HOPE: Hotspot congestion control for Clos network on chip

Najla Alfaraj, Junjie Zhang, Yang Xu, H. Jonathan Chao

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Hotspot congestion control is one of the most challenging issues when designing a high-throughput low-latency network on the chip (NOC). When a destination node is overloaded, it starts pushing back the packets destined for it, which in turns blocks the packets destined for other nodes. How to detect the occurrence(s) of hotspot and notify all source nodes to regulate their traffic to the hotspot node(s) can be quite complex because of potentially high volume of information to be collected and the non-negligible latency between the detection point of congestion and the source nodes. In this paper, we propose an effective end-to-end flow control scheme, called HOPE (HOtspot PrEvention), to resolve the hotspot congestion problem for the Clos network on the chip (CNOC). Specifically, HOPE regulates the injected traffic rate proactively by estimating the number of packets inside the switch network destined for each destination and applying a simple stop-and-go protocol to prevent hotspot traffic from jamming the internal links of the network. We evaluate HOPE's overall performance and the required hardware. Extensive simulation results based on both static and dynamic hotspot traffic patterns confirm that HOPE can effectively regulate hotspot flows and improve system performance. Our hardware analysis shows that HOPE has very small logic overhead.

Original languageEnglish (US)
Title of host publicationNOCS 2011
Subtitle of host publicationThe 5th ACM/IEEE International Symposium on Networks-on-Chip
Number of pages8
StatePublished - 2011
Event5th ACM/IEEE International Symposium on Networks-on-Chip, NOCS 2011 - Pittsburgh, PA, United States
Duration: May 1 2011May 4 2011

Publication series

NameNOCS 2011: The 5th ACM/IEEE International Symposium on Networks-on-Chip


Other5th ACM/IEEE International Symposium on Networks-on-Chip, NOCS 2011
Country/TerritoryUnited States
CityPittsburgh, PA


  • Clos network on-chip
  • congestion control
  • hotspot traffic
  • saturation-tree congestion

ASJC Scopus subject areas

  • Hardware and Architecture
  • Electrical and Electronic Engineering


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