16198597
Effective delay control for high rate heterogeneous real-time flows
This paper presents a new method to control the delay performance for high rate heterogeneous real-time traffic flows based on a novel traffic control algorithm which is a generalization of traditional (/spl sigma/, /spl rho/) regulator. Our new control algorithm operates like the traditional regulator under the normal loading situation, but provides more regulation for the high rate (heavy load condition) of the traffic. For a set of heterogenous real-time traffic flows R we can show that D/sub r/(R) /spl les/ D(R) where D/sub r/(R) and D(R) are the worst-case delay bounds with our new control algorithm and that with (/spl sigma/, /spl rho/) regulator respectively. More specifically, we develop a set of formula that can be used to set the parameters in our new traffic controller so that the worst case delay bound is minimized by streaming the traffic flow. We can prove that there exists a minimum (average) input rate p* such that D/sub r/(R) = D(R) for /spl rho/ /spl les/ /spl rho/* and D/sub r/(R) < D(R) for /spl rho/ > /spl rho/*. Using the extended regulator can effectively control the delay when the average heterogeneous traffic rate is high. The issues are particularly useful for Integrated Services where a flow may over claim its share of resource and for Differentiated Services where a class of traffic flows may possess very high rates.
35665703
Implementation of QoS-Provisioning system for voice over IP
In this paper, we address issues related to implementing Voice-over-IP (VoIP) services in packet switching networks. VoIP has been identified as a critical real-time application in the network QoS research community and has been implemented in commercial products. To provide competent quality of service for VoIP, the call admission control (CAC) mechanism has to be introduced to prevent packet losing and over-queuing. Several well-designed CAC mechanisms, such as the Site- Utilization-Based CAC and the link-utilization-based CAC mechanisms, are in place. However, the existing commercial VoIP systems have not been able to adequately apply and support these CAC mechanisms, and hence unable to provide QoS guarantees to VoIP. We have designed and implemented a QoS-Provisioning system that can be seamlessly integrated to the existing VoIP system to overcome its weakness in offering QoS guarantees. As a result, our system has been realized at Internet2 Voice Over IP Testbed in Texas A&M University.
14103668
Static priority scheduling for ATM networks
Static priority scheduling is popular for traffic scheduling in ATM switches because it is less costly than dynamic priority scheduling while being sensitive to the delay constraints of connections. We study delay computation and priority assignment problems in an ATM network with static priority scheduling. Given an ATM network with arbitrary topology, it is possible that the traffic on it may become unstable (i.e., packet delays become unbounded) due to the potential cyclic dependency of the traffic. An unstable network is definitely unacceptable for many delay sensitive applications. We start by formally deriving a simple condition under which the network is guaranteed to be stable. We then develop a numerical method to compute worst case end to end delays in an ATM network with arbitrary topology. Convergence of the method is formally proved and a closed form for the computing error is obtained. Despite its advantages, static priority scheduling remains sensitive to proper priority assignment. We describe two simple priority assignment methods, which we show to outperform other commonly used methods.
16063472
On the confidential auditing of distributed computing systems
We propose a confidential logging and auditing service for distributed information systems. We propose a cluster-based TTP (trusted third party) architecture for the event log auditing services, so that no single TTP node can have the full knowledge of the logs, and thus no single node can misuse the log information without being detected. On the basis of a relaxed form of secure distributed computing paradigms, one can implement confidential auditing service so that the auditor can retrieve certain aggregated system information, e.g. the number of transactions, the total volume, the event traces, etc., without having to access the full log data. Similar to the peer relationship of routers to provide global network routing services, the mutually supported, mutually monitored cluster TTP architecture allows independent systems to collaborate in network-wide auditing without compromising their private information.
3254470
Providing absolute differentiated services with statistical guarantees in static-priority scheduling networks
The authors propose and analyze a methodology for providing absolute differentiated services with statistical performance guarantees for real time applications in networks that use static priority schedulers. We extend previous work on delay analysis and develop a method that can be used to derive statistical delay guarantees in a flow-unaware fashion. While traditional delay analysis methods depend on flow population information, we have developed a method that relies on network (re-)configuration time analysis, and that allows us to analyze the delays without depending on the dynamic status of flow population. With this new method, we are able to reduce the runtime admission control to a simple utilization test. No explicit delay computation is necessary at admission time, making this approach scalable to large systems.
11547845
Local synchronous capacity allocation schemes for guaranteeing message deadlines with the timed token protocol
The problem of guaranteeing synchronous message deadlines in communication networks using the timed token medium access control protocol is studied. To ensure the transmission of synchronous messages before their deadlines, synchronous capacities must be properly allocated to individual nodes. A class of local synchronous capacity allocation schemes, which allocate the synchronous capacity to a node without using information about messages on the other nodes, is developed, analyzed, and evaluated in terms of the ability of the schemes to guarantee message deadlines. It is shown that one of the local allocation schemes proposed can achieve the same performance as that of the best global allocation scheme known to date.<<ETX>>
205343629
A network flow approach to the Minimum Common Integer Partition Problem
In the k-Minimum Common Integer Partition Problem, abbreviated as k-MCIE we are given k multisets X1,...,Xk of positive integers, the goal is to find an integer multiset T of the minimum size such that for every i, we can partition each of the integers in Xi so that the disjoint (multiset) union of their partitions equals T. This problem has applications in computational molecular biology, in particular, ortholog assignment and DNA hybridization fingerprint assembly. The problem is known to be NP-hard for any k ≥ 2. In this article, we improve the approximation ratio for k-MCIP by viewing this problem as a flow decomposition problem in some flow network. We show an efficient 0.5625k-approximation algorithm, improving upon the previously best known 0.6139k-approximation algorithm for this problem.
446110
Controlling the mobility of multiple data transport ferries in a delay-tolerant network
As technology rapidly progresses, more devices will combine both communication and mobility capabilities. With mobility in devices, we envision a new class of proactive networks that are able to adapt themselves, via physical movement, to meet the needs of applications. To fully realize these opportunities, effective control of device mobility and the interaction between devices is needed. In this paper, we consider the message ferrying (MF) scheme which exploits controlled mobility to transport data in delay-tolerant networks, where end-to-end paths may not exist between nodes. In the MF scheme, a set of special mobile nodes called message ferries are responsible for carrying data for nodes in the network. We study the use of multiple ferries in such networks, which may be necessary to address performance and robustness concerns. We focus on the design of ferry routes. With the possibilities of interaction between ferries, the route design problem is challenging. We present algorithms to calculate routes such that the traffic demand is met and the data delivery delay is minimized. We evaluate these algorithms under a variety of network conditions via simulations. Our goal is to guide the design of MF systems and understand the tradeoff between the incurred cost of multiple ferries and the improved performance. We show that the performance scales well with the number of ferries in terms of throughput, delay and resource requirements in both ferries and nodes.
2955672
Grammatically Interpreting Feature Compositions
Abstract : Feature modeling is a popular domain analysis method for describing the commonality and variability among the domain products. The current formalisms of feature modeling do not have enough support for automated domain product configuration and validation. We have developed a theory of feature modeling: a feature model is analogous to a definition of a language; a particular feature composition instance (domain product) is analogous to a program written in that language; and the way the features can be assembled to form a product is analogous to the way various tokens can be assembled to form a program. To apply this theory, we have developed a meta-language Two-Level Grammar++ to specify feature models. The interpreter derived from the feature model specification performs automated product configuration and product quality validation.
9212782
A reservation-based coordination protocol for Web services
Traditional transaction semantics are not appropriate for business activities that involve long-running transactions in a loosely-coupled distributed environment, in particular, for Web services that operate between different enterprises over the Internet. In this paper we describe a novel reservation-based extended transaction protocol that can be used to coordinate such business activities. The protocol avoids the use of compensating transactions, which can result in undesirable effects. In our protocol, each task within a business activity is executed as two steps. The first step involves an explicit reservation of resources. The second step involves the confirmation or cancellation of the reservation. Each step is executed as a separate traditional short-running transaction. We show how our protocol can be implemented as a reservation protocol on top of the Web services transaction specification or, alternatively, as a coordination protocol on top of the Web services coordination specification.
47079351
A language based formalism for domain driven development
The evolution of programming languages (e.g. machine languages, assembly languages and high level languages) has been the driving force for the evolution of software development from the machine-centric to the application-centric. The 4th generation languages (4GLs), languages defined directly by the composition of domain features, serve as the language-based formalism for the emerging Domain Driven Development paradigm. The 4GLs are defined in Two-Level Grammar++ and can be compiled into 3GLs using the 4GL compiler framework.