This paper presents an architecture for restorable call allocation and fast virtual path (VP) restoration in mesh ATM networks. In this architecture, virtual working and spare capacities needed for call allocation and restoration are reserved and released dynamically on a call-by-call basis at the time of call admission and termination. This obviates the need for advance assignment of spare and working capacities. To shorten the call processing delay, this is done in a parallel-distributed fashion. To provide restorable call allocation, parallel-distributed call processing algorithms of sender-chooser type are suggested. The algorithms integrate, on the call level, virtual bandwidth allocation, virtual spare-capacity assignment, and fixed, alternate, or state-dependent routing. Each routing scheme leads to a particular tradeoff between call processing complexity, call setup delay, and bandwidth efficiency. For each pair of nodes, two sets of VPs are provisioned. The first, working VP (WVP) set, is used for call allocation during the normal operation. The second, spare VP (SVP) set, is used for WVP restoration in the event of failures of network elements. Each SVP protects a preassigned subset of the node pair's WVPs. Each SVP is selected to be link/node disjoint from the WVPs that it is assigned to protect. This assures a protection of the WVP set by a small number of SVPs. Since SVPs are preset and appropriate virtual spare capacities are reserved in advance, the architecture guarantees full restorability and provides very fast restoration. The restoration is done on the VP level in a self-healing manner. The suggested architecture requires only local information to be maintained at each node.

We present the architecture for burst level congestion control (BLCC) in ATM networks which is well suited for bursty self-similar traffic. The architecture is based upon pre-planned virtual path (PVP) set and preassigned maximal permitted route rates (MPR). The PVP set and MPR are engineered to meet QoS requirements of multi-service demand. The suggested burst level control maintains the maximal rate of cell admission on any PVP below its MPR. This is done at each PVP's source node by regulating bursts admission and by reserving the burst peak rate for each admitted burst. The reservation can be performed very fast since it is done at PVP's source node without any communication with other nodes. The MPR and PVP set are adjusted in a relatively slow, for instance hourly, timeframe adapting to the changes in the demand. The paper also presents an efficient technique for multiclass QoS engineering of burst admission that can be applied to engineer networks with large number of nodes and service classes.

This paper presents an architecture for restorable call allocation and fast virtual path (VP) restoration in mesh ATM networks. In this architecture, virtual working and spare capacities needed for call allocation and restoration are reserved and released dynamically on a call-by-call basis at the time of call admission and termination. The architecture does not require advance assignment of spare and working capacities. To shorten the call processing delay, this is done in a parallel-distributed fashion. To provide restorable call allocation, parallel-distributed call processing algorithms of the sender-chooser type are suggested. The algorithms integrate on the call level virtual bandwidth allocation, virtual spare capacity assignment with fixed, alternate, or state-dependent routing. Each routing scheme leads to a particular tradeoff between call processing complexity, call setup delay, and bandwidth efficiency. For each pair of nodes, two sets of VPs are provisioned. The first is a working VP (WVP) set, to be used for call allocation during the normal operation. The second is a spare VP (SVP) set, to be used for VP restoration in the event of failure of network elements (NE). Each SVP protects a preassigned subset of the node pair WVPs. Each SVP is selected to be link/node disjoint from the WVPs that it is assigned to protect. This assures protection of the WVP set by a small number of SVPs. Since SVPs are preset and appropriate virtual spare capacities are reserved in advance, the architecture guarantees full restorability and provides very fast restoration. The restoration is done on the VP level in a self-healing manner. The suggested architecture requires only local information to be maintained at each node.

This paper presents a new scheme for real-time bandwidth allocation and path restoration (BARS) in mesh networks via SONET wideband digital cross-connect systems (WDCSs) in response to demand and load dynamics and link and/or node failure(s). The scheme dynamically maximizes bandwidth allocation while ensuring full service restorability. Since the physical network capacity is limited, sometime not all the demand can be accommodated under the full restorability requirement. This demand in SONET BARS is rejected fairly at the network boundary even if capacity for allocation is available. Bandwidth allocation and fair demand admission are optimized jointly under the full restorability requirements. The implementation of SONET WDCS does not need excessive storage. An efficient parallel algorithm for solving the optimization problem is also presented. The algorithm produces superior spare capacity assignments compared to the results in the literature.

The authors briefly overview the basic characteristics of legacy network management systems used in telephone operating companies (telcos) and highlight their deficiencies for the emerging network. They further propose a network management methodology for supporting both the embedded base and the new generation of network technologies and services. The proposed approach differs from earlier network management methodologies in three major ways: it is driven by managing service performance and network robustness, rather than managing network equipment; it is based on a global network model that makes "end-to-end" management possible, in contrast to today's highly segmented management; and its decision support and automated applications are "network-state" dependent as opposed to being solely driven by "raw" network measurements.>

The joint access-control and routing problem for distributed networks is formulated as an equilibrium programming problem (EPP). The strategy, for an upcoming control period, decreases call blocking and balances network load by maximizing network residual capacity, and fairly rejects at the source the source-destination demands that are expected to exceed network capacity. The EPP formulation allows for both decentralized implementation of the joint access control and routing problem and massive parallelization of the optimization procedure to satisfy real-time requirements. The computational complexity of the algorithm decreases proportionally with the number of processors used. The convergence of the decentralized algorithm to the network-wide optimum is proved. Compared to the case where subnet EPPs are solved independently by each controller, simulation results show significantly better utilization of network resources when subnet controllers jointly solve the network-wide EPP. Performance analysis of the algorithm and numerical studies show that the algorithm is well suited for real-time implementation in large networks or internetworks.>

The authors propose a congestion control framework for ATM networks that requires simple protocols and that provides guaranteed grade of service The authors suggest that the network provides two different services: express service and first-class service. Express service is appropriate for real-time applications, whereas first-class service is appropriate for nonreal-time applications. To provide such services, the proposed congestion control scheme prevents congestion inside the network by controlling the congestion at two levels: VC (virtual circuit) level and cell level. The VC-level control takes place during the call setup in the form of (logical) bandwidth reservation for individual VCs. The cell-level control is exercised across the network interface in the form of the choking/relieving of only first-class VC traffic in case of congestion. The authors analyze the performance of the proposed scheme, and show how to engineer various parameters to satisfy cell-level performance requirements (e.g., cell delay and loss).>

The authors describe a data network design model based on a mixed integer/linear programming (MILP) formulation that does not, as do most other approaches, separate link capacity and facility selection from routing and topological design; it fully integrates these processes to capture the important couplings that exist between them. The performance constraints are incorporated into the model in such a way that they are linear, but lead to the same grade of service for a balanced network as nonlinear average network delay constraints. It is shown that this formulation leads to a natural decomposition of the optimal design problem into two subproblems solvable sequentially. In the absence of capacity allocation constraints, the capacity and flow assignment problem is solved optimally and efficiently as part of the overall design process. Moreover, the model leads directly to the solution of multifacility design problems. A fast link reduction algorithm that efficiently designs single or multifacility networks and yields robust local extrema is presented. This algorithm is based on a special-purpose monotonic greedy drop heuristic procedure. An important application of this model is the design of multifacility networks.>

A congestion control framework for ATM (asynchronous transfer mode) networks is proposed. Specifically, it is suggested that the network provide two different services: express service and first-class service. Express service is appropriate for real-time applications (e.g., voice and video) whereas first-class service is appropriate for non-real-time applications (e.g., data). To provide such services, the proposed congestion control scheme prevents congestion inside the network by controlling the congestion at two levels: virtual circuit (VC) level and packet level. Express VC traffic is not subject to any flow control. At each intermediate node, transit packets are simply relayed with no traffic control. Various issues related to this scheme are discussed and its performance analyzed.>

Consideration is given to the optimal circuit routing problem in an existing circuit-switched network. The objective is to find circuit routing which accommodates a given circuit demand while maximizing the residual capacity of the network. In addition, the cost of accommodating the circuit demand should not exceed a given amount. Practical considerations require that a solution be robust to the variations in circuit demand and cost. The objective function for the optimal circuit routing problem is not a smooth one. In order to overcome the difficulties of nonsmooth optimization, the objective function is approximated by smooth concave functions. The optimization algorithm for the circuit routing problem is obtained as a limiting case of the sequence of optimal routing strategies for the corresponding smooth convex optimization problems, and the proof of its convergence to the optimal solution is given. An approach to calculating the optimal multicommodity flow is presented. The optimization algorithm efficiently handles networks with a large number of commodities, satisfies the robustness requirements, and can be used to solve circuit routing problems for large networks.>

A network optimization model (NOM) that provides a tool for performance analysis and optimal design of a broad class of routing strategies is presented. It can evaluate and optimize both static and dynamic, local and global routing strategies. The tool is applicable to both packet-switched and circuit-switched networks. NOM software is based on original modeling methods and optimization algorithms. It is user-friendly and menu-driven, and has extensive 'what if' capabilities. NOM can be used for performance evaluation of existing routing strategy and for optimal routing design for a given performance criterion. As a performance evaluation tool, for a given network topology, link and node capacities, point-to-point demand matrix, and routing strategy, NOM models the routing and computes important characteristics of network performance. As a routing optimization tool, for a given network topology, link and node capacities, point-to-point demand matrix, and performance criterion, NOM generates the optimal routing, and computes important characteristics of network performance. The current Telenet local dynamic routing strategy is compared with a set of optimal routing strategies designed for various performance criteria.>