Costly circuits, submodular schedules and approximate Carathéodory Theorems

Shaileshh Bojja Venkatakrishnan, Mohammad Alizadeh, Pramod Viswanath

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Hybrid switching—in which a high bandwidth circuit switch (optical or wireless) is used in conjunction with a low bandwidth packet switch—is a promising alternative to interconnect servers in today’s large-scale data centers. Circuit switches offer a very high link rate, but incur a non-trivial reconfiguration delay which makes their scheduling challenging. In this paper, we demonstrate a lightweight, simple and nearly optimal scheduling algorithm that trades off reconfiguration costs with the benefits of reconfiguration that match the traffic demands. Seen alternatively, the algorithm provides a fast and approximate solution toward a constructive version of Carathéodory’s Theorem for the Birkhoff polytope. The algorithm also has strong connections to submodular optimization, achieves a performance at least half that of the optimal schedule and strictly outperforms the state of the art in a variety of traffic demand settings. These ideas naturally generalize: we see that indirect routing leads to exponential connectivity; this is another phenomenon of the power of multi-hop routing, distinct from the well-known load balancing effects.

Original languageEnglish (US)
Pages (from-to)311-347
Number of pages37
JournalQueueing Systems
Issue number3-4
StatePublished - Apr 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Statistics and Probability
  • Computer Science Applications
  • Management Science and Operations Research
  • Computational Theory and Mathematics


  • Approximation algorithms
  • Bridges and switches
  • Circuit networks
  • Data center networks
  • Network flows
  • Submodular optimization


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