Experimental Assessments of SDN-enabled Optical Polling Flow Control for Contention Resolution in Optical DCNs

Xuwei Xue, Fu Wang, Sai Chen, Fulong Yan (Corresponding author), Bitao Pan, Kristif Prifti, Xiaotao Guo, Shaojuan Zhang, Chongjin Xie, Nicola Calabretta

Research output: Contribution to journalArticleAcademicpeer-review

4 Citations (Scopus)


Due to the lack of optical buffer, high packer loss caused by packet contention is one of the main challenges for the optical switching data centers (DCs). Flow control (FC) protocol employing electrical buffers at the top of racks (ToRs) and exploiting packet retransmission mechanism in case of contention has been extensively investigated to decrease the packet loss in optical DCs. However, the packet retransmission and the head-of-line (HOL) blocking in electrical buffers at substantial load traffic introduce extra latency and buffer-overflow that still cause packet loss. To overcome these issues, a novel contention resolution technique based on a software-defined networking (SDN) enabled optical polling flow control is proposed and experimentally assessed in this article. Experimental assessments show that the proposed contention resolution scheme achieves zero packet loss and 7.4 μs latency performance at the load of 0.4. In addition, we numerically modelled and investigated the scalability of the proposed contention resolution technique in a large scale DCN based on the experimental parameters. Results prove the excellent scalability performance of OPFC scheme, in which the packet loss increases from 2.1E-3 to 9.02E-3 and the average latency increases 5.17 μs at the load of 0.5 as the OPFC based network scales from 4 to 40960 servers.

Original languageEnglish
Article number9286537
Pages (from-to)2652-2660
Number of pages9
JournalJournal of Lightwave Technology
Issue number9
Early online date8 Dec 2020
Publication statusPublished - 1 May 2021


  • optical data center
  • Optical switching
  • packet contention
  • software-defined networking


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