Growing half-balls: Minimizing storage and communication costs in content delivery networks

Reuven Bar-Yehuda, Erez Kantor, Shay Kutten, Dror Rawitz

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The dynamic content distribution problem addresses the trade-off between storage and delivery costs in modern virtual content delivery networks (CDNs). That is, a video file can be stored in multiple places so that the request of each user is served from a location that is near the user. This minimizes the delivery costs, but is associated with a storage cost. This problem is NP-hard even in grid networks. In this paper, we present a constant factor approximation algorithm for grid networks. We also present an O(log δ)-competitive algorithm, where δ is the normalized diameter of the network, for general networks with general metrics. We show a matching lower bound by using a reduction from online undirected Steiner tree. Our algorithms use a rather intuitive approach that has an elegant representation in geometric terms.

Original languageEnglish
Pages (from-to)1903-1921
Number of pages19
JournalSIAM Journal on Discrete Mathematics
Issue number3
StatePublished - 2018

Bibliographical note

Publisher Copyright:
© 2018 Society for Industrial and Applied Mathematics.


  • Approximation algorithm
  • Content delivery network
  • Online Steiner tree
  • Online algorithm


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