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Reconfigurable datacenter networks use fast optical circuit switches to provide high bandwidths at low cost, therefore emerging as a compelling alternative to packet switching. These switches offer micro- and nano-second reconfiguration, and reacting to demand at this time scale is infeasible. Proposed designs have therefore largely been oblivious, supporting arbitrary traffic patterns. However, this imposes a fundamental latency-throughput tradeoff that significantly limits the benefits of these switches. In this paper, we illustrate the feasibility of semi-oblivious reconfigurable datacenter networks that periodically adapt to large-scale structural patterns in traffic. We argue that such patterns are predictable in modern datacenters, that optimizing for them can provide latency-throughput scaling superior to oblivious designs, and that existing fast circuit-switched technologies support coarse-grained flexibility to adapt to these patterns.
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Shale: A Practical, Scalable Oblivious Reconfigurable Network
Circuit-switched technologies have long been proposed for handling high-throughput traffic in datacenter networks, but recent developments in nanosecond-scale reconfiguration have created the enticing possibility of handling low-latency traffic as well. The novel Oblivious Reconfigurable Network (ORN) design paradigm promises to deliver on this possibility. Prior work in ORN designs achieved latencies that scale linearly with system size, making them unsuitable for large-scale deployments. Recent theoretical work showed that ORNs can achieve far better latency scaling, proposing theoretical ORN designs that are Pareto optimal in latency and throughput. In this work, we bridge multiple gaps between theory and practice to develop Shale, the first ORN capable of providing low-latency networking at datacenter scale while still guaranteeing high throughput. By interleaving multiple Pareto optimal schedules in parallel, both latency- and throughput-sensitive flows can achieve optimal performance. To achieve the theoretical low latencies in practice, we design a new congestion control mechanism which is best suited to the characteristics of Shale. In datacenter-scale packet simulations, our design compares favorably with both an in-network congestion mitigation strategy, modern receiver-driven protocols such as NDP, and an idealized analog for sender-driven protocols. We implement an FPGA-based prototype of Shale, achieving orders of magnitude better resource scaling than existing ORN proposals. Finally, we extend our congestion control solution to handle node and link failures.
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- PAR ID:
- 10511251
- Publisher / Repository:
- Association of Computing Machinery (ACM)
- Date Published:
- Journal Name:
- ACM Special Interest Group on Data Communication (SIGCOMM)
- Format(s):
- Medium: X
- Location:
- Sydney, Australia
- Sponsoring Org:
- National Science Foundation
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