Per-hop Behavior Research Articles

Alternative Best Effort (ABE) for Service Differentiation: Trading Loss Versus Delay

The idea of an Alternative Best Effort (ABE) per-hop behaviour (PHB) emerged about 20 years ago. It provides a low-delay traffic class in the Internet at the expense of more packet loss than Best Effort (BE). Therefore, ABE is better suited than BE for loss-tolerant but delay-sensitive applications. Furthermore, ABE traffic should not degrade the service for BE traffic in terms of packet loss and delay. Therefore, Internet service providers may leave the choice of using BE or ABE to their customers as they achieve service differentiation without compromising other traffic. In this work, we revisit ABE and pursue the fundamental question whether an ABE service is technically feasible, how its service would look like and interact with existing transport protocols? We present a novel scheduler called Deadlines, Saved Credits, and Decay (DSCD) for combined scheduling of BE and ABE traffic. It allows to control ABE’s delay advantage over BE and copes with varying bandwidth. We provide an implementation of DSCD in the Linux network stack and demonstrate its efficiency. A side product of the implementation is an efficient approximation of the exponential function in the kernel and a bandwidth estimation method that even works at moderate link utilization. We study DSCD in a semi-virtualized testbed with real networking stacks to understand implications for transport protocols in a BE/ABE Internet. The study analyzes ABE’s impact on loss and delay under various conditions and gives recommendations for configuration.

Evaluation of Differentiated Services Policies in Multihomed Networks Based on an Interface-Selection Mechanism

Quality of service metrics and differentiated service mechanism policies are the most important criteria to deliver essential Internet requirements, especially during user handover, due to the rapid growth of users, multimedia applications, and traffic. DiffServ routers provide per-hop behaviors to manage traffic for services, whereas their policies have been applied to several types of Internet traffic, such as hypertext transfer protocol, file transfer protocol, and content-based routing. Multihoming aims to improve the reliability, scalability, and performance of data communications networks. This paper evaluated DiffServ various policies compared in a systematic manner (in two stages) over the multihomed networks to utilize and adopt the best policy for communicating packets, and enhanced the overall performance in terms of throughput, end-to-end latency, and processing time. Moreover, the paper introduced an interface-selection technique for multihomed nodes to select a proper interface, which provides the best services and links the behaviors that this interface yields. The overall results showed how the introduced multihoming-based interface-selection mechanism managed to maintain communication with the multihomed node. Furthermore, our results showed that the DiffServ time-sliding window with a three-color marking policy achieved the best system performance compared with the remaining policies.

An on demand load balancing multi-path routing protocol for differentiated services in MWSN

As an important part of the Internet of Things, mobile wireless sensor network (MWSN) will generate traffic with different service quality requirements due to the multi-sensor integration of nodes and application diversity. Due to the topological changes, resource constraints and self-organizing characteristics of MWSN, the Per-Hop Behavior (PHB) approach in the traditional Diff-Serv model has many challenges in providing differential service. In this paper, a path reservation multipath routing (PRMR) protocol is proposed, which can provide a suitable path for each type of traffic with service requirements. PRMR protocol includes path discovery algorithm and packet scheduling algorithm. In addition, the path scheduling model and scheduling algorithm in PRMR solve the problem of load imbalance among reserved paths caused by different types of traffic. In scenarios with different number of nodes, three types of traffic, integrity sensitive data, delay sensitive data and normal data, are used to verify the performance of PRMR differential service and load balancing. Simulation experiments not only compare the quality of service provided by each reserved path in PRMR, but also compare the differential service performance between PRMR and several multipath routing algorithms. Simulation results show that PRMR routing algorithm can guarantee high packet delivery rate and low delay for integrity-sensitive data and delay-sensitive data, respectively. In addition, the simulation results of the average residual energy index show that the protocol can achieve network energy balance.

QoS-Classifier for VPN and Non-VPN traffic based on time-related features

The Quality of Service (QoS) is a continuous challenge issue in the telecommunication industry, mainly for having an impact on telco services provision. Traffic Classification, Traffic Marking, and Policing are general stages of QoS managing. Different approaches have focused on Traffic Classification and Traffic Marking, which machine learning algorithms arise as promising techniques ones. However, Traffic Marking overtime-related features is not widely explored, especially for Virtual Private Network (VPN) traffic. Hence, a specific QoS classifier for VPN traffic based on per-hop behavior (PHB) for a specific domain was proposed. To this end, a baseline QoS-Marked dataset was generated from a characterized VPN traffic; to which some machine learning algorithms were compared and a T-Tester was performed. As a result, Bagging-based learning model has the best behavior for all scenarios in which the higher value achieved was a 94,42% accuracy. Consequently, a QoS classifier is an effective approach for traffic treatment on Differentiated Services (DiffServ) networks.

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.

Research on QoS Services to MPLS Enabled Industrial Control Network

In general, data exchanged on an industrial network can be classified into two groups: realtime and non-realtime data. Non-real-time data do not have stringent time limits on their communication delays experienced during the data exchange. In contrast, real-time data have very strict time limits and the data’s value is diminished greatly as the communication delay grows larger. Therefore, when building an industrial network, the designer must configure the network to satisfy these requirements. MPLS provides extensive support for both integrated services/RSVP, and diff-serv QoS classes. Service providers can use MPLS to define classes of service (gold, premium, best-effort, etc.) and to define per-hop behavior (PHB) for each class to support the service. We use OPNET Modeler to design MPLS capabilities incorporating IntServ/DiffServ mechanisms into on an industrial network to ensure QoS under network failure conditions. We demonstrate how modern MPLS with QoS management techniques can control, but also complicate, prediction, and will finally illustrate how semi-empirical statistical techniques offer some resolution.

A provision-aware fair bandwidth distribution marker algorithm for DiffServ networks

The rise in demand for real-time applications on the Internet necessitates Quality of Service (QoS). Differentiated Services (DiffServ) is one of the technologies used currently to provide QoS and service differentiation. It is simple and scalable. It provides service differentiation to aggregates, mainly through the Assured Forwarding (AF) per-hop behaviour. Previous work on fair sharing of network bandwidth did not adequately address the Under-Provisioned Network (UPN) condition. In this paper, we propose a new three-colour marker, named paItswTCM (provision-aware Improved TSW based Three-Colour Marker). We compare our new algorithm with both time-sliding window markers and token-bucket-based markers using simulations. Results show that our new provision-aware marker outperforms these previous algorithms not only in the UPN condition but also for low to medium network provision levels. We conclude that to achieve proportional sharing of bandwidth, no packet type should be injected at the expense of others.

A Delivery System for Streaming Video Over DiffServ Networks

In this letter, we develop a general delivery system for streaming using various coding standards over DiffServ (DS) networks. In the delivery system, the coder at the application layer pre-marks the compressed data according to their importance in terms of the current configuration and characteristics of the coder. Then the system maps these pre-marks to a fixed number of source marks at the real-time transport protocol layer. In terms of the current network congestion state, the edge router of a DS network uses the improved two rate three color maker to map these source marks to differentiated services code points. At last, the core routers transmit these packets according to the per-hop forwarding behaviors. Experimental results show that this system can greatly improve the end-to-end delivery quality of a streaming application.

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.

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

Improving fairness in a WRED-based DiffServ network: A fluid-flow approach

The DiffServ architecture has been proposed as a scalable approach for upgrading the Internet, adding service differentiation functionalities. However, several aspects of this architecture still have to be analyzed and solved. For this reason, network designers need to be provided with tools which are able to estimate the average behavior of a DiffServ network with a high level of accuracy and in a short time. In this paper a fluid-flow model of a DiffServ network supporting Assured Forwarding Per-Hop Behavior (PHB) and loaded with TCP flows is proposed. At the edge of the network, two rate three color markers (TRTCM) are employed as profile meters, while within the network core routers implement a Weighted RED (WRED) buffer management mechanism. In order to demonstrate the high accuracy of the proposed model, a comparison between model and simulation results is performed, taking into account not just a bottleneck link, but a complex network topology. The proposed analytical framework is then used to analyze the impact of several factors on the fair sharing of network resources between traffic aggregates with the same traffic profile, and to achieve some guidelines for WRED parameter settings with the aim of reducing unfairness.

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.

A Performance Model and Measurement Framework for DiffServ Implementations

Providers of data network services are in search of new solutions for service offerings over integrated service packet networks which can accommodate voice and video traffic in addition to data traffic. The goal is to provide users with cutting-edge services such as IP telephony, video conferencing, video on demand, telemedicine, etc. As the traditional design of data networks has had little or no support in providing the required traffic characteristics to voice and video streams, architectures for quality of service (QoS) have been defined. Of these architectures, differentiated services (DiffServ) is seen as a significant contributor to the migration of current data networks to next-generation networks capable of providing a broader range of services. However, the way they have been defined, these architectures lack precise formal specifications, and therefore, their performance is strongly related to the quality of each implementation. This paper presents an abstract model for DiffServ with assured forwarding (AF) per-hop behavior (PHB). The model is meant for a better illustration of the dynamics of QoS parameters. After a thorough review of existing methodologies for performance measurements for DiffServ, this paper proposes a dynamic model for AF and a framework for its performance measurement, which is illustrated by a number of experiments run on a live network (NCIT*net 2). This paper is the starting point for the detailed specification of DiffServ PHBs. Experimental results illustrate, verify, and justify the model introduced.

Per-domain packet scale rate guarantee for expedited forwarding

The expedited forwarding per-hop behavior (EF PHB) was recently replaced by a new definition, called packet scale rate guarantee (PSRG), under the Differentiated Services (DiffServ) framework. This replacement raises two challenges. One is the implementation of a PSRG server. Another is the provision of per-domain PSRG. Specifically, for the former, an open issue is whether hierarchical schedulers can provide PSRG; for the latter, it is not clear whether and how per-domain PSRG can be provided in the presence of flow aggregation. Since, in DiffServ networks, flow aggregation is a natural phenomenon and hierarchical scheduling is high-likely desired, these two challenges become even more critical. To address the first challenge, we introduce a new concept called latency-rate worst-case service guarantee (LR-WSG). We prove that, if a server provides LR-WSG, it also provides PSRG. We show that many well-known schedulers support LR-WSG, which include not only one-level schedulers but also their hierarchical versions. To address the second challenge, we first prove that PSRG can be extended from per-node to per-domain if no flow aggregation is performed. The proof is notable in that it depends solely on the concept of PSRG itself. We then investigate the provision of per-domain PSRG in presence of flow aggregation. We propose to use packet scale fair aggregator (PSFA) to aggregate flows. We show that, with PSFA, per-domain PSRG can be provided in spite of flow aggregation. We finally provide a brief discuss on the viability of using PSFA in DiffServ networks and define an expedited forwarding per-domain behavior (EF PDB).

Edge-to-Edge Quality-of-Service Domain

Researchers have proposed numerous approaches to providing Quality-of-Service (QoS) across the Internet. The IETF has proposed two reservation approaches: hop-by-hop bandwidth reservation (IntServ); and per-hop behaviour bandwidth reservation (DiffServ). An edge router generates traffic, accepts per-flow reservation and classifies them into predetermined service class; while a core router ensures different QoS guarantees for each service class. We propose an Edge-to-Edge Quality-of-Service Domain in which packet trains with the same service requirements aggregated using packet deadline at edge router. The properties of a packet train like Inter-Packet Departure Time, Inter-flow Departure Time and accumulated packet delay are embedded and used by our quantum-based scheduler and QoS packet forwarding scheme in core routers. Thus, we are able to extract per-queue and per-flow information. Each queue is reconstructed at core router with packets having an expected departure time that is relative to the ingress router. Useful functions like instantaneous service rate and fine granular dropping scheme can be derived with a combination of embedded information and relative virtual clock technique. The encapsulation of our packet train information converges mathematically. Through simulations, we show that our architecture can provide delay and rate guarantees and minimise jitter for QoS-sensitive flows that requires LR-coupled or LR-decoupled reservations.

Fluid flow analysis of TCP flows in a DiffServ environment

AbstractThe differentiated services (DiffServ) architecture allows IP networks to offer different QoS levels to different users and applications. In this architecture, routers in the core network offer the same per‐hop behaviour (PHB) to all packets classified as belonging to the same class at the edge of the network. One of the most important types of PHB is assured forwarding (AF) PHB. Within each AF class, IP packets can be marked with different drop precedence (DP) values, and treated differently in congested DS nodes. To this end, DiffServ nodes in the core network implement active queue management (AQM) mechanisms. The target of this paper is to provide network designers with an accurate fluid‐flow analytical model of a DiffServ network, where the RED with in/out and coupled average queues (RIO‐C), RED with in/out and decoupled average queues (RIO‐DC) and Weighted RED (WRED) AQM techniques are implemented. We address a network simultaneously loaded with both greedy and data‐limited TCP flows, and we consider one AF class in which two DPs are defined, one for packets complying with the negotiated profile (IN packets), and another for packets that do not respect it (OUT packets). A token bucket marking mechanism is modelled for this purpose. The proposed model is applied to a complex network topology. Comparison between model and simulation results demonstrates that the model is able to capture both transient and steady‐state network behaviour with a high degree of accuracy, even when not all network routers implement the same AQM technique. These characteristics make our modelling approach suitable to address the issue of network parameter optimisation. As an example, the link capacity dimensioning problem in a DiffServ domain by means of an iterative optimisation algorithm is presented. Copyright © 2006 AEIT

Resource management and QoS control in multiple traffic wireless and mobile Internet systems

AbstractEnd‐to‐end quality of service (QoS) control for multiple traffic in wired networks is carried out through Differentiated services (DiffServ). Edge routers in DiffServ domain classify incoming flows into different per‐hop behavior (PHB) groups and give a policy‐based QoS guarantee to these behavior aggregates. As Internet extends into the wireless and mobile section, different traffic flows should be treated differently not only in wired core network, but also in wireless resource allocations. In this paper, we propose a preemptive priority handoff and adaptive resource allocation scheme. DiffServ PHB groups are mapped into different wireless and mobile QoS classes. Traffic flows are categorized into these classes in order to allow the system to allocate different bandwidth and make resource reservation according to their priorities. Higher priority traffic flows are permitted to preempt lower priority flows in service. Lower ones, on the contrary, can expand their bandwidth into areas reserved for higher priority traffic flows for better resource utilization. We use both analytical model and simulation to evaluate the system performance in terms of blocking probabilities, forced termination probabilities, and delay. The forced termination probability of high priority traffic flows can be decreased significantly by introducing the preemptive priority scheme. Therefore, this scheme can be used in wireless part of the system along with DiffServ to give further guarantee for low delay, low jitter, and low loss services to high priority services. Copyright © 2005 John Wiley & Sons, Ltd.

Service differentiation with MEDF scheduling in TCP/IP networks

The Differentiated Services architecture implements appropriate Per Hop Behaviors (PHBs) for service differentiation to achieve Quality of Service (QoS) in Next Generation Networks (NGNs). In this paper, we review several buffer management and scheduling algorithms that may be applied in this context. The major part of this work focuses on the interaction between TCP and the Modified Earliest Deadline First (MEDF) scheduling algorithm. It is an appealing option for service differentiation because it relies on a single parameter only and because this parameter can be configured independently of the current share of high priority traffic in the network. This is contrary to many other scheduling disciplines or buffer management strategies. The unavailability of this information in today's Internet makes MEDF an interesting candidate for commercial application.

Reinforcement learning-based dynamic bandwidth provisioning for quality of service in differentiated services networks

The issue of bandwidth provisioning for Per Hop Behavior (PHB) aggregates in Differentiated Services (DiffServ) networks is imperative for differentiated QoS to be achieved. This paper proposes an adaptive provisioning scheme that determines at regular intervals the amount of bandwidth to provision for each PHB aggregate, based on traffic conditions and feedback received about the extent to which QoS is being met. The scheme adjusts parameters to minimize a penalty function that is based on the QoS requirements agreed upon in the service level agreement (SLA). The novel use of a continuous-space, gradient-descent reinforcement learning algorithm enables the scheme to work effectively without accurate traffic characterization or any assumption about the network model. Using ns-2 simulations, we show that the algorithm is able to converge to a policy that provisions bandwidth such that QoS requirements are satisfied.

A novel framework for IP DiffServ over optical burst switching networks

This paper presents a novel framework for IP Differentiated Services (DiffServ) over optical burst switching (OBS), namely, DS-OBS. The network architecture, functional model of edge nodes and core nodes, the control packet format, a novel burst, assembly scheme at ingress nodes and scheduling algorithm of core nodes are presented. The basic idea is to apply DiffServ capable burst assembly at ingress nodes and perform different per hop behavior (PHB) electronic treatments for control packets of different QoS class services at core nodes. Simulation results show that the proposed schemes can provide the best differentiated service for expedited forwarding (EF), assured forwarding (AF) and best, effort (BE) services in terms of end-to-end delay, throughput and IP packet loss probability.