Wireless Future - Telenor

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Figure 2-3 Mobile IPv6 architecture 86 Mobile node Foreign network Security Unlike Mobile IPv4, Mobile IPv6 utilizes IP Security (IPsec) for all security requirements (sender authentication, data integrity protection, and replay protection) for Binding Updates (which serve the role of both registration and Route Optimisation in Mobile IPv4). Mobile IPv4 relies on its own security mechanisms for these functions, based on statically configured mobility security associations. IP-tunnelling Most packets sent to a mobile node while away from home in Mobile IPv6 are sent using an IPv6 Routing header rather than IP encapsulation, whereas Mobile IPv4 must use encapsulation for all packets. The use of a Routing header requires less additional header bytes to be added to the packet, reducing the overhead of Mobile IP packet delivery. To avoid modifying the packet in flight, however, packets intercepted and tunnelled by a mobile node’s Home Agent in Mobile IPv6 must still use encapsulation for delivery to the mobile node. Agent Advertisements Mobile IPv6 defines an Advertisement Interval option on Router Advertisements (equivalent to Agent Advertisements in Mobile IPv4), allowing a mobile node to decide for itself how many Router Advertisements (Agent Advertisements) it is willing to miss before declaring its current router unreachable. 2.5.1 Movement Detection As soon as a mobile node detects that it has moved from one link to another and it has discovered a new default router, it registers its new care-of address with its Home Agent on the home link using a BU. The primary movement detection mechanism for Mobile IPv6 uses the facilities of IPv6 Neighbour Discovery [9], IPv6 network Home Agent Corresponding node including Router Discovery and Neighbour Unreachability Detection. In IPv6 there is a limit for how often a Router Advertisement can be sent. This limitation, however, is not suitable for providing timely movement detection for mobile nodes. Mobile nodes detect their own movement by learning the presence of new routers as the mobile node moves into wireless transmission range of them (or physically connects to a new wired network), and by learning that previous routers are no longer reachable. Mobile nodes must be able to quickly detect when they move to a link served by a new router, so that they can acquire a new care-of address and send Binding Updates to register this care-of address with their Home Agent and to notify correspondent nodes as needed. Thus, to provide good support for mobile nodes, Mobile IPv6 relaxes this limit such that routers may send unsolicited multicast Router Advertisements more frequently; in particular, on network interfaces where the router is expecting to provide service to visiting mobile nodes (e.g. wireless network interfaces), or on which it is serving as a Home Agent to one or more mobile nodes. A mobile node may use any combination of mechanisms available to it to detect when it has moved from one link to another, and the mobile node can supplement the movement detection mechanism with other information available to the mobile node (e.g. from lower protocol layers). 2.5.2 Further Work One can think of the Mobile IPv6 protocol as solving the network-layer mobility management problem. Some mobility management applications, for example handoff among wireless transceivers, each of which covers only a very small geographic area, have been solved using link-layer techniques. For example, in many current wireless LAN products, link-layer mobility Telektronikk 1.2001
mechanisms allow a handoff of a mobile node from one cell to another, re-establishing linklayer connectivity to the node in each new location. Within the natural limitations imposed by link-management solutions, and as long as such handoff occurs only within cells of the mobile node’s home link, such link-layer mobility mechanisms may offer faster convergence and lower overhead than Mobile IPv6. Extensions to the Mobile IPv6 protocol have been proposed to support a more local, hierarchical form of mobility management. 3 Micro-mobility and Fast Handoff 3.1 Background The design of Mobile IP is based on the assumption that the rate of movement between subnets is low. This leads to the fact that the protocol is not suited for micro-mobility support for which the change of IP subnet is assumed to be frequent. More specifically, the registration process requires that a new registration is sent to the Home Agent for every change of subnet. This registration process induces unnecessary high signalling load on the global Internet and high processing needs in the Home Agents. It also leads to unnecessary latency during handoff from one subnet to another. Several schemes have been proposed to solve the issue of micro-mobility management. All of these proposals assume a hierarchy in order to localise the scope of the mobility management to a domain (collection of subnet administrated by a single provider). Doing so reduces the global signalling traffic and enables a lower latency period during a change of subnet. These proposals assume Mobile IP for inter domain mobility and mainly focus on the intra domain mobility. There are two main concepts for managing the intra-domain mobility: The Host-based routing approach: Mobility management is distributed among all the nodes within the domain. Host-specific routing is employed to keep track of the current location of the Mobile Host (MH) within the domain. Special routers are thus needed. The address of the user is the care-of address assigned/authorised by the domain. The multiple Care-of Address approach: The Mobile Host is assigned multiple care-of addresses (COA), with each address identifying a specific agent/node in the hierarchy. Packets are routed through each node in the hierarchy using the corresponding care-of address. The Mobile Host only changes the care-of address of the lowest hierarchical level at every change of subnet. This approach uses conventional IP rout- Telektronikk 1.2001 ing in the domain and distributes the mobility management over only a subset of nodes in the mobility domain. In the following we present these two concepts in more detail. We also review some of the proposed schemes and analyse their strong points and deficiencies. We note that at this point in time the schemes presented are in the form of Internet drafts and are thus under discussion in the IETF. 3.2 Host based Routing Schemes 3.2.1 Principles Many schemes belonging to the host based routing category have been proposed. The Cellular IP and Hawaii schemes have received most of the attention thus far. Figure 3-1 illustrates the basic functional architecture and the implied tree like network topology of the Hawaii and Cellular IP solutions. Both approaches create hostspecific entries through a specific path in the network topology. The ingress point into the domain is the root of the tree and is called the Gateway (GW) for Cellular IP and Domain Root Router (DRR) for the Hawaii scheme. Packets destined to the MH are forwarded through the sequence of nodes, the first one being the ingress point and the last one being the MH. It should be noticed that the edge device may not be a base station so that the schemes are applicable to solving mobility management in fix access networks as well. As an MH moves inside this Cellular IP/Hawaii Domain Internet GW/DRR Router* Router* Figure 3-1 Cellular IP and Hawaii architecture Router* Router* Router* Router* MH * Router with CIP or Hawaii Protocol 87
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Telektronikk Volume 97 No. 1 - 2001
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Per Hjalmar Lehne (42) obtained his
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Stein Svaet (41) is Senior Research
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Pbit/day 6 150 125 100 75 50 25 0 F
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8 Video communication as a utility
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10 The idea of reconfigurable mobil
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12 Switched lobe Dynamically phased
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Figure 10 The All IP vision Figure
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16 The IP world has some problems t
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18 Abbreviations and acronyms less
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Jorge Pereira (40) obtained his Eng
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(Millions) Figure 1 Exponential gro
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24 Defining Generation based upon D
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Multi-mode Terminal by Software Rad
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distribution layer possible return
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30 A Co-Ordinated Approach to 4G As
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Figure 2 Applications will grow fas
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Figure 5 Evolution from multi-mode
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Page 40 and 41: Radio network subsystem - service c
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Page 44 and 45: Figure 3 Two arrays with M and N el
Page 46 and 47: Figure 5 Cumulative probability dis
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Page 50 and 51: 48 Conclusion The challenge of prov
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Page 58 and 59: 56 7 Conclusion and Further Researc
Page 60 and 61: Dave Wisely (39) graduated in 1982
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Page 68 and 69: Figure 2 The Bluetooth protocol sta
Page 70 and 71: Figure 5 A Bluetooth radio module i
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Page 76 and 77: Table 1 Allocated HiperLAN bands (i
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Page 110 and 111: Figure 2 The first use case diagram
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Anne Lise Lillebø (52) is Adviser
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140 with other SDOs (Standards Deve
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142 Box 2 - ETNO Declaration We, th
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