SONET/SDH is historically the dominant telecom transport infrastructure for backbone networks, and it is optimized for reliable delivery of voice and private-line services. Efficient utilization of the existing infrastructure through novel methods and algorithms can lead to higher revenue, which is attractive for network operators. In this study, we examine a network of inter-connected SONET/SDH rings that use dual-node interconnection employing the drop-and-continue facility, which is the de-facto standard for interworking SONET/SDH protection architectures. We develop an efficient algorithm for provisioning in such a network while keeping fragmentation of capacity low and taking into account the various constraints imposed by the underlying physical layer. We examine the case of dual-node-interconnected ring networks employing both contiguous and virtual concatenation (a next-generation SONET/SDH architecture), and as expected, we discover that provisioning higher-bandwidth connections with virtual concatenation offers significant improvement. The stringent time-slot alignment and contiguity constraints imposed by contiguous concatenation are further compounded by the constraints imposed by the ring interworking architecture, and virtual concatenation allows capacity to be used more efficiently.

Optical Burst Transport network is a novel WDM ring architecture for Metropolitan Area Networks (MAN). It leverages the advantages of optical burst switching and WDM rings, while using a token-based medium access scheme. In this paper, we investigate protection together with spatial reuse property. Specifically we show how protection in OBT can be different from conventional protection and propose three algorithms for implementing a fast and low implementation cost, unidirectional 1:1 protection scheme. We analyzed the performance of these schemes via simulation and found an optimum algorithm for minimizing data loss and maximizing data delivery during the fault.

This paper investigates the effectiveness of data gathering protocols for in-body biomedical sensor networks. We studied the performance of representatives from each of three major protocol categories: (1) low energy adaptive clustering hierarchy (LEACH), a cluster-based protocol, (2) power efficient gathering for sensory information systems (PEGASIS), a chain-based protocol, and (3) hybrid indirect transmissions (HIT), a hybrid of chains and clusters. First, the ability of each protocol to perform in-network source separation was judged. We consider a human-machine interaction application in which implanted bio-sensors communicate motor unit actions of human muscles to a remote computer. Motor unit action potentials (MUAPs) were modeled, and source separation and recovery at each sensor was simulated. We compare the performance of HIT and LEACH in terms of signal distortion ratios and the energy costs of fusion and communication. Second, we report on the efficiency of each protocol for in-body data collection, using Gupta et al's propagation loss model for biomedical applications (PMBA) - an accurate model of power loss due to signal absorption by the human body. We investigate the effectiveness of HIT, LEACH, and PEGASIS under this model, and compare their performance in terms of energy efficiency and network lifetime

One major challenge in sensor networks is to maximize network life under the constraint of extremely limited power supply. Thus, an important design issue of routing and data-gathering protocols is minimizing energy. This paper investigates the energy efficiency of two data gathering protocols, based on distributed versions of Shortest Path Tree (SPT) and Maximum Leaf Tree (MLT) algorithms [1]. The two have been extended to be dynamic by applying localized tree-reconstruction mechanism [2] to handle joining and leaving (death) of sensor nodes. Accurate energy consumption has been carefully modeled for both leaf-nodes and intermediate nodes, when sending and receiving data. Performance is evaluated through detailed simulation, including exchange of control messages among sensor nodes. Simulation results have shown that SPT, due to its simplicity and smaller number of control messages, achieves better energy efficiency and less delay in tree constructions, data transmissions, and dynamic tree reconstructions.

Internet traffic analysis and prediction is important for network operators to prepare for future demand. The traditional approach of curve-fitting on historical data becomes less effective as technologies advance at a fast pace. To address the problem, a simulation framework is developed with flexibility and modularity in mind so that simulations can be quickly constructed for new applications and scenarios. We show how to use the framework to simulate Web traffic demand over the Internet. Our approach provides important new insights on traffic properties as the effects of different parameters on traffic demand are explored. We verify the simulation models and parameters using current Internet traffic measures and demonstrate the use of the models to predict future Web traffic demand.

Failure protection and restoration is gaining significance as high capacity optical networks become increasingly ubiquitous. An important design issue that faces the network operator, lies in utilizing the wavelength sharing potential presented by non-concurrent failure events. In this study we propose a novel link metric and a set of routing algorithms that aim to maximally exploit these sharing opportunities. With the introduction of the light-weight aggregated link metrics termed "buckets", we provide guidance to construct the protection routes with minimal wavelength consumption. We show by simulations that our scheme significantly improves upon the baseline mechanism that lacks the proposed intelligence. We also extend the solution to a generic node-based approach, and show that further performance gain can be achieved by improving upon the way one applies our algorithms.

As the Internet grows into a commercial infrastructure, more and more network services require routers to classify packets based on one or more fields in the header in order to provide QoS differentiation. The biggest challenge for packet classification is to keep the classification time and storage requirements small. We design a fast 2-dimensional packet classification algorithm with small memory requirement. The algorithm draws on computational geometry techniques-segment tree and fractional cascading to achieve logarithmic classification time. For a database of N filters, the proposed algorithm can complete a classification in O(logN) time and the memory requirement is in the order of O(NlogN).

We consider problems in traffic integration and routing for virtual path (VP)-based multiservice networks. The objective is to exploit statistical multiplexing among various traffic types in order to improve system utilization. Difficulties arise due to statistical multiplexing since a connection's bandwidth requirement depends on the characteristics of the interfering traffic. We first consider whether segregating heterogeneous traffic with different quality of service (QoS) requirements on separate VPs is desirable. Next we consider routing heterogeneous permanent connections given a predefined traffic type mix onto multiple VPs between a source destination pair. We show that it is not necessarily advantageous to have each VP carry every traffic type. In fact, perhaps surprisingly, an optimum solution to this problem suggests that only a small number of traffic types, or even homogeneous traffic, need be present on each VP. Based on this observation, we propose a simple alternative routing algorithm with routing sequences depending on the traffic mix.

We propose a novel explicit rate flow control algorithm intended for available-bit-rate (ABR) service on an ATM network subject to loss and fairness constraints. The goal is to guarantee low cell loss in order to avoid throughput collapse due to retransmission by higher level protocols. The mechanism draws on measuring the current queue length and bandwidth availability, as well as tracking the current number of active sessions contending for capacity, to adjust an explicit bound on the source transmission rates. We identify the factors that affect queue overflows and propose simple design rules aimed at achieving transmission with controlled loss in a dynamic environment. We also discuss how conservative design rules might be relaxed by accounting for statistical multiplexing in bandwidth sharing among bursty ABR sources and variable-bit-rate (VBR) sources.

ATM-based integrated services networks are likely to rely on the virtual path (VP) concept as an intermediate resource management layer wherein key decisions concerning resource allocation, sharing, and flow aggregation are made. In this paper we consider the impact that statistically multiplexing heterogeneous services on VP connections will have on network design and management. Based on simple models we consider several questions including the following: given two traffic types with different quality of service requirements, should one segregate such flows on their own VPs, or is it to the network's advantage to multiplex the flows on a single VP guaranteeing the most stringent QoS requirement? Assuming two VPs have been set up between a given origin-destination pair and heterogeneous flows are to be carried, how should one route the connections to achieve good performance?.

In this paper we upper-bound the overflow probability of superpositions of off-line, e.g., stored video and real-time traffic streams based on deterministic traffic descriptors, e.g., leaky buckets. In the off-line scenario, we compute the empirical envelope function of the cumulative arrivals of a given traffic stream and use this envelope to bound the overflow probability for multiplexing N such streams at a single node. In the real-time scenario, we assume the traffic is policed by a dual leaky bucket and use the parameters of the device to give an upper bound for overflow probability without referring to the traffic statistics.