On providing blocking probability and throughput guarantees in a multi‐service environment

As the Internet evolves from a packet network supporting a single best effort service class towards an integrated infrastructure supporting several service classes—some with QoS guarantees—there is a growing interest in the introduction of admission control and in devising bandwidth sharing strategies, which meet the diverse needs of QoS‐assured and elastic services. In this paper we show that the extension of the classical multi‐rate loss model is possible in a way that makes it useful in the performance analysis of a future admission control based Internet that supports traffic with peak rate guarantee as well as elastic traffic. After introducing the model, it is applied for the analysis of a single link, where it sheds light on the trade‐off between blocking probability and throughput. For the investigation of this trade‐off, we introduce the throughput‐threshold constraint, which bounds the probability that the throughput of a traffic flow drops below a predefined threshold. Finally, we use the model to determine the optimal parameter set of the popular partial overlap link allocation policy: we propose a computationally efficient algorithm that provides blocking probability‐ and throughput guarantees. We conclude that the model and the numerical results provide important insights in traffic engineering in the Internet. Copyright © 2002 John Wiley & Sons, Ltd.     

Modified least loaded routing in virtual path based ATM networks

We consider a Virtual Path (VP) based ATM network supporting multiple traffic classes with heterogeneous traffic characteristics. Using simple FIFO scheduling policy at the ATM multiplexer, we assume that all traffic require identical end‐to‐end quality of service (QoS) requirement. The concept of effective bandwidth is used to determine the required bandwidth to guarantee the specified QoS requirement. We study the problem of using dynamic routing to VP‐based ATM networks by transforming it into an equivalent multi‐rate circuit‐switched network problem. To further simplify the analysis, we restrict the choice of path to single‐link and two‐link routes. We propose a dynamic routing algorithm based on the Least Loaded Routing (LLR) with packing. Simulation results are used to compare the performance of this algorithm with other dynamic routing schemes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simulation analyses of weighted fair bandwidth‐on‐demand (WFBoD) process for broadband multimedia geostationary satellite systems

Advanced resource management schemes are required for broadband multimedia satellite networks to provide efficient and fair resource allocation while delivering guaranteed quality of service (QoS) to a potentially very large number of users. Such resource management schemes must provide well‐defined service segregation to the different traffic flows of the satellite network, and they must be integrated with some connection admission control (CAC) process at least for the flows requiring QoS guarantees. Weighted fair bandwidth‐on‐demand (WFBoD) is a resource management process for broadband multimedia geostationary (GEO) satellite systems that provides fair and efficient resource allocation coupled with a well‐defined MAC‐level QoS framework (compatible with ATM and IP QoS frameworks) and a multi‐level service segregation to a large number of users with diverse characteristics. WFBoD is also integrated with the CAC process. In this paper, we analyse via extensive simulations the WFBoD process in a bent‐pipe satellite network. Our results show that WFBoD can be used to provide guaranteed QoS for both non‐real‐time and real‐time variable bit rate (VBR) flows. Our results also show how to choose the main parameters of the WFBoD process depending on the system parameters and on the traffic characteristics of the flows. Copyright © 2005 John Wiley & Sons, Ltd.     

Dynamic connection provisioning with shared protection in IP/WDM networks

Internet protocol (IP) traffic connections arrive dynamically at wavelength‐division multiplexing (WDM) network edges with low data rates compared with the wavelength capacity, availability, and quality‐of‐service (QoS) constraints. This paper introduces a scheme to be integrated into the control and management plane of IP/WDM networks to satisfy the availability and QoS required for IP traffic connections bundled onto a single wavelength (lightpath) in WDM networks protected by shared‐backup path protection (SBPP). This scheme consists of two main operations: (i) routing multi‐granular connections and traffic grooming policies, and (ii) providing appropriate shared protection on the basis of subscribers’ service‐level agreements in terms of data rate, availability, and blocking probability. Using the Markov chain process, a probabilistic approach is developed to conceive connection blocking probability models, which can quantify the blocking probability and service utilization of M:N and 1:N SBPP schemes. The proposed scheme and developed mathematical models have been evaluated in terms of bandwidth blocking ratio, availability satisfaction rate, network utilization, and connection blocking probability performance metrics. The obtained research results in this paper provide network operators an operational setting parameter, which controls the allocation of working and backup resources to dynamic IP traffic connections on the basis of their priority and data rate while satisfying their requirements in terms of bandwidth and availability. Copyright © 2013 John Wiley & Sons, Ltd.     

LEO multi-service routing algorithm based on multi-objective decision making

In low earth orbit(LEO) satellite networks,in view of the unbalanced link resource,it's difficult to meet differentiated quality of service(QoS) requirements and easily lead to reduce the efficiency of the whole network.A routing algorithm based on multi-objective decision making was proposed which defined LEO satellite network transmission service as the delay sensitive,sensitive bandwidth and reliability sensitive three categories.It used the eigenvector method to calculate service weights,and used the consistency ratio to determine whether it can be accepted.Based on the multi-objective decision making theory,it combined with the actual state of satellite network nodes and links and the specific requirements of the business,calculating the path that meets the QoS requirements of the service,so as to realize the LEO satellite network multi objective dynamic routing optimization.Established simulation platform based on the iridium network system simulated network delay,the uncertain characteristics like the residual bandwidth and packet error rate,route planning for the randomly generated three classes of business.The simulation results show that,the algorithm not only satisfies the QoS constrain while balancing the traffic load of the satellite link effectively,but also improves the performance on the throughput.     

A novel QoS routing protocol for LEO and MEO satellite networks

The rapid advance of communication and satellite technology pushes broadband satellite networks to carry on multimedia traffic. However, the function of onboard routing cannot be provided in existing satellite networks with inter‐satellite links, and quality of service (QoS) of satellite networks cannot be reliably guaranteed because of great difficulties in processing of long distance‐dependent traffic. In this paper, a two‐layered low‐Earth orbit and medium‐Earth orbit satellite network (LMSN) is presented. A novel hierarchical and distributed QoS routing protocol (HDRP) is investigated, and an adaptive bandwidth‐constrained minimum‐delay path algorithm is developed to calculate routing tables efficiently using the QoS metric information composed of delays and bandwidth. The performance of LMSN and HDRP is also evaluated through simulations and theoretical analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

Performance analysis of path rerouting algorithms for handoffcontrol in mobile ATM networks

This paper studies the effects of user mobility and handoff path rerouting on the traffic distributions in a mobile network environment. In mobile ATM networks, extra traffic load may be added to network links due to user mobility and handoff path rerouting. This requires higher network link capacity and possible topology reengineering in order to support the same quality of service (QoS) for mobile services. To capture the dynamic variations in mobile ATM networks, we propose to use a flow model. The model represents the mobile-generated traffic as a set of stochastic flows over a set of origin-destination (OD) pairs. The user mobility is defined by transfer probabilities of the flows and the handoff path rerouting algorithm is modeled by a transformation between the routing functions for traffic flows. The analysis shows that user mobility may cause temporal variations as well as smoothing effects on the network traffic. Using the flow network model, typical handoff path rerouting algorithms are evaluated through both analytical and experimental approaches. The evaluation methodology can be used for either redesigning the network topology for a given path rerouting algorithm or selecting a path rerouting algorithm for a given network topology under a specific mobile service scenario     

Providing rate guarantees for internet application traffic across ATM networks

The TCP⁄IP protocol suite is the standard requirement for all applications that need to communicate over the Internet. As TCP⁄IP applications are unable to specify the QoS parameters needed for most Asynchronous Transfer Mode (ATM) services, they tend to use the unspecified bit rate (UBR) service category when running across ATM networks. The UBR service utilizes any bandwidth that is left unused by the rest of the ATM services. This has led the ATM Forum's Traffic Management Group to define a new service category called guaranteed frame rate (GFR). GFR is intended to provide minimum cell rate guarantees and fair access to excess bandwidth left over from higher-priority services. This article first presents a tutorial overview of GFR and then presents a survey of the research work that has been carried out toward the design and implementation of associated ATM switch mechanisms.     

Improved priority access, bandwidth allocation and traffic scheduling for DOCSIS cable networks

The Data Over Cable Service Interface Specifications (DOCSIS) is intended to support IP flows over HFC (hybrid fiber/coax) networks with significantly higher data rates than analog modems and Integrated Service Digital Network (ISDN) links for high quality audio, video and interactive services. To support quality-of-service (QoS) for such applications, it is important for HFC networks to provide effective media access and traffic scheduling mechanisms. In this paper, we first present a multilevel priority collision resolution scheme with adaptive contention window adjustment. The proposed collision resolution scheme separates and resolves collisions for different traffic priority classes (such as delay-sensitive and best effort streams), thus achieving the capability for preemptive priorities. Second, a novel MAC (media access control) scheduling mechanism and a new bandwidth allocation scheme are proposed to support multimedia traffic over DOCSIS-compliant cable networks. It is shown through simulation results that throughput and delay performance have been improved for the transmission of real-time VBR (variable bit rate) traffic as compared to current DOCSIS specifications.     

Delay constraint multipath routing for wireless multimedia ad hoc networks

According to the disadvantages of real time and continuity for multimedia services in ad hoc networks, a delay constraint multipath routing protocol for wireless multimedia ad hoc networks, which can satisfy quality of service (QoS) requirement (QoS multipath optimized link state routing [MOLSR]), is proposed. The protocol firstly detects and analyzes the link delay among the nodes and collects the delay information as the routing metric by HELLO message and topology control message. Then, through using the improved multipath Dijkstra algorithm for path selection, the protocol can gain the minimum delay path from the source node to the other nodes. Finally, when the route is launched, several node‐disjoint or link‐disjoint multipaths will be built through the route computation. The simulation and test results show that QoS‐MOLSR is suitable for large and dense networks with heavy traffic. It can improve the real time and reliability for multimedia transmission in wireless multimedia ad hoc networks. The average end‐to‐end delay of QoS‐MOLSR is four times less than the optimized link state routing. Copyright © 2014 John Wiley & Sons, Ltd.     

QoS routing in ad hoc wireless networks

The emergence of nomadic applications have generated much interest in wireless network infrastructures that support real-time communications. We propose a bandwidth routing protocol for quality-of-service (QoS) support in a multihop mobile network. The QoS routing feature is important for a mobile network to interconnect wired networks with QoS support (e.g., ATM, Internet, etc.). The QoS routing protocol can also work in a stand-alone multihop mobile network for real-time applications. This QoS routing protocol contains end-to-end bandwidth calculation and bandwidth allocation. Under such a routing protocol, the source (or the ATM gateway) is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real-time applications. In addition, it enables more efficient call admission control. In the case of ATM interconnection, the bandwidth information can be used to carry out intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit (VC) service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine the system performance in various QoS traffic flows and mobility environments via simulation. Simulation results suggest distinct performance advantages of our protocol that calculates the bandwidth information. It is particularly useful in call admission control. Furthermore, “standby” routing enhances the performance in the mobile environment. Simulation experiments show this improvement     

Controlled use of excess backbone bandwidth for providing new services in IP-over-WDM networks

We study an approach to quality-of-service (QoS) that offers end-users the choice between two service classes defined according to their level of transmission protection. The fully protected (FP) class offers end-users a guarantee of survivability in the case of a single-link failure; all FP traffic is protected using a 1:1 protection scheme at the wavelength-division multiplexing (WDM) layer. The best effort protected (BEP) class is not protected; instead restoration at the IP layer is provided. The FP service class mimics what Internet users receive today. The BEP traffic is designed to run over the large amounts of unused bandwidth that exist in today's Internet. The goal is to increase the load carried on backbone networks without reducing the QoS received by existing customers. To support two such services, we have to solve two problems: the off-line problem of mapping logical links to pairs of disjoint fiber paths, and an on-line scheduling problem for differentiating packets from two classes at the IP layer. We provide an algorithm based on a Tabu Search meta-heuristic to solve the mapping problem, and a simple but efficient scheduler based on weighted fair queueing for service differentiation at the IP layer. We consider numerous requirements that carriers face and illustrate the tradeoffs they induce. We demonstrate that we can successfully increase the total network load by a factor between three and ten and still meet all the carrier requirements.     

Integrated dynamic distributed routing and admission control in ATM networks

A node-by-node admission control and routing scheme for ATM networks is devised. The scheme is based on the subdivision of traffic into a number of classes, characterized by different performance requirements. At each network node, for all outgoing links, link capacity partitions are periodically assigned to the traffic classes, as the result of an optimization problem over a fixed time interval. Local access control rules compute the maximum number of connections of each class that a link can accept within the assigned capacity. Incoming call connection requests are forwarded in a hop-by-hop fashion. Each node traversed, first checks the presence of resources needed to accept a new connection and guarantee all quality of service (QoS) requirements. This is done by using the local access control rule. Then, it chooses the next node along the path on the basis of a distributed routing strategy. This minimizes a cost function accounting for local instantaneous information, as well as for aggregate information that is passed periodically among adjacent nodes. Two routing strategies are introduced. In the first scheme, a new call is rejected if, at a certain node along the path, there are not enough resources to guarantee QoS requirements, and no recovery mechanism is implemented. In the second scheme, an alternative path is looked for after the first failure. Simulation results are presented which show a comparison between the two proposed routing strategies. Comparison is also made between the proposed scheme and the other approaches. © 1997 John Wiley & Sons, Ltd.     

Bandwidth allocation and connection admission control in ATMnetworks

Asynchronous transfer mode (ATM) is the transmission format for almost all future communication networks, including broadband integrated services digital networks (B-ISDN). The key feature of ATM is its high flexibility in bandwidth allocation. Instead of reserving capacity for each connection, the bandwidth is allocated on demand. As a consequence, packets (called cells in ATM terminology) might be lost. To guarantee a given quality of service (QoS), some kind of control is needed to decide whether to accept or to reject an incoming connection. A connection is accepted only if the network has sufficient resources to achieve the QoS required by the user without affecting the QoS of the existing connections. In ATM networks, connection admission control (CAC) is responsible for this decision. It is a very complex function because the traffic may vary greatly and have poorly known characteristics. This paper describes CAC procedures proposed in the literature and discusses issues related to bandwidth allocation in ATM networks. It shows that CAC and statistical multiplexing are only needed for certain connections     

Evaluating the impact of stale link state on quality-of-servicerouting

Quality-of-service (QoS) routing satisfies application performance requirements and optimizes network resource usage by selecting paths based on connection traffic parameters and link load information. However, distributing link state imposes significant bandwidth and processing overhead on the network. This paper investigates the performance tradeoff between protocol overhead and the quality of the routing decisions in the context of the source-directed link state routing protocols proposed for IP and ATM networks. We construct a detailed model of QoS routing that parameterizes the path-selection algorithm, link-cost function, and link state update policy. Through extensive simulation experiments with several network topologies and traffic patterns, we uncover the effects of stale link state information and random fluctuations in traffic load on the routing and setup overheads. We then investigate how inaccuracy of link state information interacts with the size and connectivity of the underlying topology. Finally, we show that tuning the coarseness of the link-cost metric to the inaccuracy of underlying link state information reduces the computational complexity of the path-selection algorithm without significantly degrading performance. This work confirms and extends earlier studies, and offers new insights for designing efficient quality-of-service routing policies in large networks     

Capacity Planning of DiffServ Networks with Best-Effort and Expedited Forwarding Traffic

For networks providing a specific level of service guarantees, capacity planning is an imperative part of network management. Accurate dimensioning is especially important in DiffServ networks, where no per-flow signaling or control exists. In this paper, we address the problem of capacity planning for DiffServ networks with only Expedited Forwarding (EF) and best effort (BE) traffic classes. The problem is formulated as an optimization problem, where the total link cost is minimized, subject to the performance constraints of both EF and BE classes. The edge to edge EF demand pairs and the BE demands on each link are given. The variables to be determined are the non-bifurcated routing of EF traffic, and the discrete link capacities. We show that Lagrangian relaxation and subgradient optimization methods can be used to effectively solve the problem. Computational results show that the solution quality is verifiably good while the running time remains reasonable on practical-sized networks. This represents the first work for capacity planning of multi-class IP networks with non-linear performance constraints and discrete link capacity constraints.     

The extended connection‐dependent threshold model for call‐level performance analysis of multi‐rate loss systems under the bandwidth reservation policy

Firstly, we reviewed two extensions of the Erlang multi‐rate loss model, whereby we can assess the call‐level QoS of telecom networks supporting elastic traffic: (i) the extended Erlang multi‐rate loss model, where random arriving calls of certain bandwidth requirements at call setup can tolerate bandwidth compression while in service; and (ii) the connection‐dependent threshold model, where arriving calls may have several contingency bandwidth requirements, whereas in‐service calls cannot tolerate bandwidth compression. Secondly, we proposed a new model, the extended connection‐dependent threshold model. Calls may have alternative bandwidth requirements at call setup and can tolerate bandwidth compression while in service. We proposed a recurrent formula for the efficient calculation of link occupancy distribution and consequently call blocking probabilities, link utilization, and throughput per service class. Furthermore, in the proposed model, we incorporated the bandwidth reservation policy, whereby we can (i) equalize the call blocking probabilities of different service classes, (ii) guarantee specific QoS per service class, and (iii) implement different maximum bandwidth compression/expansion rate per service class so that the network supports both elastic and stream traffic. The accuracy of the new model is verified by simulation. Moreover, the proposed model performs better than the existing models. Finally, we generalize the proposed model by incorporating service classes with either random or quasi‐random arrivals. Copyright © 2011 John Wiley & Sons, Ltd.     

合理构筑宽带IP网的骨干网

在ＩＰ业务的冲击下对下一代ＩＰ网络方案的讨论如火如荼。本文在对各种方案 本介绍的基础上，对ＩＰｏｖｅｒＡＴＭ和ＩＰｏｖｅｒＳＤＨ两种方案进行了比较。前者在ＱｏＳ、多业务支持及带宽管理方面具有优势２，而后者的带宽利用率较高，且组网简单。前者地传统电信运营商的网络，后者则对所新兴的ＩＰ业务运营商更为有利。