3,100 research outputs found
Performance Implications of NoCs on 3D-Stacked Memories: Insights from the Hybrid Memory Cube
Memories that exploit three-dimensional (3D)-stacking technology, which
integrate memory and logic dies in a single stack, are becoming popular. These
memories, such as Hybrid Memory Cube (HMC), utilize a network-on-chip (NoC)
design for connecting their internal structural organizations. This novel usage
of NoC, in addition to aiding processing-in-memory capabilities, enables
numerous benefits such as high bandwidth and memory-level parallelism. However,
the implications of NoCs on the characteristics of 3D-stacked memories in terms
of memory access latency and bandwidth have not been fully explored. This paper
addresses this knowledge gap by (i) characterizing an HMC prototype on the
AC-510 accelerator board and revealing its access latency behaviors, and (ii)
by investigating the implications of such behaviors on system and software
designs
Performance, Validation and Testing with the Network Simulation Cradle
Much current simulation of TCP makes use of simplified models of TCP, which is a large and complex protocol with many variations possible between implementations. We use direct execution of real world network stacks in the network simulator ns-2 to compare TCP performance between implementations and reproduce existing work. A project called The Network Simulation Cradle provides the real world network stacks and we show how it can be used for performance evaluation and validation. There are large differences in performance between simplified TCP models and TCP implementations in some situations. Such differences are apparent in some reproduced research, with results using the Network Simulation Cradle very different from the results produced with the ns-2 TCP models. In other cases, using the real implementations gives very similar results, validating the original research
TCP over High Speed Variable Capacity Links: A Simulation Study for Bandwidth Allocation
New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case
QoS-based multipath routing for the Internet
The new generation of network services is being developed for incorporation in communication infrastructure. These services, generally called Quality of Services (QoS), should accommodate data file, video, and audio applications. The different performance requirements of these applications necessitate a re-examination of the main architectural components of today\u27s networks, which were designed to support traditional data applications. Routing, which determines the sequence of network nodes a packet traverses between source and destination, is one such component. Here, we examine the potential routing problems in future Internet and discuss the advantages of class-based multi-path routing methods. The result is a new approach to routing in packet-switched networks, which is called Two-level Class-based Multipath routing with Prediction (TCMP). In TCMP, we compute multiple paths between each source and destination based on link propagation delay and bottleneck bandwidth. A leaky bucket is adopted in each router to monitor the bottleneck bandwidth on equal paths during the network\u27s stable period, and to guide its traffic forwarDing The TCMP can avoid frequent flooding of routing information in a dynamic routing method; therefore, it can be applied to large network topologies
On-Line End-to-End Congestion Control
Congestion control in the current Internet is accomplished mainly by TCP/IP.
To understand the macroscopic network behavior that results from TCP/IP and
similar end-to-end protocols, one main analytic technique is to show that the
the protocol maximizes some global objective function of the network traffic.
Here we analyze a particular end-to-end, MIMD (multiplicative-increase,
multiplicative-decrease) protocol. We show that if all users of the network use
the protocol, and all connections last for at least logarithmically many
rounds, then the total weighted throughput (value of all packets received) is
near the maximum possible. Our analysis includes round-trip-times, and (in
contrast to most previous analyses) gives explicit convergence rates, allows
connections to start and stop, and allows capacities to change.Comment: Proceedings IEEE Symp. Foundations of Computer Science, 200
Hybrid routing technique for a fault-tolerant, integrated information network
The evolutionary growth of the space station and the diverse activities onboard are expected to require a hierarchy of integrated, local area networks capable of supporting data, voice, and video communications. In addition, fault-tolerant network operation is necessary to protect communications between critical systems attached to the net and to relieve the valuable human resources onboard the space station of time-critical data system repair tasks. A key issue for the design of the fault-tolerant, integrated network is the development of a robust routing algorithm which dynamically selects the optimum communication paths through the net. A routing technique is described that adapts to topological changes in the network to support fault-tolerant operation and system evolvability
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