MSTP体系结构研究

随着IP数据、话音和图像等多种业务传输需求的不断提高,现有以承载话音为主要业务的城域网在容量以及接口能力上都已经无法满足业务传输与汇聚的要求。以SDH为基础的多业务传输平台能够克服传统城域网的缺点,可以更有效地支持分组数据业务,并有助于实现从电路交换网向分组网的过度。介绍了MSTP的分类方法,给出了MSTP的分层结构,并对各功能模块的需求和特点进行了详细分析。     

On the approximation of the slot occupancy pattern in a DQDB network

This paper presents a novel approach to DQDB modeling in underload conditions; the innovative aspect lies in the representation of the slot-occupancy-pattern process on the forward bus. In the literature this process has been often modeled as a Bernoulli process, implying that the status (empty/busy) of consecutive slots are independent. Results presented in this paper, however, show that even at light loads the interdependence between slots is significant. Our model captures some of this interdependence by using a discrete-time first-order Markov process for the slot-occupancy-pattern process on the forward bus. In the paper we identify a simplified DQDB network for which we derive a closed formula for the joint probability density function for the slot occupancy pattern of two consecutive slots. The accuracy of our results is investigated via simulation. Finally, an application of our first-order Markov model is shown through an investigation of the performance of a gateway concentrating several DQDB networks in a slotted trunk.     

ATM技术在广州市电信局计算机专用网的应用

本文介绍了利用ＡＴＭ技术进行组网的原理和广州市电信局计算机专用网的建设情况，并从应用的角度分析了这种网方式的该局带来的效益。     

A journey through the DQDB network literature

The Distributed Queue Dual Bus (DQDB) network has been adopted as the subnetwork for the IEEE 802.6 metropolitan area network (MAN) standard. Since its original proposition a few years back, DQDB has attracted significant attention because of the simplicity of its medium access control (MAC) protocol. The intense scrutiny that DQDB has been subjected to has lead to the identification of a number of its potential problems, and a number of “add-on” strategies have been proposed to “fix” such problems. Moreover, a number of architectural variations have also been proposed to improve the network behavior. Since there has been a literature explosion on DQDB over the past few years, this article is intended to extract the significant features of various DQDB-based investigations, and to present them in an unified manner.     

光缆交接箱在城域网建设中的应用

针对目前城域网建设中存在的问题，介绍光缆交接箱的原理、功能以及在城域网建设中的应用。     

Physical Frame Time-Slot Technique Switching- A New Switching over DWDM

A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in defining the physical frame for PFTS and the transmission time for the maximum size of the MAC frame is defined as a physical frame time-slot （PFT）. Consequently, user data can be fed into PFTS and switched in a single layer sub-network in an asynchronous mode.     

Acid‐Responsive Transferrin Dissociation and GLUT Mediated Exocytosis for Increased Blood–Brain Barrier Transcytosis and Programmed Glioma Targeting Delivery

Receptor mediated transcytosis (RMT) is a common mechanism used for nanotherapeutics to traverse the blood–brain barrier (BBB). However, the transcytosis of ligand modified nanoparticles via RMT is likely to be trapped within brain capillary endothelial cells due to the high binding affinity of ligand with receptors, which greatly reduces the amount of nanoparticles across BBB. Here, P‐aminophenyl‐α‐D‐mannopyranoside (MAN) decorated doxorubicin‐loaded dendrigraft poly‐l‐lysine with acid‐cleavable transferrin (Tf) coating outside (DD‐MCT) is proposed. The DD‐MCT is engineered to specifically recognize the Tf receptor (TfR) on the luminal side of BBB endothelium. Then the DD‐MCT undergoes an acid‐responsive cleavage of Tf, leading to the separation of MAN‐decorated DGL‐DOX (DD‐M) from the Tf–TfR complex in endo/lysosomes. The detached DD‐M is more prone to escape from endo/lysosomes and can further be exocytosed into brain parenchyma via the mediation of glucose transporter located on the abluminal endothelial membrane. Moreover, the DD‐M in brain parenchyma can target glioma cells. Significantly, the DD‐MCT enters into brain parenchyma in greater amounts, resulting in enhanced accumulation at glioma site and thus improved antiglioma therapeutic outcome. This strategy pioneers a new path for reducing the trapping of nanotherapeutics within BBB endothelium but increasing their transcytosis into brain parenchyma.     

基于“IPv6+”的5G承载网切片技术与应用

5G承载网切片技术是满足5G业务,特别是垂直行业场景对差异化服务质量保证需求的基础。对如何在网络基础设施层、网络切片实例层以及网络切片管理层将“IPv6+”关键技术与承载网切片结合使用进行了研究。以北京联通为例,介绍了智能城域网向基于“IPv6+”的承载网切片演进的演进目标、应用场景、演进计划以及存在的问题与建议。     

城域网流量gamma分布的成因分析

通过分析西安宽带多媒体城域网主要流量源以及骨干链路流量的特征,提出了基于概率密度分布的城域网流量的总体描述,刻画了流量聚合过程的一般规律.采用统计学理论分析了城域网上典型流量聚合过程,揭示了城域网流量的概率密度分布之所以呈现为gamma分布的成因.作为城域网流量gamma分布特征的应用,对未来一段时期内城域网流量分布特征的演化进行了预测.     

10Gbit／s以太网技术探析及应用前景

在城域网中,由于以太网技术更加适应业务流量急剧分组化的趋势,可以为用户提供容量、便利性以及成本方面的优势,而且随着以太网传送技术在保护恢复、服务质量保证等能力上的增强,业界开始将以太网向城域网和广域网进行扩展,而10Gbit／s以太网正是以太网突破传统局域网向城域网和广域网延伸的关键技术。