Internet Services & Protocols. Mobile and Wireless Networks

Transcription

1 Department of Computer Science Institute for System Architecture, Chair for Computer Networks Internet Services & Protocols Mobile and Wireless Networks Dr.-Ing. Stephan Groß Room: INF

2 Today s Agenda General thoughts What do we understand by wireless communications and mobility? Dimensions of wireless and mobile networks Application scenarios Key problems Mobile IP Mobility management for the Internet 2

3 A Brief History of Wireless Communication 1880 Initial demonstration of practical radio communication (Heinrich Hertz ) wireless telegraph (Guglieimo Marconi) Commercial transatlantic telegraph Field test with television transmission Satellites for audio/ telephony later television First cellular telephony system in the USA (AMPS) Deployment of GSM, D-Net in Germany WLAN (IEEE ), WAP, Bluetooth, i- Mode in Japan GPRS in Germany First UMTS network installed on the Isle of Man i-mode in Germany 3

4 Why wireless? Advantages compared with the wired alternative Faster deployment/ installation, No cable costs, Not tied to a certain place, mobile operation Suitable for non-accessible areas Some limitations and problems At the time being high costumer charges New security requirements Hardware or software restrictions (small picture sizes, only text displays, support of WML but not HTML) Lower data rates Lower reliability 4

5 Dimensions of mobility How mobile is a user (from the network layer's point of view) e.g. Laptop carried around in a building versus internet access in a ICE train No mobility High mobility User moves only within same wireless access network User moves between access networks, shutting down while moving between networks User moves between access networks, while maintaining ongoing connections How important is the mobile node's address? e.g. access versus mobile telephony What supporting infrastructure is available? Ad hoc networking 5

6 Classification of Wireless Networks (1) 2 main types of wireless networks: satellite based and terrestrial satellite based networks Satellite based antennas in a stationary orbit determine the communication between two or more devices on earth or in the near of it. Enormous cover of scope are possible Very high data throughput possible High costs for development and installation Large transmission delays High transmission quality Classification by orbital characteristics Circular or elliptic orbits Area of orbits equatorial, polar, inclined Heights of satellites Geostationary orbit (GEO). Medium Earth orbit (MEO). Low Earth orbit (LEO). 6

7 Classification of Wireless Networks (2) Terrestrial Networks All network devices and users are located on earth. Cover of scopes are small in comparison with satellites. Provided data throughput depend on technology. Costs of development vary, less than costs for a satellite system. Marginal delayed signal dispersion. Transmission quality can vary enormously as result of surrounding conditions (interferences). Terrestrial networks can be divided roughly into: Wide Area Networks and Local Area Networks 7

8 Types of Terrestrial Wireless Networks Wireless communication systems Mobile telephony Wireless local networks Wireless personal area networks WLAN HIPERLAN Cellular mobile radio Cordless telephony WATM Radio Infrared WAN GSM GPRS UMTS DECT LAN Bluetooth IrDA 8

9 Mobile and Wireless Applications (1) Mobile, wireless applications can be categorized according to its growing complexity: Simple Messaging Simple text message exchange between wireless users (e.g. s). Provided by most modern systems. Data speeds of Kbps 9,6 or 14,4 are needed. SMS services can be used by GSM mobile radio participants. Basic Internet access Comprises downloading of simple information (weather reports, stock prices, news, etc.). Provided by most systems supporting WAP (GSM). Similar data rates as with simple messaging 9

10 Mobile and Wireless Applications (2) Multimedia Messaging (MMS) Transfer of messages which include different types of multimedia content like text, pictures, audio etc. (NOT in real time). Data throughput of several hundred Kbps needed for delivery in due time. Multimedia messaging is thought to be standard with the deployment of UMTS. Advanced Internet Access Main goal is to provide same service level as with wired internet access. Support of real time multimedia applications and other innovative Internet applications. Very high data rates up to several Mbit/s are conceivable. 10

11 Mobility and Standard IP Routing IP: stationary computers with fixed network address What happens if devices/computer are moving around between several networks? IP Routing algorithms forward packets to its correct destination network based on IP addresses Different subnets have different address prefixes Devices, which changed their subnets can t use their old addresses. Two solutions: As a consequence of the subnet change a new IP address is assigned (e.g. using DHCP Dynamic Host Configuration Protocol) Network layer will be adapted for mobile devices 11

12 Key Questions of Mobility Management How to actually find a mobile host? Adressing care-of address vs. permanent address home agent and foreign agent How to exchange messages with a mobile host? Routing Indirect Routing using encapsulation Direct Routing Triangle routing problem 12

13 Mobile IP: Overview (1) Standard: RFC 3344 & RFC 4721 Features: Home agents, foreign agents, foreign-agent registration, care-of-addresses, packet encapsulation/ tunneling (packet in packet) Components of mobile IP: Agent discovery Registration with home agents Indirect routing of datagrams 13

14 Mobile IP: Overview (2) Mobile IP for transparent problem handling of mobile users: Allows devices to keep Internet connections up and running independent of their current (changing) location Allows location tracing of mobile devices without precedent modification of their IP address No software changes of stationary (non-mobile) devices (e.g. routers) are needed Requires some add-ons in the infrastructure No geographical limitations No modifications of IP addresses or IP address formats Supports security 14

15 Mobile IP: Basics (1) The Home Network home network: permanent home of mobile (e.g., /24) home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote Permanent address: address in home network, can always be used to reach mobile e.g., wide area network correspondent 15

16 Mobile IP: Basics (2) The visited Network Permanent address: remains constant (e.g., ) Care-of-address: address in visited network. (e.g., ) wide area network visited network: network in which mobile currently resides (e.g., /24) correspondent: wants to communicate with mobile correspondent foreign agent: entity in visited network that performs mobility functions on behalf of mobile. 16

17 Mobile IP: Agent Discovery (1) agent advertisement: foreign/home agents advertise service by broadcasting ICMP messages (type field = 9, router discovery) H,F bits: home and/ or foreign agent type = 9 code = 0 = 9 router address checksum = 9 standard ICMP fields R bit: registration required type = 16 length sequence # registration lifetime RBHFMGV bits 10 or more care-ofaddresses reserved mobility agent advertisement extension 17

18 Mobile IP: Agent Discovery (2) agent solicitation: mobile node wants to learn about agents without waiting for an advertisement msg, thus it broadcasts an agent solicitation ICMP message (type field = 10) An agent receiving the solicitation unicasts an agent advertisement directly to the mobile node The mobile node proceeds as if it had received an unsolicited advertisement 18

19 Mobility: Registration home network visited network wide area network End result: Foreign agent knows about mobile Home agent knows location of mobile 2 foreign agent contacts home agent home: this mobile is resident in my network 1 mobile contacts foreign agent on entering visited network 19

20 Mobile IP: Registration Example Home agent HA: Foreign agent COA: ICMP agent adv. COA: Foreign network: /24 Mobile agent MA: registration req. COA: HA: MA: Lifetime: 9999 identification: 714 encapsulation format. registration req. COA: HA: MA: Lifetime: 9999 identification:714. registration reply HA: MA: Lifetime: 4999 Identification: 714 encapsulation format. registration reply HA: MA: Lifetime: 4999 Identification:

21 Mobility: Message Exchange Approaches Let routing handle it: not routers advertise permanent address of mobile-nodes-in-residence scalable via usual routing table exchange. to millions of routing tables indicate mobiles where each mobile located no changes to end-systems Let end-systems handle it: indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remote direct routing: correspondent gets foreign address of mobile, sends directly to mobile 21

22 Mobility via Indirect Routing home network correspondent addresses packets using home address of mobile home agent intercepts packets, forwards to foreign agent 1 wide area network 2 foreign agent receives packets, forwards to mobile 4 3 visited network mobile replies directly to correspondent 22

23 Forwarding datagrams to remote mobile Encapsulation and Decapsulation packet sent by home agent to foreign agent: a packet within a packet foreign-agent-to-mobile packet dest: dest: dest: Permanent address: dest: packet sent by correspondent Care-of address:

24 Indirect Routing: Moving between Networks suppose mobile user moves to another network registers with new foreign agent new foreign agent registers with home agent home agent updates care-of-address for mobile packets continue to be forwarded to mobile (but with new care-of-address) there is no need for a foreign agent to explicitly deregister a COA when a mobile node leaves its network Changing of foreign networks transparent: on going connections can be maintained! 24

25 Indirect Routing: Comments Mobile uses two addresses: permanent address: used by correspondent (hence mobile location is transparent to correspondent) care-of-address: used by home agent to forward datagrams to mobile foreign agent functions may be done by mobile itself triangle routing: correspondent home-network mobile inefficient when correspondent & mobile are in same network 25

26 Mobility via Direct Routing home network correspondent requests, receives foreign address of mobile correspondent forwards pkts to foreign agent wide area network foreign agent receives packets, forwards to mobile 4 visited network mobile replies directly to correspondent 26

27 Mobility via Direct Routing: Comments overcomes triangle routing problem non-transparent to correspondent: correspondent must get careof-address from home agent What happens if mobile changes networks? Notification protocol vs. chain of forwarding foreign agents This results in additional complexity! Example for direct routing: GSM telephony 27

28 Conclusion Using IPv4 additional devices are needed (home agent, foreign agent etc.) In IPv6: the mobile environment is taken into account: Only collocated care-of-addresses are used, foreign agent is removed Functionality of home agents are now part of router located in the home network, home agent as stand alone device is removed Buzzwords here are Mobile IPv6, Hierarchical Mobile IPv6 and Fast Mobile IPv6 28