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.

In this paper, we address the problems of constructing both source-based and core-based many-to-many multicast trees for applications with delay and/or delay jitter constraints. We use the source-destination delay bound and the interdestination delay fitter bound as the QoS requirement and formulate the delay and delay jitter constrained many-to-many multicast tree (D/sup 2/M/sup 3/T) problems. For the source-based, many-to-many multicast paradigm, we extend an existing scheme that builds a one-to-many, QoS-compliant multicast tree and devise a solution scheme that first finds a feasible multicast tree for each source node in the multicast group and then a minimum cover of these multicast trees such that there exists at least one feasible multicast tree in the minimum cover for each source node. For the core-based, many-to-many multicast paradigm, we first derive a necessary and sufficient condition for a core-based multicast tree to be feasible and then devise a solution scheme based on the condition derived. We validate and evaluate both proposed schemes via simulations.

In this paper, we devise a preallocation-based single-hop wavelength division multiple access (WDMA) scheme to support temporal quality of service (QoS) in star-coupled optical networks, We consider a star-coupled broadcast-and-select network architecture in which N stations are connected to a star coupler with W different wavelength channels. Each of the W wavelength channels is slotted and shared by the !V stations by means of time division multiplexing. Depending on the tunability characteristics (tunable or fixed tuned) of the transmitters/receivers, we classify the network architecture as tunable transmitter/fixed tuned receiver (TT-FR), fixed tuned transmitter/tunable receiver (FT-TR), and tunable transmitter/tunable receiver (TT-TR). We first characterize each real-time message stream M/sub i/, with two parameters, the relative message deadline D/sub i/ and the maximum (total) message size C/sub i/ that can arrive within any time interval of length D/sub i/. We then discuss a restricted case in a TT-FR (or FT-TR) system in which the message streams from a source station are assumed to be all destined for the same destination station. Under this assumption, no source destination conflicts may occur. We propose a preallocation-based slot assignment scheme to preallocate slots to a set of isochronous message streams, (M/sub i/=(C/sub i/, D/sub i/)|1/spl les/i/spl les/n) in such a way that, in any time window of size D/sub i/ slots, at least C/sub i/ slots on a wavelength channel are allocated to M/sub i/ for all i. With the solution derived in the restricted case as a basis, we then consider slot assignment in a (general) TT-TR system and propose a binary splitting scheme to assign each message stream sufficient and well-spaced slots to fulfil its temporal requirement, subject to the source/destination conflict constraints. We rigorously prove the invariance properties, and the correctness, of the binary splitting scheme.

A novel iterative algorithm is proposed to compute the theoretical minimum initiation interval of a given recurrent algorithm when there is a known, fixed inter-module communication delay. Specifically, for a twin-module implementation problem, a novel representation called necessary initiation interval is introduced to facilitate the development of an iterative algorithm which yields both the minimum initiation interval and the corresponding cut set of the cyclic iterative computational dependence graph (ICDG). The convergence of this iterative algorithm in finite iterations is also proved.

In this paper, we propose a packet eligible time calculation mechanism and its associated information update method to provide temporal QoS to multicast services, in terms of delay bound coupled with inter-message delay jitter bound and/or bounded inter-destination delay jitter bound. We assume the availability of a multicast tree on which the delay between a source and any destination falls within the end-to-end delay bound. We then exploit the idea of artificially delaying transmission of data packets until their eligible times, and model each router as a regulator followed by a packet scheduler. A data packet is not eligible to be scheduled until the current time is greater than or equal to its eligible time. For each temporal QoS required, we derive the appropriate packet eligible times. We also devise an information update method to collect/update in a decentralized manner the parameters needed in the calculation of packet eligible times. With all the parameters available, an intermediate router can calculate packet eligible times and the upper bound on the buffers needed in order to fulfill the QoS. Finally, we validate the proposed mechanism in terms of the probability of locating feasible-multicast trees and message overheads, and scalability with event-driven simulations.

In this paper, we develop efficient admission control tests for member join/leave and its associated state refresh and update procedures for receiver-initiated core-based multicast routing, e.g., core based tree (CBT) protocol, to allow construction of QoS-capable multicast trees, while making the minimum possible impact on the existing infrastructure. Specifically, we (i) derive sufficient conditions for a multicast tree to maintain its QoS; (ii) devise effective admission tests to verify whether or not a group member may join the multicast tree at adequate QoS, while not violating existing QoS guarantees to other on-tree members; and (iii) identify the minimum set of state information required for the admission tests and develop a soft state refresh and update procedure. Finally, we validate the effectiveness of the proposed mechanism by incorporating it into the CBT protocol, and evaluate it via event-driven simulations in terms of the probability of join requests being rejected, message overhead, and scalability.

We develop and evaluate a set of member join/leave and state update/refresh procedures for QoS provisioning in core-based multicast routing with explicit member join and soft state refresh procedures. Specifically, in our prior work (Hung-Ying Tyan et al., 1999), we devised eligibility tests to verify whether or not a new member can join a multicast tree at adequate QoS while not violating the existing QoS guarantees to other on-tree members. We extend our prior work, identify the tradeoff between the amount of state kept at each on-tree router and the degree of collaboration among on-tree routers to conduct the tests, and develop two member join/leave procedures that range from using the most comprehensive state update procedure (and hence the least degree of collaboration among on-tree routers) to the other extreme. Also, we evaluate the proposed framework, in terms of the probability of locating feasible multicast trees, message overheads, and scalability.

The problem of scheduling real-time periodic task has been studied extensively since its first introduction by C.L. Liu and J.W. Layland in their classic paper (1973). Due to several merits of the fixed-priority scheduling scheme, a lot of research work has focused on the analysis of fixed-priority scheduling algorithms. For the case that the deadlines of the executions of all the tasks coincide with the ends of their corresponding periods. Liu and Layland derived a worst-case utilization bound for a task set to be schedulable by the rate-monotonic (RM) algorithm. A. Burchard et al. (1995) presented another schedulability condition for RM, which has a higher utilization bound under a certain task condition. Although their closed-form utilization bounds provide a convenient way for testing the schedulability of a task set under the RM algorithm, the schedulability test using their bounds is too pessimistic since a lot of task sets with total utilizations larger than their bounds (and less than or equal to 1) are still schedulable by RM. In this paper, we propose a polynomial-time schedulability test and prove that it is better than Liu and Layland's and Burchard's utilization bounds in the sense that as long as the total utilization of a task set is less than or equal to their bounds, our schedulability test will always answer positively for the schedulability of the task set under RM and even if a feasible task set has a total utilization larger than their bounds, our schedulability test will still answer positively with a high probability. We also show how to generalize our polynomial-time schedulability test to handle general task sets scheduled by arbitrary fixed-priority scheduling algorithms.

We devise a preallocation based single hop wavelength division multiple access (WDMA) scheme to support time constrained communication in star coupled optical networks. We consider a star coupled broadcast and select network architecture in which N stations are connected to a star coupler with W different wavelength channels. Each of the W wavelength channels is slotted and shared by the N stations by means of time division multiplexing. Networks with different transceiver configurations, i.e., TT-FR, FT-TR, and TT-TR systems, are investigated. We characterize each real time message stream M, with two parameters, relative message deadline D/sub i/ and maximum (total) message size C/sub i/ that can arrive within any time interval of length D/sub i/. We then discuss a restricted case in a TT-FR system in which the message streams from a source station are assumed to be all going to the same destination station. Under this assumption, no source/destination conflicts may occur. We propose a preallocation based slot assignment scheme to allocate slots to a set of isochronous message streams, {M/sub i/=(C/sub i/, D/sub i/))|1/spl les/i/spl les/n}, so that in any time window of size D/sub i/ slots, at least C/sub i/ slots on a wavelength channel are allocated to M/sub i/ for all i. With the solution derived in the restricted case as a basis, we then consider slot assignment in a (general) TT-TR system, and propose a binary splitting scheme to assign each message stream sufficient and well spaced slots to fulfill its timing requirement, subject to source/destination conflict constraints. We rigorously prove the invariant properties and the correctness of the binary splitting scheme.