BFRA: bounded flooding routing algorithm for provisioning the globally optimal route in a hierarchical ATM network

Since routers in IP network are connected with ATM virtual path (VP) permanent virtual connection (PVC) and each VP contains bundles of VCs, a VP layer network can serve as a server layer and each IP layer network can be a client layer. Therefore the effective Internet service provisioning completely depends on the reliability of VP server layer network from the perspective of the optimality and the network survivability. This paper proposes the distributed ATM VP PVC restoration framework with the dynamic rerouting schemes in hierarchical transport network. The rerouting algorithm aims to provide rapid ATM VP PVC restoration in the case of fault or performance degradation in terms of maximization of network resource utilization and satisfaction of the end user's QoS requirement. It guarantees the IP network survivability in spite of ATM network faults or performance degradations. In addition, this paper evaluates the rerouting performance for a real network, the High Speed Information Network (HSIN).

The future Internet will support a large variety of services whose QoS requirements may vary widely. In order to provide scalable quality of service traffic aggregation may be necessary. We examine several approaches to providing scalable QoS services which includes soft QoS with relative performance guarantees, and hard performance guarantees signaled by RSVP over an aggregated cell switched core. In these approaches QoS is based on aggregate traffic. The question then arises as to what level of QoS is perceived by individual flows within the aggregate. This has an important implication on QoS guarantees which the network can make to individual users. To provide answers to the above question we analyse per-flow and aggregate QoS in an ATM virtual path (VP) which is used as an example of a cut-through handling IP flows. Using cell loss as a measure of QoS, our analysis allows us to investigate the impact of the parameters of individual flows on per-flow QoS. We then compare per-flow QoS against the QoS experienced by the aggregate flow in the VP. Based on numerical tests we find that cell loss experienced by individual flows may be very different from cell loss experienced by the aggregate flow. Thus if aggregate cell loss is used as a QoS constraint in dimensioning of VP this may lead to unfair treatment of flows and hence to potential user dissatisfaction.

Grid is a distributed infrastructure which allows large scale resources sharing and system integration. Task scheduling in grid becomes more complicated when strategy needs to combine user's QoS with system's computing performance. On the basis of analysing classic Min-min heuristic, an improved task scheduling algorithm using triangle module operator to integrate user's QoS with system's computing performance is proposed. Simulation are conducted on GridSim, and the results strongly demonstrate the proposed algorithm performs better on makespan, resource load balancing and user's QoS utility than BF-Min-min and Min-min which does not consider user's QoS requirements.

The virtual path (VP) concept in ATM networks simplifies network structure, traffic control and resource management. For VP formulation, a VP can carry traffic of the same type (the separate scheme) or of different types (the unified scheme). For VP adjustment, a certain amount of bandwidth can be dynamically assigned (reserved) to VPs, where the amount (the bandwidth incremental/decremental size) is a predetermined system parameter. In this paper, we study least loaded path-based dynamic routing schemes with various residual bandwidth definitions under different bandwidth allocation (VP formulation and adjustment) schemes. In particular, we evaluate the call blocking probability and VP set-up processing load with varying (bandwidth) incremental sizes. Also, we investigate numerically how the use of VP trades the blocking probability with the processing load. It is found that the unified scheme could outperform the separate scheme in certain incremental sizes. Moreover, we propose two ways to reduce the processing load without increasing the blocking probability. Using these methods, the separate scheme always outperforms the unified scheme.

Most studies of resource allocation mechanisms have used a performance model of the resource, where the very concept of the resource is defined in terms of measurable qualities of the service such as utilization, throughput, response time (delay) and so on. Optimization of resource allocation is defined in terms of these measurable qualities. One novelty introduced by the economic approach is to design a system which takes into account the diverse QoS requirements of users, and therefore use multiobjective (utilities)optimization techniques to characterize and compute optimum allocations. Economic modelling of computer and communication resource sharing uses a uniform paradigm described by two level modelling: QoS requirements as inputs into a performance model that is subject to economic optimization. In a first step, one transforms QoS requirements of users to a performance (example: queueing service model).This model establishes quantifiable parameterization of resource allocation. For example, average delay QoS requirement, when based on a FIFO queueing model, is a function of resources, bandwidth and buffer, and user traffic demands. These parameters are then used to establish an economic optimization model. The question of whether the resource is a piece of hardware, a network link, a software resource such as a database or a server, or a virtual network entity such as a TCP connection is not of primary importance. The first modeling transformation eliminates the details and captures the relevant behaviors and the optimization parameters. We consider a decentralized model of network and server economies , where we show efficient QoS provisioning and Pareto allocation of resources (network and server resources) among agents and suppliers, which are either network routes or servers (content providers)

Relay selection is a challenging issue in cooperative communication networks. In particular, in a multi-user multi- concurrent-transmission network, effects of the resource sharing of a relay by its served users on the relay selection strategy need to be taken into account. There is little research on this investigation in literature. In this paper, we propose a novel efficient and fair relay selection strategy, in which individual user's QoS requirement is inherently taken into account. In terms of efficiency, the proposed strategy is of low computational complexity. In terms of fairness, the system resource is utilized fairly among all relaying nodes so that the system has the best potential to accommodate as many users as possible. Simulation results indicate that the proposed selection strategy outperforms many existing ones, therefore justifying our arguments.

Discovery of suitable Web services for a given user requirement is one of the key technology. A mechanism is proposed to support QoS-based semantic web service discovery in the paper. Firstly, to reduce the overhead and enhance the discovery efficiency, genetic algorithm is adopted as a method of service clustering. Furthermore, based on user's QoS requirements, the QoS-based service matchmaker was realized. In the end, simulation results demonstrated the effectiveness of the proposed method.

The transmission of ATM cells through a virtual path (VP) which comprises one or more virtual channel (VCs) multiplexed through a VP is examined. Constant bit rate (CBR) sources are used. During the process, there are ATM cell loss, cell delay, and the performance degradation. This paper proposes the techniques of CDMA, OOCs code and 2/sup n/ prime code for improve the performance and to compare two codes when using an ATM network. The results show that when using the same code length a 2/sup n/ prime sequence code has a greater performance than OOCs code.

We introduce a meshed ring communications network which employs cross‐connect switches. The crossconnect switches can be implemented as wavelength routers resulting in WDM networks, or as ATM Virtual Path (VP) switches leading to ATM compatible network systems. We show in the paper that this network architecture results in a significant increase in throughput performance in comparison with (SDHISONET) ring networks. For a certain class of meshed rings, under a uniform traffic matrix, we derive the optimal topology which achieves maximum throughput efficiency. Using such a topology, we obtain upper and lower bounds on the number of wavelengths required to achieve that efficiency level. The network is divided into (overlapping) communities of nodes. Each community is assigned a wavelength and a subnetwork (identified as a wavelength graph). Each pair of nodes in a community can communicate across the associated wavelength graph. Wavelength graphs (subnets) are constructed to demonstrate the implementation of the routing scheme using the number of wavelengths that is equal to the derived upper bound. For practical implementation reasons, we investigate the performance of networks which employ a reduced number of wavelengths. We show that by modifying the topological layout of the meshed ring network, we can reduce substantially the number of required wavelengths, while incurring just a modest reduction in throughput efficiency.

We study the survivability of a meshed-ring communication network that employs cross-connect switches. For WDM networks, the cross-connect switches are implemented as wavelength routers. Nodes can also provide cross-connection at the ATM VP (virtual path) level. By meshing the ring, the nodal degree of connectivity is increased as compared to a ring topology, and thus more alternative (protection) paths are available. For routing purposes, wavelength subnetworks are embedded in the topology. Nodes communicate with each other across one of the subnetworks to which both belong. We consider two types of subnetwork topologies to simplify the routing in a normal (nonfailure) situation. For each type of subnetwork, different protection methods are proposed to protect against a single link and/or nodal failure. The throughput performance of such meshed-ring networks under failure conditions is clearly superior to that achieved by (SONET) ring networks. We show that certain protection methods even result in lower values of the protection capacity as well as the protection capacity ratio (i.e., the overall capacity used under a failure divided by the total capacity) as compared to ring networks. We also present methods for constructing wavelength subnetworks to achieve single-failure protection using the minimal number of wavelengths.

Reinforcement learning (RL), which is a class of machine learning, provides a framework by which a system can learn from its previous interactions with its environment to efficiently select its actions in the future. RL has been used in a number of application fields, including game playing, robotics and control, networks, and telecommunications, for building autonomous systems that improve themselves with experience. It is commonly accepted that RL is suitable for solving optimization problems related to distributed systems in general and to routing in networks in particular. RL also has reasonable overhead—in terms of control packets, memory and computation—compared to other optimization techniques used to solve the same problems. Since the mid-1990s, over 60 protocols have been proposed, with major or minor contributions in the field of optimal route selection to convey packets in different types of communication networks under various user QoS requirements. This paper provides a comprehensive review of the literature on the topic. The review is structured in a way that shows how network characteristics and requirements were gradually considered over time. Classification criteria are proposed to present and qualitatively compare existing RL-based routing protocols.

In an ATM network, a virtual path (VP) is a labeled path which can be used to transport a bundle of virtual connections (VCs) and to manage the resources used by these connections. The ATM multimedia leased line service is provided across user-to-user VPs. The customers can increase/decrease the VP bandwidth according to their demand. This paper proposes a method to derive the least required bandwidth on a VP which is the minimum amount of bandwidth estimated to satisfy the QoS requirement of the VCs. The least required bandwidth can be a warranty of the VP resource reallocation.

The more complex a network becomes, the more reliable and intelligent a network management system must be to consistently monitor the network and detect abnormal situations in a timely manner as they occur. Expert system techniques have been widely accepted to create network management systems. Despite the fact that there are a number of network management systems, most of them deal only with problems at the lower layers of the network hierarchy (the data link, or the network layer). The nature of problems at the application level significantly differ from those that occur at the lower levels. Lower layer problems are well understood while problems at the application level are complex, application dependent, and distinct from one another. Consequently, a network management system, in particular a fault management system, used at this level should be able to cope with these difficulties and dependencies. We propose a hybrid system which consists of neural network module and a rule based system for monitoring and diagnosing problems occur at the application level. The domain name system (DNS) was selected as a testbed application for the prototype system.

The static network performance and dynamic communication performance of the Hierarchical Torus Network (HTN) using dimension-order routing algorithm have already been evaluated and shown to be superior to the performance of other interconnection networks. However, the assessment of the dynamic communication performance improvement of HTN by the efficient use of both the physical link and virtual channels has not yet been evaluated. This paper addresses three adaptive routing algorithms - link-selection, channel-selection, and a combination of link-selection and channel-selection - for the efficient use of physical links and virtual channels of an HTN to enhance dynamic communication performance. It also proves that the proposed adaptive routing algorithms are deadlock-free with 3 virtual channels. The dynamic communication performances of an HTN is evaluated by using dimension-order routing and proposed adaptive routing algorithms under various traffic patterns. It is found that the dynamic communication performance of an HTN using these adaptive routing is better than when the dimension-order routing is used, in terms of network throughput.

We address the problem of optimal routing in overlay networks. An overlay network is constructed by adding new overlay nodes on top of a legacy network. The overlay nodes are capable of implementing any dynamic routing policy, however, the legacy underlay has a fixed, single path routing scheme and uses a simple work-conserving forwarding policy. Moreover, the underlay routes are pre-determined and unknown to the overlay network. The overlay network can increase the achievable throughput of the underlay by using multiple routes, which consist of direct routes and indirect routes through other overlay nodes. We develop a throughput optimal dynamic routing algorithm for such overlay networks called the Optimal Overlay Routing Policy (OORP). OORP is derived using the classical dual subgradient descent method, and it can be implemented in a distributed manner. We show that the underlay queue-lengths can be used as a substitute for the dual variables. We also propose various schemes to gather the information about the underlay that is required by OORP and compare their performance via extensive simulations.