Mobile Computing Challenges and Contributions - HAW...
Transcript of Mobile Computing Challenges and Contributions - HAW...
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1 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mobile Computing
–
Challenges
and Contributions
Anregungen für Anwendungen, Projekte & mehr
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2 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Arbeitsgruppe
o
Arbeitsgebiete:
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IPv6, Mobiles Internet, Mobile Anwendungen, P2P Overlay
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Multimediakommunikation, Hypermedia, Semantic
Web
o
Sie finden uns in:
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Raum 580 & Raum 780
o
Messen & Ausstellungen:
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CeBIT, LEARNTEC, NdW
o
Auslandskooperationen
-
Wir
vermitteln
gerne
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3 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mitarbeit in aktuellen Projekten als studentischer Mitarbeiter, Bacheland, Masterand oder Doktorand …
Moviecast hylOs
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4 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Overview
Challenges of Mobile Computing
Emerging Mobile Applications
Scalable, Mobility-Compliant Networks
Conclusions & Outlook
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5 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Challenges of Mobile Computing
o
Devices-
Capabilities: Processing, Power, …
-
For Users: Interfaces, Design, Paradigm …
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Immersive: How to embed and where?
o
Mobility Middleware-
Service Discovery, Location, Configuration
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Context Management & Transfer
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Scalability, Robustness, Security
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6 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Challenges of Mobile Computing
o
Mobile Applications√ Communication & Infotainment
o
M-Commerce, M-Learning, M-Web2.0
?
Vehicular & Sensor Networks
?
Ambient Intelligence, Location-based Services, …
o
Mobility-Compliant Networks-
Wireless Transmission + Deployment
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Scalable, Secure, Adaptive Routing
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Multiservice Capabilities
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7 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Application - Moviecast: Mobile Video & Multicast
http://moviecast.realmv6.org
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8 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Requirements
o
Rigid real-time
constraints -
(50 –
100 ms)
o
Scalable, resource-adaptive video encoding
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Mobility support on network
layer
o
Group communication enabled by network layer
o
Encryption to secure
all communication
o
Focus on
standard
compliant signalling +
communication
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9 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Starting Point
o
daViKo
Video Conference Software
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H.264 Codec
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Peer-to-Peer Communication Model
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Simple User Localisation
o
IPv4 & IPv6 – Unicast
& Multicast
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10 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Moviecast Showcases
o
Video from Train
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Video on Handheld
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11 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Building Blocks
o
Scalable, highly optimised video codec:
Based on emerging SVC standard
o
Software stack:
Secure mobile group conferencing library
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Network layer advancements: P2P mobile group conferencing in real-time
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User interfaces
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12 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Layered Software Stack
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13 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
DAVC Video Codec – Optimized H.264/SVC
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14 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
SIP Group Communication Layer
o
Critical: Determine
device
capabilities
to build optimized
overlays
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15 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
SIP + Multicast (SSM): Switch from Unicast to SSM
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16 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
SIP-SSM: Arrival of New Parties
Source –
Schmidt, Wählisch, Cycon, Palkow: Scalable Mobile Multimedia Group Conferencing based on SIP initiated SSM, In: Proc. ECUMN’07, IEEE Press, February 2007.
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17 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mobile eLearning Objects
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eLO
= eLearning Object
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Smallest self-consistent knowledge unit
o
eLOs
aggregate-
Multimedia content entities
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Meta data
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(Hyper-) Relations
o
Meta data standard: IEEE LOM
o
Portability standard: SCORM
o
Mobility: Transformation & Projection
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18 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Introducing hylOs
hylOs = Hypermedia Learning Object Systemo
eLearning content management system
o
Implements rich eLO
content modell
o
Fully LOM / SCORM compatible
o
Rigorously XML
hylOs Componentso
Presentation environment
o
eLO
instructional management
o
eLO
authoring environment
o
Semantic content augmentation
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19 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
hylOs Content Networks
Source –
Engelhardt, Hildebrand, Lange, Schmidt: Semantic Overlays in Educational Content Networks – The hylOs Approach, In: Campus-Wide Information Systems, Vol. 23, No. 4, pp. 254-267, Emerald, Sept. 2006
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20 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Application: Semantic Navigator
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21 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mobile Content on Demand
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Dynamic Content Adaptation to-
User Context-
Device Capabilities-
User Behavior & Preferences
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Content Delivery Just-in-Time
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Split Learning Objects into small Bricks
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Reduce Content Size per Learning Step-
Increase Attention between Learning Interruptions
o
Reduction of complex Semantics to feasible Content Relations
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Decrease of Complexity according to the Mobile Context-
Provide easy Understanding of Semantic Relations
Source –
Hildebrand, Schmidt, Engelhardt: Mobile eLearning Content on Demand, In: International Journal of Computing and Information Sciences-
(IJCIS), 2007
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22 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Use Case 1: iPod
Content Preparation:o
Publish Audio Material via RSS Feeds (Podcast)
o
Export Course & related Content as Notes
to the iPod:-
Provide Menu structure for seamless integration of iPod Click Wheel
-
Split Learning Objects into separate Content Bricks to meet iPod capabilities
Content Usage & Navigationo
Obtain audible, textual and visual Information
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Navigate directly on Course Content Outlineo
Discover additional Information via reduced Semantic Relations
o
Return to Course Path from related Content
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23 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Use Case 2: Playstation Portable
o
Additional Support of:-
Wireless Network Access, web browser and flash player
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Subscription access for Podcasts
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Specific haptic
controls: Analogue Joystick, Keypad, Action Keys
o
Provide typical game play by:-
Build ‘Mission’-like Scenario from Course Content
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Split Learning Objects to entertaining Mission-Steps
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Use typical course-completing self test as ‘Final-Mission’
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Transfer Semantic related content navigation to Joystick
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Support Overview Maps by visualizing Semantics in Mind-Maps
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24 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Use case 2: PSP - Sample
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25 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Scalable, Mobility-Compliant Networks
o
Threads & Challenges-
The Pure Growth
-
Multiple Attachments: Mobility Paging, Multihoming, …
-
Farewell from the Client-Server Paradigm
-
Cognitive Networks & Context Transfer
-
Group Communication Services
o
Trade-off between Management Areas-
Network Core
-
Access Networks
-
End-Nodes
o
Scalability Constraint: ≤
Logarithmic Resource Expansion
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26 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Im gegenwärtigen Internet sind nur Vorwärtsmessungen möglich:
o
Mehrfache traceroute
Scans von unterschiedlichen Quellen
o
Errechnung der jeweiligen Pfade zwischen Routern
o
Zwei große Projekte -
Skitter
(CAIDA, San Diego)
-
DIMES (Tel Aviv University)
Quellpunkte kritisch
Abenteuer: Die Entdeckung des Internets
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27 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Ist das Internet ein Zufallsgraph?
o
Strukturuntersuchung: Knotengrade
o
Ein Maß
für -
Konnektivität
- Robustheit - Verkehrs-
ströme -
Bildungs-
mechanismen
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28 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
GradkorrelationSkitter DIMES
Assortativity
CoefficientsSkitter: 0,011DIMES: 0,091
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29 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Räumliche Grad-Autokorrelation
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30 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Diskussion: Entdeckung des Internets
o
Das Internet hat viele regionale Vermaschungen-
Nur durch viele, global verteilte Monitorpunkte sichtbar
o
Es hat beinahe skaleninvariante Eigenschaften-
Potenzgesetze gelten nicht uneingeschränkt
o
Das Internet ist kein Zufallsgraph-
Korrelationen mittlerer Reichweite
-
Schwach abhängige Knotengradveränderungen: Ähnliche Vermaschung
nächster Nachbarn
Antikorrelation zwischen Autonomen Systemen
o
Was bedeutet dies für Internetmobilität?
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31 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mobilität - Schnelles Handover: Fast MIPv6 (RFC 4068)
FMIPv6 unterstützt prädiktives
und reaktives Handover
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32 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
FMIPv6 Performanz: Packetverlust in realistischer Simulation
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33 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Handover-Verhalten zwischen Access-Routern
Problem: Wie korreliert geographische Nachbarschaft mit topologischer Distanz an den Rändern des Internets?
Methode: -
Bildung von regionalen Clustern im Zugangsbereich
-
Evaluiere Access-Router
Abstände durch Scanning in den traceroute
Metriken RTT und Hops
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34 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Vorgehen
o
Cluster mithilfe von GeoIP
Datenbank (MaxMind)
o
Scans
von Quellen in Berlin, Hamburg, San Diego, Shanghai und öffentlichen traceroute
Angeboten
o
Zufallsmengen von 500 IP-Bereichen
aus jedem regionalen Cluster
o
Vergleich mit geographisch unkorrelierten Mengen
o
Vergleich mit CAIDA Daten:-
Vom gleichen Zeitraum (Oktober 2006)
-
Tracepaths
minimiert über alle 18 Monitorpunkte (CAIDA Scan-Quellen)
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35 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
RTT Verteilung - Scans
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36 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
RTT Verteilung - Caida
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37 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Folgerungen für die Handover Performanz
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38 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Zwischenresümee
o
FMIPv6 beschleunigt Netzwechsel
o
Prädiktive
verlustlose Handovers
sind realitätsfern
o
An den Rändern des Internets sind geographische und topologische Distanz korreliert
o
Ein ‚walking
User‘
kann in seiner Umgebung ein beschleunigtes Handover-Verhalten
erwarten
o
Generalitätsvermutung: -
25 ms in 802.11 (= ½
Layer
2 Handoff) ist a priori beste
Handover
Antizipationszeit
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39 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Mobile Multicast Senders
Need to Change Routing (Source Filters):-
Extend (CoA,G) states to (CoA,HoA,G)
Need to Preserve Previous Trees:-
Keep contact subsequent to handover
Idea: Morph Previous into Next Tree:-
Elongate root (modify RPF Check)
-
Discover shortcuts
-
Dismiss unneeded branches
Source -
Schmidt & Wählisch: Extending SSM to MIPv6 – Problems Solutions and Improvements, Comput. Methods in Science and Technology, Vol. 11, No. 2, 2005.
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40 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Tree Morphing
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41 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Root Elongation Phase
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42 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
First Shortcut
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43 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Optimized Tree
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44 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Implementation & Analysis
Source –
Christ, Schmidt & Wählisch: A Light-Weight Implementation Scheme of the Tree Morphing Protocol for Mobile Multicast Sources, In: Proceedings of the 33rd EUROMICRO Conference, IEEE Computer Society Press, August 2007.
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45 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Overlay Service Networks
o
Distributed Indexing (DHTs)-
Global Routing with overall Logarithmic Scaling
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Deployable on the Overlay / Application Layer
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Allows for Scalable Adaptive Services:
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Mobility Resilience
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Context Provisioning
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Group Communication Services
o
But: Performance Degradation beyond Underlay
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46 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Hybrid Shared Tree Architecture
Source –
Wählisch, Schmidt: Between Underlay and Overlay: On Deployable Efficient Mobility-agnostic Group Communication Services,, In: Internet Research, Vol. 17, No. 5, Emerald Insight, November 2007.
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47 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Multicast on Hybrid Shared Trees
o
Unmodified Layer2/3 Multicast in End System Domainso
Prefix-base Distribution Tree on Top of DHT
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HST inherits Pastry’s proximity selection benefits-
Replication load on forwarders limited by size of prefix alphabet
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Strictly predictable per packet processing costs
o
No Dedicated Overlay Nodes (e.g., Rendezvous Point) -
Advoids
bottlenecks and single points of failure
o
In Combination with Bidir–PIM: Mobility-Agnostic Routing-
Prefix tree will be built only receiver-based
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Decouples group and state management from forwarding plane
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48 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt
Conclusions & Outlook
o
Mobile Computing Today-
Open for Several Directions
o
Mobile Applications-
Moviecast
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Pushing Performance Limits
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hylOs
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Exploring the Mobile Paradigm
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Mobility-Compliant Networking-
Discovering the Internet Impact
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Evolving the Internet Core Capabilities
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Complementing IP in Hybrid Approaches