IETF INTERNET-DRAFT Thierry Ernst, WIDE and INRIA Hong-Yon Lach, Motorola Labs Paris October 2002 Network Mobility Support Terminology draft-ernst-nemo-terminology-00.txt Status of This Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document proposes a terminology for defining network mobility problems and solution requirements. Network mobility occurs when an entire network changes its point of attachment to the Internet and thus its reachability in the topology, which is referred to as a mobile network. Ernst and Lach Expires May 2003 [Page 1] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Contents Status of This Memo Abstract 1. Introduction 2. Applications 3. Terminology 3.1. Architecture Components Mobile Network Mobile Network Node (MNN) Mobile Router (MR) Fixed Node (FN) Mobile Node (MN) Node behind the MR Correspondent Node (CN) Access Router (AR) Egress Interface of a MR Ingress Interface of a MR Home subnet prefix Foreign subnet prefix Mobile Network Prefix 3.2. Functional Terms Local Fixed Node (LFN) Local Mobile Node (LMN) Visiting Mobile Node (VMN) NEMO-enabled (NEMO-node) MIPv6-enabled (MIPv6-node) 3.3. Nested Mobility root-NEMO parent-NEMO sub-NEMO Top-Level Mobile Router (TLMR) 3.4. Multihomed mobile network 3.5. Miscellaneous Terms NEMO support intra-domain mobility inter-domain mobility Idle MNN Idle Mobile Network Acknowledgments References Ernst and Lach Expires May 2003 [Page 2] INTERNET-DRAFT Network Mobility Support Terminology October 2002 1. Introduction A mobile network is an entire network, moving as a unit, which changes its point of attachment to the Internet and thus its reachability in the topology. A mobile network may be composed by one or more IP-subnets and is connected to the global Internet via one or more Mobile Routers (MR). Nodes behind the MR primarily comprise fixed nodes (nodes unable to change their point of attachment while maintaining ongoing sessions), and additionally mobile nodes (nodes able to change their point of attachment while maintaining ongoing sessions). The internal configuration of the mobile network is assumed to be relatively stable with respect to the MR. If network mobility is not explicitly supported by some mechanisms once a MR changes its point of attachment, existing sessions between CNs and nodes behind the MR are broken, and connectivity to the global Internet is lost. In addition, fixed nodes behind the MR are faced with sub-optimal routing with their correspondents in the global Internet, whereas multiple levels of mobility may cause extremely sub-optimal routing. Traditional work on mobility support as conducted in the Mobile IP working group is to provide continuous Internet connectivity to mobile hosts only (host mobility support) and are unable to support network mobility. The NEMO working group has therefore been created to specify solutions specific for network mobility support. To describe the problems and to define the requirements that will have to be met by the solutions, a new terminology is needed, which is the object of the present document. This terminology is supposed to serve as the base document produced by the NEMO WG and shall be refined once we agree on the requirements. 2. Applications Cases of mobile networks include networks attached to people (Personal Area Network or PAN, i.e. a network composed by all Internet appliances carried by people, like a PDA, a mobile phone, a digital camera, a laptop, etc.) and networks of sensors deployed in aircrafts, boats, busses, cars, trains, etc. An airline company that provides permanent on-board Internet access is an example of a mobile network. This allows passengers to use their laptops (this scenario is mentioned in [Tanenbaum] under section 1.2.4 and section 5.5.8; [Perkins] under section 5.12; [Solomon] under section 11.2; and [RFC2002] section 4.5), PDA, or mobile phone to connect to remote hosts, download music or video, browse the web. Passengers could themselves carry a network with them (a PAN). At the same time, air control traffic could be exchanged between the aircraft and air Ernst and Lach Expires May 2003 [Page 3] INTERNET-DRAFT Network Mobility Support Terminology October 2002 traffic control stations (this scenario has already been investigated by Eurocontrol, the European Organization for the safety of air navigation. During a transatlantic flight, the aircraft changes its point of attachment to the Internet and may be reachable by distinct Internet Service Providers (ISPs). Over the oceans, the aircraft gets connected to the Internet through a geostationary satellite; over the ground, it's through a radio link. Handoffs do typically not occur very often (a radio link may cover 400-500 kilometers). Another similar scenario mentioning ships and aircrafts can be found in [RFC1726, section 5.15]. Similarly, a bus, the metropolitan public transport, or the taxi company could allow passengers to connect their PAN to the Internet via the embarked network, therefore ensuring, while on-board, an alternative to the metropolitan cellular network, in terms of price or available bandwidth, access control, etc. Meanwhile, a number of Internet appliances deployed in the mobile network are used to collect traffic and navigation data from the Internet while sensors within the mobile network collect and transmit to the Internet live information, like the current number of passengers, expected time to arrival, the amount of petrol left in the tank, etc. For a number of reasons (network management, security, performance,...), it is desirable to interconnect the Internet appliances deployed in cars, trains, busses by means of, for instance, an Ethernet cable, instead of connecting them individually and directly to the Internet, therefore exhibiting the need to displace an entire network. 3. Terminology Terms introduced in this draft comply with the terminology already defined in the IPv6 [RFC2460] and Mobile IPv6 [MIPv6] specifications. Our terminology is primarily targeted toward IPv6 but is not necessarily limited to it. Some terms will only be useful for the purpose of defining the problem scope and functional requirements of network mobility support and shall be removed or refined once we agree on the requirements. The first section introduces terms to define the architecture components; the second introduces terms to discuss the requirements, the third, terms to discuss nested mobility; the forth defines multihoming, and the last, miscellaneous terms which do not fit in either sections. The terminology summarized in fig.1 to 5. Fig.1 shows a single mobile subnetwork. Fig.2. shows a larger mobile network comprising several subnetworks, attached on a foreign link. Fig.3 illustrates a node changing its point of attachment within the mobile network. Fig.4 and 5 illustrate nested mobility. 3.1. Architecture Components Ernst and Lach Expires May 2003 [Page 4] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Mobile Network An entire network, moving as a unit, which dynamically changes its point of attachment to the Internet and thus its reachability in the topology. The mobile network is connected to the global Internet via one or more mobile router(s) (MRs). From the fixed Internet, the mobile network is a cloud. 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. The internal of the mobile network will therefore not affect network mobility support protocols. Mobile Network Node (MNN) Any host or router located within the mobile network, either permanently or temporarily. A MNN could be any of a MR, LFN, VMN, or LMN. The distinction between LFN, LMN and VMN is necessary to discuss issues related to mobility management and access control, but does not preclude that mobility should be handled differently. Nodes are classified according to their function and capabilities. ____ | | | CN | |____| ___|____________________ | | | | | Internet | | | |________________________| __|_ __|_ | | Access | | | AR | Router | AR | |____| |____| ______|__ foreign __|_____________ home link __|_ link | | | MR | Mobile Router |____| _________|_______ internal __|__ __|__ link | | | | | MNN | | MNN | Mobile Network Nodes |_____| |_____| Figure 1: Architecture Components Ernst and Lach Expires May 2003 [Page 5] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Mobile Router (MR) A router which changes its point of attachment to the Internet. The MR has one or more egress interface(s) and one or more ingress interface(s) and acts as a gateway between the mobile network and the rest of the Internet. The MR thus maintains the Internet connectivity for the entire mobile network. When forwarding a packet to the Internet (i.e. upstream), the packet transmitted through one MR's egress interface; when forwarding a packet to the mobile network (i.e. downstream), the packet is transmitted through one of the MR's ingress interface. Fixed Node (FN) A node, either a host or a router, unable to change its point of attachment and its IP address without breaking open sessions. FNs are standard IPv6 nodes as defined in [IPv6-NODE] which do not support the MN functionality defined in [MIPv6] section 8.5 nor any other form of mobility support (also see [IPv6-NODE] section 7 "Mobility"). Mobile Node (MN) A node, either a host or a router, which is able to change its point of attachment and maintain continuous sessions. Node behind the MR Any MNN in a mobile network, beside the MRs connecting the mobile network to the Internet. Correspondent Node (CN) Any node that is communicating with one or more MNNs. A CN could itself be located within the mobile network. Access Router (AR) Any subsequent point of attachment of the MR at the network layer. Basically, a router on the home link or the foreign link. An AR may itself be located in a mobile network and provide access to mobile nodes. Egress Interface of a MR The interface attached to the home link if the MR is at home, or attached to a foreign link if the MR is in a foreign network. Ernst and Lach Expires May 2003 [Page 6] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Ingress Interface of a MR The interface attached to a link inside the mobile network. This interface is configured with the Mobile Network Prefix. ________________________ | | | | | Internet | | | |________________________| __|_ Access | | Router | AR | |____| foreign _____|_____________ link | | egress interface __|__ | | | ingress |____| MR | Mobile Router interface | |____| | | | | ingress interface | ____|________________ internal | __|__ __|__ link 1 _____ | | | | | | |__| | LFN | | LMN | | LFN | | |_____| |_____| |_____| | | internal link 2 Figure 2: Larger Mobile Network with 2 subnets Home subnet prefix A bit string that consists of some number of initial bits of an IP address which identifies the MR's home link within the Internet topology (i.e. the IP subnet prefix corresponding to the mobile node's home address, as defined in [MIPv6]). Foreign subnet prefix A bit string that consists of some number of initial bits of an IP address which identifies the MR's foreign link within the Internet topology. Ernst and Lach Expires May 2003 [Page 7] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Mobile Network Prefix A bit string that consists of some number of initial bits of an IP address which identifies the entire mobile network within the Internet topology. All MNNs necessarily have an address named after this prefix. 3.2. Functional Terms The distinction between LFN, LMN, and VMN as defined below it is a property of how different types of nodes can move in the topology. The rationale here is that nodes with different properties (may) have different requirements. This distinction may not be useful once we agree on the requirements. They are listed here as a means to ease and clarify the requirement discussion. Local Fixed Node (LFN) A fixed node (FN) that belongs to the mobile network and which doesn't move topologically with respect to the MR. Local Mobile Node (LMN) A mobile node (MN) or a mobile router (MR) that belongs to the mobile network (i.e. its home link is within the mobile network). It can move topologically with respect to the MR. Visiting Mobile Node (VMN) A mobile node (MN) or a mobile router (MR) that doesn't belong to the mobile network (i.e. its home link is not within the mobile network). A VMN that gets attached to a link within the mobile network obtains an address on that link and can move topologically with respect to the MR. NEMO-enabled (NEMO-node) A node that has been extended with network mobility support capabilities and that may take special actions based on that. (details of the capabilities are not known yet, but it may be implementing some sort of Route Optimization). MIPv6-enabled (MIPv6-node) A mobile node (MN) which is able to change its point of attachment and maintains continuous sessions thanks to the MN functionality as defined in [MIPv6] section 8.5. Ernst and Lach Expires May 2003 [Page 8] INTERNET-DRAFT Network Mobility Support Terminology October 2002 ________________________ | | | | | Internet | | | |________________________| __|_ __|_ | | Access | | | AR | Router | AR | |____| |____| __|_ _____|_____________ foreign | | _|__ link | MN | | | | |____| _____ |__| MR | Mobile Router | |__| |____| |--> | LMN | | __|_____________ internal | |_____| | __|__ | link 1 | _____ | | | | | |__| | LFN | | | LFN | | |_____| | | |_____| | | | | internal | | link 2 | |------------------------------| Figure 3: LMN changing subnet 3.3. Nested Mobility Nested mobility occurs when there are more than one level of mobility. A MNN acts as an Access Router and allows visiting nodes to get attached to it. There are two cases of nested mobility: - when the attaching node is a single node: VMN (see figure 4). For instance, when a passenger carrying a mobile phone gets Internet access from the public access network deployed into a bus. - when the attaching node is a router with nodes behind it, i.e.a mobile network (see figure 5). For instance, when a passenger carrying a PAN gets Internet access from the public access network deployed in the bus. Ernst and Lach Expires May 2003 [Page 9] INTERNET-DRAFT Network Mobility Support Terminology October 2002 ________________________ | | | | | Internet | | | |________________________| __|_ __|_ | | Access | | | AR | Router | AR | |____| |____| _____|_____________ home | _|__ link | | | | | _____ |__| MR | Mobile Router | | |__| |____| ----------> | VMN | | __|_____________ internal |_____| | __|__ __|__ link 1 _____ | | | | | | |__| | LFN | | LMN | | LFN | | |_____| |_____| |_____| | | internal link 2 Figure 4: Nested Mobility: single VMN attached to a mobile network In the second case, a mobile network is getting attached to a larger mobile network and the aggregated hierarchy of mobile networks becomes a single nested mobile network. In this case, we use the following terms: - root-NEMO: the mobile network at the top of the nested hierarchy. - parent-NEMO: the upstream-NEMO providing access to a mobile network down the hierarchy - sub-NEMO: the downstream-NEMO attached to a mobile network up the hierarchy. It becomes a subservient of the parent-NEMO. - Top-Level Mobile Router (TLMR): the MR(s) of the root-NEMO which are used to connect the nested mobile network to the fixed Internet. Ernst and Lach Expires May 2003 [Page 10] INTERNET-DRAFT Network Mobility Support Terminology October 2002 ________________________ | | | | | Internet | | | |________________________| __|_ __|_ | | Access | | | AR | Router | AR | |____| |____| _____|_____________ foreign _|__ link | | | | ____ |__| MR | Mobile Router (TLMR) |_| |__| |____| | | MR | | __|_____________ internal | |____| | __|__ __|__ link 1 _____ | | | | | | | | | | | LFN | | LMN | | LFN |__| | |_____| |_____| |_____| | | | | internal link 2 <-----------------> <---------------------------> sub-NEMO root-NEMO Figure 5: Nested Mobility: sub-NEMO attached to a larger mobile network 3.4. Multihomed mobile network Multihoming, as currently defined by the IETF, covers site- multihoming [MULTI6] and host multihoming. Within host-multihoming, a host may be either: - multi-addressed: multiple source addresses to choose between on a given interface; all IPv6 nodes are multi-addressed due to the presence of link-local addresses on all interfaces. - multi-interfaced: multiple interfaces according to [RFC2460] definition. - multi-linked: just like multi-interfaced but all interfaces are NOT connected to the same link. - multi-sited: when using IPv6 site-local address and attached to different sites Ernst and Lach Expires May 2003 [Page 11] INTERNET-DRAFT Network Mobility Support Terminology October 2002 So, a mobile network is multihomed when either: - a MR has multiple egress interfaces on the same foreign link - a MR has multiple egress interfaces on distinct foreign link - there are more than one MR in the mobile network 3.5. Miscellaneous Terms Host mobility support Host Mobility Support allows mobile nodes to maintain session continuity. In IPv6, it is achieved by Mobile IPv6 NEMO support Network mobility support allows mobile networks to maintain session continuity. Solutions developped to support NEtwork MObility will be referred to as "NEMO support". In Basic support, each Mobile Router has a Home Agent, and uses bidirectional tunneling between the MR and HA to preserve session continuity while the MR moves. The MR will acquire a Care-of- address from its attachment point much like what is done for Mobile Nodes using Mobile IP. This approach allows nesting of Nemos, since each MR will appear to its attachment point as a single node. In Extended support, we will seek to optimize routing between MNNs and arbitrary CNs by some means which details are not known yet. intra-domain mobility Mobility within a single administrative domain, i.e. between subnetworks topologically close in the IP hierarchy. As an instance, the displacement of a node within a limited vicinity of adjacent subnetworks, like in a campus, that belong to the same organization or between ARs that belong to the same ISP. In the literature, and depending on the definition of ``closeness'', this is also termed intra-site mobility, local mobility or micro- mobility. inter-domain mobility Mobility across administrative domain boundaries, i.e. between subnetworks topologically distant in the IP hierarchy. As an Ernst and Lach Expires May 2003 [Page 12] INTERNET-DRAFT Network Mobility Support Terminology October 2002 instance of Wide-Area Mobility, displacement of a node between distinct ISPs or organizations, or between widely separated sites of a single organization. In the literature, and depending on the definition of ``remoteness'', this is also termed inter-site mobility, global mobility, or macro-mobility. Idle MNN A MNN that does not engage in any communication. Idle Mobile Network A mobile network that does not engage in any communication outside the network may be considered idle from the global Internet. This doesn't preclude that MNNs are themselves idle. Internal traffic between any two MNNs located in the same mobile network is not concerned by this statement. Acknowledgments The material presented in this document takes most of the text from our former internet-drafts submitted to MobileIP WG and to the former MONET BOF, which where themselves based on original text from [Ernst01]. Authors would therefore like to thank both Motorola Labs Paris and INRIA (PLANETE team, Grenoble, France), for the opportunity to bring this topic to the IETF since 2000, and particularly Claude Castelluccia (INRIA) for its advices, suggestions, and direction. We also acknowledge Alexandru Petrescu (Motorola), Christophe Janneteau (Motorola), Hesham Soliman (Ericsson) and Mattias Petterson (Ericsson) and all the people on the NEMO (formerly MONET) mailing list which helped to improve this draft. Ernst and Lach Expires May 2003 [Page 13] INTERNET-DRAFT Network Mobility Support Terminology October 2002 References [Ernst01] Thierry Ernst Network Mobility Support in IPv6", PhD Thesis, University Joseph Fourier Grenoble, France. October 2001. http://www.inria.fr/rrrt/tu-0714.html [MIPv6] David B. Johnson and C. Perkins. "Mobility Support in IPv6". Internet Draft draft-ietf-mobileip-ipv6-18.txt, July 2002. Work in progress. [MULTI6] B. Black, V. Gill and J. Abley "Requirements for IPv6 Site-Multihoming Architectures" draft-ietf-multi6-multihoming-requirements-03 May 2002. Work in progress [IPv6-NODE] John Loughney "IPv6 Node Requirements" draft-ietf-ipv6-node-requirements-01.txt July 2002, Work in progress. [Perkins] C. E. Perkins. "Mobile IP, Design Principles and Practices." Wireless Communications Series. Addison-Wesley, 1998. ISBN 0-201-63469-4. [RFC1726] C. Partridge "Technical Criteria for Choosing IP the Next Generation", IETF RFC 1726 section 5.15, December 1994. [RFC2460] S. Deering and R. Hinden. "Internet Protocol Version 6 (IPv6) Specification". IETF RFC 2460, December 1998. [RFC2002] C. Perkins (Editor). "IP Mobility Support". IETF RFC 2002,October 1996. [Solomon] J. D. Solomon. "Mobile IP, The Internet Unplugged". Prentice Hall Series in Computer Networking and Distributed Systems. Prentice Hall PTR, 1998. ISBN 0-13-856246-6. [Tanenbaum] Andrew Tanenbaum "Computer Networks", Prentice-Hall, Third Edition. 1996 Ernst and Lach Expires May 2003 [Page 14] INTERNET-DRAFT Network Mobility Support Terminology October 2002 Author's Addresses Questions about this document can be directed to the authors: Thierry Ernst, INRIA, visiting researcher at WIDE Jun Murai lab. Faculty of Environmental Information, Keio University. 5322 Endo, Fujisawa-shi, Kanagawa 252-8520, Japan. Phone : +81-466-49-1100 Fax : +81-466-49-1395 E-mail: ernst@sfc.wide.ad.jp Web: http://www.sfc.wide.ad.jp/~ernst/ Hong-Yon Lach Motorola Labs Paris, Lab Manager, Networking and Applications Lab (NAL) Espace Technologique - Saint Aubin 91193 Gif-sur-Yvette Cedex, France Phone: +33-169-35-25-36 Email: Hong-Yon.Lach@crm.mot.com Ernst and Lach Expires May 2003 [Page 15]