Kutscher / Ott / Bartsch Supporting Network Access and Service Location in Dynamic Environments Dirk Kutscher Jörg Ott Steffen Bartsch TNC

Kutscher / Ott / Bartsch Trends  Service location and selection a major issue for WLAN service providers  Different use cases Information about general coverage, roaming possibilities and tariffs Facilitating automated access Providing information for diagnosis and maintenance  Existing ways for service location and selection insufficient for mobile users Fragmented information services (per provider) Inadequate solutions for automated access (Google Maps mesh-ups etc.)  no offline usage! Information often outdated

Kutscher / Ott / Bartsch Example: FON Community WLAN Approach  Web-based information service with Google Maps-based visualization  Informational only Information cannot be used for automated client device configuration  No relation to user’s current context Position, required services

Kutscher / Ott / Bartsch Selected Recent Developments  FON Connection Manager Locate and automatically connect to FON Hotspots (Symbian S60)  DeviceScape Centralized connectivity management approach Mobile clients access DeviceScape information database through DNS requests Providing WISP-specific information (how to log on) Mainly targeting automated log-on  iPass Hotspot Finder Offline hotspot finder for Windows XP, Vista Pre-downloadable maps Offline search based on different criteria

Kutscher / Ott / Bartsch Shortcomings  Many provider-specific solutions Not useful for general network service location  No structured update mechanisms Users have to manually update the application/database  Focusing on WLAN network access Other (related) services not covered VoIP access, multimedia resources etc.

Kutscher / Ott / Bartsch Service Maps: Main Concepts  Network Information Service for Heterogeneous networks Challenged environments Large scale deployment  Different take on network service location Receiver- and infrastructure-based filtering Accommodate different network architectures  Main concept Mobile nodes receive/request service information from different sources and construct network service map according to MN requirements Support offline usage Leverage locality of distribution networks (e.g., WLAN) and service scope

Kutscher / Ott / Bartsch Service Map Distribution Architecture

Kutscher / Ott / Bartsch Data Model

Kutscher / Ott / Bartsch Filtering and Aggregation  Aggregation E.g., provider-independent aggregators can combine Service Maps from multiple providers  Filtering Different types of filter operations Tag filter : specify service tags that have to be present in a service description Location filter : Filter services relevant to a specific region XPath filter : filter based on arbitrary XML content in service descriptions and refinements

Kutscher / Ott / Bartsch Service Map URNs  Motivation: Transport-independent distribution can generate multiple copies  Globally unique identification for service maps required  Uniform Resource Name (URN) as an identification mechanism for service maps, fragments and refinements  Comparison rules (subset predicate)  Resolution Mechanism based on Dynamic Delegation Discovery System (DDDS) Obtain specific URI through domain-specific translation rules urn:svcmap:example.org: :campus-wlan#coord= , ;range=100 urn:svcmap:example.org: :campus-wlan?6453#refinement-2343

Kutscher / Ott / Bartsch Bootstrapping  Automating access to Service Map information in foreign networks Identify active Service Map service, i.e., in a foreign hotspot Obtain basic configuration information, e.g., Service Map URIs  Bootstrapping defined for different environments Broadcast/Multicast: FLUTE session on standardized multicast address; simpler variant (no FLUTE) as a fallback Unicast-only: IP-auto-configuration, resolving standardized bootstrapping URN through local DNS

Kutscher / Ott / Bartsch Security  Authenticity and integrity fundamental Service Map properties Have to preclude denial-of-service attacks by forged service information  Challenge: transceiver-model is based on changes to the information base by intermediaries Filtering and aggregation must still be possible Still, receivers cannot establish trust-relationship with every possible transceivers (scalability, operational issues)  Service Map approach: maintaining security properties of Service Maps fragments across the distribution chain Authenticated data structures based on Merkle hash trees Implemented with XML Digital Signatures

Kutscher / Ott / Bartsch Implementation  Infrastructure Service Map distribution servers  Client software Web-based client  Browser-based Service Map interface for online usage Mobile client  Offline client for smaller devices, mobile phones

Kutscher / Ott / Bartsch

Kutscher / Ott / Bartsch

Kutscher / Ott / Bartsch Experiences  Larger-scale campus WLAN application Setup, operations, measurements  Enhancing connectivity in mobile scenarios Employing service maps for scheduling network access Simulations

Kutscher / Ott / Bartsch Campus Scenario

Kutscher / Ott / Bartsch  Bootstrapping in campus environment  Using FLUTE via IP-Multicast  Providing data on 400 APs  Reasonable bandwidths: 1kB – 64kB  Good performance: about 2 – 16s Campus Evaluation

Kutscher / Ott / Bartsch Mobile Scenario Evaluation  Mobile user connectivity  WLAN emulation  Either with acquiring data on APs in proximity or with sensing and probing  Relatively simple connectivity algorithm Still 10% increase in Internet connectivity

Kutscher / Ott / Bartsch Upload server UUUU HTTPS Access control + anonymization Incoming database Aggregator Data set matching + freshness handling Dynamic database Integrator Provider database Mapping reports to known hotspots Service Maps Service Map Sender Distribution UUUU Service Map Transport Contribution

Kutscher / Ott / Bartsch Hotspot Displays Revisited

Kutscher / Ott / Bartsch Conclusions  Automating access to WLAN hotspots is a major challenge for making evolving WLAN-based applications usable  First developments are becoming eminent  But: no provider-independent approach available today  Network Service Maps as a general approach: Application- and provider-independent, supporting different transport services and organizational configurations  Recent results: Large-scale operation  Leveraging community contributions through contribution interface for user-observed hotspots

Kutscher / Ott / Bartsch Dirk Kutscher