Differentiated Services Networks Research Articles

FIAC: a resource discovery-based two-level admission control for differentiated service networks

Differentiated Service (DiffServ) architecture has been proposed as a scalable QoS architecture for Internet. DiffServ, however, could not control its loads under heavy traffic conditions, and it could not provide strong QoS responses for individual traffic flow. This paper introduces at the edges of a DiffServ domain, a novel two-level admission control scheme, the Fair Intelligent Admission Control (FIAC). At per-class level, FIAC admits traffic according their fairshare and usage while preventing possible congestion within the DiffServ core. At per-flow level, FIAC estimates and allocates the fairshare for each flow within a class. Simulation results demonstrate that FIAC adheres extremely well to the bandwidth requirements of DiffServ classes while preventing congestion within the DiffServ core. With FIAC's per-flow level enabled, FIAC is able to prevent uncontrolled UDP flows from depriving TCP-controlled flows of bandwidth share when they are aggregated to the DiffServ domain.

The Analysis of Service Disciplines of Differentiated Services Flows

Currently the most relevant problem is how to improve the quality of service in IP networks. In order to secure proper quality of service, the network must react adequately to the service generated load, intended to the network and contribute proper amount of resources. In this paper we analyze the quality assurance of multiple services in IP network using differentiated services. We introduce the analytical differentiated flow service model in the router and propose assumptions to evaluate the different queuing disciplines in this paper. In the differentiated services network the classification particularity of complex flow is reflected by the management of queues. Therefore the imitation model was constructed which allows to evaluate different disciplines which serve queues for three priorities flows. There was estimated the intensity effect of different class services to analyzing classes of flows delays using FIFO, PQ, CBQ and WFQ disciplines. Ill. 14, bibl. 7 (in Lithuanian; summary in Lithuanian, English, Russian).

Assured end-to-end QoS through adaptive marking in multi-domain differentiated services networks

The issue of resource management in multi-domain Differentiated Services (DiffServ) networks has attracted a lot of attention from researchers who have proposed various provisioning, adaptive marking and admission control schemes. In this paper, we propose a Reinforcement Learning-based Adaptive Marking (RLAM) approach for providing assured end-to-end quality of service (QoS) in the form of end-to-end delay and throughput assurances, while minimizing packet transmission cost since ‘expensive’ Per Hop Behaviors like Expedited Forwarding (EF) are used only when necessary. The proposed scheme tries to satisfy per flow end-to-end QoS through control action,s which act on flow aggregates in the core of the network. Using an ns2 simulation of a multi-domain DiffServ network with multimedia traffic, the RLAM scheme is shown to be effective in significantly lowering packet transmission costs without sacrificing end-to-end QoS, when compared to the commonly used static marking scheme.

Performance of Hierarchical Aggregation in Differentiated Services Networks

We address the use of hierarchical aggregation in DiffServ networks. We propose two analytical models to study the tradeoffs between signaling load and resource utilization. In the case of the signaling load, we introduce a novel performance metric that captures, simultaneously, the state information stored and the rate of signaling messages processed at routers. In the first analytical model, based on multidimensional birth---death processes, the offered load is detailed at the flow level, which allows accurate assessment of the signaling load. The second analytical model accommodates time-varying offered loads, which allows studying the tradeoffs between the time-scale of the aggregate demand and the time-scale of signaling. Our results, which also include analysis using measured traces, show that hierarchical aggregation can introduce very high signaling gains with a small penalty in terms of resource utilization, allowing significant savings in terms of network cost.

Proportional loss rate differentiation in a FIFO queue

The relative differentiated service model is one of several models proposed for service differentiation in networks [IEEE Network Sept/Oct (1999) 26]. In this model, an assurance is given that ‘higher classes will be better, or at least no worse than lower classes.’ This paper describes a relative loss rate differentiation scheme based on RED. The scheme is used for differentially dropping packets in a FIFO queue during times of congestion. The main idea is, if packet losses are unavoidable in the FIFO queuing system, then they should be distributed among the different service classes in the queue in inverse proportion to the service price or weight assigned to each class. The simulation studies using TCP traffic show that the scheme is very effective in ensuring relative loss rate differentiation between service classes.

Modeling two-windows TCP behavior in differentiated services networks

Two important issues in assured services within differentiated services architecture are bandwidth guarantee and fair sharing of unsubscribed bandwidth among TCP flows with and without bandwidth reservations. Although the subscribed bandwidth can be guaranteed by increasing network capacity or deploying strict admission control mechanisms, the costs of such solutions are very high. The issue of fair sharing of excess bandwidth is also not well solved. To address those issues, a modified TCP, named two-windows TCP, has been proposed. The performance of the protocol is evaluated by simulations. But its effectiveness is not validated theoretically under general network conditions, which is important for understanding the benefits and costs of using the protocol. In this paper, an analytical model is developed for the purpose. The model characterizes throughput of individual two-windows TCP flow as a function of contract rate, round trip time, loss rates of In and Out packets. Extensive simulations validate the analytical model. It's shown two-windows TCP is effective not only on solving the issues of bandwidth guarantee and fair sharing of unsubscribed bandwidth, but also on increasing the utilization of bottleneck link bandwidth. Moreover, its performance is robust to network conditions, which is important for wide deployment over Internet.

Providing Absolute Differentiated Services for Real-Time Applications in Static-Priority Scheduling Networks

In this paper, we propose and analyze a methodology for providing absolute differentiated services for real-time applications. We develop a method that can be used to derive delay bounds without specific information on flow population. With this new method, we are able to successfully employ a utilization-based admission control approach for flow admission. This approach does not require explicit delay computation at admission time and, hence, is scalable to large systems. We assume the underlying network to use static-priority schedulers. We design and analyze several priority assignment algorithms and investigate their ability to achieve higher utilization bounds. Traditionally, schedulers in differentiated services networks assign priorities on a class-by-class basis, with the same priority for each class on each router. In this paper, we show that relaxing this requirement, that is, allowing different routers to assign different priorities to classes, achieves significantly higher utilization bounds.

Scalable Quasi-Dynamic-Provisioning-Based Admission Control Mechanism in Differentiated Service Networks

The architecture in a differentiated services (diffServ) network is based on a simple model that applies a per-class service in the core node of the network. However, because the network behavior is simple, the network structure and provisioning is complicated. If a service provider wants dynamic provisioning or a better bandwidth guarantee, the differentiated services network must use a signaling protocol with QoS parameters or an admission control method. Unfortunately, these methods increase the complexity. To overcome the problems with complexity, we investigated scalable dynamic provisioning for admission control in DiffServ networks. We propose a new scalable qDPM 2 mechanism based on a centralized bandwidth broker and distributed measurement-based admission control and movable boundary bandwidth management to support heterogeneous QoS requirements in DiffServ networks.

A Markovian Model for TCP Analysis in a Differentiated Services Network

In a Differentiated Services network, the use of TCP by an application impacts the service it gets from the network. TCP congestion control algorithms are designed to provide a fair sharing of resources in a best effort network as the current Internet. TCP is not conscious of the new services proposed by DiffServ, namely the different priorities packets are injected with into the network. Many schemes have been proposed to support TCP traffic in a DiffServ network. These schemes have been often validated with simulations. In this paper we propose an analytical model to study the performance of TCP in a DiffServ network under the different proposed schemes. The model is based on a Markovian fluid approach. We present first a general version of the model, then we specify it to the different proposed schemes. For each scheme, we compute the throughput achieved by a TCP connection. We compare then the service differentiation provided by the proposed schemesunder different subscription levels, different reservations, and different round-trip times. Our model forms a good tool for the evaluation of new solutions to support TCP traffic in a DiffServ network.

A parameter based admission control for differentiated services networks

The Differentiated Services architecture aims at providing scalable network Quality of Service by means of aggregate scheduling. However, the defined framework itself only gives a number of building blocks, which do not constitute services yet. In order to provide well defined services, the composition of the respective traffic aggregates has to be controlled. This is usually the task of the admission control. In this paper, we investigate a scenario, where access to advanced network services is provided by a parameter based admission control, which allows providing hard Quality of Service guarantees. We address the scenario of a Premium service which provides bandwidth on demand and which in addition allows placing deterministic bounds on the delay. According to the reservation-based approach of the Integrated Services architecture, we propose a set of admission control procedures that are part of a particular resource manager such as a Bandwidth Broker. In extending the Network Calculus principles used by the Integrated Services architecture towards aggregate based scheduling, we show how these procedures can provide reasonably tight delay-bounds.

Improving aggregate flow control in differentiated services networks

The differentiated services (DiffServ) framework provides a simple and scalable methodology for addressing quality of service issues in IP networks. Service differentiation can be achieved through the assured forwarding (AF) per hop behavior packet-handling scheme. One of the more challenging research issues in DiffServ networks is the fair distribution of bandwidth among aggregates sharing the same AF class. Several studies have shown that the number of microflows in aggregates, the round trip time, the mean packet size and TCP/UDP interactions are key factors in the throughput obtained by aggregates using this architecture. In this paper, we examine the behavior of a recent technique suggested to improve fairness in a DiffServ network: the Aggregate Flow Control mechanism. We also propose two alternatives in the control overlay of this scheme and compare them with the original approach. Simulation results indicate that our proposed modifications improve throughput assurance and fairness requirements.

Inter-Area Traffic Engineering in a Differentiated Services Network

In this paper, an off-line traffic engineering algorithm is presented that optimizes the single-path routing of Label Switched Paths in a Differentiated Services IP domain by means of explicit, Multi-Protocol Label Switching controlled nonshortest paths. This algorithm allows traffic engineering up to 2500 traffic trunks in flat networks with sizes up to 150 nodes while supporting protection, pre-emption, quality-of-service, oversubscription, and resource class affinity. The algorithm with proper extensions can be applied to hierarchical networks, thus increasing the scalability properties for network size with a factor of about 50. First the single-area algorithm is detailed, then the concept and implementation of hierarchy is introduced for inter-area traffic engineering. These topics are illustrated with simulation results.

A fuzzy approach to the balance of drop and delay priorities in differentiated services networks

Two of the objectives of Internet are to increase network capacity and offer high quality of differentiated services for traffic with real-time and nonreal-time requirements. Differentiated services (Diff-Serv) were established to fulfill such objectives. Up until now, several Diff-Serv schemes have been proposed which, among others, handle drop and delay priorities. These two priorities raise important optimization issues for the Internet but their relationship remains an open problem. This paper presents a fuzzy control algorithm to select packets in a fair and efficient manner. Simulation shows that the fuzzy controller is better than a crisp one when the fairness issue is raised.

Building Quality-of-Service Monitoring Systems for Traffic Engineering and Service Management

Deployment of quality-of-service (QoS) based value-added services in IP networks necessitates the use of traffic engineering. Traffic engineering allows service providers to use the network resources efficiently, according to the different quality levels associated with the range of services they offer. Traffic engineering relies typically on monitoring data for both “offline proactive” and “dynamic reactive” approaches. Monitoring data may be used for network provisioning, dynamic resource allocation, route management, and in-service performance verification for value-added IP services. A monitoring system should scale with the network size, the network speed, and the number of customers subscribed to use value-added IP services. This paper investigates the requirements of scalable monitoring system architectures, proposes principles for designing such systems and validates these principles through the design and implementation of a scalable monitoring system for traffic engineering and QoS delivery in IP Differentiated Services networks. Methods for assessing the relative merits of such monitoring systems are proposed. Experimental assessment results prove the scalability, accuracy, and also demonstrate the benefits of the proposed monitoring system.

Adaptive provisioning of differentiated services networks based on reinforcement learning

The issue of bandwidth provisioning for Per Hop Behavior (PHB) aggregates in Differentiated Services (DiffServ) networks has received a lot of attention from researchers. However, most proposed methods need to determine the amount of bandwidth to provision at the time of connection admission. This assumes that traffic in admitted flows always conforms to predefined specifications, which would need some form of traffic shaping or admission control before reaching the ingress of the domain. This paper proposes an adaptive provisioning mechanism based on reinforcement-learning principles, which determines at regular intervals the amount of bandwidth to provision to each PHB aggregate. The mechanism adjusts to maximize the amount of revenue earned from a usage-based pricing model. The novel use of a continuous-space, gradient-based learning algorithm, enables the mechanism to require neither accurate traffic specifications nor rigid admission control. Using ns-2 simulations, we demonstrate using Weighted Fair Queuing, how our mechanism can be implemented in a DiffServ network.

BGRP: Quiet Grafting Mechanisms for Providing a Scalable End-to-End QoS solution

The provisioning of quality of service guarantees over a region spanning multiple administrative domains is nowadays one of the most basic and crucial issues. A scalable and efficient end-to-end QoS architecture is indispensable for ensuring the desired QoS guarantees to QoS-aware services. Towards this end, this paper introduces a scalable inter-domain resource control architecture for Differentiated Services networks. The proposed architecture is based on the Border Gateway Resource Protocol framework, while scalability issues are further elaborated. Therefore, our discussion mainly extends to Quiet Grafting mechanisms, which succeed in significantly limiting the signalling load and efficiently handling the resources reserved between domains. Extended simulation scenarios verify the efficiency of the proposed ‘quiet grafting mechanisms’, while the applicability of the results, especially with respect to real world networks and scenarios is stated.

Scalable qDPMsub 2 mechanism: admission control for differentiated service networks

This paper examines the problem of achieving the QoS goals in differentiated service (DiffServ) networks, studies a dynamic provisioning mechanism for admission control in the DiffServ network, and proposes the scalable qDPM/sup 2/ mechanism based on the centralized bandwidth broker, distributed measurement based admission control and movable boundary bandwidth management.

Fuzzy logic controlled RED: congestion control in TCP/IP differentiated services networks

The use of the Internet for time-sensitive services, such as voice and video applications, requires a predictable quality of service. The TCP/IP differentiated services (Diff-Serv) architecture was introduced to achieve such performance. Network congestion control, however, still remains a critical and high priority issue. A number of researchers are looking at alternative schemes such as random early detection (RED) and its variants to handle congestion. In this paper we present the results of a fuzzy logic control approach to the implementation of RED --- Fuzzy-RED. We believe that with fuzzy logic we are able to use linguistic knowledge to implement better understood nonlinear probability discard functions, achieve better differentiation for packet discarding behaviors for aggregated flows, and so provide better quality of service to different kinds of traffic whilst maintaining high utilization.

Congestion control in differentiated services networks using Fuzzy-RED

Network congestion control remains a critical and high priority issue. The rapid growth of the Internet and increased demand to use the Internet for time-sensitive voice and video applications necessitate the design and utilization of effective congestion control algorithms, especially for new architectures, such as differentiated services (Diff-Serv). As a result, a number of researchers are now looking at alternative schemes to TCP congestion control. Random early detection (RED) and its variants are one of these alternatives to provide quality of service (QoS) in TCP/IP Diff-Serv networks. In this paper, we present the results of a fuzzy logic control approach to RED implementation, Fuzzy-RED, implemented within the Diff-Serv framework. The proposed fuzzy logic approach for congestion control allows the use of linguistic knowledge to capture the dynamics of non-linear probability discard functions and offer more effective implementation, use multiple inputs to capture the (dynamic) state of the network more accurately, enable finer tuning for packet discarding behaviors for aggregated flows, and thus provide better QoS to different types of data streams, such as TCP/FTP traffic or TCP/Web-like traffic, whilst maintaining high utilization.

Jitter analysis of homogeneous traffic in differentiated services networks

A critical challenge for networking vendors and carrier companies is to be able to accurately estimate the quality of service (QoS) that will be provided based on the network architecture, router/switch topology, and protocol applied. In addition, due to the development of technologies like multiprotocol label switching (MPLS) and generalized MPLS (GMPLS), which can deploy differentiated services (DiffServ), the variation in QoS performance based on the priority assignment is of significant importance. In this focus, this paper provides a theoretical analysis of interarrival packet jitter of homogeneous traffic based on a nonpreemptive head-of-the-line (HOL) priority scheme.