Causal consistency in mobile environment

  • Authors:
  • D. Janaki Ram;M. Uma Mahesh;N. S. K. Chandra Sekhar;Chitra Babu

  • Affiliations:
  • -;-;-;-

  • Venue:
  • ACM SIGOPS Operating Systems Review
  • Year:
  • 2001

Quantified Score

Hi-index 0.00

Visualization

Abstract

Causal consistency stipulates that causally dependent writes to data items should be executed in causal order. Traditionally this has been done by causally ordered message delivery using vector clocks. In a vector clock of size N, each element of the vector corresponds to each of the N hosts in the system and hence the message overhead is Θ(N). In a mobile environment the number of hosts can not be fixed because hosts join and leave the system dynamically. Hence traditional vector clocks are not suitable in a mobile environment. Consistency of a system consisting of M data items can be maintained using a vector in which each element corresponds to each data item. We propose a mechanism for maintaining causal consistency whose message overhead is Θ(M). Such a model will be advantageous in a mobile environment, because the message overhead is independent of the number of hosts. Further in applications such as collaboration the number of data items is small. Also, the delivery of a message is never inhibited due to causally overwritten messages.