A SpecialPurpose PeertoPeer File Sharing System for Mobile ad Hoc Networks

1
A Special-Purpose Peer-to-Peer File Sharing
System for Mobile ad Hoc Networks

• Alexander Klemm, Christoph Lindemann, and Oliver
  P. Waldhorst
• University of Dortmund
• Vehicular Technology Conference 2003 IEEE

2
Outline

• Introduction
• Related Work
• The ORION Search Algorithm
• The ORION Transfer Protocol
• Performance Results
• Conclusion

3
Introduction (cont.)

• Mobile ad hoc networks (MANET) and peer-to-peer
  (P2P) file sharing systems
• lack of fixed infrastructure
• no a-priori knowledge of arriving and departing
  peers.
• deploying P2P system in a MANET
• application layer connections among peers are
  static
• the MANET topology changes frequently due to node
  mobility

4
Introduction

• Optimized Routing Independent Overlay Network
  (ORION)
• enables routing of all types of messages required
  to operate
• overlay connections are set up on demand
• closely matching the current topology
• low overhead for search and transfers compare to
  the off-the-shelf approach
• does not depend of MANET routing protocol

5
Related Work (cont.)

• a P2P file sharing system consists of two
• a search algorithm
• a file transfer protocol
• Gnutella
• P-Grid
• virtual binary tree
• each peer maintain application layer connection
  to 2 other peers.

6
Related Work

• DHT allow queries for keys
• CAN
• maintain connections to 2d neighbors
• Chord
• maintains connections to O(log n) neighbors
• MANET
• 7DS
• local broadcast transmissions
• PDI

7
The ORION Search Algorithm (cont.)

• provides an efficient algorithm for keyword-based
  file search in MANET
• Ad Hoc On Demand Distance Vector (AODV)
• Simple Multicast and Broadcast protocol for MANET

8
The ORION Search Algorithm (cont.)

• each mobile device maintains a local repository
• each file is associated with a unique file
  identifier
• ORION maintains two routing tables
• response routing table
• file routing table
• limited maximum size and applying LRU replacement
  policy

9
The ORION Search Algorithm (cont.)

• query phase
• QUERY message one or more keywords
• RESPONSE unique file indentifiers matching a
  query
• each message contains SRC device identifier
• SEQ

10
The ORION Search Algorithm (cont.)

• circles mobile nodes
• line wireless transmission range
• rectangles local repository file routing table
• Query message
• link-layer flooding (MANET)
• route discovery process (AODV)

11
The ORION Search Algorithm (cont.)

• B stores C as feasible next hop for this file in
  the file routing table.
• B relayed a reduced RESPONSE message to A

12
The ORION Transfer Protocol (cont.)

• keep the complete control over the transfer on
  the receiver side
• a file is split into several blocks of equal size
• DATA_REQUEST message for one block
• DATA_REPLY message routed back as the same path
  in the query phase

13
The ORION Transfer Protocol (cont.)

• Basic operation, ex
• A sends DATA_REQUEST for first block of file 3
• B relays the request to C ( response first)
• C sends DATA_REPLY with corresponding part

14
The ORION Transfer Protocol (cont.)

• Maintenance of file transfer route
• As soon as node recognized link failure during
  the file transfer
• deletes sender in its routing tables
• forwards subseqent DATA_REQUEST to the now
  best-suited next hop.
• local failure recovery
• low transmission overhead
• timely recognition of link failures feedback
  from the link layer

15
The ORION Transfer Protocol (cont.)

• Maintenance of file transfer route
• ROUTE_ERROR message
• a node could not forward a DATA_REQUEST message
• Special search phase re-query
• search for file identifier instead of keywords

16
The ORION Transfer Protocol

• Packet Scheduling and Loss Recovery
• round-robin fashion until successfully
  transmitted.
• if a packet is lost or delayed, the next packet
  will be requested at most one round trip time
  later

17
Performance Results (cont.)

• Simulation Environment
• ns-2
• IEEE 802.11 standard MAC layer
• two-ray ground propagation as radio propagation
  model
• transmission power of 17.6125mW

18
Performance Results (cont.)

• Search Performance
• the fraction of received unique files in relation
  to the number of all files matching a query.

19
Performance Results (cont.)

• Search Performance
• out performs one order of magnitude
• off-the-shelf 5
• ORION 79

20
Performance Results (cont.)

• Transfer Performance
• ORION
• the inquiring node runs out of alternative paths
  after a single re-query
• off-the-shelf
• none of the nodes responding to the original
  query remains reachable

21
Performance Results

• Transfer Performance
• in percent of the total file size of 3 MB

22
Conclusion

• ORION
• is completely implemented on the application
  layer
• combines
• application-layer query processing and overlay
  network construction
• the network layer process of route discovery and
  tranparently aggregates redundant transfer routes
  on a per-file basis.
• significantly increase search accuracy and
  reduces overhead for searching
• enables more reliable file transfers with lower
  overhead