Expedited Forwarding Research Articles

Priority-based mode transformation algorithm in a multisystem-based virtual passive optical network

With the development of passive optical network, different standards will occur in the same network topology. Virtualization technology is a preferable solution for multi-standard coexistence. In this paper, priority-based mode transformation algorithm is proposed for cross-standard bandwidth management in multisystem-based virtual passive optical network (VPON) in metro-access optical network (MAON). It is aimed to improve the fairness between priority services as well as the utilization of network resources. According to service lever agreement (SLA), priority services are divided into three categories: Expedited Forwarding (EF), Assured Forwarding (AF) and Best Effort (BE). For the first time, a model transformation scenario that requires consideration of priority is analyzed. Under the model transformation scenario, multi-dimension 0/1 knapsack models of the priority-based mode transformation algorithm are established. By solving the model, an optimal combination of ONUs for mode transformation can be found. Finally, the simulation shows that the priority-based mode transformation algorithm and the single ONU mode transformation algorithm differ in the amount of each service’s transformation bandwidth. It further demonstrates the contribution of the proposed algorithm in fairness.

Genetic expression programming-based DBA for enhancing peer-assisted music-on-demand service in EPON

Today, the popularity of peer-assisted music-on-demand (MoD) has increased significantly worldwide. This service allows users to access large music library tracks, listen to music, and share their playlist with other users. Unlike the conventional voice traffic, such an application maintains music quality that ranges from 160kbps to 320kbps, which most likely consumes more bandwidth than other traffics. In the access network, Ethernet passive optical network (EPON) is one of the best candidates for delivering such a service because of being cost-effective and with high bandwidth. To maintain music quality, a stutter needs to be prevented because of either network effects or when the due user was not receiving enough resources to play in a timely manner. Therefore, in this paper, we propose two genetic expression programming (GEP)-based dynamic bandwidth allocations (DBAs). The first DBA is a generic DBA that aims to find an optimum formula for voice, video, and data services. The second DBA aims to find optimum formulas so that Optical Line Terminal (OLT) can satisfy not only the voice and Peer-to-Peer (P2P) MoD traffics but also reduce the stutter. Optical Network Unit (ONU) traits such as REPORT and GATE messages, cycle time, and mean packet delay are set to be predictor variables. Simulation results show that our proposed DBAs can satisfy the voice and P2P MoD services packet delay and monitor other overall system performances such as expedited forwarding (EF) jitter, packet loss, bandwidth waste, and system throughputs.

Performance Analysis of IPv6 QoS for Multimedia Applications Using Real Testbed

IPv6 is intended to provide better network QoS than IPv4, however, service providers still lacking confidence to claim this. The reason lies in less IPv6 QoS mechanisms, evaluation for several challenging scenarios, i.e. live streaming and video conferencing, etc. In this paper, to overcome this issue, we focus on evaluation of IPv6 QoS mechanism i.e. Traffic Class (TC) on real testbed. For Traffic Class (TC) evaluation, several scenarios are implemented with different DSCP values i.e Default PHB (Per hop behavior), Assured Forwarding (AF), Class Selector and Expedited Forwarding (EF). For evaluation, several test cases are devised with a combination of multiple DSCP values of the above four categories.

Genetic expression programming: a new approach for QoS traffic prediction in EPONs

The Ethernet passive optical network is being regarded as the most promising for next-generation optical access solutions in the access networks. In time division multiplexing, passive optical network technology (TDM-PON) and the dynamic bandwidth allocation (DBA) play a crucial key role to achieve efficient bandwidth allocation and fairness among subscribers. Therefore, the traffic prediction in DBA during the waiting time must be put into the account. In this paper, we propose a new prediction approach with an evolutionary algorithm genetic expression programming (GEP) prediction incorporated with Limited IPACT referred as GLI-DBA to tackle the queue variation during waiting times as well as to reduce the high-priority packet delay. Simulation results show that the GEP prediction in DBA can reduce the expedited forwarding (EF) packet delay, shorten the EF queue length, enhance the quality of services and maintain the fairness among the optical network units (ONUs). We conducted and evaluated the detail simulation in two different scenarios with distinctive traffic proportion. Simulation results show that the GLI-DBA has EF packet delay improvement up to 30 % over dynamic bandwidth allocation for multiple of services (DBAM). It also shows that our proposed prediction scheme performs better than the DBAM when the number of ONUs increases.

Effect Of Packet Delay Variation On Video/Voice Over Diffserv-Mpls In Ipv4/Ipv6 Networks

Over the last years, we have witnessed a rapid deployment of real-time applications on the Internet as well as many research works about Quality of Service (QoS), in particular IPv4 (Internet Protocol version 4). The inevitable exhaustion of the remaining IPv4 address pool has become progressively evident. As the evolution of Internet Protocol (IP) continues, the deployment of IPv6 QoS is underway. Today, there is limited experience in the deployment of QoS for IPv6 traffic in MPLS backbone networks in conjunction with DiffServ (Differentiated Services) support. DiffServ itself does not have the ability to control the traffic which has been taken for end-to-end path while a number of links of the path are congested. In contrast, MPLS Traffic Engineering (TE) is accomplished to control the traffic and can set up end-to-end routing path before data has been forwarded. From the evolution of IPv4 QoS solutions, we know that the integration of DiffServ and MPLS TE satisfies the guaranteed QoS requirement for realtime applications. This paper presents a QoS performance study of real-time applications such as voice and video conferencing in terms of Packet Delay Variation (PDV) over DiffServ with or without MPLS TE in IPv4/IPv6 networks using Optimized Network Engineering Tool (OPNET). We also study the interaction of Expedited Forwarding (EF), Assured Forwarding (AF) traffic aggregation, link congestion, as well as the effect of performance metric such as PDV. The effectiveness of DiffServ and MPLS TE integration in IPv4/IPv6 network is illustrated and analyzed. This paper shows that IPv6 experiences more PDV than their IPv4 counterparts.

Load-balanced differentiated services support switch

How to provide quality of service (QoS) guarantees in the routing and switching devices has become one of the key research topics in the areas of routing and switching technologies. Differentiated services architecture (DiffServ), which forwards packets based on their per-hop behaviours, is known as a promising way for supporting QoS in a high-speed backbone network scenario. Motivated by the load-balanced Birkhoff-von Neumann switch, which has received much attention recently because of its outstanding extensibility performance, in this study, the authors propose a new switch architecture called load-balanced DiffServ support switch (LBDS). LBDS consists of pipeline traffic bandwidth control, priority-based load balancing, and bandwidth-based priority scheduling to implement fast forwarding for expedited forwarding (EF) traffic and assured forwarding for AF classes of traffic. The authors evaluate LBDS by extensive theoretical analysis and comprehensive simulations. As expected, LBDS can provide bandwidth guarantees for both EF and AF traffic. We also show that under burst traffic arrivals, especially when the traffic arrival pattern is non-uniform and the load is above 0.6, LBDS performs much better delay performance than existing DiffServ support schemes.

Performance analysis of a priority queue: Expedited Forwarding PHB in DiffServ

This paper studies a two-class priority queue in order to model a DiffServ router with Expedited Forwarding Per-Hop Behavior for high-priority traffic. Normally, queueing models assume infinite queue capacity but in a DiffServ router the capacity for high-priority traffic is often small to prevent this traffic from monopolizing the output link and hence causing starvation of other traffic. The presented model takes the exact (finite) high-priority queue capacity into account and introduces a framework for queue management algorithms, enabling determination of high-priority packet loss and its influence on the performance of the system. Analytical formulas for system content and packet delay of each traffic class are determined. Numerical examples indicate the necessity of modelling the high-priority queue as finite in order to accurately capture performance in a DiffServ environment.

An Analysis of the Delay and Jitter Performance of DBA Schemes for Differentiated Services in EPONs

An Ethernet passive optical network (EPON) is a low-cost, high-speed solution to the bottleneck problem of a broadband access network. This paper analyzes the delay and the jitter performance of dynamic bandwidth allocation (DBA) schemes for differentiated services in EPONs. Especially, the average packet delay and the delay jitter of the expedited forwarding (EF) traffic class are compared, with consideration as to whether a cyclic or an interleaved polling scheme is superior. This performance evaluation reveals that the cyclic polling based DBA scheme provides constant and predictable average packet delay and improved jitter performance for the EF traffic class without the influence of load variations.

A Distributed DiffServ Supporting Scheduling Algorithm

PDF HTML阅读 XML下载 导出引用 引用提醒 一种支持DiffServ模型的全分布式调度算法 DOI: 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: Supported by the National Natural Science Foundation of China under Grant No.60572042 (国家自然科学基金); the National High-Tech Research and Development Plan of China under Grant No.2005AA121210 (国家高技术研究发展计划(863)); the National Basic Research Program of China under Grant No.2007CB307102 (国家重点基础研究发展计划(973)) A Distributed DiffServ Supporting Scheduling Algorithm Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:调度算法设计对于网络路由设备实现区分服务(DiffServ)模型的单跳行为(per hop behavior,简称PHB)至关重要.现有支持DiffServ模型的调度算法普遍基于输出排队(output queued,简称OQ)或是输入排队(input queued,简称IQ)交换结构进行设计,均无法在高速环境下提供高性能的调度.基于联合输入/交叉节点排队(combined input-crosspoint-queued,简称CICQ)交换结构提出一种支持DiffServ模型的全分布式调度算法DDSS (distributed DiffServ supporting scheduling),并通过理论分析对其公平性进行了验证.DDSS算法采用基于预约带宽的逐级流量控制机制实现所有预约带宽在快速转发(expedited forwarding,简称EF)业务与确保转发(assured forwarding,简称AF)业务之间的分配,采用优先级调度机制为EF业务提供低延迟服务,算法复杂度为O(log N).仿真结果表明,DDSS算法具有良好的时延性能和公平特性,与现有算法相比,能够更好地支持DiffServ模型. Abstract:Scheduling algorithm is very important for network design to implement per hop behaviors (PHBs) in DiffServ model. Most of the presented DiffServ supporting scheduling algorithms are based on output queued (OQ) switches or input queued (IQ) switches, which are not suitable to be used in high speed network. This paper proposes a distributed DiffServ supporting scheduling (DDSS) algorithm based on combined input-crosspoint -queued (CICQ) switches. Theoretical analysis illuminates that the DDSS algorithm can obtain good fairness. The DDSS algorithm adopts a two-stage flow control mechanism based on periodic statistic to achieve fair bandwidth allocation for expedited forwarding (EF) and assured forwarding (AF) traffic, and uses a priority scheduling mechanism to provide lower delay for EF traffic. The time complexity of the DDSS algorithm is only O(log N), hence is practical and scalable for high speed network. Simulation results show that DDSS algorithm can obtain good fairness and delay performance. It is more appropriate to be used to support the DiffServ model. 参考文献 相似文献 引证文献

A novel fault-tolerant multi-EPON system with sharing protection through bridge ONUs

In the EPON, any failure of optical line terminal (OLT) or feeder fiber can halt the entire system. Many previous studies proposed dedicated protection architectures to protect the critical components, which results in high cost for deployment. To achieve high reliability and low-cost for deployment, this article proposes a novel fault-tolerant Multi-EPON system with cost-effective shared protection through Bridge ONUs. Under failures, the Bridge ONU controls the faulty EPON, plays the role of OLT and the transmission of faulty EPONs are restored by relaying to other interconnected adjacent EPONs. The minimum hop-count relay algorithm and the relay window mechanism are also proposed for the Multi-EPON system to efficiently help data relaying to the central office (CO). Furthermore, the one-wait dynamic bandwidth allocation enables the controller of affected Passive Optical Networks (PONs) to obtain more up-to-date buffer information from each ONU in order to enhance overall system performance. The simulation results show that the proposed Multi-EPON system can provide high system performance for different failure situations in terms of throughput, average delay, maximum delay, and expedited forwarding (EF) jitter, especially in high traffic loads.

Enabling novel premium service classes in DiffServ over MPLS‐enabled network

AbstractNetwork resources dimensioning and traffic engineering influence the quality in provisioned services required by the Expedited Forwarding (EF) traffic in production networks established through DiffServ over MPLS‐enabled network. By modeling EF traffic flows and the excess of network resources reserved for it, we derive the range of delay values which are required to support these flows at DiffServ nodes. This enables us to develop an end‐to‐end (e2e) delay budget‐partitioning mechanism and traffic‐engineering techniques within a framework for supporting new premium QoS levels, which are differentiated based on e2e delay, jitter and loss. This framework enables ingress routers to control EF traffic flow admission and select appropriate routing paths, with the goal of EF traffic balancing, avoiding traffic congestion and getting the most use out of the available network resources through traffic engineering. As a result, this framework should enable Internet service providers to provide three performance levels of EF service class to their customers provided that their network is DiffServ MPLS TE aware. Copyright © 2008 John Wiley & Sons, Ltd.

Expedited forwarding end‐to‐end delay and jitter in DiffServ

AbstractThe scheduling disciplines and active buffer management represent the main components employed in the differentiated services (DiffServ) data plane, which provide qualitative per‐hop behaviors corresponding to the QoS required by supported traffic classes. In the first part of this paper, we compute the per‐hop delay bound that should be guaranteed by the different multiservice scheduling disciplines, so that the end‐to‐end (e2e) delay required by expedited forwarding (EF) traffic can be guaranteed. Consequently, we derive the e2e delay bound of EF traffic served by priority queuing–weighted fair queuing (PQ–WFQ) at every hop along its routing path. Although real‐time flows are principally offered EF service class, some simulations on DiffServ‐enabled network show that these flows suffer from delay jitter and they are negatively impacted by lower priority traffic. In the second part of this paper, we clarify the passive impact of delay jitter on EF traffic, where EF flows are represented by renewal periodic ON–OFF flows, and the background (BG) flows are characterized by the Poisson process. We analyze through different scenarios the jitter effects of these BG flows on EF flow patterns when they are served by a single class scheduling discipline, such as first‐input first‐output, and a multiclass or multiservice scheduling discipline, such as static priority service discipline. As a result, we have found out that the EF per‐hop behaviors (PHBs) configuration according to RFCs 2598 and 3246 (IETF RFC 2598, June 1999; RFC 3246, IETF, March 2002) cannot stand alone in guaranteeing the delay jitter required by EF flows. Therefore, playout buffers must be added to DiffServ‐enabled networks for handling delay jitter problem that suffers from EF flows. Copyright © 2008 John Wiley & Sons, Ltd.

Fast and efficient routing algorithms for delay-bounded and dependable channels

Quality of Service (QoS) path computation techniques have assumed a lot of importance in recent years. The goal of QoS based routing is to find a path that meets the requested QoS requirements optimizing network utilization. Real-time and multimedia applications require QoS guarantees on timeliness of message delivery and failure-recovery delay. With these goals in mind we present two new routing algorithms. The first one is an efficient routing algorithm that finds a single path given an end-to-end delay. The second algorithm uses the first one in order to obtain the primary and backup paths for dependable channels guaranteeing the required end-to-end delay. Both algorithms maximize the admission of channels in a network and have low polynomial computational cost. We evaluated these algorithms using Differentiated Services Expedited Forwarding (EF) class of service. The experiments show that these algorithms are very efficient: the admission rate (the number of channels that a network can accept) is practically the same as using the optimal routing algorithm and the computational cost is very low.

Hybrid optimization for QoS control in IP Virtual Private Networks

A multiservice IP Virtual Private Network is considered, where Quality of Service is maintained by a DiffServ paradigm, in a domain that is supervised by a Bandwidth Broker (BB). The traffic in the network belongs to three basic categories: Expedited Forwarding (EF), Assured Forwarding (AF) and Best Effort (BE). Consistently with the DiffServ environment, the Service Provider's Core Routers (CRs) only treat aggregate flows; on the other hand, the user's Edge Routers (ERs) keep per-flow information and convey it to the BB. The latter knows at each time instant the number (and the bandwidth requirements) of flows in progress within the domain for both EF and AF traffic categories. A global strategy for admission control, bandwidth allocation and routing within the domain is introduced and discussed in the paper. The aim is to minimize blocking of the ''guaranteed'' flows (EF and AF), while at the same time providing some resources also to BE traffic. In order to apply such control actions on-line, a computational structure is sought, which allows a relatively fast implementation of the overall strategy. In particular, a mix of analytical and simulation tools is applied jointly, by alternating ''local'' decisions, based on analytical models, with flow-level simulation that determine the effect of the decisions on the whole system and provide feedback information. The convergence of the scheme (under a fixed traffic pattern) is investigated and the results of its application under different traffic loads are studied by simulation on three test networks.

Robust design of communication systems: The case of expedited forwarding of voice traffic in differentiated services networks

AbstractDesign of experiments (DOE) is gaining acceptance in the community of telecommunication researchers, especially during the past several years. In this paper, a state‐of‐the‐art review on the use of DOE in the field of communication networks is presented, and the need for introducing a systematic robust design methodology to network simulations or testbed experiments is identified in ensuring robust behaviours of a network against uncontrollable sources of variation. Then, the Taguchi robust design methodology is applied for optimizing the expedited forwarding (EF) of voice traffic in a differentiated services network, and its step‐by‐step procedures are described in detail. The experimental data are collected using the ns‐2 simulator, and the SN ratio, a robustness measure, is analysed to determine an optimal design condition for each performance characteristic. The analysis results show that ‘type of queue scheduling schemes’ is a major control factor for ensuring robust behaviours of one‐way delay and jitter while ‘EF queue size’ is for throughput and loss rate. Finally, a compromised optimal design condition is identified using a desirability function approach adapted to multi‐characteristic robust design problems. Copyright © 2007 John Wiley & Sons, Ltd.

A Premium Traffic Management in DiffServ Through End-to-End Delay Budget Partitioning

Our novel Call Admission Control (CAC) scheme [1], [2] determines the number of Expedited Forwarding (EF) (Premium) flows accepted, based on e2e available bandwidth measurement. However, it does not control the number of flows that could be accepted at a node or over a link along a selected routing path for an EF flow. Hence we complemented the functionality of CAC withoriginal traffic management algorithms [2], [3] to balance EF traffic along the selected routing path for new EF flows and consequently across Differentiated Services (DiffServ) network. The novelty of these algorithms emerges from the fact that they employ an optimization dimension of EF traffic, namely the partitioning of End-to-End (e2e) delay required for a new flow into per-link or per-DiffServ node along the selected routing path. Furthermore, some network resource policies are incorporated with these algorithms to apportion the e2e resource required for EF traffic flows intoper-DiffServ node requirement along the selected routing path. We demonstrate through analysis and simulation that our proposed optimal e2e delay budget management algorithms are superior to Equi-Partitioning (EP) algorithm for DiffServ in guaranteeing e2e delay bounds required forEF flows. Furthermore, highly loaded DiffServ nodes are assigned low delay budget and the opposite for low loaded DiffServ nodes, which result in increasing DiffServ network resource utilization.

A scalable and decentralized fast-rerouting scheme with efficient bandwidth sharing

This paper focuses on the protection of virtual circuits (Label Switched Paths, LSPs) in a (G)MPLS (Generalised Multi-Protocol Label Switching) network. The proposed algorithm is designed to protect traffic with strong delay requirements such as EF (Expedited Forwarding) ordered aggregates in a DiffServ domain. Indeed, for this type of application, we need fast restoration in case of failure. The duplication of all the packets in a 1 + 1 end-to-end restoration scheme consumes a large amount of bandwidth. Furthermore, end-to-end recovery with bandwidth sharing schemes are usually considered to be far too slow. Local fast-rerouting is a solution which can compete with restoration times and bandwidth consumption offered by SONET self-healing rings. Our scheme includes a sophisticated resource mechanism based on the concepts of backup-backup aggregation and backup-primary aggregation. The path selection algorithm is also designed to efficiently reduce the resource usage. Moreover, when considering LSPs at different preemption levels, our algorithm is able to correctly calculate the amount of bandwidth that can be preempted despite the sharing of resource. We show that our approach, though local, can compete with the state-of-the-art end-to-end recovery schemes in terms of resource consumption. The major contribution of our scheme, the backup-primary aggregation, was then also used in the context of end-to-end recovery and improved its performance substantially. To be able to save a maximum amount of bandwidth in a decentralised implementation, the nodes that compute backup LSPs need to obtain a certain amount of link-state information. We propose a solution where the nodes learn almost all the information they need with RSVP messages. This drastically reduces the information that needs to be flooded in the whole network and is the first scalable decentralised solution capable of sharing a large amount of bandwidth.

A traffic-class burst-polling based delta DBA scheme for QoS in distributed EPONs

Abstract Ethernet passive optical network (EPON) preserves the merits of traditional Ethernet network while reducing complexities and improving quality of service (QoS). In this paper, a traffic-class burst-polling based delta dynamic bandwidth allocation (TCBP-DDBA) scheme is presented to provide better QoS to expedited forwarding packet and maximize channel utilization service to assure forwarding and best effort packets. The network resources are efficiently utilized and adaptively allocated to the three traffic classes by guaranteeing the requested QoS. Simulation results using OPNET show that the TCBP-DDBA scheme performs well in comparison to the conventional allocation scheme for a set of given parameters such as: packet delay, queue size, packet delay variation and channel utilization. This work considers system-wide DBA development in contrast to unit-based approach. It is concluded that the algorithm can be used for many types of EPON-based practical distributed networks.

Delay bound and packet scale rate guarantee for some expedited forwarding networks

Expedited Forwarding (EF) is a service defined under the Differentiated Services framework. Based on its recently revised definition in IETF RFC 3246, Packet Scale Rate Guarantee (PSRG) is its key construct, with which bounded nodal delay and edge-to-edge delay are provided. In this paper, we study the delay bound and PSRG for some EF networks. In these networks, each server belongs to a wide scheduler family which captures how much the server can be either late or earlier with respect to its reference fluid server. We show that edge-to-edge delay bound can be improved for EF networks of such servers. We also prove that PSRG can be derived from delay bound and call this PSRG-from-delay-bound property. With this property, we derive and discuss edge-to-edge PSRG for both a per-flow scheduling network and an aggregate scheduling network. In the derived results, delay bound and PSRG are a function of burstiness parameters of flows at the ingress edge. We hence further argue with analytical support that smoothing traffic at ingress edge can improve edge-to-edge delay bound and PSRG for the considered EF networks.

Supporting quality of service by using delta dynamic bandwidth allocations in Ethernet passive optical networks

In Ethernet passive optical networks (EPONs), dynamic bandwidth allocation (DBA) has to provide efficient and statistical multiplexing between the optical network units for better upstream use. Here a new burst-polling-based delta (DBA) scheme is proposed for quality of service (QoS) using class of service (CoS) in EPONs. The proposed scheme consists of two parts: one is inter-ONU scheduling, which is a delta DBA based on burst polling, and the other is OLT-based intra-ONU scheduling, a differentiated priority queuing method at egress, in which three kinds of traffic classes have been considered, such as expedited forwarding (EF), assured forwarding (AF), and best effort (BE). With the proposed scheme, it has been shown that the network resources are optimally utilized and adaptively allocated to the three traffic classes by guaranteeing the requested QoS. For the verification and validation of the algorithm, experimental simulation results using OPNET have been presented, and these show that the proposed scheme under varying offered loads gives an improvement compared with the other DBA schemes in the content of (criteria) packet delay, queue length, and channel utilization--especially when the offered load is beyond the system's capacity. Specifically, packet-delay variations (PDV) for different classes of traffic are demonstrated.