基于ASP的教学网站文件上传策略研究

本文分析了教学网站各种上传方式采用的技术、适用性、使用方法和优缺点,并结合应用实例进行介绍。     

MIDS: a framework for information organization and discovery

The MITRE Information Discovery System (MIDS) is a baseline system for integrating advanced processing tools for information discovery and retrieval in large-scale distributed environments. The system is built on a modular, extendible architecture that allows for system-level decoupling and allocation of component processing tools across network nodes to provide for efficient processing in distributed environments. At one level, the system provides for multi-platform user access to HTTP, Gopher, FTP, and news servers using an HTML based client interface. However, more significantly, the system provides advanced tools for metadata generation from disparate network objects, and a content routing mediation layer for classification of metadata into appropriate information brokers. This bottom-up layered information organization approach supports a wide range of information retrieval and browsing strategies.     

The transfer protocols

There are many Internet-scale messaging systems: Telnet for duplex byte streams, File Transfer Protocol (FTP) for pulling files, Simple Mail Transfer Protocol (SMTP) for reliable e-mail messaging, Network News Transfer Protocol (NNTP) for pushing e-mail, HyperText Transfer Protocol (HTTP) for pulling Web pages, and a host of other special-purpose schemes, from Finger to Network File System (NFS). How can we make sense of it all? Understanding the history of these transfer protocols (TPs) is the key to charting their future, especially as new contenders like HTTP-NG (next-generation) emerge. In this article, I set forth a general ontology-a vocabulary for describing and classifying TPs, with the aim of developing a framework to help navigate among the alternatives     

World-Wide Web proxies

A WWW proxy server, proxy for short, provides access to the Web for people on closed subnets who can only access the Internet through a firewall machine. The hypertext server developed at CERN, cern_httpd, is capable of running as a proxy, providing seamless external access to HTTP, Gopher, WAIS and FTP.cern_httpd has had gateway features for a long time, but only this spring they were extended to support all the methods in the HTTP protocol used by WWW clients. Clients do not lose any functionality by going through a proxy, except special processing they may have done for non-native Web protocols such as Gopher and FTP.A brand new feature is caching performed by the proxy, resulting in shorter response times after the first document fetch. This makes proxies useful even to the people who do have full Internet access and do not really need the proxy just to get out of their local subnet.This paper gives an overview of proxies and reports their current status.     

Who killed Gopher? An extensible murder mystery

Everyone knew there had to be an easier way to use the Internet than the Unix shell experience, mind you, but original editions of the Gopher and HyperText Transfer Protocols were painfully trivial hacks that did nothing FTP didn't already handle. So here begins our mysterious tale: why either protocol ever rose to prominence in the first place; and how the fratricidal drama eventually played out. Understanding how HTTP killed Gopher may lead us to the forces that may, in turn, topple HTTP     

交换式网络下HTTP会话的劫持研究及其对策

针对ARP协议和TCP协议的安全漏洞，在分析HTTP协议安全缺陷的基础上，提出了HTTP中间人会话劫持的理论，通过实验论证了在用户使用HTTP协议进行文件下载时引发中间人攻击的可能性。为避免此种攻击所造成的安全威胁，提出了采用静态ARP表、监控ARP缓存异常、使用HTTPS协议3种不同的安全措施来增加网络的安全性。     

基于ARM9的移动Web Server的设计与实现

以三星ARM9 S3C2410 Soc嵌入式芯片为核心,将Linux操作系统导入其中,设计并实现了一个Wi-Fi无线网络平台,此平台提供了一个移动Web Server。可以提供HTTP、FTP等服务,此平台期望在视频监控等领域得到广泛应用。     

一种高效的智能内容过滤模型

针对目前内容过滤系统中存在的问题，借鉴人工智能领域中基于范例推理(CBR)的机制，提出了一种高效的智能内容过滤模型，它可以对应用层内容协议(如FTP、HTTP、SMTP、POP3等)所携带的信息进行过滤，较好地避免了规则规模过大而对系统效率的影响，有效地处理具有相似内容的垃圾邮件，并具备一定的自学习能力。     

基于P2P协议的文件服务器技术

P2P与传统的互联网构架不同,它不区分连接在互联网上的计算机是Server还是Client。P2P协议对于互联网的发展有着划时代的意义。特别是在信息高速膨胀的今天,随着宽带网和ADSL的普及,普通用户的网速越来越快。然而相比之下使用传统的HTTP协议、FTP协议的文件服务器却因此承受着越来越大的压力。文中分析P2P协议的特点,提出和设计了基于P2P协议的网络文件服务器,该服务器与现在已有的P2P文件服务如Bittorrent,ED2K不同,它可以完全代替FTP在Internet上提供文件下载服务。性能测试显示,这种服务器不但下载速度快、连接数限制,而且对服务器性能的要求也较传统的文件服务器大大降低。使用不算强大的服务器也可以工作的很好。     

安全FTP系统的设计与实现

FTP协议是一种简单易用的文件传输协议,应用十分广泛,但是其安全问题不容忽视.在当前常用的基于SSL/TLS协议的FTP应用的基础上,设计并实现了一系列安全措施,从而大大提高了FTP系统中的用户认证、传输和文件存储安全性.     

Stability and performance analysis of randomly deployed wireless networks

A growing demand for mobile services is taking the deployment of wireless local area networks away from the notion of carefully planned and carefully managed settings into randomly deployed and independently managed (if at all) network settings. This results in contentious networks that serve highly mobile nodes. In fact, research reveals that in most metropolitan cities in Europe and the US the size of closely located and contentious access points is overwhelmingly high (in the order of thousands). Subsequently, the performance of these networks is often unstable and unpredictable. This paper aims to investigate the extent of performance fluctuations in randomly deployed networks. It also aims to investigate the contribution of various adaptation strategies at different abstraction layers to deal with these fluctuations. We present the outcome of an exhaustive simulation for different applications, including VoIP, HTTP, and FTP. We will demonstrate that collision due to hidden-terminals is a minor influence on the performance and stability of these networks, whereas dynamic channel allocation greatly affects them. Moreover, HTTP applications are less affected by both inter- and intra-channel interferences compared with FTP and VoIP applications.     

An SSD-based accelerator for directory parsing in storage systems containing massive files

Data explosion introduces new challenges to storage systems. In a file system for big data, a large number of directories and files exist, which are usually organized in a large tree. Parsing directories in a large tree is difficult. In this paper, we propose an accelerator, which helps file systems to fetch the metadata of files rapidly. Contributions of this work include two aspects. First, we propose an accelerator for directory parsing. The accelerator is actually an SSD-based (Solid State Drive-based) cache, which keeps the metadata of frequently or recently accessed files and directories. When a file is demanded, the accelerator attempts to obtain its metadata directly from SSD. If the metadata is kept in SSD, the file system can rapidly obtain the metadata. However, if the metadata is not in SSD, the accelerator consumes a long time to access SSD, but to no avail. In order to avoid non-beneficial SSD accesses, the accelerator predicts whether the metadata is kept by SSD before issuing a read request. Only if the metadata has a high probability of being kept in SSD, the accelerator issues a request to the SSD. The second contribution of this paper is a new bloom filter used to predict whether a piece of data is kept in SSD. Bloom filter is a space-efficient data structure supporting membership query. But, the standard bloom filter cannot support element deletion. Whereas, our accelerator is a cache, which evicts items periodically. The standard bloom filter is not suitable for our accelerator. In this work, we designed a new bloom filter with low overhead, which supports element deletion. The new bloom filter perfectly suits the proposed accelerator. With the prediction of our bloom filter, the accelerator can accelerate the process of directory parsing with nearly no negative impact. We evaluated the accelerator by using a prototype. Experimental results demonstrate that, the accelerator can speed up the directory parsing process by nearly four times compared with a file system without an accelerator.     

网络流量测量与监控系统的设计与实现

在基于TCP/IP网络的SNMP管理协议的基础上,设计完成了B/S模式的动态网络监控系统,实现了网络流量数据获取,网络报文数据获取,流量分析与实时监控的功能。通过重组、分析所获得的数据,将其还原成完整的HTTP、FTP、TELNET应用的内容,并建立保存相应记录的数据库。     

防火墙应用代理的设计与实现

介绍了FW1．0防火墙的应用代理的设计与实现，应用代理包括HTTP代理、FTP代理、TELNET代理和SMTP代理，详细介绍了其实现的具体技术细节。FW1．0构建于Linux基础之上，具有较好的灵活性以及较高的效率。     

Artexte metadata conversion to EPrints: adaptation of digital repository software to visual and media arts documentation

The following research questions structured our analysis: Does an open access institutional repository model respond to the needs of a non-academic documentation centre? Is EPrints software a good match to support the needs of the existing metadata describing Artexte’s collection? What are the customizations required to accommodate the existing Artexte metadata using EPrints? In order to address these questions, in this study we exported the existing metadata schema and sample data in Artexte’s three databases, performed a manual evaluation of metadata quality and compared the 49 Artexte fields to those available within the EPrints schema. We identified the metadata elements that mapped by default without the need for customization or modification and those which would need to be added to EPrints using configuration files. We also identified the customized software development to accommodate Artexte metadata using EPrints: the bilingual controlled vocabulary demands an extension of the EPrints subject taxonomy model with thesaurus semantic relationships. Comparing Artexte and EPrints metadata schemas, we found that 15 out of 49 fields mapped by default without the need for modification, 25 fields would need to be added to EPrints configuration files, and one field will be removed during the migration. With only the remaining eight fields requiring some special attention, we conclude that EPrints is suitable to the needs of Artexte’s bibliographic data management.     

Metagit: Decentralised metadata management with Git

Version control systems are used widely for tracking edits to data files, especially when working in teams with simultaneous editors. They track who made edits and when, and provide tools for comparing changes made and for resolving conflicts when the same file is edited by two people. Attaching metadata to files which stays with the data and tracking changes can be difficult if the file format does not support it. In this paper we present a new and innovative architecture for recording key-value metadata for objects in a revision control system, specifically Git. The utility and maturity of version control system tools make them a good candidate for a metadata store. We take advantage of Git's data store to permit the values to be blobs, opening up other possibilities such as defining thumbnails for files and folders. Propagation rules are presented, detailing when metadata follows a file after modifications to the repository. A prototype version of a tool is presented and the usefulness of the architecture is demonstrated with a number of examples. Adapting the approach to other systems such as Mercurial and Subversion is also discussed.     

Using provenance to efficiently improve metadata searching performance in storage systems

In cloud storage systems, more than 50% of requests are metadata operations, and thus the file system metadata search performance has become increasingly important to different users. With the rapid growth of storage system scales in volume, traditional full-size index trees cannot offer high-performance metadata search due to hierarchical indexing bottleneck. In order to alleviate the long latency and improve the quality-of-service (QoS) in cloud storage service, we proposed a novel provenance based metadata-search system, called PROMES. The metadata search in PROMES is split into three phases: (i) leveraging correlation-aware metadata index tree to identify several files as seeds, most of which can satisfy the query requests, (ii) using the seeds to find the remaining query results via relationship graph search, (iii) continuing to refine and rerank the whole search results, and sending the final results to users. PROMES has the salient features of high query accuracy and low latency, due to files’ tight and lightweight indexing in relationship graph coming from provenance’s analysis. Compared with state-of-the-art metadata searching schemes, PROMES demonstrates its efficiency and efficacy in terms of query accuracy and response latency.     

量化测试高性能L5-Dispatcher

主要内容是关于HTTP Splicing的性能评测．HTTP Splicing是针对TCP Splicing的缺陷而提出的，TCP Splicing现被广泛应用在L5-Dispatcher(即基于内容的Web交换机)中．测试内容包括开销测试、性能测试、与L4-Dispatcher的对比测试、与TCP Splicing的对比测试和扩展性测试．所获得的结论为：当尽力(best effort)访问1KB大小的文件时，HTTP Splicing的性能要比TCP Splicing至少快3．5倍，而当尽力访问10KB大小的文件时，HTTP Splicing的性能比TCP Splicing的性能高22％．当尽力访问307KB大小的文件时，HTTP Splicing的一种实现——WebPatcher-的最好性能值为5556．8replies／s，超过了ArrowPoint公司的CS-100(1193 replies／s)和Alteon公司的ACEdirector3(v6．0．25)(1356replies／s)．     

Towards efficient data distribution on computational desktop grids with BitTorrent

Datacentric applications are still a challenging issue for large-scale distributed computing systems. The emergence of new protocols and software for collaborative content distribution over the Internet offers a new opportunity for efficient and fast delivery of a high volume of data. This paper presents an evaluation of the BitTorrent protocol for computational desktop grids. We first present a prototype of a generic subsystem dedicated to data management and designed to serve as a building block for any desktop grid system. Based on this prototype we conduct experiments to evaluate the potential of BitTorrent compared to a classical approach based on FTP data server. The preliminary results obtained with a 65-node cluster measure the basic characteristics of BitTorrent in terms of latency and bandwidth and evaluate the scalability of BitTorrent for the delivery of large input files. Moreover, we show that BitTorrent has a considerable latency overhead compared to FTP but clearly outperforms FTP when distributing large files or files to a high number of nodes. Tests on a synthetic application show that BitTorrent significantly increases the communication/computation ratio of the applications eligible to run on a desktop grid system.     

一种嵌入式终端多应用网络资源分配协议

为了在嵌入式终端多应用之间合理分配有限的网络带宽资源,提出一种嵌入式终端多应用网络资源分配协议。根据应用特性对网络数据包进行分类,结合实时探测的可用带宽,为每种类型数据包分别添加不同的延迟时间,依据延迟大小调度数据包。将该协议应用于实际IP机顶盒中,在同时运行HTTP流媒体应用和FTP下载应用的环境中,能够优先保证前台流媒体应用的流畅播放。实验结果表明,该协议在多应用运行环境下,能够优先满足用户关注度高的应用网络带宽需求,实现了网络资源在嵌入式终端上的合理分配。