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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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Page 1: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

1 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Mobile Computing

Challenges

and Contributions

Anregungen für Anwendungen, Projekte & mehr

Page 2: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

2 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Arbeitsgruppe

o

Arbeitsgebiete:

-

IPv6, Mobiles Internet, Mobile Anwendungen, P2P Overlay

-

Multimediakommunikation, Hypermedia, Semantic

Web

o

Sie finden uns in:

-

Raum 580 & Raum 780

o

Messen & Ausstellungen:

-

CeBIT, LEARNTEC, NdW

o

Auslandskooperationen

-

Wir

vermitteln

gerne

Page 3: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 4: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 5: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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 …

-

Immersive: How to embed and where?

o

Mobility Middleware-

Service Discovery, Location, Configuration

-

Context Management & Transfer

-

Scalability, Robustness, Security

Page 6: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

-

Scalable, Secure, Adaptive Routing

-

Multiservice Capabilities

Page 7: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

7 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Application - Moviecast: Mobile Video & Multicast

http://moviecast.realmv6.org

Page 8: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

o

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

Page 9: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

9 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Starting Point

o

daViKo

Video Conference Software

o

H.264 Codec

o

Peer-to-Peer Communication Model

o

Simple User Localisation

o

IPv4 & IPv6 – Unicast

& Multicast

Page 10: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

10 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Moviecast Showcases

o

Video from Train

o

Video on Handheld

Page 11: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

o

Network layer advancements: P2P mobile group conferencing in real-time

o

User interfaces

Page 12: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

12 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Layered Software Stack

Page 13: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

13 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

DAVC Video Codec – Optimized H.264/SVC

Page 14: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 15: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

15 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

SIP + Multicast (SSM): Switch from Unicast to SSM

Page 16: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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.

Page 17: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

17 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Mobile eLearning Objects

o

eLO

= eLearning Object

o

Smallest self-consistent knowledge unit

o

eLOs

aggregate-

Multimedia content entities

-

Meta data

-

(Hyper-) Relations

o

Meta data standard: IEEE LOM

o

Portability standard: SCORM

o

Mobility: Transformation & Projection

Page 18: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 19: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 20: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

20 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Application: Semantic Navigator

Page 21: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

21 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Mobile Content on Demand

o

Dynamic Content Adaptation to-

User Context-

Device Capabilities-

User Behavior & Preferences

o

Content Delivery Just-in-Time

o

Split Learning Objects into small Bricks

-

Reduce Content Size per Learning Step-

Increase Attention between Learning Interruptions

o

Reduction of complex Semantics to feasible Content Relations

-

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

Page 22: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

o

Navigate directly on Course Content Outlineo

Discover additional Information via reduced Semantic Relations

o

Return to Course Path from related Content

Page 23: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

-

Subscription access for Podcasts

-

Specific haptic

controls: Analogue Joystick, Keypad, Action Keys

o

Provide typical game play by:-

Build ‘Mission’-like Scenario from Course Content

-

Split Learning Objects to entertaining Mission-Steps

-

Use typical course-completing self test as ‘Final-Mission’

-

Transfer Semantic related content navigation to Joystick

-

Support Overview Maps by visualizing Semantics in Mind-Maps

Page 24: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

24 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Use case 2: PSP - Sample

Page 25: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 26: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 27: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 28: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

28 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

GradkorrelationSkitter DIMES

Assortativity

CoefficientsSkitter: 0,011DIMES: 0,091

Page 29: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

29 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Räumliche Grad-Autokorrelation

Page 30: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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?

Page 31: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 32: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

32 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

FMIPv6 Performanz: Packetverlust in realistischer Simulation

Page 33: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 34: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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)

Page 35: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

35 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

RTT Verteilung - Scans

Page 36: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

36 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

RTT Verteilung - Caida

Page 37: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

37 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Folgerungen für die Handover Performanz

Page 38: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Page 39: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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.

Page 40: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

40 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Tree Morphing

Page 41: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

41 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Root Elongation Phase

Page 42: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

42 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

First Shortcut

Page 43: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

43 Prof. Dr. Thomas Schmidt http:/www.informatik.haw-hamburg.de/~schmidt

Optimized Tree

Page 44: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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.

Page 45: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

-

Deployable on the Overlay / Application Layer

-

Allows for Scalable Adaptive Services:

-

Mobility Resilience

-

Context Provisioning

-

Group Communication Services

o

But: Performance Degradation beyond Underlay

Page 46: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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.

Page 47: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

-

HST inherits Pastry’s proximity selection benefits-

Replication load on forwarders limited by size of prefix alphabet

-

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

-

Decouples group and state management from forwarding plane

Page 48: Mobile Computing Challenges and Contributions - HAW …users.informatik.haw-hamburg.de/~schmidt/tt/mobile-computing.pdf · Mobile Computing – Challenges and Contributions Anregungen

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

Pushing Performance Limits

-

hylOs

Exploring the Mobile Paradigm

o

Mobility-Compliant Networking-

Discovering the Internet Impact

-

Evolving the Internet Core Capabilities

-

Complementing IP in Hybrid Approaches