MPLS-based satellite constellation networks

Nongeostationary satellite constellations with intersatellite links are a challenge for networking due to their continuously changing topology. In order to make maximal use of the network's capacities, special attention has to be paid to routing and traffic engineering. Multiprotocol label switching (MPLS) as underlying protocol is an interesting candidate for this task since it offers many possibilities to exert influence on traffic flows and supports today's dominating Internet protocol traffic very well. This paper describes a general MPLS-based networking concept for satellite networks and discusses different scenarios considering the particularities and constraints of the dynamic topology. Functional elements of MPLS like ingress, egress, or core routers have to be mapped onto the physical entities of the network and prerequisites for traffic engineering are discussed. Routing and rerouting of paths is of key interest since this affects route computation effort and routing performance. Thus, an analytical estimation of routing effort is deduced and numerical and simulation results are presented.     

Multicast traffic aggregation in MPLS-based VPN networks

This article gives an overview of the current practical approaches under study for a scalable implementation of multicast in layer 2 and 3 VPNs over an IP-MPLS multiservice network. These proposals are based on a well-known technique: the aggregation of traffic into shared trees to manage the forwarding state vs. bandwidth saving trade-off. This sort of traffic engineering mechanism requires methods to estimate the resources needed to set up a multicast shared tree for a set of VPNs. The methodology proposed in this article consists of studying the effect of aggregation obtained by random shared tree allocation on a reference model of a representative network scenario.     

Performance analysis of data packet discarding in ATM networks

Data performance in ATM networks should be measured on the packet level instead of the cell level, since one or more cell losses within each packet is equivalent to the loss of the packet itself. Two packet-level control schemes, packet tail discarding and early packet discarding, were proposed to improve data performance. In this paper, a new stochastic modeling technique is developed for performance evaluation of two existing packet-discarding schemes at a single bottleneck node. We assume that the data arrival process is independent of the nodal congestion, which may represent the unspecified bit-rate traffic class in ATM networks, where no end-to-end feedback control mechanism is implemented. Through numerical study, we explore the effects of buffer capacity, control threshold, packet size, source access rate, underlying high-priority real-time traffic, and loading factor on data performance, and discuss their design tradeoffs. Our study shows that a network system can he entirely shut down in an overload period if no packet-discarding control scheme is implemented, under the assumption that there are no higher layer congestion avoidance schemes. Further, unless with sufficiently large buffer capacity, early packet discarding (EPD) always outperforms packet tail discarding (PTD) significantly under most renditions. Especially under the overload condition, EPD can always achieve about 100% goodput and 0% badput, whereas the PTD performance deteriorates rapidly. Among all the factors, the packet size has a dominant impact on EPD performance. The optimal selection of the EPD queue control threshold to achieve the maximum goodput is found to be relatively insensitive to traffic statistics     

一种基于MPLS的无线接入网微移动方案

将MPLS技术应用到基于IP的无线接入网络是近年越来越受到关注的新课题.本文提出了一种基于MPLS的微移动方案,方案采用在基站进行缓冲的方法降低切换时的分组丢失.最后对方案的性能从算法所产生的网络开销、切换时延与分组丢失几个方面进行了分析和讨论,结果表明本方案适用于高速微蜂窝及微微蜂窝的移动通信环境,并能满足一般的数据及实时业务的需求.     

The available bit rate service for data in ATM networks

The authors describe the purpose of the available bit rate (ABR) service in the context of other ATM services and review the agreements on the traffic control mechanism. They describe the recent progress towards standardization of the new service. The general nature of the ABR service is described in comparison with constant bit rate (CBR) and variable bit rate (VBR) services     

An adaptive FEC scheme for data traffic in wireless ATM networks

A new adaptive forward-error-correction scheme (AFEC) is introduced at the link layer for TCP/IP data traffic in wireless ATM networks. The fading and interference in wireless links cause high and variable error rates, as well as bursty errors. The purpose of the AFEC scheme is to provide a dynamic error-control mechanism by using Reed-Solomon coding to protect the ATM cell payload, as well as the payload type indicator/cell loss priority fields in the ATM cell header. In order to enhance the error tolerance in cell framing and correct delivery, the AFEC scheme functions within a new concept called LANET framing and addressing protection mechanisms. The AFEC scheme has been validated using a simulation testbed of a low-speed wireless ATM network     

多网融合中WLAN发现机制的能耗分析

研究3GPP(third generation partnership project)蜂窝网络与WLAN(wireless local area network)融合的无线异构网络中WLAN发现机制的能耗问题,提出一种终端能耗分析模型,分析了基于寻呼的WLAN发现机制以及其他4种WLAN发现机制的能耗.理论分析和仿真结果表明:基于寻呼的WLAN发现机制能耗最小,终端始终处于扫描状态的机制能耗最大.结果还表明:终端仅在与WLAN重叠的蜂窝小区内进行周期扫描的机制,与终端在所有的区域中进行周期扫描的机制比较,二者能耗相当.     

Traffic profiles in ATM networks

A lot of studies have been made to characterize and model sources of ATM traffic (voice, data, video) and to evaluate the performance of a multiplexer whose input is a superposition of these sources, using different methods and techniques (fluid flow, matrix-analytic, etc.). However, in order to better understand the end-to-end performance of ATM connections, characterizations and models of ATM traffic inside the network (i.e. after passage through one or more network elements) are needed. In this paper we intend to study the following problems: (i) Traffic profile of an ATM connection after being policed, in particular worst case traffic, and evaluation of the performance of the related statistical multiplexer. (ii) Traffic profile of the output of a multiplexer (characterized by means of the interdeparture time distribution and the index of dispersion for counts and the index of dispersion for interarrival times). (iii) Traffic profile of a single connection after passing a multiplexer. The aim is to obtain useful characterizations and models of ATM traffic in order to evaluate the performance and the efficiency of ATM network elements and of traffic control functions.This work was supported in part by the Commission of the European Communities, under project RACE R2024 (Research and Development on Advanced Communications in Europe) on Broadband Access Facilities.     

Cell multiplexing in ATM networks

Formulates, analyzes, and compares several connection multiplexing algorithms for a multiplexer residing in the equivalent terminal of the asynchronous transfer mode (ATM) layer at the user premise. The primary goal is to find an algorithm that efficiently combats the cell delay variation (CDV) introduced by the multiplexer. Several performance criteria are examined, one of which is unique to ATM networks. This one is the proportion of arriving cells that do not conform to the traffic contract of the connection. The conformance is being tracked by a generic cell rate algorithm (GCRA) recommended (but not mandatory) by CCITT. Other criteria are the classical buffer requirements and the cell delay. Service fairness among connections is also evaluated with respect to each performance criterion. The impact of the following five multiplexing policies on the performance criteria are evaluated for constant bit rate (CBR) traffic sources. The policies are first in, first out (FIFO), round robin (RR), least time to reach bound (LTRB), most behind expected arrival (MBEA), and golden ratio (GR). Extensive numerical examples reveal that there is no single policy that is best across all criteria. With respect to cell conformance, most behind expected arrival (MBEA) emerges as the preferred one. FIFO is best with respect to cell delay, except for high utilizations where RR dominates. The LTRB is marginally better than all other policies with respect to buffer requirements     

Neuro-fuzzy control in ATM networks

The aynchronous transfer mode (ATM) has been deemed the transfer technique of choice in an integrated environment supporting multimedia services. The authors present an extensive review of fuzzy-logic-based and artificial-neural-network-based traffic control mechanisms that have been proposed in the field of asynchronous transfer mode networking. Following a qualitative review of the models used, system architectures suggested and results obtained, future trends and directions are briefly discussed     

在基于MPLS的层次化移动IP网络中支持DiffServ的研究

MPLS支持DiffServ、流量工程,能为网络提供较好的QoS保证,而移动IP(MIP)能为移动设备提供较好的移动性支持。文章探讨了在无线接入网中MPLS和MIP结合实现DiffServ的方案,并给出了一种在基于MPLS的层次化MIP网络结构中支持DiffServ的体系结构,设计了其节点功能模型和关键协议。方案中利用了层次化结构的区域注册和重路由机制,减少了切换时延和网络的信令负荷。     

Data communication in ATM networks

An increasing number of customers require LAN access with high bandwidth and low delay over long distances. To satisfy these needs, several high-speed network techniques have been developed. Asynchronous transfer mode (ATM) is superior compared to other networking technologies, as it offers high bandwidth and is scalable in the sense that the bandwidth capacity of an ATM system is not fundamentally limited to the technology itself. Initial ATM installations will operate as subnetworks of existing networks and MAC layer protocols. One of the main challenges in ATM is the transparent support of existing connectionless LAN services. Several activities have been launched within international standard bodies and forums to specify ways of providing data communication services over ATM. Most notable examples are Switched Multimegabit Data Service (SMDS) and the similar Connectionless Broadband Data Service (CBDS) supported mostly by public network service providers. But also other approaches such as IP over ATM, and LAN emulation that show more adherence to the existing local and campus area networking paradigms. The article presents the requirements and architecture of the LAN emulation service. It describes the alternative methods for carrying IP packets over ATM, a public broadband service architecture and CBDS. The traffic management aspects of the data communication services are also discussed     

Cooperative localization for next-generation converged networks with closed-form solution

In this article, a novel cooperative wireless localization scheme based on information fusion is proposed. The scheme combines large-scale arrival time and small-scale distance measurements obtained from the next-generation converged networks. The maximum likelihood (ML) estimate of the terminai's position is derived with closed-form solution, and the Cramtr-Rao lower bound (CRLB) of the estimate error is investigated. Both theoretical analysis and simulation results verify that the proposed localization scheme can significantly enhance the location precision. Moreover, the mean square error of position estimate approximates the CRLB when the number of reference stations increases, which indicates that the proposed ML estimator is asymptotically efficient.     

A QoE handover architecture for converged heterogeneous wireless networks

The convergence of real-time multimedia applications, the increasing coverage of heterogeneous wireless networks and the ever-growing popularity of mobile devices are leading to an era of mobile human-centric multimedia services. In this scenario, heterogeneous communications will co-exist and ensure that the end-user is always best connected. The rigorous networking demands of wireless multimedia systems, beyond quality-oriented control strategies, are necessary to guarantee the best user experience over time. Therefore, the Quality of Experience (QoE) support, especially for 2D or 3D videos in multi-operator environments, remains a significant challenge and is crucial for the success of multimedia systems. This paper proposes a QoE Handover Architecture for Converged Heterogeneous Wireless Networks, called QoEHand. QoEHand extends the Media Independent Handover (MIH)/IEEE 802.21 with QoE-awareness, seamless mobility and video adaptation by integrating a set of QoE-based decision-making modules into MIH, namely a video quality estimator, a dynamic class of service mapping and content adaptation schemes. The QoEHand video estimator, mapping and adaptation components operate by coordinating information about video characteristics, available wireless resources in IEEE 802.11e and IEEE 802.16e service classes, and QoE-aware human experience. The video quality estimator works without the need for any decoding, which saves time and minimises processing overheads. Simulations were carried out to show the benefits of QoEHand and its impact on user perception by using objective and subjective QoE metrics.     

在基于MPLS的ATM交换机上的RIO分组丢弃算法性能研究

如何利用基于多协议的标签交换（ＭＰＬＳ）机制来支持有差别的业务类型,是目前研究的热点。本文研究了在基于多协议标签交换机制的ＡＴＭ交换机上支持有差别业务类型的一种实现算法。经研究表明：ＲＩＯ算法通过有效的活动缓存管理机制,在采用最简单的ＦＩＦＯ排队策略的情况下,能够较好地支持有差别的业务类型。     

ATM local area networks

LAN emulation offers a best-effort, connectionless, packet transfer service at the MAC sublayer, implemented on top of a connection-oriented ATM network LAN emulation using switched virtual connections requires address resolution to locate the destination end station followed by connection establishment to the resulting ATM address. Address resolution may be implemented by a broadcast technique or by an address server. The broadcast method is the simplest for small networks but a combination of both is probably better. The use of the MAC address to identify an end station, with dynamic binding to its current physical location in the ATM network, allows the ATM LAN segment to be viewed as a virtual LAN. The virtual LAN model permits end stations to move and change physical location while maintaining connection to the same ATM LAN segment. This greatly simplifies the management of large data networks     

Reconfiguration of spare capacity for MPLS-based recovery in the Internet backbone networks

This paper introduces a novel approach, called Short Leap Shared Protection with spare capacity Reallocation (SLSP-R), to deal with dynamic reconfiguration of spare capacity for MPLS-based recovery in the Internet backbone networks. SLSP-R is based on the SLSP framework and is designed to quantify the impact of computation complexity on network performance. The basic idea for SLSP-R is to subdivide a lengthy optimization process into several subtasks in order to trade the optimization quality with computation time. For this purpose, we compare three strategies for grouping working paths before an integer programming (InP) formulation is solved, namely, the Most Overlapped, Most Diverse, and Randomly Distributed. Analytical modeling of the problem is provided to show the feasibility of the subgrouping strategy. A numerical experiment as well as simulation-based study are conducted on four networks with different topology to evaluate the SLSP-R algorithm. The design methodology to determine the size of each subset of working paths is verified in the simulation.     

Framework for MPLS-based control of optical SDH/SONET networks

The suite of protocols that defines multiprotocol label switching is in the process of enhancement to generalize its applicability to the control of optical networks. One area of prime consideration is to use these generalized MPLS protocols in upgrading the control plane of optical transport networks. This article describes those extensions to MPLS directed toward controlling SDH/SONET networks. SDH/SONET networks are ideal candidates for this process since they possess a rich multiplex structure, and a variety of protection/restoration options are well defined and widely deployed. We discuss the extensions to MPLS routing protocols to disseminate information needed for transport path computation and network operations and the extensions to MPLS label distribution protocols needed for provisioning of transport circuits     

QoS issues in the converged 3G wireless and wired networks

The Internet evolution delineated through the last years has urged the wireless network community to support the deployment of IP multimedia services with guaranteed quality of service (QoS) in 3G wireless networks. This article copes with the interoperability between 3G wireless networks and wired next-generation IP networks, for the provision of services with an a priori known quality level over both environments. More specifically, the UMTS architecture as well as a prototypical implementation of the next-generation Internet based on DiffServ are considered. The article focuses on the mapping among the traffic classes of the two networks at the point where the networks converge, and discusses the requirements and possible solutions for their proper interworking at the signaling and user levels. Simulations prove that proper mapping among the traffic classes of each world is necessary in order to achieve the desired end-to-end traffic characteristics.