MIP4 Working Group N. A. Fikouras INTERNET DRAFT K. Kuladinithi Expires: August 2004 C. Goerg ComNets-ikom, Uni. Bremen C. Bormann TZI, Uni. Bremen May 2004 Mobile IPv4 Flow Mobility Problem Statement draft-nomad-mip4-flow-mobility-pb-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 obsolete 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 Internet capable mobile or portable devices are already a modern commodity while it is becoming all the more common that such devices are hosts to more then one wireless interface. The aim of this document is to show that a mobile user may make best use of this property by using multiple wireless interfaces in parallel. This would incline that the mobile user can distribute active flows across the available wireless interfaces and is able to seamlessly transfer them between the wireless interfaces in mid-session without interruption. Table of Contents 1. Introduction....................................................2 3. Scenarios for multiple interface management and flow mobility...3 3.1 Scenario 1......................................................3 3.2 Scenario 2......................................................3 3.3 Scenario 3......................................................4 4. Related Work....................................................4 4.1 Mobile IP.......................................................4 4.2 Stream Control Transmission Protocol............................5 4.3 Resource reservation Protocol...................................5 4.4 Filters for Mobile IP...........................................6 References.........................................................6 Authors' Addresses.................................................7 Intellectual Property Statement....................................7 MIP4 Flow Mobility PB Expires August 2004 1 Internet Draft MIP4 Flow Mobility PB February 2004 1. Introduction It is forecasted that by 2005 an increasing portion of Internet users will be using wireless devices such as web-enabled cell phones and PDAs to go online as the number of worldwide Internet users will nearly triple to 1.17 billion [1]. As a response to the explosive growth of mobile Internet users, operators have urged for the deployment of packet services in wide-area cellular networks. This was accompanied by a rollout of standards for license free personal and local area communication networks. The increasing availability of a range of heterogeneous wireless technologies is a strong indication that future mobile Internet communication systems will be built upon wireless overlay networks [2]. It is understood that in order to make best use of this property one must be able to selectively and intelligently utilise in parallel any number of wireless networks in his/her vicinity while dynamically distributing active flows across the available wireless network links. The benefits of taking advantage of this property can be grouped in three main areas, namely: o The aggregation of network resources available over a selection of the wireless networks. o The matching of individual flows and wireless network links with respect to attributes such as cost, quality of service parameters or a specific service. o Achieving loss-less handoffs with minimal effect to active communications. The purpose of this draft is to: o Raise awareness on the opportunities aroused by the increasing availability of multi-interfaced mobile nodes. o Articulate the problems of simultaneously using multiple wireless network links with existing protocols. o Argument that a solution can best be provided with an extension of the Mobile IP protocol. 2 Problem Overview In homogeneous networks, a hand-off is initiated only when a mobile unit eludes the boundaries of an administered domain and enters another. However, in heterogeneous networks, a mobile unit does not need to move in order to initiate a hand-off. Algorithms for hand- offs between heterogeneous networks are different from those for homogeneous networks. Any hand-off decision is bound to affect a range of active communications with different attributes and requirements, benefiting some while degrading the performance of others. The simultaneous use of multiple wireless network links reduces the effect of this problem by a factor equivalent to the number of network connections. To that end, the mobile node should be able to move individual flows between network links with respect to the requirements of the flow and the user’s preferences. The management of flows should require minimal interaction with communication peers while the differentiation of flows should take place as close to the mobile node as possible. This will allow for fast reaction times while restricting the amount of signaling that traverses the core network fabric. The requirements for any proposed solution aim at providing support for multiple wireless interface management and flow mobility include: o solution should operate in a transparent fashion to higher layer MIP4 Flow Mobility PB Expires August 2004 2 Internet Draft MIP4 Flow Mobility PB February 2004 protocols and applications. o solution should involve a minimum amount of signaling that should be restricted to the mobile nodes vicinity and not communicated to the Internet. o solution should dictate a minimum amount of alterations to nodes other than the mobile node and the mobility management support infrastructure. o solution should not compromise the security of involved nodes. o solution should be backwards compatible, i.e. remain functional even in environments where their operational requirements are not supported. 3. Scenarios for multiple interface management and flow mobility The following scenarios describe a tactical application and two everyday life situations aimed at highlighting the need for simultaneous use of multiple wireless links and flow mobility. 3.1 Scenario 1 An ambulance is called at the scene of a car accident. A paramedic initiates a communication to a hospital via a wide area cellular link for the relay of low bit-rate live video from the site of the crash to assess the severity of the accident. It is identified that one of the passengers has suffered a severe head injury. The paramedic decides to consult a specialist via video conferencing. This session is initiated from the specialist via the same wide area cellular link. Meanwhile, the paramedic requests for the download of the patient’s medical records from the hospital’s servers. The paramedic decides in mid-session that the wide area cellular link is too slow for this download and transfers the download to the ambulance satellite link. Even though this link provides a significantly faster bit rate it has a longer traversal delay and only down-link is available. For this, only the down-stream of the download is transferred while up-stream proceeds over the wide area cellular link. Connectivity with the ambulance is managed over a wireless local area link between the paramedic and the ambulance. Even though the paramedic has performed a partial hand-off for the transfer of the download down-stream to the satellite link, the upstream and the video conferencing session remains on the wide area cellular link. This serves best the time constraint requirements of the real time communication. 3.2 Scenario 2 Mr. Smith is on his way to work waiting at a train station. He uses this opportunity and the presence of a wireless LAN hot-spot to download the news from his favorite on-line news channel. His train is announced and Mr. Smith decides to buy a ticket. However, the ticket reservation service is only available via a wide area cellular link of a specific provider. While Mr. Smith is downloading the news and accessing the train ticket reservation service he receives a phone call. This connection is receives over a separate wide area cellular link. Mr. Smith answers the call to be informed that a colleague is also at the train station and would like to travel with him. Mr. Smith decides he wishes to initiate a video flow for this communication. The bandwidth and traversal delay of the wide area cellular link is not adequate for the video conference, so both flows (video/audio) are transferred to a wireless local area link via a hot-spot. This transfer occurs transparently and without affecting any other active flows. MIP4 Flow Mobility PB Expires August 2004 3 Internet Draft MIP4 Flow Mobility PB February 2004 In order to cater for the communication means of the modern man, communication devices should be equipped with a range of heterogeneous wireless interfaces providing with several points of attachment to the global Internet. 3.3 Scenario 3 Alice is at the airport waiting to board the plane. She receives a call by her husband. This audio communication is received via a wireless local area link realized over one of the available hot- spots. She knows this is going to be a long flight and wishes to catch up on some work. Alice uses a wireless LAN connection to download the necessary data. However, there is not enough time and Alice decides to accelerate the download. Her notebook is equipped with an additional wireless local area network interface. Alice decides to distribute the different download flows between the multiple interfaces to accelerate the download. This scenario illustrates the capacity of mobile nodes with multiple points of attachment not just to distribute and transfer whole flows between the wireless links. The scenarios illustrate several requirements of day-to-day as well as tactical applications, namely: 1) The seamless interoperability of heterogeneous wireless networks that allows for vertical mobility across the various layers of the wireless overlay network. These will include wide area cellular networks for the connectivity of units on the move as well as local area wireless networks for connectivity either via hot-spots or mobile ad-hoc networks. 2) Access for all mobile users to resources on the global Internet and more importantly reachability on a globally unique, permanent identity. 3) Policy based selection of the type of communication network for different types of communications. The high correlation between type of mobility, position, reposition and type of communication/service that a mobile user may request or receive must be reflected in this policy. 4) Simultaneous use of multiple wireless networks. Without this feature these scenarios would not be feasible as mobile units would be required to switch between available wireless networks in order to more efficiently communicate with others or to access specific services. As awareness is raised for the opportunities made possible by multi-interfaced mobile nodes, policy based routing will gain importance. The following section gives a discussion of existing solutions to the problem of mobility, flow and multiple interface management and explains the shortcoming of each such solution. 4. Related Work 4.1 Mobile IP The Mobile IP [3] is currently the dominant solution for the provision of Internet mobility management. However, Mobile IP has been designed with a focus on mobile nodes with a single wireless link to the Internet. Mobile IP introduces the notion of Internet layer hand-offs that are initiated every time that a mobile node MIP4 Flow Mobility PB Expires August 2004 4 Internet Draft MIP4 Flow Mobility PB February 2004 moves across Internet administrative domains. Mobile IP Mobility Agents are unable to distinguish between individual flows and with every subsequent Mobile IP hand-off all active flows are redirected to the most recently registered location. This behavior restricts mobile nodes with multiple access interfaces that in order to take advantage of that property should be able to determine on a per flow basis how to have them distributed across the available wireless links. A solution to the problem of simultaneous multiple access interface management can be provided with the combination of multi-homing and Mobile IP route optimization. By sharing acquired care-of addresses and home IP addresses between the available access interfaces, it is possible with route optimization to distribute flows from different communication peers between the access interfaces. However, such a solution would require that for every change of state signaling information would have to be relayed to the corresponding communication peer. In addition, it would be impossible to differentiate between incoming flows from the same source and addressed to the same home IP address. Furthermore, multi-homing is based on the high availability of Internet addresses, several of which would be allocated to each mobile node, globally. Even though this might be feasible for IPv6 it is not possible for IPv4 where Internet addresses are scarce. It is considered that capability to simultaneously use multiple access interfaces and to move flows between them should be available to IPv4 and IPv6 mobile nodes alike. [4] highlights the goals and benefits of multi-homing in IPv6. 4.2 Stream Control Transmission Protocol The same problem could be resolved with the help of transport layer protocols such as the SCTP [5]. The SCTP is like TCP a reliable transport service. Similar to TCP, SCTP is a session-oriented mechanism, meaning that a relationship between the endpoints of an SCTP communication is negotiated prior to data transmission. SCTP includes native support for multi-homing but only for redundancy purposes. This means that, SCTP endpoints exchange lists of addresses during initiation of the association while a single one is chosen for the SCTP data transmission. Should that IP address become unavailable or when demonstrating high packet loss, the communication will fall- back to another home IP address until the first becomes again available. In combination with Mobile IP, SCTP could guarantee the reachability of the mobile node on any one of those home IP addresses. This behavior resembles the requirement for flow mobility but is only initiated for redundancy purposes and not otherwise controlled by the mobile node. Even if renegotiation of communication parameters was possible in mid-session it would involve exchanging signaling information between communication peers that would propagate through the Internet fabric. A final argument against the use of SCTP for the realization of multiple access interface management and flow mobility is that the support of SCTP in the existing Internet infrastructure is minimal. 4.3 Resource reservation Protocol A key issue in flow mobility is the capacity to differentiate between individual flows destined for a particular mobile node. The RSVP [6] has been designed specifically for hosts to request specific qualities of service from the network for particular flows. However, RSVP does not perform its own routing; instead it uses underlying routing protocols to determine where it should carry reservation requests and subsequently flows. Consequently, a mobile node that wishes to move a flow between two access interfaces would be able to MIP4 Flow Mobility PB Expires August 2004 5 Internet Draft MIP4 Flow Mobility PB February 2004 use RSVP to identify a flow but would not be able to alter routing in order to have the flow delivered to selected access interface. 4.4 Filters for Mobile IP Filters for Mobile IPv4 bindings [7] enables mobile nodes to associate one or more Filters with mobility bindings during registration. Flows that match a Filter will be processed as defined by the Filter. In this manner, it is possible for a mobile node to distribute flows among available wireless links, or to request that such flows are dropped before reaching the mobile node. Filters for Mobile IP does not introduce any additional signaling, it dictates that filters and filtering management extensions should be piggybacked by registration signaling. This protocol extension to Mobile IP does not introduce any security requirements as existing security considerations are adequate. Filters for Mobile IP is compatible with hierarchical Mobile IP organizations that enables the localized management of flow mobility and restricts signaling from reaching communication peers. Even in this absence of hierarchical Mobile IP considerations, filtering information is terminated at the Home Agent and is not propagated further. This extension inherits the property of the basic Mobile IP to operate transparently to active communications. As such filtering occurs in a manner transparent to transport layer protocols and applications. For the deployment of Filters for Mobile IP no changes are required to Correspondent Nodes while any alterations affect only the mobile node requesting for filtering services and the Mobile IP infrastructure that wishes to provide this service. Filters for Mobile IP is backwards compatible with standard Mobile IP and can be deployed in conjunction with multi-homing; for every home IP address separately. There are currently several proposals aimed at introducing filters in Mobile IP [7-10]. [7] has been successfully implemented and experimentally evaluated [11] proving the feasibility of this approach. References MIP4 Flow Mobility PB Expires August 2004 6 Internet Draft MIP4 Flow Mobility PB February 2004 [1] eTForecasts, "Internet Users Will Surpass 1 Billion in 2005," http://www.etforecasts.com/pr/pr201.htm. [2] R. H. Katz and E. A. Brewer, "The Case for Wireless Overlay Networks," in Mobile Computing, T. Imielinski and H. F. Korth, Eds.: Kluwer Academic Publishers, 1996, pp. 621-650. [3] C. E. Perkins, "IP Mobility Support for IPv4," IETF RFC3344, August 2002. [4] T. Ernst, N. Montavont, R. Wakikawa, C. Ng, T. Noel, E. Paik, and K. Kuladinithi, "Goals and Benefits of Multihoming," IETF http://www.ietf.org/internet-drafts/draft-ernst-generic- multihoming-pb-statement-00.txt, February 2004. [5] L. Ong and J. Yoakum, "An Introduction to the Stream Control Transmission Protocol (SCTP)," IETF RFC3286, May 2002. [6] R. Braden, L. Zhang, S. Berson, S. Herzog, and S. Jamin, "Resource ReSerVation Protocol (RSVP) - Version 1 Functional Specification," IETF RFC2205, September 1997. [7] N. A. Fikouras, A. Udugama, K. Kuladinithi, C. Görg, and W. Zirwas, "Filters for Mobile IP Bindings (NOMAD)," IETF http://www.ietf.org/internet-drafts/draft-nomad-mobileip-filters- 05.txt, October 2003. [8] K. Kuladinithi, N. A. Fikouras, and C. Görg, "Filters for Mobile IPv6 Bindings (NOMADv6)," IETF http://www.ietf.org/internet- drafts/draft-nomadv6-mobileip-filters-01.txt, October 2003. [9] N. Montavont and T. Noel, "Home Agent Filtering for Mobile IPv6," IETF http://www.ietf.org/internet-drafts/draft-montavont-mobileip- ha-filtering-v6-00.txt, 1/2004 2004. [10] H. Soliman, K. Malki, and C. Castelluccia, "Per-flow movement in MIPv6," IETF http://www.ietf.org/internet-drafts/draft-soliman- mobileip-flow-move-03.txt, 7/2003 2003. [11] N. A. Fikouras, A. Udugama, C. Görg, W. Zirwas, and J. M. Eichinger, "Experimental Evaluation of Load Balancing for Mobile Internet Real-Time Communications," presented at Proceedings of the Sixth International Symposium on Wireless Personal Multimedia Communications (WPMC), Yokosuka, Kanagawa, Japan, 2003. Authors' Addresses Niko A. Fikouras Departmnt of Communication Networks (ComNets) Center for Information and Communication Technology (ikom) University of Bremen Phone: +49-421-218-3339 D-28219 Bremen, Germany Email: niko@comnets.uni-bremen.de Koojana Kuladinithi Department of Communication Networks (ComNets) Center for Information and Communication Technology (ikom) University of Bremen Phone: +49-421-218-8264 D-28219 Bremen, Germany Email: koo@comnets.uni-bremen.de Carmelita Goerg Department of Communication Networks (ComNets) Center for Information and Communication Technology (ikom) University of Bremen Phone: +49-421-218-2277 D-28219, Bremen, Germany Email: cg@comnets.uni-bremen.de Carsten Bormann Technologie-Zentrum Informatik (TZI) University of Bremen Phone: +49-421-218-7024 D-28219, Bremen, Germany Email: cabo@informatik.uni-bremen.de Intellectual Property Statement The IETF takes no position regarding the validity or scope of any MIP4 Flow Mobility PB Expires August 2004 7 Internet Draft MIP4 Flow Mobility PB February 2004 intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. 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