Multistage Packet-Switching Fabrics for Data Center Networks

Recent applications have imposed stringent requirements within the Data Center Network (DCN) switches in terms of scalability, throughput and latency. In this thesis, the architectural design of the packet-switches is tackled in different ways to enable the expansion in both the number of connected endpoints and traffic volume. A cost-effective Clos-network switch with partially buffered units is proposed and two packet scheduling algorithms are described. The first algorithm adopts many simple and distributed arbiters, while the second approach relies on a central arbiter to guarantee an ordered packet delivery. For an improved scalability, the Clos switch is build using a Network-on-Chip (NoC) fabric instead of the common crossbar units. The Clos-UDN architecture made with Input-Queued (IQ) Uni-Directional NoC modules (UDNs) simplifies the input line cards and obviates the need for the costly Virtual Output Queues (VOQs). It also avoids the need for complex, and synchronized scheduling processes, and offers speedup, load balancing, and good path diversity. Under skewed traffic, a reliable micro load-balancing contributes to boosting the overall network performance. Taking advantage of the NoC paradigm, a wrapped-around multistage switch with fully interconnected Central Modules (CMs) is proposed. The architecture operates with a congestion-aware routing algorithm that proactively distributes the traffic load across the switching modules, and enhances the switch performance under critical packet arrivals. The implementation of small on-chip buffers has been made perfectly feasible using the current technology. This motivated the implementation of a large switching architecture with an Output-Queued (OQ) NoC fabric. The design merges assets of the output queuing, and NoCs to provide high throughput, and smooth latency variations. An approximate analytical model of the switch performance is also proposed. To further exploit the potential of the NoC fabrics and their modularity features, a high capacity Clos switch with Multi-Directional NoC (MDN) modules is presented. The Clos-MDN switching architecture exhibits a more compact layout than the Clos-UDN switch. It scales better and faster in port count and traffic load. Results achieved in this thesis demonstrate the high performance, expandability and programmability features of the proposed packet-switches which makes them promising candidates for the next-generation data center networking infrastructure

Multistage Packet-Switching Fabrics for Data Center Networks

Recent applications have imposed stringent requirements within the Data Center Network (DCN) switches in terms of scalability, throughput and latency. In this thesis, the architectural design of the packet-switches is tackled in different ways to enable the expansion in both the number of connected endpoints and traffic volume. A cost-effective Clos-network switch with partially buffered units is proposed and two packet scheduling algorithms are described. The first algorithm adopts many simple and distributed arbiters, while the second approach relies on a central arbiter to guarantee an ordered packet delivery. For an improved scalability, the Clos switch is build using a Network-on-Chip (NoC) fabric instead of the common crossbar units. The Clos-UDN architecture made with Input-Queued (IQ) Uni-Directional NoC modules (UDNs) simplifies the input line cards and obviates the need for the costly Virtual Output Queues (VOQs). It also avoids the need for complex, and synchronized scheduling processes, and offers speedup, load balancing, and good path diversity. Under skewed traffic, a reliable micro load-balancing contributes to boosting the overall network performance. Taking advantage of the NoC paradigm, a wrapped-around multistage switch with fully interconnected Central Modules (CMs) is proposed. The architecture operates with a congestion-aware routing algorithm that proactively distributes the traffic load across the switching modules, and enhances the switch performance under critical packet arrivals. The implementation of small on-chip buffers has been made perfectly feasible using the current technology. This motivated the implementation of a large switching architecture with an Output-Queued (OQ) NoC fabric. The design merges assets of the output queuing, and NoCs to provide high throughput, and smooth latency variations. An approximate analytical model of the switch performance is also proposed. To further exploit the potential of the NoC fabrics and their modularity features, a high capacity Clos switch with Multi-Directional NoC (MDN) modules is presented. The Clos-MDN switching architecture exhibits a more compact layout than the Clos-UDN switch. It scales better and faster in port count and traffic load. Results achieved in this thesis demonstrate the high performance, expandability and programmability features of the proposed packet-switches which makes them promising candidates for the next-generation data center networking infrastructure

Tiled microprocessors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 251-258).Current-day microprocessors have reached the point of diminishing returns due to inherent scalability limitations. This thesis examines the tiled microprocessor, a class of microprocessor which is physically scalable but inherits many of the desirable properties of conventional microprocessors. Tiled microprocessors are composed of an array of replicated tiles connected by a special class of network, the Scalar Operand Network (SON), which is optimized for low-latency, low-occupancy communication between remote ALUs on different tiles. Tiled microprocessors can be constructed to scale to 100's or 1000's of functional units. This thesis identifies seven key criteria for achieving physical scalability in tiled microprocessors. It employs an archetypal tiled microprocessor to examine the challenges in achieving these criteria and to explore the properties of Scalar Operand Networks. The thesis develops the field of SONs in three major ways: it introduces the 5-tuple performance metric, it describes a complete, high-frequency SON implementation, and it proposes a taxonomy, called AsTrO, for categorizing them.(cont.) To develop these ideas, the thesis details the design, implementation and analysis of a tiled microprocessor prototype, the Raw Microprocessor, which was implemented at MIT in 180 nm technology. Overall, compared to Raw, recent commercial processors with half the transistors required 30x as many lines of code, occupied 100x as many designers, contained 50x as many pre-tapeout bugs, and resulted in 33x as many post-tapeout bugs. At the same time, the Raw microprocessor proves to be more versatile in exploiting ILP, stream, and server-farm workloads with modest to large amounts of parallelism.by Michael Bedford Taylor.Ph.D

System architecture and hardware implementations for a reconfigurable MPLS router

With extremely wide bandwidth and good channel properties, optical fibers have brought fast and reliable data transmission to today’s data communications. However, to handle heavy traffic flowing through optical physical links, much faster processing speed is required or else congestion can take place at network nodes. Also, to provide people with voice, data and all categories of multimedia services, distinguishing between different data flows is a requirement. To address these router performance, Quality of Service /Class of Service and traffic engineering issues, Multi-Protocol Label Switching (MPLS) was proposed for IP-based Internetworks. In addition, routers flexible in hardware architecture in order to support ever-evolving protocols and services without causing big infrastructure modification or replacement are also desirable. Therefore, reconfigurable hardware implementation of MPLS was proposed in this project to obtain the overall fast processing speed at network nodes. The long-term goal of this project is to develop a reconfigurable MPLS router, which uniquely integrates the best features of operations being conducted in software and in run-time-reconfigurable hardware. The scope of this thesis includes system architecture and service algorithm considerations, Verilog coding and testing for an actual device. The hardware and software co-design technique was used to partition and schedule the protocol code for execution on both a general-purpose processor and stream-based hardware. A novel RPS scheme that is practically easy to build and can realize pipelined packet-by-packet data transfer at each output was proposed to take the place of the traditional crossbar switching. In RPS, packets with variable lengths can be switched intelligently without performing packet segmentation and reassembly. Primary theoretical analysis of queuing issues was discussed and an improved multiple queue service scheduling policy UD-WRR was proposed, which can reduce packet-waiting time without sacrificing the performance. In order to have the tests carried out appropriately, dedicated circuitry for the MPLS functional block to interface a specific MAC chip was implemented as well. The hardware designs for all functions were realized with a single Field Programmable Gate Array (FPGA) device in this project. The main result presented in this thesis was the MPLS function implementation realizing a major part of layer three routing at the reconfigurable hardware level, which advanced a great step towards the goal of building a router that is both fast and flexible

Efficient Q. S support for higt-performance interconnects

Las redes de interconexión son un componente clave en un gran número de sistemas. Los mecanismos de calidad de servicio (qos) son responsables de asegurar que se alcanza un cierto rendimiento en la red. Las soluciones tradicionales para ofrecer qos en redes de interconexión de altas prestaciones normalmente se basan en arquitecturas complejas. El principal objetivo de esta tesis es investigar si podemos ofrecer mecanismos eficientes de qos. Nuestro propósito es alcanzar un soporte completo de qos con el mínimo de recursos. Para ello, se identifican redundancias en los mecanismos propuestos de qos y son eliminados sin afectar al rendimiento. Esta tesis consta de tres partes. En la primera comenzamos con las propuestas tradicionales de qos a nivel de clase de tráfico. En la segunda parte, proponemos como adaptar los mecanismos de qos basados en deadlines para redes de interconexión de altas prestaciones. Por último, también investigamos la interacción de los mecanismos de qos con el control de congestión

A Scalable Packet-Switch Architecture Based on OQ NoCs for Data Center Networks

Data Center switches need guarantee high throughput, resiliency and scalability for large-scale networks with constantly floating requirements. Multistage packet switches have been a pervasive solution to implement high-capacity Data Center Networks (DCNs) switches and routers. Yet, classical multistage switching architectures with their Space-Memory variants have shown limited performance. Most proposals prove either too complex to implement or not cost effective. In this paper, we present a highly scalable packet-switch for the DCN environment, in which we exploit the Network-on-Chip (NoC) design paradigm to replace the single-hop crossbars with multi-hop Switching Elements (SEs). In particular, we describe a three-stage switch with Output-Queued Unidirectional NoCs (OQ-UDN) in the central stage of the Clos-network. The design has several advantages over conventional multistage switches. First, it uses a simple Round-Robin (RR) packet dispatching scheme and avoids the need for complex and costly input modules. Besides, it offers better load balancing, a pipelined scheduling and more path-diversity. We assess the performance of the switch in terms of throughput, end-to-end latency and blocking probability using Markov chain analysis, and we propose an analytical model that integrates the various design parameters. Through extensive simulations, we show that the switching architecture achieves high performance under different types of traffic, and that both the analytical and experimental results correlate over wide range of evaluation settings

Distributed Time-Predictable Memory Interconnect for Multi-Core Architectures

Multi-core architectures are increasingly adopted in emerging real-time applications where execution time is required to be bounded in the worst case (i.e., time predictability) and low. Memory access latency is the main part forming the overall execution time. A promising approach towards time predictability is to employ distributed memory interconnects, either locally arbitrated interconnects or globally arbitrated interconnects, with arbitration schemes, and the pipelined tree-based structure can break the critical path of multiplexing into short steps with small logic size. It scales to a large number of processors that high clock frequency can be synthesised. This research explores timing behaviour of multi-core architectures with shared distributed memory interconnects and improves distributed time-predictable memory interconnects for multi-core architectures. The contributions are mainly threefold. First, the generic analytical flow is proposed for time-predictable behaviour of memory accesses across multi-core architectures with locally arbitrated interconnects. It guarantees time predictability and safely bound the worst case without exact memory access profiles. Second, the root queue modification with the root queue management is proposed for multi-core architectures with locally arbitrated interconnects that variation of memory access latency is reduced and timing behaviour analysis is facilitated. Third, Meshed Bluetree is proposed as the distributed time-predictable multi-memory interconnect, enabling multiple processors to simultaneously access multiple memory modules

A Dynamically Reconfigurable Parallel Processing Framework with Application to High-Performance Video Processing

Digital video processing demands have and will continue to grow at unprecedented rates. Growth comes from ever increasing volume of data, demand for higher resolution, higher frame rates, and the need for high capacity communications. Moreover, economic realities force continued reductions in size, weight and power requirements. The ever-changing needs and complexities associated with effective video processing systems leads to the consideration of dynamically reconfigurable systems. The goal of this dissertation research was to develop and demonstrate the viability of integrated parallel processing system that effectively and efficiently apply pre-optimized hardware cores for processing video streamed data. Digital video is decomposed into packets which are then distributed over a group of parallel video processing cores. Real time processing requires an effective task scheduler that distributes video packets efficiently to any of the reconfigurable distributed processing nodes across the framework, with the nodes running on FPGA reconfigurable logic in an inherently Virtual\u27 mode. The developed framework, coupled with the use of hardware techniques for dynamic processing optimization achieves an optimal cost/power/performance realization for video processing applications. The system is evaluated by testing processor utilization relative to I/O bandwidth and algorithm latency using a separable 2-D FIR filtering system, and a dynamic pixel processor. For these applications, the system can achieve performance of hundreds of 640x480 video frames per second across an eight lane Gen I PCIe bus. Overall, optimal performance is achieved in the sense that video data is processed at the maximum possible rate that can be streamed through the processing cores. This performance, coupled with inherent ability to dynamically add new algorithms to the described dynamically reconfigurable distributed processing framework, creates new opportunities for realizable and economic hardware virtualization.\u2

Spatial parallelism in the routers of asynchronous on-chip networks

State-of-the-art multi-processor systems-on-chip use on-chip networks as their communication fabric. Although most on-chip networks are implemented synchronously, asynchronous on-chip networks have several advantages over their synchronous counterparts. Timing division multiplexing (TDM) flow control methods have been utilized in asynchronous on-chip networks extensively. The synchronization required by TDM leads to significant speed penalties. Compared with using TDM methods, spatial parallelism methods, such as the spatial division multiplexing (SDM) flow control method, achieve better network throughput with less area overhead.This thesis proposes several techniques to increase spatial parallelism in the routers of asynchronous on-chip networks.Channel slicing is a new pipeline structure that alleviates the speed penalty by removing the synchronization among bit-level data pipelines. It is also found out that the lookahead pipeline using early evaluated acknowledgement can be used in routers to further improve speed.SDM is a new flow control method proposed for asynchronous on-chip networks. It improves network throughput without introducing synchronization among buffers of different frames, which is required by TDM methods. It is also found that the area overhead of SDM is smaller than the virtual channel (VC) flow control method -- the most used TDM method. The major design problem of SDM is the area consuming crossbars. A novel 2-stage Clos switch structure is proposed to replace the crossbar in SDM routers, which significantly reduces the area overhead. This Clos switch is dynamically reconfigured by a new asynchronous Clos scheduler.Several asynchronous SDM routers are implemented using these new techniques. An asynchronous VC router is also reproduced for comparison. Performance analyses show that the SDM routers outperform the VC router in throughput, area overhead and energy efficiency.EThOS - Electronic Theses Online ServiceGBUnited Kingdo