Lanes A Lightweight Overlay for Service Discovery in Ad hoc Networks

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3rd Workshop on Applications and Services in
Wireless Networks (ASWN)Berne, Switzerland July
2-4, 2003
Lanes A Lightweight Overlay for Service
Discovery in Ad hoc Networks
Michael Klein, Birgitta König-Ries, Philipp
Obreiter Institute for Program Structures and
Data Organization Chair Prof. Peter C.
Lockemann Universität Karlsruhe,
Germany http//www.ipd.uni-karlsruhe.de/DIANE
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Scenario
Where and when do my database classes take place?
More on SQL?
My Mails?
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Research Question
Goal Service Discovery
Ancillary condition 1 Ontology-based service
description

• How can we
• efficiently advertise and query
• semantically complex services
• in mobile ad hoc networks?

Ancillary condition 2 Highly dynamic
topology Limited device capabilities
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Ancillary Condition 1 Semantic Description
Example Simple document service

• Non-linear structure
• Needs domain dependent matching
• Similarity matching necessary
• Must be completed in a negotiation phase

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Ancillary Condition 2 Ad hoc Network

• a) Highly Dynamic Topology
• Moving participants
• Appearing obstacles
• Logins / Logoffs
• unpredictable failures

• b) Limited Device Capabilities
• small energy reservoirs
• limited radio range

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Service Discovery Basic Approaches (1)
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Service Discovery Basic Approaches (2)
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Basic Idea
Overlay no fixed graph, but a set of overlay
conditions
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Content Addressable Network (CAN)

• Let D be an n-dimensional hypercuboid
• Each node owns a non-empty hypercuboid of D
• All these cuboids are disjoint and their union
  exactly yields D
• Each node knows the addresses of all nodes with
  hypercuboids that are adjacent to the own one
• ? Virtual Address Space

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Using 2D-CAN for Service Discovery

• CANs hashing mechanism cannot be used (ac 1)
• Separate service description from overlay
• Only use fundamental semantics
• Two dimensions service announcement service
  search
• 2D-CAN overlay
• y-axis for service announcement
• x-axis for service search

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service announcement
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service search
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Guaranteeing Structural Conditions of CAN

• General Problem Algorithms developed for
  internet-based peer-to-peer networks
• Login
• Split randomly chosen hypercuboid
• structure is not adapted later on
• ? Overlay links increasingly inefficient
• ? Not aligned with physical topology
• Detection of unreachable nodes
• Many PING messages by constantly checking at
  least 4 neighbors
• Strict grid structure too rigid
• Weaken it for ad hoc networks
• Keep possibility to route messages efficiently

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Lanes Idea

• Give up fixed assignment in x direction?
  parallel Lanes of nodes
• Within Lane Fixed neighbors
• From outside All nodes within a lane are equal
• use anycast routing in x direction

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any cast
any cast
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Lanes Service Trading
service announcement

• Service Announcements
• have long term effect
• have to be persisted, maintained removed
  (lifecycle)
• need well known storing nodes
• ? proactive y axis
• Service Requests
• one time action
• no persistence necessary
• ? reactive x axis

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any cast
any cast
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service search
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Correcting Intended Structural Changes

• Login N
• Insert N into lane that is physically close
• Logoff N
• Delete service announcements of N in lane
• Repair lane by linking Ns neighbors

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Correcting Unintended Structural Changes

• Detection
• Periodical PING message
• (1) Node vanished
• (2) Network partition
• (3) Network reunion
• Correction
• (1) - Delete its announcements- Connect
  neighbors
• (2)- Invalidate foreign announcemts- Assign
  unique partition IDs- Continue trading
  independently
• (3)- Connect lanes at their ends- Reactivate
  announcements

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PING
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Optimizing the Structure
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• Optimizing Inner Lane Connections
• Detecting inefficiencies with the PING message
• Correcting by logoff and login
• Lane length
• Optimal lane length depends on
• announce/request ratio
• network stability
• Determine dynamically by collecting profile
  information
• Split or merge lanes in a zipper like fashion
  when necessary
• (topology-aware)

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Advantages of Lanes

• Specialized for dynamic topologies
• Fewer conditions
• One periodical PING message only
• Topology-aware algorithms
• Algorithms for partition and reintegration
• Algorithms for adapting the structure to the
  current local network profile
• Fully decentralized, no flooding, no hashing, no
  leases
• Independent from service descriptionBut
  Specialized for service trading (?2 dimensions)
• ? Compromise between loose and tight structure

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Outlook

• Algorithms for self-tuning parameters
• optimal lane length
• optimal time between PING messages
• etc.
• Hierarchical lanes?
• Complete regions act as single node within a
  lane
• Implementation and evaluation
• Currently being implemented within diploma thesis

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T
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...for your attention!
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Do you have any questions?
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Further information http//www.ipd.uni-karlsruhe.
de/DIANE