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  1. Previous studies have observed that TCP pacing evenly spacing out packets-minimizes traffic burstiness, reduces packet losses, and increases throughput. However, the main drawback of pacing is that the number of flows and the bottleneck link capacity must be known in advance. With this information, pacing is achieved by manually tuning sender nodes to send at rates that aggregate to the bottleneck capacity. This paper proposes a scheme based on programmable switches by which rates are dynamically adjusted. These switches store the network's state in the data plane and notify sender nodes to update their pacing rates when the network's state changes, e.g., a new flow joins or leaves the network. The scheme uses a custom protocol that is encapsulated inside the IP Options header field and thus is compatible with legacy switches (i.e., the scheme does not require all switches to be programmable). Furthermore, the processing overhead at programmable switches is minimal, as custom packets are only generated when a flow joins or leaves the network. Simulation results conducted in Mininet demonstrate that the proposed scheme is capable of dynamically notifying hosts to adapt the pacing rate with a minimum delay, increasing throughput, mitigating the TCP sawtooth behavior, and achieving better fairness among concurrent flows. The proposed scheme and preliminary results are particularly attractive to applications such as Science DMZ, where typically a small number of large flows must share the bandwidth capacity. 
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  2. Science and engineering applications are now generating data at an unprecedented rate. From large facilities such as the Large Hadron Collider to portable DNA sequencing devices, these instruments can produce hundreds of terabytes in short periods of time. Researchers and other professionals rely on networks to transfer data between sensing locations, instruments, data storage devices, and computing systems. While general-purpose networks, also referred to as enterprise networks, are capable of transporting basic data, such as e-mails and Web content, they face numerous challenges when transferring terabyte- and petabyte-scale data. At best, transfers of science data on these networks may last days or even weeks. In response to this challenge, the Science Demilitarized Zone (Science DMZ) has been proposed. The Science DMZ is a network or a portion of a network designed to facilitate the transfer of big science data. The main elements of the Science DMZ include: 1) specialized end devices, referred to as data transfer nodes (DTNs), built for sending/receiving data at a high speed over wide area networks; 2) high-throughput, friction-free paths connecting DTNs, instruments, storage devices, and computing systems; 3) performance measurement devices to monitor end-to-end paths over multiple domains; and 4) security policies and enforcement mechanisms tailored for high-performance environments. Despite the increasingly important role of Science DMZs, the literature is still missing a guideline to provide researchers and other professionals with the knowledge to broaden the understanding and development of Science DMZs. This paper addresses this gap by presenting a comprehensive tutorial on Science DMZs. The tutorial reviews fundamental network concepts that have a large impact on Science DMZs, such as router architecture, TCP attributes, and operational security. Then, the tutorial delves into protocols and devices at different layers, from the physical cyberinfrastructure to application-layer tools and security appliances, that must be carefully considered for the optimal operation of Science DMZs. This paper also contrasts Science DMZs with general-purpose networks, and presents empirical results and use cases applicable to current and future Science DMZs. 
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