OVS的编程扩展技术

OVS (open vSwitch)作为一款开源的SDN软件交换机,得到了广泛关注.但在复杂多变的网络环境下,易出现数据层失去控制器控制和流表项学习老化等故障问题,严重制约了SDN性能.针对以上问题,研究设计了OVS的编程扩展技术架构,包含链接状态处理、故障感知、二三层自学习转发等核心功能的扩展,使OVS实现自动快速恢复、流表表项及时更新,保障了SDN吞吐量,从而减小了控制器失联对通信的影响,增强了SDN的稳定性和可靠性.     

一种支持网络功能演进的可重构数据平面

传统网络体系在安全、服务质量保证、流量调度等方面难以适应互联网的发展,而新型网络体系如SDN （Software Defined Networking）、NDN（Named Data Networking）等,由于路由器、交换机等传统网络设备电路固化,限制了新型网络功能的试验和部署。针对此问题,本文设计了支持网络功能演进的可重构数据平面（Reconfigurable Dataplane for network Function Evolution,RDFE）,通过插入用户配置单元的方式对数据包解析、匹配和处理过程进行编程,从而支持用户自定义的功能部署;其次,针对RDFE提出基于树型结构的解析映射和匹配映射算法,将用户定制功能映射到硬件结构中;最后,基于NetFPGA-10G板卡完成了RDFE的原型实现,与现有的Kangroo、EPC（Elastic Protocol Cus-tomizable）、LabelCast等方案相比具有更高的转发速率和更低的资源利用率。     

应用于协议无感知转发交换机的流缓存方法

协议无感知转发支持任意协议的解析和处理,增强了软件定义网络的可编程能力。为提高转发性能,该文提出一种应用于协议无感知转发交换机的流缓存方法,通过识别匹配和动作的依赖关系,得到匹配字段的绝对位置,用以预先解析报文。为确保流缓存的加速效果,根据匹配类型与表项数量选择应用流缓存的流表。此外,该文对比了单流表缓存与多流表缓存对转发性能的提升,并提出了根据网络流量实际情况的自适应切换策略。通过扩展POFSwitch实现所提方法,并用实际规则与骨干网流量进行验证,应用流缓存后,交换机报文转发速率提升了220%。流缓存可以为可编程数据平面提供更高的转发性能。     

SDN组网关键技术及标准化研究

本文首先介绍了软件定义网络(SDN)逻辑层次、网络结构和组网特性.对SDN网络建模、路由算法、可编程转发平面技术、控制器技术、扩展技术等关键技术进行简要介绍,调研并分析SDN发展趋势和标准化进程,以及SDN技术在各领域的应用场景,最后对SDN可扩展技术等关键技术的发展趋势进行了展望分析,提出SDN面对日益复杂的网络环境亟需解决的问题.     

Xilinx推出“软”定义网络(SDNet)解决方案

正近日,灵思公司推出"软"定义网络解决方案,将可编程能力和智能化功能从控制层扩展至数据层。全新SDNet软件定义规范环境可实现可编程数据层功能设计,而且功能规范可自动编译到赛灵思的All Programmable FPGA和SoC中。与采用固定数据层硬件,并通过狭窄南向API连接到控制层的传统SDN架构不同,SDNet采用可编程的数据     

赛灵思为SDN实现可编程数据层功能

赛灵思公司近日宣布推出“软”定义网络（“Softly”Defined Networks）解决方案，将SDN网络的可编程能力和智能化功能从控制层扩展至数据层。     

基于SMIoT的软件定义移动自组织物联网组网机制研究

文章充分结合SDN集中管控、MANET分布灵活和IoT智能感知的优势,采用SDN+MANET+IoT的思路实现异构网络融合组网,满足智能巡检的需求。利用可编程性高的树莓派智能小车作为IoT硬件平台,并在此基础上搭建分布式MANET网络,实现智能小车集群的自组织组网。同时,为实现智能巡检和相互协作,将OVS交换机移植到树莓派平台,利用扩展的OpenFlow协议,对分布式智能小车集群实施基于SDN技术的集中管控,统一管理集群的物理感知能力、移动监控能力和数据转发能力,进而搭建SMIoT。     

基于OVS的SDN移动自组网络架构设计及实现

在SDN移动自组网络中,控制转发策略集中于控制器中,使得基于流表匹配的数据转发变得简单高效。但是,由于移动自组网环境复杂多变、无线信号不稳定和网络拓扑多变等原因,容易出现数据层面失去控制器控制和流表学习老化等问题,这严重制约网络性能。针对以上问题,设计了一种基于Open v Switch的SDN移动自组网络架构,架构包含状态处理与应用感知等核心功能。状态处理服务实现控制器与交换机连接状态的跟踪检测、Open Flow协议的状态匹配字段拓展和数据包在不同状态场景下进行感知处理等功能,应用感知服务实现转发策略在数据层面被灵活调度的功能。在Open v Switch和Ryu开源控制器上进行协议开发和原型系统搭建。实验结果表明,控制器连发生接故障后,业务恢复时延低于100 ms,流表项可以及时更新,这可以保障网络吞吐量的稳定性。因此,设计的架构有效减小控制器失连故障对通信的影响,增强了基于SDN的移动自组网络的稳定性和可靠性。     

软件定义网络中基于密码标识的报文转发验证机制

针对软件定义网络(SDN)中缺乏安全高效的数据来源验证机制问题,该文提出基于密码标识的报文转发验证机制。首先,建立基于密码标识的报文转发验证模型,将密码标识作为IP报文进出网络的通行证。其次,设计SDN批量匿名认证协议,将SDN控制器的验证功能下放给SDN交换机,由SDN交换机进行用户身份验证和密码标识验证,快速过滤伪造、篡改等非法报文,提高SDN控制器统一认证与管理效率,同时可为用户提供条件隐私保护。提出基于密码标识的任意节点报文抽样验证方案,任何攻击者无法通过推断采样来绕过报文检测,确保报文的真实性的同时降低其处理延迟。最后,进行安全性分析和性能评估。结果表明该机制能快速检测报文伪造和篡改及抵抗ID分析攻击,但同时引入了大约9.6%的转发延迟和低于10%的通信开销。     

SDN中基于全局拓扑感知的自适应流量均衡算法

针对软件定义网络(Software-Defined Networking,SDN)中控制平面和数据平面之间的控制链路性能受限导致的Packet_In传输瓶颈问题,提出了一种自适应的流量均衡算法,利用SDN网络控制平面拥有全局拓扑和交换机实时状态的特点,运用阈值对流量均衡起止条件进行控制,通过将超载交换机中流量重定向到邻居交换机的一跳转发的自适应方法,解决上行控制链路瓶颈问题.与现有方法相比,减小了33％的上行控制链路负载与50％的Packet-In消息丢包率,且部署开销小.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Call for Papers

正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its