Performance evaluation of a measurement-based algorithm for distributed admission control in a DiffServ framework

Optimal Protection from Impact, Shock, and Vibration

The assured forwarding per hop behavior (AF PHB) has been devised by the IETF differentiated services (DiffServ) working group to provide drop level differentiation. This paper shows, quite surprisingly, that a standard AF PHB class is semantically capable of supporting per flow admission control. This is obtained by adopting the AF PHB as the core router forwarding mechanism in conjunction with an end point admission control mechanism running at the network edges. Our work appears to prove that the extent of the AF PHB can be larger than was originally expected, since it can support an admission control mechanism, which is deemed necessary in recent RFCs to offer QoS aware services. An interesting related issue is whether the expedited forwarding PHB, devised to support flows with strict delay requirements, and based on a single DSCP tag, should be redesigned as a PHB class to comply with end point admission control. Preliminary performance results show that, under suitable assumptions, our scheme can provide as much as hard QOS guarantees (see Bianchi, G. et al., IEEE Globecom, 2001; http://drake.diei.unipg.it/netweb/GRIP/sub -/tech/sub -/rep.pdf).

Allocating resources for multimedia traffic flows with real-time performance requirements is an important challenge for future packet networks. However, in large-scale networks, individually managing each traffic flow on each of its traversed routers has fundamental scalability limitations, in both the control plane's requirements for signaling, state management, and admission control, and the data plane's requirements for per-flow scheduling mechanisms. In this paper, we develop a scalable architecture and algorithm for quality-of-service management termed egress admission control. In our approach, resource management and admission control are performed only at egress routers, without any coordination among backbone nodes or per-flow management. Our key technique is to develop a framework for admission control under a general "black box" model, which allows for cross traffic that cannot be directly measured, and scheduling policies that may be ill-described across many network nodes. By monitoring and controlling egress routers' class-based arrival and service envelopes, we show how network services can be provisioned via scalable control at the network edge. We illustrate the performance of our approach with a set of simulation experiments using highly bursty traffic flows and find that despite our use of distributed admission control, our approach is able to accurately control the system's admissible region under a wide range of conditions.

The IEEE 802.11e standard provides many mechanisms for quality of service (QoS) support at the MAC layer level. However, the service differentiation provided in IEEE 802.11e is not enough to meet the QoS requirements of time bounded multimedia traffic. These can be better satisfied, if we employ admission control and bandwidth reservation mechanisms. In this paper, we discuss a measurement based distributed admission control mechanism, for the IEEE 802.11e wireless local area network (WLAN) functioning in infrastructure mode. We call the scheme PLUS-DAC (priority, load and utilization based scheme for distributed admission control). PLUS-DAC measures the load and utilization in the BSS and adapts the transmission opportunity (TXOP) allocation dynamically. Our results show that, PLUS-DAC can achieve quasi-optimal utilization and continue to satisfy QoS guarantees given to multimedia flows.

Distributed queue dual bus (DQDB) metropolitan area networks (MANs) provide data and isochronous services using the connection-less queued arbitrated (QA) and connection-oriented pre-arbitrated (PA) access schemes, respectively. Essentially, the DQDB-PA scheme adopts a connection management procedure which requires laborious exchanges of control messages. Besides, the scheme disregards how bandwidth is allocated for each type of traffic. This paper proposes a distributed admission control (DAC) mechanism for supporting isochronous traffic in DQDB MANs. DAC is composed of two components, the bandwidth allocator and the connection manager. Based on a Markovian model, the bandwidth allocator dynamically allocates appropriate bandwidth to isochronous data according to the current and imminent isochronous traffic load. The bandwidth allocator consequently assures a given quality of service (QOS) requirement of the isochronous traffic with respect to the blocking probability. Moreover, requiring no direct confirmation exchanges, the connection manager allows connections to be admitted and disconnected in an implicit and distributed manner. Finally the paper also presents simulation results which demonstrate the performance superiority of DAC with respect to a set of QOS indexes, such as call admission delay, call blocking probability, and aggregate system throughput.

We investigate the performance of distributed admission control with quality of service (QoS) provisioning and dynamical channel allocation for mobile/wireless networks where the co-channel reuse distance is considered as the only limiting factor to channel sharing. We first provide a QoS metric feasible for admission control with dynamically allocated channels. We then derive a criterion analytically using the QoS measure for distributed call admission control with dynamic channel allocation (DCA). When maximum packing is used as the DCA scheme, the results obtained are independent of any particular algorithm that implements dynamic channel assignments. Our results, thereby, provide the optimal performance achievable for the distributed admission control with the QoS provisioning by the best DCA scheme in the given setting.

The transmission of multimedia streams with a particular and guaranteed quality of service (QoS) is a major challenge in multimedia communication over IP networks. In this paper, we analyze the distributed architecture of a video on demand (VoD) system to design global request handling and admission control strategies. We describe a highly available distributed VoD service using existing telephone network, which is inherently scalable and fault tolerant. The VoD service is provided by media server farms (MSF), which may reside in different local telephone exchange of a telephone network. We present the design and simulation results for a new distributed admission control and QoS adaptation controller architecture, called semi-distributed admission control (SD-AC) architecture for a set of MSFs

We explore how 802.1Q(p) can be successfully exploited within the DIFFSERV framework. Borrowing from work on INTSERV and SBM, but in keeping with a KISS philosophy, we analyze how, in combination with admission control and bandwidth management, we can deliver services with guarantees of quality for applications such as VoIP on a per-VLAN basis. In conclusion, we show that it possible to use a pure layer-2 infrastructure to support large-scale deployment of new services in a wide regional area.

Distributed service-oriented traffic control mechanisms, operating with minimum impact on network performance, assume a crucial role as regards controlling services quality and network resources transparent and efficiently. In this way, we describe and specify a lightweight distributed admission control (AC) model which provides an uniform solution for managing QoS and SLSs in multiclass and multidomain environments. Taking advantage of the consensual need of on-line service monitoring and traffic control at the network edges, AC decisions are driven by feedback from systematic edge-to-edge measurements of relevant QoS parameters for each service type and SLS utilization. This allows self-adaptive service and resource management, while abstracting from network core complexity and heterogeneity. In this paper, introducing an expressive notation, we specify the high-level entities for multiservice provisioning in a domain and formalize service-dependent AC equations to assure both intra and interdomain model operation. A proof-of-concept of the AC criteria effectiveness in satisfying each service class commitments while achieving high network utilization is provided through simulation.

Geometrically nonlinear mode approximations for impulsively loaded homogeneous viscous beams and frames

Understanding the dynamic response of accelerometers is critical to interpreting data obtained in impulsive loading conditions. While this information is commonly provided by manufacturers, the estimated properties are typically obtained at levels below the full range of the sensor. Using high bandwidth operating data of varying amplitudes, the damping ratio and principle resonant frequency of shock accelerometers are estimated using a simple dynamic model. While the resonance is shown to be essentially amplitude-invariant, the damping ratio is shown to vary with the excitation amplitude. Possible causes related to the frequency content of the excitation and the presence of repeated roots are discussed.KeywordsShock accelerometersMicroelectromechanical systems (MEMS)SensorsDampingOperating modal analysis

With the means of rigid-elastic coupled tire model, the in-plane vibration characteristic of heavy truck tire is investigated and the time-domain vibration response with the proposed tire model is discussed. With the means of finite difference method, rigid–elastic coupled tire model is developed from flexible beam on elastic foundation tire model and the nonlinear radial stiffness of sidewall is derived and related with the inflation pressure and geometrical feature of sidewall curved arc. In-plane vibration characteristic of heavy truck tire, including transfer function and modal parameters is investigated by experimental hammer test. Taking the error between the analytical and experimental modal frequency as the object value, Genetic Algorithm is utilized to identify the un-known structural parameters. In-plane time-domain dynamics response of heavy truck tire utilizing the proposed tire model with linear/nonlinear sidewall radial stiffness is researched and compared with experimental result. Experimental and theoretical results shows that in-plane rigid–elastic coupled tire model with nonlinear sidewall stiffness can be used to better the precision on predicting the vibration feature excited by the random irregular signal. Rigid–elastic coupled tire model with nonlinear sidewall stiffness can be extended to other heavy truck tire with a large section ratio or tires under impulsive loading conditions.

This paper presents new distributed power and admission control algorithms for ad-hoc wireless networks in random channel environments. Previous work in this area has focused on distributed control for ad-hoc networks with fixed channels. We show that the algorithms resulting from such formulations do not accurately capture the dynamics of a time-varying channel. The performance of the network in terms of power consumption and generated interference can be severely degraded when power and admission control algorithms that are designed for deterministic channels are applied to random channels. In particular, some well-known optimality results for deterministic channels no longer hold. In order to address these problems we propose a new criterion for power optimality in ad-hoc wireless networks. We then show that the optimal power allocation for this new criterion can be found through an appropriate stochastic approximation algorithm. We also present a modified version of this algorithm for tracking nonstationary equilibria, which allows us to perform admission control. Ultimately, the iterations of the stochastic approximation algorithms can be decoupled to form fully distributed on-line power and admission control algorithms for ad-hoc wireless networks with time-varying channels.

An integrated bandwidth allocation and admission control framework for the support of heterogeneous real-time traffic in class-based IP networks

In this paper, we present an innovative distributed quality of service routing scheme suitable to operate in networks of general topology implementing a Diff-Serv service model for QoS support. The proposed scheme is based on a game theoretic non-cooperative model which exploits, on the one hand, the topological information distributed within the network by the current (non-QoS) link-state and distance-vector routing protocols and, on the other hand, the QoS information locally available at the node where the forwarding process takes place. In order to guarantee the satisfaction of a stability condition at each node, a distributed admission control (DAC) scheme is proposed to jointly operate with the non-cooperative routing scheme. The DAC decides if a new flow can be accepted without violating the nodes' stability constraints and provides each node with cumulative information about the status of the network downstream from its outgoing links.