Libpcap数据包捕获机制剖析与研究

数据包截获与分析是网路管理中的基本技术,本文深入研究了国外优秀的数据包捕获函数库Libpcap。介绍了用于用户层数据包截获的系统独立的api接口Libpcap库,给出了利用BPF和Libpcap设计基于包捕获的应用程序的应用框架。     

BPF数据包过滤器的分析与研究

随着网络的迅速发展,信息量的增大,大量的无效数据降低了网络监控的效率,对网络数据包的捕获和过滤变得尤为必要了.BPF数据包过滤器以其简洁的结构在计算机内核中对数据报进行第1层过滤,减轻了用户层工作的负担并且提高了抓包率.研究了BPF的工作原理和过滤模型并且提出了在Windows系统下如何运用BPF过滤器开发包过滤系统.BPF数据包过滤器在网络监控方面有巨大的研究和使用价值.     

BPF的实现机制分析与性能优化研究

BSD包过滤器(BSD Packet Filter,BPF)是BSD Unix操作系统提供的网络数据包捕获及过滤机制的内核组件。该文描述了BPF的组成及工作过程,分析了BPF采用的无环控制流图过滤模式,介绍了此模式基于虚拟机的实现。为了提高过滤器性能,必须解决BPF虚拟机指令生成器处理多个过滤条件组合时存在的指令冗余问题,通过引入静态单赋值(SSA),结合冗余谓词消除和窥孔优化等技术,可以有效缩短CFG图的平均路径长度,从而实现对过滤器性能的优化。     

基于多采集器网络流量测量系统的设计与实现

网络流量1测量系统提供了一种测量和理解网络流量特性的工具。该文首先介绍了网络流量测量系统框架和当前流行的抓包构件BPF的原理,深入分析了造成基于BPF构件的被动网络测量系统可能的丢包因素,并给出了相应的解决办法;设计和实现了一种基于多采集器的网络流量测量系统;测试表明,与基于单采集器的被动网络流量测量系统相比,该系统明显减少了采集器端的丢包率,提高了系统测量的准确性。     

基于BPF模型的包捕获与过滤机制的研究及应用

通过对网络监听原理、BPF工作过程以及BPF过滤模式的分析,阐述运用BPF在实时操作系统vxWorks环境下实现网络监听与包过滤技术的具体方法,同时对其过滤性能给出了评测.     

网络嗅探器Sniffer软件源代码浅析3:采用Libpcap库的通用设计

在BSD数据包过滤器（BPF）的基础上,对Libpcap库函数接口作了简单的介绍,并给出了采用ibpcap库的通用Sniffer设计实例,通过这一系列的文章介绍,希望能够阐明网络Sniffer软件的整体设计思路,对应用程序设计人员有所帮助。     

在FOXBASE＋程序中实现DOS SHELL功能

介绍了在FOXBASE~+应用程序中实现DOS SHELL功能的具体方法。该方法为应用程序提供了一个DOS操作接口。     

包捕获技术:原理、防范和检测

包捕获是进行网络监测、负载分析等网管活动中所使用的基本技术 ,同时Internet上基于包捕获技术的嗅包程序的泛滥给网络安全带来了极大的危害。本文讨论了当前常用的包捕获机制 ,重点讨论了BPF机制 ,并提出了一些针对Internet上嗅包程序的防范和检测技术。     

要闻 信息 商情

一个完整的DirectX应用程序接口应由以下部分组成: DirectDraw:该应用程序接口负责显示内存的管理。 DirectSound:对声音设备进行统一支持,同时在游戏应用中还增加了特殊的3D效果。 DirectPlay:它可以提供有效方法使游戏满足个人微机的     

一种并行内存缓冲系统及其实现技术

为支持数据挖掘应用,对NOW机群系统的分布式共享存储管理机制进行了适当的简化1～2,结合数据挖掘中数据处理的特点,设计了一个并行内存缓冲系统。该缓冲系统为应用程序提供上下两层应用接口,既可以保证内存操作的透明性,又为应用程序自主操作数据提供了极大的灵活性。缓冲系统可以充分利用网络结点的存储空间为应用程序实现网络虚拟存储环境,同时也可以很好地支持应用程序对数据文件的并行化处理。     

基于BPF和LIBPCAP库的包捕获应用系统的设计

包捕获和包分析是网络管理中使用的基本技术,它可用于网络测试,重构端到端的会话及监测网络运行状况等。本文分析了多种包捕获机制,着重探讨了ＢＰＦ技术,介绍了一个用于用户层包捕获的系统独立的ＡＰＩ接口Ｌｉｂｐｃａｐ库,给出了利用ＢＰＦ和Ｌｉｂｐｃａｐ设计基于包捕获的应用程序的应用框架。     

基于BPF包过滤机制的数据采集系统的设计与实现

为了捕获校园网中访问各个数据库检索系统的数据包，利用BPF包过滤机制、以太网的广播传输特性等技术设计和实现数据采集系统。同时为了提高了系统的效率，还引人多线程技术，使得数据采集系统在同一时刻既能采集数据包又能实时处理数据包并写入后台数据库中。     

LTCC‐based monolithic system‐in‐package (SiP) module for millimeter‐wave applications

A miniature LTCC system‐in‐package (SiP) module has been presented for millimeter‐wave applications. A typical heterodyne 61 GHz transmitter (Tx) has been designed and fabricated in a type of the SiP module as small as 36 × 12 × 0.9 mm³. Five active chips including a mixer, driver amplifier, power amplifier, and two frequency multipliers were mounted on the single LTCC package substrate, in which all passive circuits such as a stripline (SL) BPF, 2 × 2 array patch antenna, surface‐mount technology (SMT) pads, and intermediate frequency (IF) feeding lines have been monolithically embedded by using vertical and planar transitions. The embedded SL BPF shows the center frequency of 60.8 GHz, BW of 4.1%, and insertion loss of 3.74 dB. The gain and 3‐dB beam width of the fabricated 2 × 2 array patch antenna are 7 dBi and 36 degrees, respectively. The assembled LTCC 61 GHz Tx SiP module achieves an output power of 10.2 dBm and an up‐conversion gain of 7.3 dB. Because of the integrated BPF, an isolation level between a local oscillation (LO) and RF signal is below 26.4 dBc and the spurious level is suppressed by lower than 22.4 dBc. By using a 61 GHz receiver (Rx) consisting of off‐the‐shelf modules, wireless communication test was demonstrated by comparing measured IF spectrums at the Tx and Rx part.     

Compact tunable tri-band bandpass filter using varactor diodes for wireless fidelity,wireless local area network,and worldwide interoperability for microwaves access applications

The purpose of this paper is to present a tri-band bandpass filter (BPF) with compact structure. This filter consists of 50 Ω transmission line, varactor diode, positive-intrinsic-negative (PIN) diode, symmetrical square-shaped half-loop resonator pair, and three pairs of rectangular half circle that a T-stub is placed in it. By using the add PIN and varactor diodes in the proposed structure, it is possible to connect and disconnect each band, and change the central frequency up to 400 MHz. In addition, there is a situation to disconnect and connect all three bands simultaneously and asynchronously (unconditionally). This filter contains a low ripple value in all three bands. In this regard, the maximum ripple value does not exceed 0.3 dB and rejection is greater than 25 dB in total stop-band. An experimental tri-band BPF has been developed for wireless fidelity, wireless local area network, and worldwide interoperability for microwaves access applications. The measured results are properly accommodated with simulated results.     

A balanced dual‐band bandpass filter with independently tunable differential‐mode frequencies

A balanced dual‐band bandpass filter (BPF) with independently tunable differential‐mode (DM) frequencies is proposed in this letter. The proposed BPF is composed of complementary split‐ring resonators (CSRRs) etched on the ground and varactors loaded on the resonators. A balanced stepped‐impedance microstrip‐slotline transition structure is introduced to transfer the DM signals successfully and block the common‐mode (CM) signals transmission. Good DM transmission and CM suppression can be achieved. Moreover, by changing the reverse bias voltages of the varactors loaded on coupling CSRRs, two DM resonant frequencies of the proposed balanced BPF can be tuned independently. To verify the feasibility of the design method, a balanced BPF with DM frequency ranging from 0.80 GHz to 1.12 GHz and 1.55 GHz to 2.05 GHz is fabricated and measured. Good agreement between the simulation and measurement results demonstrate the validity of the design.     

Compact differential dual‐band bandpass filter using single quad‐mode metal‐loaded dielectric resonator

This letter presents a novel miniaturized differential dual‐band bandpass filter (BPF) using a single quad‐mode metal‐loaded dielectric resonator (DR). The differential dual‐band BPF is designed in a single‐cavity configuration with one quad‐mode DR and four feeding probes, featuring compact size. The rectangular DR is directly mounted on the bottom of the metal cavity and covered by a metal plate on the top surface. It allows two pairs of orthogonal modes (LSE₁₀ and LSM₁₀), which can be differentially excited and coupled by introducing proper perturbation for constructing dual‐band differential‐mode frequency response. To validate the proposed idea, a compact differential BPF with good performance using a quad‐mode DR cavity is designed, fabricated, and measured. The simulated and measured results with good agreement are presented.