FireFly: a cross-layer platform for real-time embedded wireless networks

We propose a cross-layer approach with tightly-coupled time synchronization for real-time support and predictable lifetime in battery-operated sensor networks. Our design spans a sensor hardware platform with hardware-based global time synchronization, a TDMA link layer protocol with collision-free multi-hop support and node scheduling algorithms for maximum concurrency and streaming. Our dual-radio sensor platform, FireFly, features an IEEE 802.15.4 transceiver and supports global time synchronization indoors by using an AM radio carrier-current method and an atomic clock receiver for outdoors. A TDMA-based link protocol, RT-Link, leverages the hardware for fixed and mobile nodes with a near-optimal and predictable node lifetime of over 2 years. It outperforms comparable sensor network link protocols such as B-MAC and S-MAC in terms of end-to-end latency and throughput and node lifetime across all duty cycle ratios. Operating over RT-Link is MAX, a scheduling framework which offers optimal transmission concurrency and bandwidth management for networks with regular structure. Through analysis and experiments we show that global time sync is a robust, economical and scalable alternative to in-band software-based techniques. To illustrate the capabilities and flexibility of our platform, we describe our experiences with two-way voice streaming over multiple hops. We have deployed a 42-node network with sub-100 μs synchronization accuracy in the NIOSH experimental coal mine for people-tracking and voice communication.

基于网络处理器的零拷贝技术*

通过分析网络处理器系统的收发机制,提出了一种基于网络处理器的零拷贝技术。该技术不仅实现了在网络处理器系统下的零拷贝技术,而且也体现出网络处理器中不同数据处理层的协作框架。     

一种安全高效的无线群组密钥分配协议*

由于无线用户的移动性和无线移动设备计算能力、存储能力、电池供电能力和带宽资源的局限性,使得有线环境中的群组通信协议不能直接应用于无线移动环境中.基于单向积聚函数,采用集中式与分布式密钥管理相结合的方法,提出了一种新的安全无线群组通信协议,新协议提供组成员的认证、匿名性,具有后向保密性和前向保密性.经过比较,所提出的协议具有存储空间要求少、运算量小、安全性高、结构简单和易于实现的特点,适用于无线网络环境.     

Advanced networking services for distributed multimedia streaming applications

Increased network speeds coupled with new services delivered via the Internet have increased the demand for intelligence and flexibility in network systems. This paper argues that both can be provided by new hardware platforms comprised of heterogeneous multi-core systems with specialized communication support. We present and evaluate an experimental network service platform that uses an emergent class of devices—network processors—as its communication support, coupled via a dedicated interconnect to a host processor acting as a computational core. A software infrastructure spanning both enables the dynamic creation of application-specific services on the network processor, mediated by middleware and controlled by kernel-level communication support. Experimental evaluations use a Pentium IV-based computational core coupled with an IXP 2400 network processor. The sample application services run on both include an image manipulation application and application-level multicasting.

银行交易系统灾备技术研究与应用

简要介绍银行在大集中后省级分行的灾难备份情况,以某省行交易系统为例,从省级分行的灾备需求出发,通过过多次实验,包括“从SAN中的共享磁盘启动小型机”和生产数据中心和备份中心灾难切换,设计了省级行以玲备份方式进行的灾难备份及恢复实施方案,有助于犬集中后省级行建立灾难恢复中心的建设,保证银行业务持续性稳定发展。     

Algorithmic and architectural design for real-time and power-efficient Retinex image/video processing

This paper presents novel algorithmic and architectural solutions for real-time and power-efficient enhancement of images and video sequences. A programmable class of Retinex-like filters, based on the separation of the illumination and reflectance components, is proposed. The dynamic range of the input image is controlled by applying a suitable non-linear function to the illumination, while the details are enhanced by processing the reflectance. An innovative spatially recursive rational filter is used to estimate the illumination. Moreover, to improve the visual quality results of two-branch Retinex operators when applied to videos, a novel three-branch technique is proposed which exploits both spatial and temporal filtering. Real-time implementation is obtained by designing an Application Specific Instruction-set Processor (ASIP). Optimizations are addressed at algorithmic and architectural levels. The former involves arithmetic accuracy definition and linearization of non-linear operators; the latter includes customized instruction set, dedicated memory structure, adapted pipeline, bypasses, custom address generator, and special looping structures. The ASIP is synthesized in standard-cells CMOS technology and its performances are compared to known Digital signal processor (DSP) implementations of real-time Retinex filters. As a result of the comparison, the proposed algorithmic/architectural design outperforms state-of-art Retinex-like operators achieving the best trade-off between power consumption, flexibility, and visual quality.

一种基于VPN的安全电子邮件

随着电子政务和电子商务的逐渐普及,通过电子邮件在Internet上传递的机密信息也在迅速增加,因此对电子邮件的安全性和非公开性提出了更高的要求。论述了网络监听对当前电子邮件形成的安全威胁及VPN的安全机制,并在Linux环境下实现了一个基于IPSec的安全电子邮件网关模型。     

WindowsNT的安全问题探讨

从WindowsNT操作系统的应用角度出发,针对NT操作系统本身存在的安全隐患,讨论了比较典型和重大的安全漏洞,并给出了对这些漏洞的解决及防范措施,为基于NT的服务器和工作站的网络安全建设提供了有价值的参考意见。     

关于我国反病毒技术发展的若干思考

通过调查、分析和比较国内外病毒、反病毒技术的发展情况,指出民族软件产业在反病毒技术方面的不足,并从管理上、技术上、策略上提出了相应的应变措施,希望能为我国民族软件业能在世界反病毒领域占有一席之地有所帮助。     

移动IP切换对TCP性能影响的分析

介绍了移动IP切换的发展过程及原理,描述了切换造成TCP性能下降原因和一些实验验证数据。说明为了更好地满足用户需求,移动IP和TCP需要作进一步改进,并提出了相应的解决办法。