 signal to a receiver over a slightly different path to overcome 913 fading. 915 Macro diversity 917 Duplicating or combining actions taking place over multiple APs, 918 possibly attached to different ARs. This may require support 919 from the network layer to move the radio frames between the base 920 stations and a central combining point. 922 IP diversity 924 The splitting and combining of packets at the IP level. 926 4.6. Paging, and Mobile Node States and Modes 928 Mobile systems may employ the use of MN states in order to operate 929 more efficiently without degrading the performance of the system. The 930 term 'mode' is also common and means the same as 'state'. 932 A MN is always in one of the following three states: 934 Active state 936 When the AN knows the MN's SAR and the MN can send and receive IP 937 packets. The AL may not be active, but the radio layer is able 938 to establish one without assistance from the network layer. The 939 MN has an IP address assigned. 941 Dormant state 943 A state in which the mobile restricts its ability to receive 944 normal IP traffic by reducing its monitoring of radio channels. 945 The AN knows the MN's Paging Area, but the MN has no SAR and so 946 packets cannot be delivered to the MN without the AN initiating 947 paging. 949 Time-slotted dormant mode 951 A dormant mode implementation in which the mobile alternates 952 between periods of not listening for any radio traffic and 953 listening for traffic. Time-slotted dormant mode implementations 954 are typically synchronized with the network so the network can 955 deliver traffic to the mobile during listening periods. 957 Inactive state 959 the MN is in neither the Active nor Dormant State. The MN is no 960 longer listening for any packets, not even periodically, and not 961 sending packets. The MN may be in a powered off state, it may 962 have shut down all interfaces to drastically conserve power, or 963 it may be out of range of a radio access point. The MN does not 964 necessarily have an IP access address from the AN. 966 Note: in fact, as well as the MN being in one of these three states, 967 the AN also stores which state it believes the MN is in. Normally 968 these are consistent; the definitions above assume so. 970 Here are some additional definitions for paging, taking into account 971 the above state definitions. 973 Paging 975 A procedure initiated by the Access Network to move an Idle MN 976 into the Active State. As a result of paging, the MN establishes 977 a SAR and the IP routes are set up. 979 Location updating 981 A procedure initiated by the MN, by which it informs the AN that 982 it has moved into a new paging area. 984 Paging area 986 A part of the Access Network, typically containing a number of 987 ARs/APs, which corresponds to some geographical area. The AN 988 keeps and updates a list of all the Idle MNs present in the area. 989 If the MN is within the radio coverage of the area it will be 990 able to receive paging messages sent within that Paging Area. 992 Paging area registrations 994 Signaling from a dormant mode mobile node to the network, by 995 which it establishes its presence in a new paging area. Paging 996 Area Registrations thus enable the network to maintain a rough 997 idea of where the mobile is located. 999 Paging channel 1001 A radio channel dedicated to signaling dormant mode mobiles for 1002 paging purposes. By current practice, the protocol used on a 1003 paging channel is usually dictated by the radio link protocol, 1004 although some paging protocols have provision for carrying 1005 arbitrary traffic (and thus could potentially be used to carry 1006 IP). 1008 Traffic channel 1010 The radio channel on which IP traffic to an active mobile is 1011 typically sent. This channel is used by a mobile that is 1012 actively sending and receiving IP traffic, and is not 1013 continuously active in a dormant mode mobile. For some radio 1014 link protocols, this may be the only channel available. 1016 4.7. Context Transfer 1018 Context 1020 The information on the current state of a routing-related service 1021 required to re-establish the routing-related service on a new 1022 subnet without having to perform the entire protocol exchange 1023 with the MN from scratch. 1025 Feature context 1027 The collection of information representing the context for a 1028 given feature. The full context associated with a MN is the 1029 collection of one or more feature contexts. 1031 Context transfer 1033 The movement of context from one router or other network entity 1034 to another as a means of re-establishing routing related services 1035 on a new subnet or collection of subnets. 1037 Routing-related service 1039 A modification to the default routing treatment of packets to and 1040 from the MN. Initially establishing routing-related services 1041 usually requires a protocol exchange with the MN. An example of a 1042 routing-related service is header compression. The service may 1043 also be indirectly related to routing, for example, security. 1044 Security may not affect the forwarding decision of all 1045 intermediate routers, but a packet may be dropped if it fails a 1046 security check (can't be encrypted, authentication failed, etc.). 1047 Dropping the packet is basically a routing decision. 1049 4.8. Candidate Access Router Discovery 1051 Capability of AR 1053 A characteristic of the service offered by an AR that may be of 1054 interest to an MN when the AR is being considered as a handoff 1055 candidate. 1057 Candidate AR (CAR) 1059 An AR to which MN has a choice of performing IP-level handoff. 1060 This means that MN has the right radio interface to connect to an 1061 AP that is served by this AR, as well as the coverage of this AR 1062 overlaps with that of the AR to which MN is currently attached. 1064 Target AR (TAR) 1066 An AR with which the procedures for the MN's IP-level handoff are 1067 initiated. TAR is selected after running a TAR Selection 1068 Algorithm that takes into account the capabilities of CARs, 1069 preferences of MN and any local policies. 1071 4.9. Types of Mobility 1073 Different sorts of mobility management may be required of a mobile 1074 system. We can differentiate between personal, host and network 1075 mobility. 1077 Personal mobility support 1079 Provides the ability to track the user's location and provide the 1080 user's current location to allow sessions to be initiated by and 1081 towards the user by anyone on any other network. Personal 1082 mobility is also concerned with enabling associated security, 1083 billing and service subscription authorization made between 1084 administrative domains. 1086 Host mobility support 1088 Refers to the function of allowing a mobile node to change its 1089 point of attachment to the network, without interrupting IP 1090 packet delivery to/from that node. There may be different sub- 1091 functions depending on what the current level of service is being 1092 provided; in particular, support for host mobility usually 1093 implies active and idle modes of operation, depending on whether 1094 the node has any current sessions or not. Access Network 1095 procedures are required to keep track of the current point of 1096 attachment of all the MNs or establish it at will. Accurate 1097 location and routing procedures are required in order to maintain 1098 the integrity of the communication. Host mobility is often called 1099 'terminal mobility'. 1101 Network mobility support 1103 Refers to the function of allowing an entire network to change 1104 its point of attachment to the Internet, and, thus, its 1105 reachability in the topology, without interrupting IP packet 1106 delivery to/from that mobile network. 1108 Two subcategories of mobility can be identified withing either host 1109 mobility and network mobility: 1111 Global mobility 1113 Same as Macro mobility. 1115 Local mobility 1117 Same as Micro mobility. 1119 Macro mobility 1121 Mobility over a large area. This includes mobility support and 1122 associated address registration procedures that are needed when a 1123 MN moves between IP domains. Inter-AN handovers typically involve 1124 macro-mobility protocols. Mobile-IP can be seen as a means to 1125 provide macro mobility. 1127 Micro mobility 1129 Mobility over a small area. Usually this means mobility within 1130 an IP domain with an emphasis on support for active mode using 1131 handover, although it may include idle mode procedures also. 1132 Micro-mobility protocols exploit the locality of movement by 1133 confining movement related changes and signalling to the access 1134 network. 1136 Local mobility management 1138 Local mobility management (LMM) is a generic term for protocols 1139 dealing with IP mobility management confined within the access 1140 network. LMM messages are not routed outside the access network, 1141 although a handover may trigger Mobile IP messages to be sent to 1142 correspondent nodes and home agents. 1144 5. Specific Terminology for Mobile Ad-Hoc Networking 1146 Cluster 1148 A group of nodes located within close physical proximity, 1149 typically all within range of one another, which can be grouped 1150 together for the purpose of limiting the production and 1151 propogation of routing information. 1153 Cluster head 1155 A cluster head is a node (often elected in the cluster formation 1156 process) that has complete knowledge about group membership and 1157 link state information in the cluster. Each cluster should have 1158 one and only one cluster head. 1160 Cluster member 1162 All nodes within a cluster EXCEPT the cluster head are called 1163 members of that cluster. 1165 Convergence 1167 The process of approaching a state of equilibrium in which all 1168 nodes in the network agree on a consistent collection of state 1169 about the topology of the network, and in which no further 1170 control messages are needed to establish the consistency of the 1171 network topology. 1173 Convergence time 1175 The time which is required for a network to reach convergence 1176 after an event (typically, the movement of a mobile node) which 1177 changes the network topology. 1179 Laydown 1181 The relative physical location of the nodes within the ad hoc 1182 network. 1184 Pathloss matrix 1186 A matrix of coefficients describing the pathloss between any two 1187 nodes in an ad hoc network. When the links are asymmetric, the 1188 matrix is also asymmetric. 1190 Scenario 1192 The tuple 1193 characterizing a class of ad hoc networks. 1195 6. Security-related Terminology 1197 This section includes terminology commonly used around mobile and 1198 wireless networking. Only a mobility-related subset of the entire 1199 security terminology is presented. 1201 Authorization-enabling extension 1203 An authentication which makes a (registration) message acceptable 1204 to the ultimate recipient of the registration message. An 1205 authorization-enabling extension must contain an SPI [12]. 1207 Mobility security association 1209 A collection of security contexts, between a pair of nodes, which 1210 may be applied to mobility-related protocol messages exchanged 1211 between them. In Mobile IP, each context indicates an 1212 authentication algorithm and mode, a secret (a shared key, or 1213 appropriate public/private key pair), and a style of replay 1214 protection in use. Mobility security associations may be stored 1215 separately from the node's IPsec Security Policy Database (SPD) 1216 [12]. 1218 Registration key 1220 A key used as the basis of a Mobility Security Association 1221 between a mobile node and a foreign agent. A registration key is 1222 typically only used once or a very few times, and only for the 1223 purposes of verifying a small volume of Authentication data [14]. 1225 Security context 1227 A security context between two routers defines the manner in 1228 which two routers choose to mutually authenticate each other, and 1229 indicates an authentication algorithm and mode. 1231 Security Parameter Index (SPI) 1233 An index identifying a security context between a pair of routers 1234 among the contexts possible in the mobility security association. 1236 Stale challenge 1238 Any challenge that has been used by the mobile node in a 1239 Registration Request message and processed by the Foreign Agent 1240 by relaying or generating The Foreign Agent may not be able to 1241 keep records for all previously used challenges [13]. 1243 Unknown challenge 1245 Any challenge from a particular mobile node that the foreign 1246 agent has no record of having put either into one of its recent 1247 Agent Advertisements or into a registration reply message to that 1248 mobile node [13]. 1250 Unused challenge 1252 A challenge that has not been already accepted by the Foreign 1253 Agent challenge in a corresponding Registration Reply message -- 1254 i.e., a challenge that is neither unknown nor previously used 1255 [13]. 1257 The Mobile IPv6 specification includes more security terminology 1258 related to MIPv6 bindings [11]. 1260 7. Security Considerations 1262 This document presents only terminology. There are no security issues 1263 in this document. 1265 8. Contributors 1267 This draft was initially based on the work of 1269 o Tapio Suihko, VTT Information Technology, Finland 1270 o Phil Eardley and Dave Wisely, BT, UK 1271 o Robert Hancock, Siemens/Roke Manor Research, UK, 1272 o Nikos Georganopoulos, King's College London 1273 o Markku Kojo and Jukka Manner, University of Helsinki, Finland. 1275 Since revision -02 of the document draft-manner-seamoby-terms-02.txt, 1276 Charles Perkins has given as input terminology related to ad-hoc 1277 networks. 1279 Thierry Ernst has provided the terminology for discussing mobile 1280 networks. 1282 9. Change log 1284 Changes from -04 1285 - Removed User mobility, and related discussions elsewhere 1286 - Added terms to Appendix B 1287 - Capitalizing fixes 1288 - Added "Subnet" 1289 - Clarified "link" and gave pointer to "access link" 1290 - Added "(HoA)" to "Home Address" 1291 - Refined definition of Mobile Node (added MH and MR) 1292 - Separated ingress and egress interfaces from the definition of MR 1293 - Revised use of terms MN/MH/node/host 1294 - minor edits 1296 Changes from -03 1297 - Added comments from Randy Presuhn and Thierry Ernst 1299 Changes from -02 1300 - Updated the terminology related to mobile networks 1302 Changes from -01 1303 - Added security terminology 1304 - Miscellaneous small refinements of definitions 1306 Changes from -00 1307 - Added definition for Routing Proxy 1308 - Added basic terminology about mobile networks 1309 - Added Link-Layer Trigger from FMIPv6 1310 - Edited the CAR terminology section 1311 - Added definitions for MPR, CoA, BU 1312 - Changed the definition of Home Address 1313 - Added a mobile network into Figure 1 1314 - Edited the Network Components section 1316 10. Acknowledgement 1318 This work has been partially performed in the framework of the IST 1319 project IST-2000-28584 MIND, which is partly funded by the European 1320 Union. Some of the authors would like to acknowledge the help of 1321 their colleagues in preparing this document. 1323 Randy Presuhn did a very thorough and helpful review of the -02 1324 version of the terminology. 1326 Some definitions of terminology have been adapted from [1], [7], [3], 1328 [2], [4], [9], [10], [11] and [12]. 1330 11. Informative References 1332 [1] Blair, D., Tweedly, A., Thomas, M., Trostle, J. and 1333 Ramalho, M., "Realtime Mobile IPv6 Framework", Work in 1334 Progress. 1336 [2] Calhoun, P., Montenegro, G. and Perkins, C., "Mobile IP 1337 Regionalized Tunnel Management", Work in Progress. 1339 [3] Deering, S. and Hinden, R., "Internet Protocol, Version 6 1340 (IPv6) Specification". RFC 2460, December 1998. 1342 [4] Dommety, G. (ed.), "Fast Handovers for Mobile IPv6", Work in 1343 Progress. 1345 [5] Yavatkar, R., Pendarakis, D. and Guerin, R., "A Framework for 1346 Policy-based Admission Control". RFC 2753, January 2000. 1348 [6] Kempf, J., McCann, P. and Roberts, P., "IP Mobility and the 1349 CDMA Radio Access Network: Applicability Statement for Soft 1350 Handoff", Work in Progress. 1352 [7] Kempf, J. (ed.), "Problem Description: Reasons For Doing 1353 Context Transfers Between Nodes in an IP Access Network". 1354 RFC 3374, September 2002. 1356 [8] Pandya, R., "Emerging Mobile and Personal Communication 1357 Systems". IEEE Communications Magazine, 33:44--52, June 1995. 1359 [9] Ramjee, R., La Porta, T., Thuel, S., Varadhan, K. and 1360 Salgarelli, L., "IP micro-mobility support using HAWAII", Work 1361 in Progress. 1363 [10] Trossen, D., Krishnamurthi, G., Chaskar, H. and Kempf, J., 1364 "Issues in candidate access router discovery for seamless 1365 IP-level handoffs", Work in Progress. 1367 [11] Johnson, D., Perkins, D. and Arkko, J., "Mobility 1368 Support in IPv6", Work in Progress. 1370 [12] Perkins, C. (ed.), "IP Mobility Support for IPv4". RFC 3344, 1371 August 2002. 1373 [13] Perkins, C., Calhoun, P. and Bharatia, J., "Mobile 1374 IPv4 Challenge/Response Extensions (revised)", Work in 1375 Progress. 1377 [14] Perkins, C. and Calhoun, P., "AAA Registration Keys for Mobile 1378 IP", Work in Progress. 1380 [15] Ernst, T. and Lach, H., "Network Mobility Support 1381 Terminology", Work in Progress. 1383 12. Authors' Addresses 1385 Questions about this document may be directed to: 1387 Jukka Manner 1388 Department of Computer Science 1389 University of Helsinki 1390 P.O. Box 26 (Teollisuuskatu 23) 1391 FIN-00014 HELSINKI 1392 Finland 1394 Voice: +358-9-191-44210 1395 Fax: +358-9-191-44441 1396 E-Mail: jmanner@cs.helsinki.fi 1398 Markku Kojo 1399 Department of Computer Science 1400 University of Helsinki 1401 P.O. Box 26 (Teollisuuskatu 23) 1402 FIN-00014 HELSINKI 1403 Finland 1405 Voice: +358-9-191-44179 1406 Fax: +358-9-191-44441 1407 E-Mail: kojo@cs.helsinki.fi 1409 Charles E. Perkins 1410 Communications Systems Lab 1411 Nokia Research Center 1412 313 Fairchild Drive 1413 Mountain View, California 94043 1414 USA 1415 Phone: +1-650 625-2986 1416 E-Mail: charliep@iprg.nokia.com 1417 Fax: +1 650 625-2502 1419 Tapio Suihko 1420 VTT Information Technology 1421 P.O. Box 1203 1422 FIN-02044 VTT 1423 Finland 1425 Voice: +358-9-456-6078 1426 Fax: +358-9-456-7028 1427 E-Mail: tapio.suihko@vtt.fi 1428 Phil Eardley 1429 BTexaCT 1430 Adastral Park 1431 Martlesham 1432 Ipswich IP5 3RE 1433 United Kingdom 1435 Voice: +44-1473-645938 1436 Fax: +44-1473-646885 1437 E-Mail: philip.eardley@bt.com 1439 Dave Wisely 1440 BTexaCT 1441 Adastral Park 1442 Martlesham 1443 Ipswich IP5 3RE 1444 United Kingdom 1446 Voice: +44-1473-643848 1447 Fax: +44-1473-646885 1448 E-Mail: dave.wisely@bt.com 1450 Robert Hancock 1451 Roke Manor Research Ltd 1452 Romsey, Hants, SO51 0ZN 1453 United Kingdom 1455 Voice: +44-1794-833601 1456 Fax: +44-1794-833434 1457 E-Mail: robert.hancock@roke.co.uk 1459 Nikos Georganopoulos 1460 King's College London 1461 Strand 1462 London WC2R 2LS 1463 United Kingdom 1465 Voice: +44-20-78482889 1466 Fax: +44-20-78482664 1467 E-Mail: nikolaos.georganopoulos@kcl.ac.uk 1469 13. Appendix A - Examples 1471 This appendix provides examples for the terminology presented. 1473 A.1. Mobility 1475 Host mobility is logically independent of the mobility of users, 1476 although in real networks, at least the address management functions 1477 are often required to initially attach the MN to the network. In 1478 addition, if the network wishes to determine whether access is 1479 authorized (and if so, who to charge for it), then this may be tied 1480 to the identity of the user of the terminal. 1482 Personal mobility support typically amounts to the maintenance and 1483 update of some sort of address mapping database, such as a SIP server 1484 or DNS server; it is also possible for the personal mobility support 1485 function to take a part in forwarding control messages between end 1486 user and correspondent rather than simply acting as a database. SIP 1487 is a protocol for session initiation in IP networks. It includes 1488 registration procedures which partially support personal mobility 1489 (namely, the ability for the network to route a session towards a 1490 user at a local IP address). 1492 Personal mobility has been defined in [8] as "the ability of end 1493 users to originate and receive calls and access subscribed 1494 telecommunication services on any terminal in any location, and the 1495 ability of the network to identify end users as they move. Personal 1496 mobility is based on the use of a unique personal identity (i.e., 1497 personal number)." 1499 Roaming, in its original (GSM) sense, is the ability of a user to 1500 connect to the networks owned by operators other than the one having 1501 a direct formal relationship with the user. More recently (e.g., in 1502 data networks and UMTS) it also refers providing user-customized 1503 services in foreign networks (e.g., QoS profiles for specific 1504 applications). 1506 HAWAII, Cellular IP, Regional Registration and Edge Mobility 1507 Architecture (EMA) are examples of micro mobility schemes, with the 1508 assumption that Mobile IP is used for macro mobility. 1510 Public Land Mobile Networks (GSM/UMTS) typically have extensive 1511 support for both user and host mobility. Complete sets of protocols 1512 (both over the air and on the network side) are provided for user 1513 mobility, including customized service provision. Handover for host 1514 mobility is also supported, both within access networks, and also 1515 within the GSM/UMTS core network for mobility between access networks 1516 of the same operator. 1518 A.2. Handovers 1520 A hard handover is required where a MN is not able to receive or send 1521 traffic from/to two APs simultaneously. In order to move the traffic 1522 channel from the old to the new access point the MN abruptly changes 1523 the frequency/timeslot/code on which it is transmitting and listening 1524 to new values associated with a new access point. Thus, the handover 1525 is a break-before-make handover. 1527 A good example of hard handover is GSM where the mobile listens for 1528 new base stations, reports back to the network the signal strength 1529 and identity of the new base station(s) heard. When the old base 1530 station decides that a handover is required it instructs the new base 1531 station to set up resources and, when confirmed, instructs the mobile 1532 to switch to a new frequency and time slot. This sort of hand over 1533 is called hard, mobile assisted, network initiated and backward 1534 (meaning that the old base station is responsible for handling the 1535 change-over). 1537 In a Time-Division Multiple Access (TDMA) system, such as GSM, the 1538 hard hand over is delayed until the mobile has moved well within the 1539 coverage of the new base station. If the handover threshold was set 1540 to the point where the new base station signal exceeded the old then 1541 there would be a very large number of handovers as the mobile moved 1542 through the region between the cells and radio signals fluctuated, 1543 this would create a large signalling traffic. To avoid this a large 1544 hysteresis is set, i.e. the new base station must be (say) 10dB 1545 stronger for handover to occur. If the same was done in Wideband 1546 Carrier Division Multiple Access (W-CDMA) then the mobile would be 1547 transmitting a powerful signal to the old base station and creating 1548 interference for other users, since in CDMA everyone else's 1549 transmissions are seen as noise, thus reducing capacity. To avoid 1550 this soft handover is used, giving an estimated doubling in capacity. 1551 Support for soft handover (in a single mode terminal) is 1552 characteristic of radio interfaces which also require macro diversity 1553 for interference limitation but the two concepts are logically 1554 independent. 1556 A good example of soft handover is the UTRAN FDD mode. W-CDMA is 1557 particularly suited to soft handover because of the design of the 1558 receivers and transmitters: typically a rake receiver will be used 1559 to overcome the multi-path fading of the wide-band channel. Rake 1560 receivers have a number of so-called fingers, each effectively 1561 separate detectors, that are tuned to the same signal (e.g. 1562 spreading code) but delayed by different times. When the delay times 1563 are correctly adjusted and the various components properly combined 1564 (this is micro diversity combining) the effect of multi-path fading 1565 is removed. The rake receiver can also be used to detect signals 1566 from different transmitters by tuning the fingers to different 1567 spreading codes. Soft handover is used in UTRAN FDD mode to also 1568 increase capacity. 1570 Every handover can be seen as a context-aware Handover. In PLMNs the 1571 context to be fulfilled is that the new AP can accommodate the new 1572 mobile, for example, the new GSM cell can serve the incoming phone. 1573 Lately, the notion of Context-aware Handovers has been enlarged by, 1574 for example, QoS-aware handovers, meaning that the handover is 1575 governed by the need to support the QoS-context of the moving mobile 1576 in order to keep the service level assured to the user of the MN. 1578 A.3. Diversity combining 1580 In the case of UMTS it is radio frames that are duplicated at some 1581 point in the network, at the serving Radio Network Controller (RNC), 1582 and sent to a number of basestations and, possibly via other (drift) 1583 RNCs. The combining that takes place at the serving RNC in the uplink 1584 direction is typically based on some simple quality comparison of the 1585 various received frames, which implies that the various copies of 1586 these frames must contain identical upper layer information. The 1587 serving RNC also has to do buffering data frames to take account of 1588 the differing time of flight from each basestation to the RNC. 1590 A.4. Miscellaneous 1592 In a GPRS/UMTS system the Access Network Gateway node could be the 1593 GGSN component. The ANG can provide support for mobility of hosts, 1594 admission control, policy enforcement, and Foreign Agent 1595 functionality [9]. 1597 When presenting a mobile network topology, APs and ARs are usually 1598 pictured as separate components (see Figure 1). This is the case 1599 with GSM/GPRS/UMTS presentations, for example. From the IP point of 1600 view APs are not directly visible. An AP should only be seen from 1601 the MN's or AR's IP layer as a link (interface) connecting MNs to the 1602 AR. 1604 When the mobile moves through the network, depending on the mobility 1605 mechanism, the OAR will forward packets destined to the old MNs 1606 address to the SAR which currently serves the MN. At the same time 1607 the handover mechanism may be studying CARs to find the best NAR 1608 where the MN will be handed next. 1610 14. Appendix B - Index of Terms 1612 Access Link (AL) ............................................... 12 1613 Access Network (AN) ............................................ 13 1614 Access Network Gateway (ANG) ................................... 12 1615 Access Network Router (ANR) .................................... 12 1616 Access Point (AP) .............................................. 12 1617 Access Router (AR) ............................................. 12 1618 Active state ................................................... 19 1619 Administrative Domain (AD) ..................................... 13 1620 Asymmetric link ................................................. 5 1621 Authorization-enabling extension ............................... 24 1622 Backward handover .............................................. 16 1623 Bandwidth ....................................................... 3 1624 Bandwidth utilization ........................................... 3 1625 Beacon .......................................................... 3 1626 Binding Update (BU) ............................................. 3 1627 Break-before-make (BBM) ........................................ 17 1628 Candidate AR (CAR) ............................................. 21 1629 Candidate Access Router (CAR) .................................. 13 1630 Capability of AR ............................................... 21 1631 Care-of-Address (CoA) ........................................... 3 1632 Channel ......................................................... 3 1633 Channel access protocol ......................................... 3 1634 Cluster ........................................................ 23 1635 Cluster head ................................................... 23 1636 Cluster member ................................................. 23 1637 Context ........................................................ 21 1638 Context transfer ............................................... 21 1639 Control message ................................................. 3 1640 Convergence .................................................... 23 1641 Convergence time ............................................... 24 1642 Distance vector ................................................. 4 1643 Dormant state .................................................. 19 1644 Egress interface ............................................... 11 1645 Exposed terminal problem ....................................... 18 1646 Fairness ........................................................ 4 1647 Fast handover .................................................. 17 1648 Feature context ................................................ 21 1649 Fixed Node (FN) ................................................ 11 1650 Flooding ........................................................ 4 1651 Foreign subnet prefix ........................................... 4 1652 Forward handover ............................................... 16 1653 Forwarding node ................................................. 4 1654 Global mobility ................................................ 22 1655 Goodput ........................................................ 18 1656 Handover ....................................................... 14 1657 Handover latency ............................................... 17 1658 Hidden-terminal problem ........................................ 18 1659 Home Address (HoA) .............................................. 4 1660 Home subnet prefix .............................................. 4 1661 Horizontal Handover ............................................ 15 1662 Host mobility support .......................................... 22 1663 IP access address ............................................... 4 1664 IP diversity ................................................... 19 1665 Inactive state ................................................. 19 1666 Ingress interface .............................................. 11 1667 Inter-AN handover .............................................. 14 1668 Interface ....................................................... 4 1669 Inter-technology handover ...................................... 15 1670 Intra-AN handover .............................................. 14 1671 Intra-AR handover .............................................. 14 1672 Intra-technology handover ...................................... 15 1673 Laydown ........................................................ 24 1674 Layer 2 handover ............................................... 14 1675 Link ............................................................ 5 1676 Link establishment .............................................. 5 1677 Link state ...................................................... 5 1678 Link-layer trigger (L2 Trigger) ................................. 5 1679 Link-level acknowledgement ...................................... 5 1680 Local broadcast ................................................. 6 1681 Local mobility ................................................. 22 1682 Local mobility management ...................................... 23 1683 Location updating .............................................. 20 1684 Loop-free ....................................................... 6 1685 Macro diversity ................................................ 19 1686 Macro mobility ................................................. 22 1687 Make-before-break (MBB) ........................................ 17 1688 Medium Access Protocol (MAC) .................................... 6 1689 Micro diversity ................................................ 18 1690 Micro mobility ................................................. 23 1691 Mobile Host (MH) ............................................... 11 1692 Mobile Network Node (MNN) ...................................... 12 1693 Mobile Node (MN) ............................................... 11 1694 Mobile Router (MR) ............................................. 11 1695 Mobile network ................................................. 11 1696 Mobile network prefix ........................................... 6 1697 Mobile-assisted handover ....................................... 16 1698 Mobile-controlled handover ..................................... 16 1699 Mobile-initiated handover ...................................... 15 1700 Mobility factor ................................................. 6 1701 Mobility security association .................................. 24 1702 Multipoint relay (MPR) .......................................... 6 1703 Neighbor ........................................................ 6 1704 Neighborhood .................................................... 6 1705 Network mobility support ....................................... 22 1706 Network-assisted handover ...................................... 16 1707 Network-controlled handover .................................... 16 1708 Network-initiated handover ..................................... 15 1709 New Access Router (NAR) ........................................ 13 1710 Next hop ........................................................ 7 1711 Old Access Router (OAR) ........................................ 13 1712 Paging ......................................................... 20 1713 Paging area .................................................... 20 1714 Paging area registrations ...................................... 20 1715 Paging channel ................................................. 20 1716 Pathloss ....................................................... 18 1717 Pathloss matrix ................................................ 24 1718 Payload ......................................................... 7 1719 Personal mobility support ...................................... 22 1720 Planned handover ............................................... 16 1721 Prefix .......................................................... 7 1722 Previous Access Router (PAR) ................................... 13 1723 Radio Cell ..................................................... 12 1724 Registration key ............................................... 24 1725 Roaming ........................................................ 13 1726 Route activation ................................................ 7 1727 Route entry ..................................................... 7 1728 Route establishment ............................................. 7 1729 Route table ..................................................... 7 1730 Routing proxy ................................................... 7 1731 Routing-related service ........................................ 21 1732 Scenario ....................................................... 24 1733 Seamless handover .............................................. 17 1734 Security Parameter Index (SPI) ................................. 25 1735 Security context ............................................... 25 1736 Serving Access Router (SAR) .................................... 13 1737 Signal strength ................................................. 7 1738 Smooth handover ................................................ 17 1739 Source route .................................................... 8 1740 Spatial re-use .................................................. 8 1741 Stale challenge ................................................ 25 1742 Subnet .......................................................... 8 1743 System-wide broadcast ........................................... 8 1744 Target AR (TAR) ................................................ 21 1745 Throughput ..................................................... 17 1746 Time-slotted dormant mode ...................................... 19 1747 Topology ........................................................ 8 1748 Traffic channel ................................................ 20 1749 Triggered update ................................................ 8 1750 Unassisted handover ............................................ 16 1751 Unknown challenge .............................................. 25 1752 Unplanned handover ............................................. 16 1753 Unused challenge ............................................... 25 1754 Vertical Handover .............................................. 15 1755 Full Copyright Statement 1757 Copyright (C) The Internet Society (2001). All Rights Reserved. 1759 This document and translations of it may be copied and furnished to 1760 others, and derivative works that comment on or otherwise explain it 1761 or assist in its implementation may be prepared, copied, published 1762 and distributed, in whole or in part, without restriction of any 1763 kind, provided that the above copyright notice and this paragraph are 1764 included on all such copies and derivative works. However, this 1765 document itself may not be modified in any way, such as by removing 1766 the copyright notice or references to the Internet Society or other 1767 Internet organizations, except as needed for the purpose of 1768 developing Internet standards in which case the procedures for 1769 copyrights defined in the Internet Standards process must be 1770 followed, or as required to translate it into languages other than 1771 English. 1773 The limited permissions granted above are perpetual and will not be 1774 revoked by the Internet Society or its successors or assigns. 1776 This document and the information contained herein is provided on an 1777 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 1778 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 1779 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 1780 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 1781 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.