湖南西风网络安全产品介绍

“东方网警”入侵检测系统 “东方网警“入侵检测系统具有良好的分布性能和扩展性。该系统将基于网络(NIDS)和基于主机(HIDS)的入侵检测方法有机地结合在一起,提供集成化的检测、报告和响应功能,另外,系统还能与防火墙互动,共同构建动态安全防护体系,确保用户的网络安全。     

An introduction to network programming the Python way [book review]

This article is a review of the book, 'Foundations of Python Network Programming' by John Goerzen, published by Apress, 2004. The book covers the standard Python distribution's client protocol implementations-such as HTTP, DNS (Domain Name System), SMTP (Simple Mail-Transfer Protocol), FTP, POP (Post Office Protocol), IMAP (Internet Message Access Protocol), and XML-RPQ and server frameworks (for "out of the box" HTTP and XML-RPC servers). The Database Clients chapter admirably introduces DB-API 2.0, the Python equivalent of Java database connectivity or open database connectivity. Other chapters explain Python interfaces to the Secure Sockets Layer, HTML/XML parsing, and the mod/spl I.bar/python Apache module, as well as more advanced network programming topics such as IPv6 support, multithreaded servers, and nonblocking 1/0. The book also incorporates third-party networking libraries such as Twisted and PyDNS. Each chapter's text thoroughly explains the code samples, which are far more comprehensive than in the standard documentation. The reviewer feels that the book complements other introductory texts.     

A hybrid approach to the transmission of telephony over a passive optical network

Passive optical networks (PONs) are attractive for the provision of telephony via optical fibre in the local loop, and have generally tended to concentrate on the use of time-division multiple access for transmission. This paper describes a hybrid transmission method using sub-carrier multiplexing (SCM) and time division multiplexing (TDM) which seeks to reduce the overall complexity of the system, thereby lowering costs.     

An introduction to chaos

Chaos, apparently disordered behaviour which is nonetheless deterministic, is a universal phenomenon which occurs in many systems in all areas of science. For it to take place, the equations describing the situation must be nonlinear and, therefore, they are rarely solvable in closed form. Since the advent of fast digital computers, the theory of nonlinear systems has become much more accessible to study and is now undergoing rapid development. The authors review some of the universal aspects of chaos and its ramifications in the field of electronics     

An introduction to CTBI

CTBI provides a simple mechanism that bonds multiple levels of multiple lanes (electrical and optical) in a single step through 66-bit block striping with low overhead and no need lo backpressure or flow control the MAC layer, and allows for a very simple optical module even if the number of optical lanes and electrical lanes are not equal (in / n).     

LTE网络性能智能优化平台

伴随着4G网络建设的快速发展,运营商在覆盖、干扰和容量方面均面临着更大的挑战.如何在这3个维度之间找好平衡点,最大限度提升网络性能,是中国移动各省公司在日常优化工作中面临的痛点和难点.基于这一现状,针对传统网优模式存在的问题和一线生产的重点难点,并以能输出解决方案提升网络性能为目标,我们自主研发了LTE网络性能智能优化平台.整个平台设计方案围绕LTE网络性能提升这一核心,横向涵盖了覆盖和干扰优化、以及容量和业务关联分析优化,纵向打通了网络优化全流程,实现了集中化、自动化网优的目标.本文从平台的整体架构和功能设计出发,依次介绍了各专项分析功能模块的设计和实现,最后介绍了平台在现网优化中的应用情况,以及下一步的重点研发计划.     

An analytical simulator for deploying IP telephony

Deploying IP telephony or voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queuing network analysis to compute two key performance bounds for VoIP: delay and bandwidth. The simulator is GUI‐based and has an interface with drag‐and‐drop features to easily construct any generic network topology. The simulator has an engine that automates and implements the analytical techniques. The engine determines the number of VoIP calls that can be sustained by the constructed network while satisfying VoIP QoS requirements and leaving adequate capacity for future growth. As a case study, the paper illustrates how the simulator can be utilized to assess the readiness to deploy VoIP for a typical network of a small enterprise. We have made the analytical simulator publicly available in order to improve and ease the process of VoIP deployment. Copyright © 2008 John Wiley & Sons, Ltd.     

An architecture for residential Internet telephony service

A new architecture that can be used for offering an Internet telephony service to residential customers is introduced. The architecture addresses scalability and availability requirements of mass-market deployment of carrier-grade services and supports interconnection with SS7 for Internet telephony calls to the public switched telephone network. The architecture is based on the concept of a gateway decomposition that separates the media transformation function of today's H.323 gateways from the gateway control function of the gateways and centralizes the intelligence in a call agent. The media gateway control protocol is introduced as the protocol between the call agent that assumes the gateway control function and the gateway that provides just the media transformation function. Interworking between the architecture and the public switched telephone network, the session initiation protocol, and H.323 are also discussed     

Supplementary services in the H.323 IP telephony network

Traditionally, different networks were developed to handle voice, data, and video. The circuit-switched telephone network carried voice and the packet network carried data. Due to different deployment of these networks, different services were developed, such as voice mail in the telephone network and electronic mail on the Internet. With the revolution of multimedia in the computer industry, voice, video, and data are now being carried on both networks. Supplementary services, such as transfer and forwarding (which were originally developed for private telephone networks and later migrated to public telephone networks) are now being developed for packet networks. The standards for packet networks are being defined in the H.323-based series of ITU-T recommendations. This article provides the H.323 architecture for supplementary services, the differences in deployment of these services between the circuit-switched and packet-switched networks, and interworking of these services across hybrid networks     

An introduction to factor graphs

Graphical models such as factor graphs allow a unified approach to a number of key topics in coding and signal processing such as the iterative decoding of turbo codes, LDPC codes and similar codes, joint decoding, equalization, parameter estimation, hidden-Markov models, Kalman filtering, and recursive least squares. Graphical models can represent complex real-world systems, and such representations help to derive practical detection/estimation algorithms in a wide area of applications. Most known signal processing techniques -including gradient methods, Kalman filtering, and particle methods -can be used as components of such algorithms. Other than most of the previous literature, we have used Forney-style factor graphs, which support hierarchical modeling and are compatible with standard block diagrams.     

An introduction to Cu electromigration

Electromigration is a major reliability concern in today’s integrated circuits due to the aggressive scaling of interconnect dimensions and the ever-increasing current densities at operation. In addition, the recent introduction of new materials and processing schemes lead to even more challenges in guaranteeing interconnect robustness against electromigration failure. In this article, we review basic electromigration physics in which the main differences between Al- and Cu-based interconnects relevant to electromigration are covered. We also discuss recent process-related advances in electromigration reliability such as the use of alloys and metal caps. Next, the impact of low-k inter-level dielectrics (ILD) on electromigration performance is addressed. Finally, the methodology of electromigration lifetime extrapolation, including reliability assessments of more complex interconnect geometries, is covered.     

An introduction to Web Services

This paper provides an introduction to Web Services. A brief history of Web Services is given, leading into an overview of the key Web Services technologies. The paper describes the way in which the IT industry has embraced Web Services and the uses to which the technologies are currently being applied. It concludes with a view of the role of both the key developers and standards bodies in the creation of Web Services and discusses the ways in which this process needs to be supported in order for Web Services to evolve. This revised version was published online in July 2006 with corrections to the Cover Date.     

An introduction to contemporary cryptology

An appraisal is given of the current status, both technical and nontechnical, of cryptologic research. The principal concepts of both secret-key and public-key cryptography are described. C.E. Shanon's theory of secrecy (1949) and G.J. Simon's theory authenticity (1984) are reviewed for the insight that they give into practical cryptographic systems. Public-key concepts are illustrated through consideration of the Diffie-Hellman public-key-distribution system and the Rivest-Shamir-Adleman public-key cryptosystem. The subtleties of cryptographic protocols are shown through consideration of some such specific protocols     

An introduction to policy management

Policy management is an all-encompassing term that describes how the QoS policies applied to a network would be managed. This paper illustrates the complexity of policy management, and goes on to explain how the end result of installing a new network policy only happens after a range of both business and network rules are followed. Business rules check that the requested policy is permitted under the customer’s agreed service package and other non-network variables such as the time of day, while network rules include access control functions that check the network has sufficient free capacity before admitting the new policy. Various examples illustrate the importance of co-ordinating policies across the network and that the most appropriate policy is installed in the first place. Poor policy management may result in a next generation network appearing to offer a worse quality of service than the completely best-effort network it is replacing.     

An introduction to voice search

Voice search is the technology underlying many spoken dialog systems (SDSs) that provide users with the information they request with a spoken query. The information normally exists in a large database, and the query has to be compared with a field in the database to obtain the relevant information. The contents of the field, such as business or product names, are often unstructured text. This article categorized spoken dialog technology into form filling, call routing, and voice search, and reviewed the voice search technology. The categorization was made from the technological perspective. It is important to note that a single SDS may apply the technology from multiple categories. Robustness is the central issue in voice search. The technology in acoustic modeling aims at improved robustness to environment noise, different channel conditions, and speaker variance; the pronunciation research addresses the problem of unseen word pronunciation and pronunciation variance; the language model research focuses on linguistic variance; the studies in search give rise to improved robustness to linguistic variance and ASR errors; the dialog management research enables graceful recovery from confusions and understanding errors; and the learning in the feedback loop speeds up system tuning for more robust performance. While tremendous achievements have been accomplished in the past decade on voice search, large challenges remain. Many voice search dialog systems have automation rates around or below 50% in field trials.