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Author

Hong-Yi Tzeng

Other affiliations: Alcatel-Lucent
Bio: Hong-Yi Tzeng is an academic researcher from University of California, Irvine. The author has contributed to research in topics: Asynchronous Transfer Mode & Network congestion. The author has an hindex of 7, co-authored 9 publications receiving 683 citations. Previous affiliations of Hong-Yi Tzeng include Alcatel-Lucent.

Papers
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Journal ArticleDOI
TL;DR: An algorithmic framework is established that allows for a variety of dynamic SPT algorithms including dynamic versions of the well-known Dijkstra, Bellman-Ford, D'Esopo-Pape algorithms, and to establish proofs of correctness for these algorithms in a unified way.
Abstract: The open shortest path first (OSPF) and IS-IS routing protocols widely used in today's Internet compute a shortest path tree (SPT) from each router to other routers in a routing area Many existing commercial routers recompute an SPT from scratch following changes in the link states of the network Such recomputation of an entire SPT is inefficient and may consume a considerable amount of CPU time Moreover, as there may coexist multiple SPTs in a network with a set of given link states, recomputation from scratch causes frequent unnecessary changes in the topology of an existing SPT and may lead to routing instability We present new dynamic SPT algorithms that make use of the structure of the previously computed SPT Besides efficiency, our algorithm design objective is to achieve routing stability by making minimum changes to the topology of an existing SPT (while maintaining shortest path property) when some link states in the network have changed We establish an algorithmic framework that allows us to characterize a variety of dynamic SPT algorithms including dynamic versions of the well-known Dijkstra, Bellman-Ford, D'Esopo-Pape algorithms, and to establish proofs of correctness for these algorithms in a unified way The theoretical asymptotic complexity of our new dynamic algorithms matches the best known results in the literature

283 citations

Journal ArticleDOI
20 Oct 1994
TL;DR: A rate-based scheme that is now referred to by the ATM Forum as 'intelligent congestion control' and is currently considered as one of the most promising approaches to traffic management of available bit rate (ABR) service is described.
Abstract: The emergence of asynchronous transfer mode (ATM) technology has generated new challenging problems for computer network designers. One of these challenges lies in the efficient management of ATM traffic so that the communication bandwidth of the network can be optimally utilized. Considerable standardization efforts in recent ATM Forum activities have been centered on the traffic management of available bit rate (ABR) service. In this paper, we examine congestion control schemes for ABR service in ATM networks. We describe a rate-based scheme that is now referred to by the ATM Forum as 'intelligent congestion control' and is currently considered as one of the most promising approaches. Moreover, we present analytical and simulation results illustrating the characteristics of the proposed scheme.

199 citations

Patent
25 Aug 1998
TL;DR: In this article, a data structure in a router helps to compute viable next hops for forwarding a data packet from a router to its destination along multiple alternate loop-free paths, which are not necessarily of shortest distance.
Abstract: A novel data structure in a router helps to compute viable next hops for forwarding a data packet from a router to its destination along multiple alternate loop-free paths, which are not necessarily of shortest distance. Each viable next hop may also be specified with a degree of optimality, which enables a route to perform QoS routing and fault-tolerant routing efficiently. The data structure can be implemented as an add-on software to existing routing protocols and may be implemented in existing networks which use shortest path protocols, even where less than all of the routers use the data structure and multiple path scheme described herein.

114 citations

Proceedings ArticleDOI
11 Oct 1999
TL;DR: A novel algorithm that minimizes the amount of information distributed by link-state routing protocols, which will distribute the link- state changes to the minimum number of routers that are needed to ensure loop-free routing upon a link failure.
Abstract: Link-state protocols such as OSPF are the dominant routing technology in today's Internet. Despite their many advantages, these protocols require the flooding of new information across the entire routing area after changes in any link state (e.g., link failures). As the routing area grows or the frequency of link-state changes increases, the overhead (in terms of bandwidth and processing cost) of flooding becomes prohibitive. Furthermore, such flooding over a large area will cause temporary inconsistency of link states among many routers, potentially creating many transient routing loops that can last for a long time. This limits the scalability of the routing protocols to large routing areas. To overcome such problems, we present in this paper a novel algorithm that minimizes the amount of information distributed by link-state routing protocols. Upon a link failure, our algorithm will distribute the link-state changes to the minimum number of routers that are needed to ensure loop-free routing. Moreover, implementing our algorithm requires only a simple extension to any existing link-state protocol.

39 citations

Proceedings ArticleDOI
14 Nov 1995
TL;DR: A unified framework is established to derive a multicast congestion control protocol for ABR service from a given rate-based unicast protocol, and it is shown that the resulting multicast protocol derived using this framework preserves fairness characteristics of the underlyingunicast protocol.
Abstract: In recent ATM Forum activities, considerable efforts have focused on the congestion control of point-to-point available-bit-rate (ABR) service. In this paper, we present a novel approach that extends the existing point-to-point (unicast) congestion control protocol to a point-to-multipoint (multicast) environment. In particular, we establish a unified framework to derive a multicast congestion control protocol for ABR service from a given rate-based unicast protocol. We first generalize a known necessary and sufficient condition on the max-min fairness of unicast rate allocation for multicast service. Then we show that the resulting multicast protocol derived using our framework preserves fairness characteristics of the underlying unicast protocol. The practical significance of our approach is illustrated by extending a standard congestion control mechanism for ABR service to a multicast environment. The performance of the resulting multicast protocol is examined using benchmark network configurations suggested by the traffic management subworking group at the ATM Forum, and simulation results are presented to substantiate our claims.

24 citations


Cited by
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Journal ArticleDOI
TL;DR: LPA* is developed, an incremental version of A* that combines ideas from the artificial intelligence and the algorithms literature and repeatedly finds shortest paths from a given start vertex to a given goal vertex while the edge costs of a graph change or vertices are added or deleted.

584 citations

Patent
02 May 2000
TL;DR: In this paper, a method of determining a geographic location of an Internet user involves determining if the host is on-line, determining ownership of the host name, and then determining the route taken in delivering packets to the user.
Abstract: A method of determining a geographic location of an Internet user involves determining if the host is on-line, determining ownership of the host name, and then determining the route taken in delivering packets to the user. Based on the detected route, the method proceeds with determining the geographic route based on the host locations and then assigning a confidence level to the assigned location. A system collects the geographic information and allows web sites or other entities to request the geographic location of their visitors. The database of geographic locations may be stored in a central location or, alternatively, may be at least partially located at the web site. With this information, web sites can target content, advertising, or route traffic depending upon the geographic locations of their visitors. Through web site requests for geographic information, a central database tracks an Internet user's traffic on the Internet whereby a profile can be generated. In addition to this profile, the central database can store visitor's preferences as to what content should be delivered to an IP address, the available interface, and the network speed associated with that IP address.

449 citations

Journal ArticleDOI
TL;DR: This paper proposes an architecture that significantly reduces this implementation complexity yet still achieves approximately fair bandwidth allocations, called Core-Stateless Fair Queueing, and presents simulations and analysis on the performance.
Abstract: Router mechanisms designed to achieve fair bandwidth allocations, such as Fair Queueing, have many desirable properties for congestion control in the Internet. However, such mechanisms usually need to maintain state, manage buffers, and/or perform packet scheduling on a per-flow basis, and this complexity may prevent them from being cost-effectively implemented and widely deployed. In this paper, we propose an architecture that significantly reduces this implementation complexity yet still achieves approximately fair bandwidth allocations. We apply this approach to an island of routers--that is, a contiguous region of the network--and we distinguish between edge routers and core routers. Edge routers maintain per-flow state; they estimate the incoming rate of each flow and insert a label into each packet based on this estimate. Core routers maintain no per-flow state; they use first-in-first-out packet scheduling augmented by a probabilistic dropping algorithm that uses the packet labels and an estimate of the aggregate traffic at the router. We call the scheme Core-Stateless Fair Queueing. We present simulations and analysis on the performance of this approach.

428 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed receding horizon control (RHC) as a straightforward method for designing feedback controllers that deliver good performance while respecting complex constraints, such as the objective, constraints, prediction method, and horizon.
Abstract: In this article we have shown that receding horizon control offers a straightforward method for designing feedback controllers that deliver good performance while respecting complex constraints. A designer specifies the RHC controller by specifying the objective, constraints, prediction method, and horizon, each of which has a natural choice suggested directly by the application. In more traditional approaches, such as PID control, a designer tunes the controller coefficients, often using trial and error, to handle the objectives and constraints indirectly. In contrast, RHC con trollers can often obtain good performance with little tuning. In addition to the straightforward design process, we have seen that RHC controllers can be implemented in real time at kilohertz sampling rates. These speeds are useful for both real-time implementation of the controller as well as rapid Monte Carlo simulation for design and testing purposes. Thus, receding horizon control can no longer be considered a slow, computationally intensive policy. Indeed, RHC can be applied to a wide range of control problems, including applications involving fast dynamics.

379 citations

Journal ArticleDOI
TL;DR: An incremental version of ISOMAP, one of the key manifold learning algorithms, is described and it is demonstrated that this modified algorithm can maintain an accurate low-dimensional representation of the data in an efficient manner.
Abstract: Understanding the structure of multidimensional patterns, especially in unsupervised cases, is of fundamental importance in data mining, pattern recognition, and machine learning. Several algorithms have been proposed to analyze the structure of high-dimensional data based on the notion of manifold learning. These algorithms have been used to extract the intrinsic characteristics of different types of high-dimensional data by performing nonlinear dimensionality reduction. Most of these algorithms operate in a "batch" mode and cannot be efficiently applied when data are collected sequentially. In this paper, we describe an incremental version of ISOMAP, one of the key manifold learning algorithms. Our experiments on synthetic data as well as real world images demonstrate that our modified algorithm can maintain an accurate low-dimensional representation of the data in an efficient manner.

289 citations