3,031 research outputs found
DCCast: Efficient Point to Multipoint Transfers Across Datacenters
Using multiple datacenters allows for higher availability, load balancing and
reduced latency to customers of cloud services. To distribute multiple copies
of data, cloud providers depend on inter-datacenter WANs that ought to be used
efficiently considering their limited capacity and the ever-increasing data
demands. In this paper, we focus on applications that transfer objects from one
datacenter to several datacenters over dedicated inter-datacenter networks. We
present DCCast, a centralized Point to Multi-Point (P2MP) algorithm that uses
forwarding trees to efficiently deliver an object from a source datacenter to
required destination datacenters. With low computational overhead, DCCast
selects forwarding trees that minimize bandwidth usage and balance load across
all links. With simulation experiments on Google's GScale network, we show that
DCCast can reduce total bandwidth usage and tail Transfer Completion Times
(TCT) by up to compared to delivering the same objects via independent
point-to-point (P2P) transfers.Comment: 9th USENIX Workshop on Hot Topics in Cloud Computing,
https://www.usenix.org/conference/hotcloud17/program/presentation/noormohammadpou
Merlin: A Language for Provisioning Network Resources
This paper presents Merlin, a new framework for managing resources in
software-defined networks. With Merlin, administrators express high-level
policies using programs in a declarative language. The language includes
logical predicates to identify sets of packets, regular expressions to encode
forwarding paths, and arithmetic formulas to specify bandwidth constraints. The
Merlin compiler uses a combination of advanced techniques to translate these
policies into code that can be executed on network elements including a
constraint solver that allocates bandwidth using parameterizable heuristics. To
facilitate dynamic adaptation, Merlin provides mechanisms for delegating
control of sub-policies and for verifying that modifications made to
sub-policies do not violate global constraints. Experiments demonstrate the
expressiveness and scalability of Merlin on real-world topologies and
applications. Overall, Merlin simplifies network administration by providing
high-level abstractions for specifying network policies and scalable
infrastructure for enforcing them
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
Object Replication Algorithms for World Wide Web
Object replication is a well-known technique to improve the accessibility of the Web sites. It generally offers reduced client latencies and increases a site's availability. However, applying replication techniques is not trivial and a large number of heuristics have been proposed to decide the number of replicas of an object and their placement in a distributed web server system. This paper presents three object placement and replication algorithms. The first two heuristics are centralized in the sense that a central site determines the number of replicas and their placement. Due to the dynamic nature of the Internet traffic and the rapid change in the access pattern of the World-Wide Web, we also propose a distributed algorithm where each site relies on some locally collected information to decide what objects should be replicated at that site. The performance of the proposed algorithms is evaluated through a simulation study. Also, the performance of the proposed algorithms has been compared with that of three other well-known algorithms and the results are presented. The simulation results demonstrate the effectiveness and superiority of the proposed algorithms
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