NEMO Working Group Thierry Ernst, Editor Internet-Draft INRIA and WIDE February, 2003 "Network Mobility Support Requirements" 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 Network mobility arises when an entire network changes its point of attachment to the Internet and thus its reachability in the topology. The mobile network is viewed as a unit and is connected to the global Internet by one or more mobile routers. In contrast with host mobility support which aims at providing continuous Internet connectivity to mobile hosts only, network mobility support is to provide continuous Internet sessions not only to the mobile router connecting the mobile network to the global Internet, but also to nodes behind the mobile router. The purpose of this document is to list the requirements that must be met by network mobility support solutions in IPv6. Ernst et al. Expires August 2003 [Page 1] INTERNET-DRAFT Network Mobility Support Requirements February 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 03 2. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 04 3. Network Mobility Goals and Methodology . . . . . . . . . . . 04 4. General Purpose Guidelines for the Solutions . . . . . . . . 05 5. One-liner Requirements for Basic NEMO Support. . . . . . . . 09 A. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . 11 B. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 C. Editors' Addresses . . . . . . . . . . . . . . . . . . . . . 12 D. Full Copyright Statement . . . . . . . . . . . . . . . . . . 12 Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. Ernst et al. Expires August 2003 [Page 2] INTERNET-DRAFT Network Mobility Support Requirements February 2003 1. Introduction Network mobility support is concerned with managing the mobility of an entire network, viewed as a single unit, which changes its point of attachment to the Internet and thus its reachability in the Internet topology. Such kind of network is referred to as a mobile network and includes one or more mobile routers (MRs) which connect it to the global Internet. Nodes behind the MR(s) (MNNs) are both fixed (keeping the same address on the mobile network at all times), and mobile (entering and leaving the mobile network as they roam with respect to it). In most cases, the internal structure of the mobile network will in effect be relatively stable (no dynamic change of the topology), but this is not a general assumption. Cases of mobile networks include for instance: - networks attached to people (Personal Area Networks or PANs): a cell-phone with one cellular interface and one Bluetooth interface together with a Bluetooth-enabled PDA constitute a very simple instance of a mobile network. The cell-phone is the mobile router while the PDA is used for web browsing or runs a personal web server. - networks of sensors and computers deployed in vehicles: vehicles are more and more embedded with a number of processing units for safety and ease of driving reasons, as advocated by ITS (Intelligent Transportation Systems) applications. - access networks deployed in public transportation (buses, trains, taxis, aircrafts): they provide Internet access to IP devices carried by passengers (laptop, camera, mobile phone: host mobility within network mobility or PANs: network mobility within network mobility, i.e. nested mobility). - ad-hoc networks connected to the Internet via a MR: for instance students in a train that both need to set up an ad-hoc network among themselves and to get Internet connectivity through the MR connecting the train to the Internet. Traditional work conducted so far on mobility support was to provide continuous Internet connectivity to mobile hosts only (host mobility support). In contrast with host mobility support, network mobility support is to provide continuous Internet sessions not only to the mobile router connecting the mobile network to the global Internet, but also to nodes behind the mobile router. Mobility of networks does not cause MNNs to change their own physical point of attachment, however they happen to change their topological Ernst et al. Expires August 2003 [Page 3] INTERNET-DRAFT Network Mobility Support Requirements February 2003 location with respect to the global Internet which results in lack of Internet access and broken sessions if no supporting mechanisms are deployed. In addition, communication between a MNN and an arbitrary Correspondent Node (CN) may result in extremely suboptimal paths, particularly when mobile networks are nested or when the CN is itself mobile. The mechanisms required for handling such mobility issues are currently lacking within the IETF standards. The NEMO working group has therefore been set up to deal with those. The purpose of this document is thus to detail the methodology that will be followed by the NEMO working group and to list requirements for network mobility support. This document is structured as follows: first, section 2 introduces the terminology for network mobility. In section 3, we define the goals and methodology of the working group and we emphasize the stepwise approach the working group has decided to follow. A number of guidelines are listed in section 4 and are used in section 5 to edict the requirements for basic network mobility support. 2. Terminology Terms used in this document are taken from [MIPv6] and [MOBILITY- TERMS]. Additional terms pertaining to network mobility specifically are defined in [NEMO-TERMS]. [NOTE FROM THE EDITOR: parts from draft [NEMO-TERMS] will probably be moved to [MOBILITY-TERMS] whereas the remaining terms would then be pasted in this present document. THIS IS TO BE DISCUSSED] 3. Network Mobility Goals and Methodology The primary goal of the NEMO work is to specify a solution which allows mobile network nodes (MNNs) to remain connected to the Internet and continuously reachable at all times while the mobile network they are attached to changes its point of attachment. Secondary goals of the work is to investigate the effects of network mobility on various aspects of internet communication such as routing protocol changes, implications of realtime traffic and fast handovers, optimizations. These should all support the primary goal of reachability for mobile network nodes. Security is an important consideration too, and efforts should be made to use existing solutions if they are appropriate. Although a well-designed solution may include security inherent in other protocols, mobile networks also introduce new challenges. Ernst et al. Expires August 2003 [Page 4] INTERNET-DRAFT Network Mobility Support Requirements February 2003 For doing so, the NEMO working group has decided to take a stepwise approach by standardizing a basic solution to preserve session continuity (basic network mobility support), and at the same time study the possible approaches and issues with providing more optimal routing with potentially nested mobile networks (extended network mobility support). However, the working group is not chartered to actually standardize a solution to such route optimization at this point in time. For basic NEMO support, the working group will assume that none of the nodes behind the MR will be aware of the network's mobility, thus the network's movement needs to be completely transparent to the nodes inside the mobile network. This assumption will be made to accommodate nodes inside the network that are not generally aware of mobility. The efforts of the Mobile IP working group have resulted in the Mobile IPv4 [7] and Mobile IPv6 [6] protocols, which have already solved the issue of host mobility support. Since challenges to enabling mobile networks are vastly reduced by this work, basic network mobility support will adopt the methods for host mobility support used in Mobile IP, and extend them in the simplest way possible to achieve its goals. The basic support solution is for each MR to have a Home Agent, and use 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 (MN) using Mobile IP. This approach allows nested mobile networks, since each MR will appear to its attachment point as a single node. 4. General Purpose Guidelines for the Solutions This section lists a number of guidelines which are used to edict the requirements that MUST or SHOULD be met by forthcoming network mobility support solutions, for both basic NEMO support and extended NEMO support. - Migration Transparency: a permanent connectivity to the Internet MUST be provided to all MNNs while continuous sessions MUST be maintained as the mobile router changes its point of attachment. For doing so, MNNs will be reachable via their permanent IP addresses. - Performance Transparency (Seamless Mobility): NEMO support SHOULD provide limited signaling overhead and ideally SHOULD minimize the impact of handover on applications, in terms of packet loss or delay. Variable delays of transmission and losses Ernst et al. Expires August 2003 [Page 5] INTERNET-DRAFT Network Mobility Support Requirements February 2003 between MNNs and their respective CNs as the network is moving are not considered lack of performance transparency. - Network Mobility Support Transparency: MNNs behind the MR(s) don't change their own point of attachment as a result of the mobile network's displacement in the Internet topology. Consequently, NEMO support is better performed by the sole MR(s) and specific support functions on any other nodes than the MR(s) SHOULD be avoided. - Operational Transparency: NEMO support MUST be implemented at the IP layer level. It MUST be transparent to any upper layer so that any upper layer protocol can run unchanged on top of an IP layer extended with NEMO support. - Arbitrary Configurations: The formation of a mobile network can exist in various levels of complexity. In the simplest case, a mobile network contains just a mobile router and a host. In the most complicated case, a mobile network is multi-homed and is itself a multi-level aggregation of mobile networks with collectively thousands of mobile routers and hosts. While the list of potential configurations of mobile networks cannot be limited, at least the following configurations are desirable: o mobile networks of any size, ranging from a sole subnet with a few IP devices to a collection of subnets with a large number of IP devices, o multi-homed mobile network (see definition in [NEMO-TERMS]. o foreign mobile nodes that attach to the mobile network. o nodes that change their point of attachment within the mobile network. o nested mobile networks (see definition in [NEMO-TERMS]. o mobile networks displaced within a domain boundary (local mobility) or between domain boundaries (global mobility). o distinct mobility frequencies. o distinct access medium. In order to keep complexity minimal, transit networks are excluded from this list. A transit network is one in which data would be forwarded between two endpoints outside of the network, so that Ernst et al. Expires August 2003 [Page 6] INTERNET-DRAFT Network Mobility Support Requirements February 2003 the network itself simply serves as a transitional conduit for packet forwarding. A stub network (leaf network), on the other hand, does not serve as a data forwarding path. Data on a stub network is either sent by or addressed to a node located within that network. - Administration: the solution MUST not prevent mobile networks and mobile nodes owned by administratively different entities to attach to any part of the Internet topology for any other considerations than administrative and security policies (both global mobility and local-mobility are desirable). - Scalability: NEMO support signaling and processing MUST scale to a potentially large number of mobile networks irrespective of their configuration, mobility frequency, and number of CNs. - Backward Compatibility: NEMO support MUST be able to co-exist and not interfere with existing IPv6 standards. The solution MUST reuse standards defined in other IETF working groups and MAY only extend them if deemed necessary. For instance, the following mechanisms defined by other working groups MUST still function: o Address allocation and configuration mechanism. o Host mobility support: the solution MUST not prevent mobile nodes and correspondent nodes, either located within or outside the mobile network, to keep operating protocols defined by the Mobile IP working group. o Multicast support: the solution MUST maintain ongoing multicast sessions of MNNs as the mobile router changes its point of attachment. Group membership is currently gathered by MLD. o Access control protocols and mechanisms: NEMO support MUST not disallow protocols and mechanisms used by visiting mobile hosts and routers to be authenticated and authorized to gain access to the Internet via the mobile network infrastructure (MRs). o Security protocols and mechanisms o Routing protocols and mechanisms: routers deployed in mobile networks may be routers like the others and therefrom are expected to run in some situations a number of protocols such as a routing protocol, Neighbor Discovery, ICMP, Router Renumbering and others. NEMO support MUST thus not prevent Ernst et al. Expires August 2003 [Page 7] INTERNET-DRAFT Network Mobility Support Requirements February 2003 usual routing protocols and mechanisms to keep working within the mobile network and to interact with the global Internet (home network only in the case of basic NEMO support) when necessary. o Seamless Mobility: the solutions MUST be compatible with FMIPv6 - Security: NEMO support MUST comply with usual IETF security policies and recommendations and MUST have its specific security issues fully addressed. In practice, all NEMO support control messages transmitted in the network MUST ensure an acceptable level of security to prevent intruders to usurp identities. Specifically, the following issues have to be addressed: o Authentication of the sender to prevent identity usurpation. o Authorization, to make sure the sender is granted permission to perform the operation as indicated in the control message. o Confidentiality of the data contained in the control message. o Location Privacy: means to hide the actual location of MNNS to third parties other than the HA if desired. Ernst et al. Expires August 2003 [Page 8] INTERNET-DRAFT Network Mobility Support Requirements February 2003 5. One-liner Requirements for Basic NEMO Support The NEMO WG will specify a unified and unique solution for "Basic Network Mobility Support". The solution will allow all nodes in the mobile network to be reachable via permanent IP addresses, as well as maintain ongoing sessions as the MR changes its point of attachment to the Internet topology. This will be done by maintaining a bidirectional tunnel between the MR and its Home Agent. The Working Group will investigate reusing the existing Mobile IPv6 mechanisms for the tunnel management, or extend it if deemed necessary. The following requirements are placed on the Basic NEMO support solution, hereafter referred to as "the solution": R01: The solution MUST be implemented at the IP layer level. R02: The solution MUST set up a bi-directional tunnel between MR and MR's Home Agent. R03: All traffic exchanged between a MNN and a CN in the global Internet MUST transit through the bidirectional tunnel. R04: MNNs MUST be reachable at a permanent IP address and name. R05: The solution MUST maintain continuous sessions (both unicast and multicast) between MNNs and arbitrary CNs after IP handover of (one of) the MR. R06: The solution MUST not require modifications to any node other than MRs and HAs. R07: The solution MUST support fixed nodes, mobile hosts and mobile routers in the mobile network. R08: The solution MUST allow MIPv6-enabled MNNs to use a mobile network link as either a home link or a foreign link. R09: The solution MUST not prevent the proper operation of Mobile IPv6 (i.e. the solution MUST support MIPv6-enabled MNNs and MUST also allow MNNs to receive and process Binding Updates from arbitrary Mobile Nodes.) R10: The solution MUST treat all the potential configurations the same way (whatever the number of subnets, MNNs, nested levels of MRs, egress interfaces, ...) R11: The solution MUST support mobile networks attaching to other mobile networks (nested mobile networks). Although it is not Ernst et al. Expires August 2003 [Page 9] INTERNET-DRAFT Network Mobility Support Requirements February 2003 fully clear how many layers of topology MUST be supported, or the complexity requirements of those nested networks, the goal is to support arbitrary levels of recursive networks, and only in the case where this is impractical and protocol concerns preclude this support should the solution impose restrictions on nesting (e.g. path MTU). R12: The solution MUST function for multi-homed mobile networks. More precisely: R13.1: The solution MUST support mobile networks with multiple MRs, R13.2: The solution MUST support MR with multiple interfaces, R13.3: The solution must support MR with multiple global addresses on an egress interface. R14: Signaling messages between the HA and the MR MUST be secured: R14.1: The receiver MUST be able to authenticate the sender R14.2: The function performed by the sender MUST be authorized for the content carried R14.3: Anti-replay MUST be provided R14.4: The signaling messages SHOULD be encrypted R15: The solution MUST ensure transparent continuation of routing and management operations over the bi-directional tunnel when the MR is away from home. (this includes e.g. routing protocols, router renumbering, DHCPv6, etc) R16: The solution MUST not impact on the routing fabric neither on the Internet addressing architecture R17: The solution MUST ensure backward compatibility with other standards defined by the IETF. Ernst et al. Expires August 2003 [Page 10] INTERNET-DRAFT Network Mobility Support Requirements February 2003 A. Acknowledgments The material presented in this document takes most of its text from discussions and previous documents submitted to the NEMO working group. This includes initial contributions from Motorola, INRIA, Ericsson and Nokia. We are particularly grateful to Hesham Soliman (Ericsson) and the IETF ADs (Erik Nordmark and Thomas Narten) who highly helped to set up the NEMO working group. We are also grateful to all the following people whose comments highly contributed to the present document: TJ Kniveton (Nokia), Alexandru Petrescu (Motorola), Christophe Janneteau (Motorola), Pascal Thubert (CISCO), Hong-Yon Lach (Motorola), Mattias Petterson (Ericsson) and all the others people who have expressed their opinions on the NEMO (formely MONET) mailing list. Thierry Ernst wish to personally grant support to its previous employers, INRIA, and Motorola for their support and direction in bringing this topic up to the IETF, particularly Claude Castelluccia (INRIA) and Hong-Yon Lach (Motorola). B. References [IPv6-NODE] John Loughney "IPv6 Node Requirements" draft-ietf-ipv6-node-requirements-01.txt July 2002, Work in progress. [MIPv6] David B. Johnson and C. Perkins. "Mobility Support in IPv6" draft-ietf-mobileip-ipv6-20.txt, January 2002. Work in progress. [MOBILITY-TERMS] J. Manner "Mobility Related Terminology August 2002. Work in progress [NEMO-TERMS] Thierry Ernst and Hong-Yon Lach "Terminology for Network Mobility Support", draft-ernst-nemo-terminology.txt. Work in progress. [RFC1122] R. Braden (editor). "Requirements for Internet Hosts - Communication Layers". IETF RFC 1122, October 1989. [RFC2119] S. Bradner "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, IETF, March 1997. Ernst et al. Expires August 2003 [Page 11] INTERNET-DRAFT Network Mobility Support Requirements February 2003 [RFC2460] S. Deering and R. Hinden. "Internet Protocol Version 6 (IPv6) Specification" IETF RFC 2460, December 1998. C. Editors's Addresses Questions about this document can be directed to the NEMO working group chairs: Thierry Ernst, Keio University. 5322 Endo, Fujisawa-shi, Kanagawa 252-8520, Japan. Phone : +81-466-49-1100 Fax : +81-466-49-1395 Email : ernst@sfc.wide.ad.jp T. J. Kniveton Communications Systems Lab Nokia Research Center 313 Fairchild Drive Mountain View, California 94043, USA Phone : +1 650 625-2025 Fax : +1 650 625-2502 EMail : Timothy.Kniveton@Nokia.com D. Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. Ernst et al. Expires August 2003 [Page 12] INTERNET-DRAFT Network Mobility Support Requirements February 2003 This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Funding for the RFC editor function is currently provided by the Internet Society. Ernst et al. Expires August 2003 [Page 13]