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Distributed Token Circulation in Mobile Ad Hoc Networks. Navneet Malpani , Intel Corp. Nitin Vaidya , Univ. Illinois Urbana-Champaign Jennifer Welch , Texas A&M Univ . Presented at Int’l Conf. on Network Protocols, Nov 2001 http://faculty.cs.tamu.edu/welch/papers/icnp01.ps or pdf.

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distributed token circulation in mobile ad hoc networks
Distributed Token Circulation in Mobile Ad Hoc Networks

Navneet Malpani, Intel Corp.

Nitin Vaidya, Univ. Illinois Urbana-Champaign

Jennifer Welch, Texas A&M Univ.

Presented at Int’l Conf. on Network Protocols, Nov 2001

http://faculty.cs.tamu.edu/welch/papers/icnp01.ps or pdf

introduction
Introduction
  • Mobile Ad Hoc Networks (MANETs)
    • Formed by a collection of wireless mobile hosts, without making use of any existing infrastructure (such as base stations or telephone lines).
    • Pair of nodes communicate with each other either over a wireless link between the two nodes, or by traversing a sequence of wireless links over several other intermediate nodes.
introduction continued
Introduction continued
  • Usefulness
    • Disaster recovery
    • Search and rescue in remote areas
    • Military operations
  • Characteristics of Mobile Ad Hoc Networks
    • Highly dynamic topology
    • Highly variable message delays
    • Variable transmission error rates
    • Constraints on energy consumption
    • Constraints imposed by wireless interfaces
token circulation definition
Token Circulation Definition
  • Ensure that a token circulates throughout the network, visiting every node infinitely often.
  • Round: Minimal length sequence of nodes visited to ensure that every node is visited at least once.
token circulation example
Token Circulation Example

T

T

A

B

A B C E D C A B C E D C A ...

T

T

C

Length of round 1: 5

Length of round 2: 6

Length of round 3: 6

D

E

T

T

token circulation application
Token Circulation Application
  • Total order of message delivery in a group communication service
  • Key features of a group communication service:
    • Maintaining information regarding group membership
    • Communication among nodes in the group in an ordered manner
token circulation application1
Token Circulation Application
  • Token carries a sequence number, which is always incremented. Sender multicasts message with sequence number; receiver delivers in order. OR
  • Messages are stored in the token itself (large token).
  • Additional mechanisms are needed to obtain desired level of reliability.
token circulation algorithms
Token Circulation Algorithms
  • Local Least Recently Visited (LR): forward token to neighbor visited least recently
  • Local Least Frequently Visited (LF): forward to neighbor visited least frequently

A

B

LR: ACBCDE CACBCDE CACBCD E...

C

LF: ACBCDE DECACB CDEDEDECACB C...

D

E

more tc algorithms
More TC Algorithms

Choose next destination among all nodes.

  • Global Least Recently (GR): forward to any node in network visited least recently
  • Least Frequently (GF): forward to any node in network visited least frequently
yet more tc algorithms
Yet More TC Algorithms
  • GRN: Global Least Recently + visit intermediate nodes on the path
  • GFN: Global Least Frequently + visit intermediate nodes on the path (not studied)
  • Iterative Search: try to find Hamiltonian Path using more history information (see paper for more details)
performance measures
Performance Measures
  • Round length: number of nodes visited by the token in a round
  • Message overhead: number of bytes sent per round
  • Time overhead: time required to complete a to complete a round
simulation results
Simulation Results
  • ns-2 simulator with CMU extensions
  • System contains 20 nodes initially placed randomly in a 1000m x 300m box
  • Random Waypoint mobility model
  • Each algorithm runs as an application on top of TCP and DSR protocol
  • Results for Static and Dynamic topologies
static topologies
Static Topologies
  • Plots of
    • number of nodes visited
    • number of bytes sent
    • amount of time taken

during each round, averaged over 50 different scenarios

discussion of static results
Discussion of Static Results
  • LF diverges
  • GR and GF trivially have best round length, but not so good on messages & time
  • LR is quite good
  • Iterative Search is best overall
dynamic topologies
Dynamic Topologies
  • Varying speed (6, 12, 18 and 24 m/sec) with constant hello interval of 0.5 sec
  • Varying hello interval (0.1, 0.3, 0.5 and 0.7 sec) with constant speed of 12 m/sec
  • Hello Threshold: 3
  • Number of scenarios: 30
  • Duration of simulation was varied inversely with the speed
discussion of dynamic results
Discussion of Dynamic Results
  • Random Nature of Results
    • Effect of uncertainty in the topology knowledge due to the hello protocol
    • Effect of the TCP timeout intervals when partitions occur
    • Chaotic nature of the algorithms themselves
  • LR is the best! Close to optimal round length.
conclusion
Conclusion
  • Identified new problem for MANETs -- token circulation
  • Proposed several distributed algorithms
  • Compared them by simulation
  • Overall best algorithm :
    • Iterative Search in the static case
    • LR algorithm in the dynamic case
future work
Future Work
  • Identify characteristics of graphs on which LR has good performance -- there are graphs on which it has exponential round length (cf. recent work by Yu Chen)
  • Integrate token circulation with mechanisms for complete group communication service
  • Make tolerant of token loss / partitions
  • Find lower bounds on possible performance and find optimal algorithms