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Mobility Management Prof. Dr.-Ing. habil. Andreas Mitschele-Thiel Dipl.-Ing. Ali Diab Integrated HW/SW Systems Group Ilmenau University of Technology Integrierte Hard- und Softwaresysteme Outline • Introduction • Mobility Management Approaches in the TCP/IP Reference Model • Link Layer Mobility Management • Network Layer Mobility Management • Conclusions • Questions Catalog Mobility Management 2 Integrierte Hard- und Softwaresysteme Introduction Mobility Management 3 Integrierte Hard- und Softwaresysteme Motivation • The Internet and mobile communication experiencing an enormous growth • Future networks will interconnect various heterogeneous networks by means of a common IP core, also referred to as All-IP • Goals: always-on connectivity, higher bandwidth, reduced delay, lower cost, etc. • Challenge: support mobility between cells connected through an IP core while satisfying real-time requirements Mobility Management networks are 4 Integrierte Hard- und Softwaresysteme Problem Statement TCP UDP 153 . 12 . 0 . 0 Internet 165 . 115 . 0 . 0 153 . 12 . 24 . 118 Mobility Management 5 Integrierte Hard- und Softwaresysteme Problem Statement TCP Dropping UDP Slow start mechanism Internet 165 . 115 . 0 . 0 153 . 12 . 0 . 0 165 . 115 . 215 . 9 Communication disruption should be minimized or even eliminated Mobility Management 6 Integrierte Hard- und Softwaresysteme Mobility Management Requirements • Fast and smooth handoffs (lossless handoffs are the ideal case) • Fixed identifier for the Mobile Node (MN) • Inter-working properly with IP • Minimized signaling cost • No impairments of ongoing applications • No additional security vulnerabilities • Scalability, robustness and deployability Mobility Management 7 Integrierte Hard- und Softwaresysteme Mobility Management Approaches in the TCP/IP Reference Model Mobility Management 8 Integrierte Hard- und Softwaresysteme Which Layer Handles Mobility? Application layer Application layer mobility Presentation layer Application layer Session layer Session layer mobility Transport layer Transport layer Transport layer mobility Network layer Internet layer Network layer mobility Data link layer Link layer mobility Network Interface Hardware Physical layer ISO/OSI Mobility Management Required to build radio links TCP/IP 9 Integrierte Hard- und Softwaresysteme Which Layer Handles Mobility? • Link layer mobility management is responsible for the establishment of a radio link between the MN and the new Access Point (AP) • No more procedures are required if the old as well as the new AP belongs to the same subnet • If the new AP belongs to a new subnet, we need mobility support either – in the network layer, i.e. the Internet layer of the TCP/IP reference model, – in the transport layer or – in the application layer Mobility Management 10 Integrierte Hard- und Softwaresysteme Mobility Management in Different Layers, Why? • Link layer mobility – Required when changing the point of attachment – Responsible for establishment of a wireless link • Network layer mobility – Transparency to higher layer protocols, e.g. TCP and UDP – Applications on mobiles can further communicate with existing applications without any modifications – Change of network architecture is allowed • Transport layer mobility – End-to-end mobility management infrastructure unchanged while keeping the Internet – End hosts take care of mobility, i.e. TCP and UDP are updated to support mobility Mobility Management 11 Integrierte Hard- und Softwaresysteme Mobility Management in Different Layers, Why? • Session layer mobility – Migration of sessions between devices • Application layer mobility – No changes to current networks – Extending IP telephony infrastructure to fulfill mobility requirements – Usage of SIP protocol and support for mobility by change of the mapping between a name of a user (e.g. mail address) and the IP address • Hybrid layer mobility – Optimization of the performance of a certain layer mobility management approach using information from other layers or the Integration of solutions from several layers – Synchronization between layers is essential Mobility Management 12 Integrierte Hard- und Softwaresysteme Link Layer Mobility Management Mobility Management 13 Integrierte Hard- und Softwaresysteme Link Layer Handoff • Responsible for the establishment of a radio link between the MN and the AP • The handoff comprises 4 phases – – – – Recognizing the loss of the wireless connection Search for and detection of a new adequate AP Re-/Authentication with the new discovered AP Re-/Association with the new discovered AP Mobility Management 14 Integrierte Hard- und Softwaresysteme Recognizing the Loss of the Wireless Connection • Connection loss is detected based on – Weakness of the received signal or – Failed frame transmissions • Weakness of the received signal – Most frequently used approach – A layer 2 handoff is prompted, if the received signal strength goes below a certain threshold • Failed frame transmissions – Slower than received-signal-strength-based approach – The MN first assumes a collision as reason for failed frame transmissions; if not, radio signal fading is assumed; if not, an out of range is declared Mobility Management 15 Integrierte Hard- und Softwaresysteme Search and Detection of A New Adequate AP • Passive scanning Change to frequency B Change to frequency A AP operating in frequency A AP operating in frequency B Mobility Management Beacon Beacon 100 msec Change to frequency C t t Beacon Beacon t 16 Integrierte Hard- und Softwaresysteme Search and Detection of A New Adequate AP • Active scanning No activities on this channel Change to frequency A Probe delay AP operating in frequency B Probe request MinChannelTime Change to frequency B Probe delay Probe request t MinChannelTime MaxChannelTime Probe response t t AP operating in frequency C Mobility Management 17 Integrierte Hard- und Softwaresysteme Re-/Authentication With the New Discovered AP • The MN authenticates itself to the new AP • Two authentication methods are defined for the IEEE 802.11 standard – Open system: null-authentication (default method) – Shared key authentication: none null-authentication • Exchange of authentication request & authentication response messages • More messages can be exchanged between the authentication request & response; details depend on the authentication algorithm Mobility Management 18 Integrierte Hard- und Softwaresysteme Re-/Association With the New Discovered AP • Exchange of messages • After this phase, the wireless link is established Mobility Management association request & association response 19 Integrierte Hard- und Softwaresysteme Link Layer Handoff MN APs Probe requ es • • ts Large variation for the same hardware with same configuration mainly due to stochastic behavior of radio interface Scanning is the main factor in the latency, it accounts for – about 90 % of the overall handoff delay and – 80 % of the messages exchanged (depends on mobility and radio conditions) Mobility Management spons e r e b o Pr es Authentica tion reques t r es po n o i t a tic Authen Association New AP nse request respo n o i t a i Assoc nse 20 Integrierte Hard- und Softwaresysteme Research Issues • Speeding up the layer 2 handoff requires accelerating the scanning phase – Periodic scanning • Scanning the medium while the MN is still connected to the old AP • When the signal strength of the current AP is decreasing, the MN switches to another frequency for a short time and scans for other available APs – Selective scanning • Use of a channel mask to reduce the channels that must be scanned – Information about neighbors • Utilizing information about neighbor APs to reduce the number of channels that must be scanned Mobility Management 21 Integrierte Hard- und Softwaresysteme Network Layer Mobility Management Mobility Management 22 Integrierte Hard- und Softwaresysteme Overview • End-to-end mobility management • Implemented in – Network layer of the ISO/OSI reference model or – Internet layer of the TCP/IP protocol suite • Termed as layer 3 mobility management as well • Benefits – Transparency to higher layer protocols, e.g. TCP and UDP – Applications on MNs can further communicate with existing applications without any modifications • However – The infrastructure has to be adapted Mobility Management 23 Integrierte Hard- und Softwaresysteme Network Layer Mobility Management Approaches • Terminal-based mobility management approaches – Mobility support in the network and MNs – MNs participate in mobility procedures – Status • Wide range of solutions has been developed • Employed in current networks – Disadvantages • MNs have to be updated, which is mostly not preferable by users – Classification • Terminal-based macro mobility management solutions • Terminal-based micro mobility management solutions Mobility Management 24 Integrierte Hard- und Softwaresysteme Network Layer Mobility Management Approaches • Network-based mobility management – Mobility support in the network only (terminals with legacy IP stack can be mobile) – No interaction between the network and MNs – Status • Under development – Disadvantages • Many features are hard to realize, e.g. route optimization • Focus is on support of global mobility; achieving fast and smooth handoffs is not the focus yet – Classification • Network-based macro mobility management solutions • Network-based micro mobility management solutions Mobility Management 25 Integrierte Hard- und Softwaresysteme Terminal-Based Mobility Management • Macro mobility management approaches – Aim at global mobility support – Base protocols: Mobile IPv4 (RFC 3344) & Mobile IPv6 (RFC3775) • Micro mobility management approaches – Performance improvements through localizing the mobility processing inside administrative domains – Introducing of new intermediate nodes to the network – Hierarchical network topology is typically required – Categorized in • Proxy Agent Approaches (PAA) and • Localized Enhanced Routing Schemes (LERS) Mobility Management 26 Integrierte Hard- und Softwaresysteme Macro Mobility Management – Mobile IPv6 (MIPv6) CN Internet Corresponding Node (CN) Home Agent (HA) No support for mobility (standard IPv6 router) AR AR Access Router (AR) AR Periodic broadcast of Router Advertisements (RA) Mobility Management Mobility support; use of two IP addresses (Home Address (HoA) & Care of Address (CoA)) 27 Integrierte Hard- und Softwaresysteme MIPv6 - Handoff CN Internet CN HA AR Binding Updates (BUs) AR AR AR Mobility Management 28 Integrierte Hard- und Softwaresysteme MIPv6 - Handoff CN Internet CN HA Binding Acknowledgements (BAs) AR AR AR AR Mobility Management 29 Integrierte Hard- und Softwaresysteme MIPv6 – Data Communication CN Internet CN HA AR Uplink data packets are dealt with as standard IP packets AR AR AR Mobility Management 30 Integrierte Hard- und Softwaresysteme MIPv6 - Pros & Cons • Pros – Enabling end-to-end mobility – Transparency to upper layer protocols – Works properly with IP • Cons – Overhead due to encapsulation – High handoff latencies due to contacting the HA and the CN each time the MN changes the point of attachment Æ Communication disruption – Considerable signaling load due to frequent BUs especially when MNs move at high speeds – Sub-optimal routing and increased end-to-end delay due to triangular routing where CN is not MIPv6 enabled (binding updates) or due to lack of security Mobility Management 31 Integrierte Hard- und Softwaresysteme Micro Mobility Management HA is not aware of each change in the point of attachment HA Internet Movements inside the domain are controlled by the intermediate node, also called intra-domain mobility Intermediate node Administrative domain Administrative domain Movements between different domains are typically handled by MIP, also called interdomain mobility Mobility Management 32 Integrierte Hard- und Softwaresysteme Proxy Agent Approaches (PAA) • Extend the principle of MIP to provide micro mobility • Introduce new intermediate nodes to the network to process the mobility inside an administrative domain locally • Data packets destined to the MN are forwarded to the intermediate node, which tunnels them towards the MN’s current point of attachment • Examples – Hierarchical MIPv6 (HMIPv6), Seamless MIP (S-MIP), etc. Mobility Management Anchor Foreign Agent (AFA), 33 Integrierte Hard- und Softwaresysteme HMIPv6 HA is not aware of the MN’s mobility as long as the RCoA has not been changed Internet HA CN RCoA MAP Mobility Anchor Point (MAP) AR1 AR2 AR3 AR4 AR5 AR6 LCoA MN registers a Regional CoA (RCoA), i.e. a CoA in the MAP’s subnet, in its HA as the MN’s CoA; the location of the MN inside the domain is defined by the local CoA (LCoA), which is a CoA in the current AR subnet Mobility Management 34 Integrierte Hard- und Softwaresysteme HMIPv6 – Handoff Internet HA CN RCoA MAP MAP BA AR1 AR3 AR2 LCoA AR4 AR5 AR6 Local BU RA The MN configures a new LCoA Mobility Management 35 Integrierte Hard- und Softwaresysteme HMIPv6 – Data Communication Internet HA MAP MAP AR1 Mobility Management AR2 CN AR3 AR4 AR5 AR6 36 Integrierte Hard- und Softwaresysteme HMIPv6 – Pros & Cons • Pros – Localizing of mobility management inside administrative domains – Improving the performance: reduced handoff latency compared to MIPv6, reduced packet loss, etc. – Reducing the signaling load traveling towards the HA • Cons – Restrictions on the network topology – Single point of failure (all traffic passes through the MAP) – Increased signaling and packet forwarding overhead inside the domain – Security issues: how to authenticate arriving MNs? Mobility Management 37 Integrierte Hard- und Softwaresysteme Localized Enhanced Routing Schemes (LERS) • Similar principle as PAA approaches • Typically introduce a new dynamic layer 3 routing protocol inside the domain (per-hop routing) • Data packets destined for the MN are forwarded to the intermediate node controlling the domain, which forwards them hop per hop towards the MN • All nodes in the domain should be mobility-aware • Examples – Cellular IP, HAWAII Mobility Management 38 Integrierte Hard- und Softwaresysteme Cellular IP CN Internet HA Gateway The gateway controls the domain IP-based routing of data packets inside the domain is replaced by a special CIP routing and location management BS2 BS1 BS3 Beacon messages flooded periodically Æ all BSs know how to route packets towards the gateway BS4 BS5 The MN registers the address of the gateway as its CoA; inside the domain, the MN uses its HoA Mobility Management 39 Integrierte Hard- und Softwaresysteme Cellular IP – Hard Handoff CN Internet HA Gateway Update its routing cache and starts forwarding data packets towards the new location of the MN BS3 BS4 Beacon Mobility Management BS2 BS1 BS5 Route-update 40 Integrierte Hard- und Softwaresysteme Cellular IP – Semi-Soft Handoff CN Internet HA Gateway Update its routing cache and starts forwarding data packets towards the MN via the old and new BS BS2 BS1 BS3 BS4 BS5 Semi-soft packet The MN detects a handoff in the near future Æ it switches for a short time to the radio of the new BS Mobility Management 41 Integrierte Hard- und Softwaresysteme Cellular IP – Semi-Soft Handoff CN Internet HA Gateway Update its routing cache and stops forwarding to the old BS BS2 BS1 BS3 BS4 BS5 Route-update After the layer 2 handoff, the MN sends a route-update packet to stop the bicast Mobility Management 42 Integrierte Hard- und Softwaresysteme Cellular IP – Data Communication CN Internet HA Routed using IP towards their destination Gateway Uplink packets are forwarded hop by hop towards the gateway; they are used to refresh the routing caches BS3 Mobility Management BS2 BS1 BS4 BS5 43 Integrierte Hard- und Softwaresysteme Cellular IP – Pros & Cons • Pros – Localizing of mobility management inside administrative domains – Improving the performance: reduced handoff latency, less lost packets, etc. – Reducing the signaling traveling towards the HA – Mobile to mobile communication in the domain is routed via the gateway • Cons – – – – Restrictions on the network topology Single point of failure (all traffic travels through the gateway) Signaling and packet forwarding overhead inside the domain A new layer 3 dynamic routing protocol is implemented, which highly reduces the throughput of TCP – Every node in the domain have to be mobility-aware – Security issues: authentication of arriving MNs, authentication of routeupdate messages, etc. Mobility Management 44 Integrierte Hard- und Softwaresysteme Network-Based Mobility Management • Macro mobility management approaches – Aim at global network-based mobility support – Base protocols: Proxy MIPv6 (RFC 5213) – Developed by the IETF-NETLMM working group • Micro mobility management approaches – Use similar principles as terminal-based micro mobility management approaches – Performance improvements through localizing the mobility processing inside administrative domains – Introduction of new intermediate nodes to the network and deploying a hierarchical topology – Example: Terminal Independent MIP (TIMIP) Mobility Management 45 Integrierte Hard- und Softwaresysteme Macro Mobility Management – Proxy MIPv6 Internet Corresponding Node (CN) Localized Mobility Anchor (LMA) Support of mobility is required in the MAGs; each MAG emulates the home network of each MN served by it MAG Mobile Access Gateway (MAG) MAG MAG RA MN does not have to understand mobility; from the MN´s point of view, it is located in its home network and the whole domain represents a single point of attachment Unicast RA with the Home Network Prefix (HNP) of the MN Mobility Management 46 Integrierte Hard- und Softwaresysteme Proxy MIPv6 – Handoff Start a timer to delete the mobility binding of the MN Internet CN LMA Proxy Binding Acknowledgement (PBAck) De-Registration Proxy Binding Update (DeReg PBU) MAG MAG MAG The MAG detects a detach event MAG Mobility Management 47 Integrierte Hard- und Softwaresysteme Proxy MIPv6 – Handoff Accepts the binding, allocates MN-HNP and sets up a tunnel to the MAG Internet CN LMA PBAck The MAG detects an attach event & acquires the MN-ID and profile, from AAA server for example PBU MAG RA MAG MAG MAG A unicast RA with the MN-HNP Æ the MN assumes that it is located in its home network and thus there is no need for a re-configuration of its IP address Mobility Management 48 Integrierte Hard- und Softwaresysteme Proxy MIPv6 – Data Communication Internet CN LMA MAG MAG MAG MAG Mobility Management 49 Integrierte Hard- und Softwaresysteme Proxy MIPv6 – Pros & Cons • Pros – Transparency to MNs (MNs with no mobility support can be mobile) – Protocol is robust against control messages dropping (no control messages are sent on wireless links) – Reduced signaling cost – Terminating the tunnel in the MAG instead of MNs reduces the data traffic volume sent over the wireless link • Cons – Triangular routing Æ increased end-to-end delay – Overhead due to the encapsulation – Handoff latency due to contacting the LMA each time the MN moves from one point of attachment to another Æ communication disruption – Route optimization is not possible Mobility Management 50 Integrierte Hard- und Softwaresysteme Research Issues • Fast and smooth handoffs without restricting the network or introducing new nodes • Privacy through location-independent addressing • IP-based mobility between different access topologies, also called vertical handoffs • Support of route management • Security & scalability Mobility Management optimization for network-based mobility 51 Integrierte Hard- und Softwaresysteme Conclusions • Mobility management in future networks is IP-based • Mobility can be implemented in different layers of the TCP/IP reference model; each layer has positive and negative impacts • Network layer mobility approaches are the most deployed solutions – Terminal-based approaches interact with MNs to support mobility – Network-based approaches do not involve MNs in mobility support – Both approaches are categorized into macro and micro mobility management approaches • Macro mobility approaches aim at supporting global mobility • Micro mobility approaches aim at accelerating the mobility management through processing of mobility locally Mobility Management 52 Integrierte Hard- und Softwaresysteme Control Questions • Where do we need mobility support in case the MN has moved to an AP belonging to a different subnet? Why do we need such mobility support? • What are the advantages obtained when supporting mobility in the network layer? • Propose a solution to accelerate the layer 2 handoff procedure. • What are the differences between terminal-based and network-based mobility management approaches? • Compare between MIPv6 and HMIPv6? • What are the differences between PAA and LERS approaches? • What is the main idea behind network-based mobility management? How can such mobility support be realized? • Propose some mechanisms to improve Proxy MIPv6? Mobility Management 53 Integrierte Hard- und Softwaresysteme References • E. Weiss, A. Otyakmaz, E. López, B. Xu, “Design and Evaluation of a new Handoff Protocol in IEEE 802.11 Networks”, Proceedings of the 11th European Wireless conference 2005, Nicosia, Cyprus 2005. • IEEE Computer Society, “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, Standard IEEE 802.11, ISBN: 0-7381-5656-6 SS95708, June 2007. • C. Perkins, “IP Mobility Support for IPv4”, RFC 3344, August 2002. • D. Johnson, C. Perkins, J. Arkko, “Mobility Support in IPv6”, RFC 3775, June 2004. • H. Soliman, C. Castelluccia, K. El-Malki, L. Bellier, “Hierarchical Mobile IPv6 mobility management (HMIPv6)”, RFC 4140, August 2005. • A. G. Valko, “Cellular IP - A New Approach to Internet Host Mobility”, in the proceeding of ACM Computer Communication Review, January 1999. • S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury, B. Patil, “Proxy Mobile IPv6”, RFC 5213, August 2008. Mobility Management 54