TCP flow classification and bandwidth aggregation in optically interconnected data center networks

Houman Rastegarfar, Madeleine Glick, Nicolaas Viljoen, Mingwei Yang, John Wissinger, Lloyd LaComb, Nasser Peyghambarian

Research output: Contribution to journalArticlepeer-review

32 Scopus citations


Optical functionality is being used to realize new data center architectures that minimize electronic switching overheads, pushing the processing to the edge of the network. A challenge in optically interconnected data center networks is to identify the large, bandwidthhungry flows (i.e., elephants) and efficiently establish the optical circuits. Moreover, the amount of optical resources to be provisioned during the network planning phase is a critical design problem. Flow classification accuracy affects the efficiency of optical circuits. Optical channel bandwidth, on the other hand, directly relates to the additive- increase, multiplicative-decrease congestion control mechanism of the transmission control protocol and affects the effective bandwidth allocated to elephant flows. In this paper, we simultaneously investigate the impact of two important mechanisms on data center network performance: traffic flow classification accuracy and optical bandwidth aggregation (i.e., the consolidation of several low-capacity channels into a single high-capacity one by employing advanced modulation formats for short-reach communications). We develop a discrete-event simulator for a hybrid data center network, enabling the tuning of flow classification parameters. Our simulations indicate that data center performance is highly sensitive to the aggregation level.We could observe up to a 74.5% improvement in network throughput only due to consolidating the optical channel bandwidth. We further noticed that the role of flow classification becomes more pronounced with higher bandwidth per wavelength as well as with more hot-spot traffic. Compared to a random classification benchmark, adaptive flow classification could lead to throughput improvements as large as 54.7%.

Original languageEnglish (US)
Article number7588243
Pages (from-to)777-786
Number of pages10
JournalJournal of Optical Communications and Networking
Issue number10
StatePublished - 2016


  • Bandwidth aggregation
  • Congestion control
  • Data center
  • Elephant flow
  • Flow classification
  • Machine learning
  • Mouse flow
  • TCP protocol

ASJC Scopus subject areas

  • Computer Networks and Communications


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