1. Feb 5, 20071 ECET 581/CPET/ECET 499 Mobile Computing Technologies & Apps Data Dissemination and Management 2 of 3 Lecture 7 Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology Indiana University-Purdue University Fort Wayne

2. Feb 5, 20072 Data Dissemination and Management - Topics Introduction Introduction Challenges Challenges Data Dissemination Data Dissemination Mobile Data Caching Mobile Data Caching Mobile Cache Maintenance Schemes Mobile Cache Maintenance Schemes Mobile Web Caching Mobile Web Caching Summary Summary

3. Feb 5, 20073 Data Dissemination and Management – Topics (cont.) Introduction Introduction Pull (On-Demand) Mode Pull (On-Demand) Mode Push (Publish-Subscribe) Mode Push (Publish-Subscribe) Mode Information Caching Information Caching Challenges Challenges Architecture-based Architecture-based Architecture-less Architecture-less Data Dissemination Data Dissemination Bandwidth Allocation for Publishing Bandwidth Allocation for Publishing Broadcast Disk Scheduling Broadcast Disk Scheduling

4. Feb 5, 20074 Data Dissemination and Management - Challenges Challenges Challenges Architecture-based Architecture-based Architecture-less Architecture-less Environment Challenges Environment Challenges Intermittent Power Intermittent Power Intermittent Connectivity Intermittent Connectivity Long Travel Times Long Travel Times Variable Population Density Variable Population Density Lack of Secure Storage Lack of Secure Storage User Challenges User Challenges Mobile Workforce Mobile Workforce User Education Levels User Education Levels

5. Feb 5, 20075 Data Dissemination and Management - Challenges Architecture-Based Cellular Mobile Networks Architecture-Based Cellular Mobile Networks 1.Weak Connectivity 2.Severe Resource Constraints 3.Asymmetric Communication Links 4.Location and Time (context) Dependent Architecture-less Mobile Ad Hoc Network (MANET) Architecture-less Mobile Ad Hoc Network (MANET) 1.Weak Connectivity 2.Severe Resource Constraints

6. Feb 5, 20076 Data Dissemination and Management - Challenges 1. Architecture-Based Cellular Mobile Networks - Weak Connectivity 1. Architecture-Based Cellular Mobile Networks - Weak Connectivity How to ensure high data availability in mobile computing environment where frequent disconnections may occur because the clients and server may be weakly connected? How to ensure high data availability in mobile computing environment where frequent disconnections may occur because the clients and server may be weakly connected?

7. Feb 5, 20077 Data Dissemination and Management - Challenges 2. Architecture-Based Cellular Mobile Networks - Severe Resource Constraints 2. Architecture-Based Cellular Mobile Networks - Severe Resource Constraints How to minimize resource consumption (e.g. energy and bandwidth) for data management while ensuring a desired level of data consistency? How to minimize resource consumption (e.g. energy and bandwidth) for data management while ensuring a desired level of data consistency?

8. Feb 5, 20078 Data Dissemination and Management - Challenges 3. Architecture-Based Cellular Mobile Networks - Asymmetric Communication Links 3. Architecture-Based Cellular Mobile Networks - Asymmetric Communication Links How can the asymmetric nature of wireless connectivity be exploited to ensure low data access latency and resource consumption? How can the asymmetric nature of wireless connectivity be exploited to ensure low data access latency and resource consumption?

9. Feb 5, 20079 Data Dissemination and Management - Challenges 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent A mobile user ↔ Query database periodically to retrieve location dependent and time-dependent informationA mobile user ↔ Query database periodically to retrieve location dependent and time-dependent information Traveler ↔ restaurants, hotelsTraveler ↔ restaurants, hotels Salesman ↔ up-to-date product priceSalesman ↔ up-to-date product price Caching and pre-fetching can be an effective technique to reduce the impact of Caching and pre-fetching can be an effective technique to reduce the impact of Low-bandwidthLow-bandwidth Intermittent wireless linksIntermittent wireless links

10. Feb 5, 200710 Data Dissemination and Management - Challenges 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent 4. Architecture-Based Cellular Mobile Networks - Location and Time (context) Dependent The decision to cache or replace a data item also depends on the context (location) of the mobile node in addition to the temporal or spatial localityThe decision to cache or replace a data item also depends on the context (location) of the mobile node in addition to the temporal or spatial locality How do you enhance existing cache management technique for context- dependent data? How do you enhance existing cache management technique for context- dependent data?

11. Feb 5, 200711 Data Dissemination and Management - Challenges Architecture-less Mobile Ad Hoc Network (MANET) Architecture-less Mobile Ad Hoc Network (MANET) 1.Weak Connectivity 2.Severe Resource Constraints Data availability and bandwidth/energy efficiency still need to be addressed Data availability and bandwidth/energy efficiency still need to be addressed Can the data management schemes used developed for an Cellular Mobile Networks be used directly to solve problems in a MANET? Can the data management schemes used developed for an Cellular Mobile Networks be used directly to solve problems in a MANET?

12. Feb 5, 200712 Data Dissemination and Management - Challenges Gateways of MANET/Cellular Mobile Networks Gateways of MANET/Cellular Mobile Networks Gateways (MANET) – unreliable mobile computing devicesGateways (MANET) – unreliable mobile computing devices Base Stations – reliable dedicated networking devicesBase Stations – reliable dedicated networking devices MANETs Remote Communication LinksMANETs Remote Communication Links Unreliable, Low Bandwidth Links: Radio Frequency Wireless Links Unreliable, Low Bandwidth Links: Radio Frequency Wireless Links High-latency, unreliable Links: Satellite channels High-latency, unreliable Links: Satellite channels Base Stations Remote Communication LinksBase Stations Remote Communication Links High-speed wired networks High-speed wired networks

13. Feb 5, 200713 Data Dissemination and Management - Challenges Network Architectures of MANET/Cellular Mobile Networks Network Architectures of MANET/Cellular Mobile Networks Peer-to-peer (P2P) networks – MANETsPeer-to-peer (P2P) networks – MANETs Client-Server – Cellular Mobile NetworksClient-Server – Cellular Mobile Networks Data Management ApproachesData Management Approaches Cooperative Caching Cooperative Caching Caching hierarchy – backbone caches Caching hierarchy – backbone caches Hyper Text Transfer Protocol (HTTP) Hyper Text Transfer Protocol (HTTP) Internet Caching Protocol (ICP) Internet Caching Protocol (ICP)

14. Feb 5, 200714 Data Dissemination and Management - Challenges Internet Cache Protocol, RFC 2187 Internet Cache Protocol, RFC 2187 Hypertext Transfer Protocol, http://www.w3.org/Protocols/ Hypertext Transfer Protocol, http://www.w3.org/Protocols/ http://www.w3.org/Protocols/