1,913 research outputs found
Scheduling for Weighted Flow and Completion Times in Reconfigurable Networks
New optical technologies offer the ability to reconfigure network topologies
dynamically, rather than setting them once and for all. This is true in both
optical wide area networks (optical WANs) and in datacenters, despite the many
differences between these two settings. Because of these new technologies,
there has been a surge of both practical and theoretical research on algorithms
to take advantage of them. In particular, Jia et al. [INFOCOM '17] designed
online scheduling algorithms for dynamically reconfigurable topologies for both
the makespan and sum of completion times objectives. In this paper, we work in
the same setting but study an objective that is more meaningful in an online
setting: the sum of flow times. The flow time of a job is the total amount of
time that it spends in the system, which may be considerably smaller than its
completion time if it is released late. We provide competitive algorithms for
the online setting with speed augmentation, and also give a lower bound proving
that speed augmentation is in fact necessary. As a side effect of our
techniques, we also improve and generalize the results of Jia et al. on
completion times by giving an -competitive algorithm for arbitrary sizes
and release times even when nodes have different degree bounds, and moreover
allow for the weighted sum of completion times (or flow times).Comment: 10 pages. Appears in INFOCOM 202
Datacenter Traffic Control: Understanding Techniques and Trade-offs
Datacenters provide cost-effective and flexible access to scalable compute
and storage resources necessary for today's cloud computing needs. A typical
datacenter is made up of thousands of servers connected with a large network
and usually managed by one operator. To provide quality access to the variety
of applications and services hosted on datacenters and maximize performance, it
deems necessary to use datacenter networks effectively and efficiently.
Datacenter traffic is often a mix of several classes with different priorities
and requirements. This includes user-generated interactive traffic, traffic
with deadlines, and long-running traffic. To this end, custom transport
protocols and traffic management techniques have been developed to improve
datacenter network performance.
In this tutorial paper, we review the general architecture of datacenter
networks, various topologies proposed for them, their traffic properties,
general traffic control challenges in datacenters and general traffic control
objectives. The purpose of this paper is to bring out the important
characteristics of traffic control in datacenters and not to survey all
existing solutions (as it is virtually impossible due to massive body of
existing research). We hope to provide readers with a wide range of options and
factors while considering a variety of traffic control mechanisms. We discuss
various characteristics of datacenter traffic control including management
schemes, transmission control, traffic shaping, prioritization, load balancing,
multipathing, and traffic scheduling. Next, we point to several open challenges
as well as new and interesting networking paradigms. At the end of this paper,
we briefly review inter-datacenter networks that connect geographically
dispersed datacenters which have been receiving increasing attention recently
and pose interesting and novel research problems.Comment: Accepted for Publication in IEEE Communications Surveys and Tutorial
Brief Announcement: Minimizing Congestion in Hybrid Demand-Aware Network Topologies
Emerging reconfigurable optical communication technologies enable demand-aware networks: networks whose static topology can be enhanced with demand-aware links optimized towards the traffic pattern the network serves. This paper studies the algorithmic problem of how to jointly optimize the topology and the routing in such demand-aware networks, to minimize congestion. We investigate this problem along two dimensions: (1) whether flows are splittable or unsplittable, and (2) whether routing on the hybrid topology is segregated or not, i.e., whether or not flows either have to use exclusively either the static network or the demand-aware connections. For splittable and segregated routing, we show that the problem is 2-approximable in general, but APX-hard even for uniform demands induced by a bipartite demand graph. For unsplittable and segregated routing, we show an upper bound of O(log m/ log log m) and a lower bound of ?(log m/ log log m) for polynomial-time approximation algorithms, where m is the number of static links. Under splittable (resp., unsplittable) and non-segregated routing, even for demands of a single source (resp., destination), the problem cannot be approximated better than ?(c_{max}/c_{min}) unless P=NP, where c_{max} (resp., c_{min}) denotes the maximum (resp., minimum) capacity. It is still NP-hard for uniform capacities, but can be solved efficiently for a single commodity and uniform capacities
Self-Evaluation Applied Mathematics 2003-2008 University of Twente
This report contains the self-study for the research assessment of the Department of Applied Mathematics (AM) of the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) at the University of Twente (UT). The report provides the information for the Research Assessment Committee for Applied Mathematics, dealing with mathematical sciences at the three universities of technology in the Netherlands. It describes the state of affairs pertaining to the period 1 January 2003 to 31 December 2008
OSMOSIS: Enabling Multi-Tenancy in Datacenter SmartNICs
Multi-tenancy is essential for unleashing SmartNIC's potential in
datacenters. Our systematic analysis in this work shows that existing on-path
SmartNICs have resource multiplexing limitations. For example, existing
solutions lack multi-tenancy capabilities such as performance isolation and QoS
provisioning for compute and IO resources. Compared to standard NIC data paths
with a well-defined set of offloaded functions, unpredictable execution times
of SmartNIC kernels make conventional approaches for multi-tenancy and QoS
insufficient. We fill this gap with OSMOSIS, a SmartNICs resource manager
co-design. OSMOSIS extends existing OS mechanisms to enable dynamic hardware
resource multiplexing on top of the on-path packet processing data plane. We
implement OSMOSIS within an open-source RISC-V-based 400Gbit/s SmartNIC. Our
performance results demonstrate that OSMOSIS fully supports multi-tenancy and
enables broader adoption of SmartNICs in datacenters with low overhead.Comment: 12 pages, 14 figures, 103 reference
Packet Transactions: High-level Programming for Line-Rate Switches
Many algorithms for congestion control, scheduling, network measurement,
active queue management, security, and load balancing require custom processing
of packets as they traverse the data plane of a network switch. To run at line
rate, these data-plane algorithms must be in hardware. With today's switch
hardware, algorithms cannot be changed, nor new algorithms installed, after a
switch has been built.
This paper shows how to program data-plane algorithms in a high-level
language and compile those programs into low-level microcode that can run on
emerging programmable line-rate switching chipsets. The key challenge is that
these algorithms create and modify algorithmic state. The key idea to achieve
line-rate programmability for stateful algorithms is the notion of a packet
transaction : a sequential code block that is atomic and isolated from other
such code blocks. We have developed this idea in Domino, a C-like imperative
language to express data-plane algorithms. We show with many examples that
Domino provides a convenient and natural way to express sophisticated
data-plane algorithms, and show that these algorithms can be run at line rate
with modest estimated die-area overhead.Comment: 16 page
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