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Computer Communications and Networks, 1998. Proceedings. 7th International Conference on

Date 15-15 Oct. 1998

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Displaying Results 1 - 25 of 122
  • Author index

    Page(s): 926 - 929
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    Freely Available from IEEE
  • Proceedings 7th International Conference on Computer Communications and Networks (Cat. No.98EX226)

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    Freely Available from IEEE
  • Jitter reduction in CBR HDTV transport stream packet communications over lossy ATM network

    Page(s): 12 - 19
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    For the reduction of the jitter originated from the cell losses in an ATM network when CBR traffic is transferred on AAL5, we propose that the receiver maintain a timer whose expiration time is proportional to the cell time of the source traffic plus the standard deviation of the 1-point CDV of the received ATM cells. Moreover to enhance the granularity of the error or loss detection mechanism in the AAL5 PDUs, we also modified the AAL5 PDU trailer fields so that each cell comprising the AAL5 PDU has a sequence number field. The simulation results show that the peak-to-peak PDV of the AAL5 PDU by the proposed method is less than 69.4% to that by AAL5. Moreover, the AAL5 user-HDTV decoder-receives the same or more error-free transport packets in the proposed algorithm than those in the ITU-T AAL5 for the same network simulation environment View full abstract»

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  • Wireless LAN: study of hidden-terminal effect and multimedia support

    Page(s): 422 - 431
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    Wireless local area networks (WLAN) are expected to be a major growth factor for communication networks in the up-coming years. They are expected to provide a transparent connection for mobile hosts to communicate with other mobile hosts, and wired hosts on the wired LAN and broadband networks. Two WLAN projects have undergone the standardization process: the IEEE 802.11 and the ETSI HIPERLAN. Most of the existing study of the two MAC protocols focused on simulation results, and none of them has formally analyzed the hidden-terminal effect, which is both crucial and unavoidable in wireless/mobile environment. We formally analyze the hidden-terminal effect on HIPERLAN. Through mathematical analysis, we formulate network throughput under hidden-terminal influence in terms of the original (clear-channel) throughput, hidden-terminal probability, and other protocol parameters. We show that when hidden probability is greater than zero, the achievable throughput is reduced by more than the percentage of hidden probability. We evaluate and compare the two WLAN MAC protocols by simulation of the effect of hidden terminals on (1) network throughput, (2) real-time voice delay, and (3) number of voice and data stations supported while guaranteeing delay for voice. We also evaluate how well the two MAC protocols support real-time traffic while considering the effects of frame size and other network parameters, and measure (1) the distribution of voice delay and (2) number of voice and data stations supported while guaranteeing their quality of service. We found that, compared with IEEE 802.11, HIPERLAN provides real-time packet voice traffic with shorter delay, and at the same time provides the non-real-time packet data with a higher bandwidth View full abstract»

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  • Bandwidth allocation in ATM networks: heuristic approach

    Page(s): 20 - 25
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    In this paper, we present a heuristic approach to analyze a boundary of network bandwidth allocated to the source(s). This approach can be applied for call admission control (CAC) in ATM networks. Our approach applies two characteristic functions, a time ε-quantile function to characterize the source behavior and a function to characterize a maximum amount of network bandwidth served by the multiplexer. These two functions are computed independently and when used simultaneously, it allows us to obtain a new and useful notion of the statistical bandwidth allocation. Moreover, we demonstrate the use of our approach on stochastic and deterministic sources. For the deterministic source, we apply our approach to the source characterized by dual leaky bucket-based traffic descriptor. Its upper bound on bandwidth requirement can be easily obtained for performing a CAC function in real time while providing a significant improvement of network utilization when compared to the peak rate-based bandwidth allocation View full abstract»

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  • A study on a management interface for VP protection switching

    Page(s): 539 - 546
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    With advances in various ATM network services, the ATM network is expected to grow larger and larger. An ATM VP (virtual path) protection switching system and management system will be required to ensure high reliability of this large ATM network. Models of management interfaces are being studied based on a TMN (telecommunications management network). These interfaces are called managed objects. For example, there are some ITU-T recommendations for simple protection switching models such as various kinds of equipment and SDH paths. Although these models are well implemented, study has started on the VP protection model and associated scheme. This paper first lists requirements specific to this VP protection from the management point of view. It also explains why existing standard models do not meet the requirements. Our proposed new model not only solves these problems but is also easy to implement, based on our experience of ATM-network management prototype systems View full abstract»

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  • Efficient distributed channel allocation for mobile cellular networks

    Page(s): 50 - 57
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    There are two approaches to design a distributed channel allocation algorithms: search and update. The update approach has shorter acquisition delay and lower call blocking rate, but higher message complexity. On the other hand, the search approach has lower message complexity, but longer acquisition delay and higher call blocking rate. In this paper we first propose a novel distributed acquisition algorithm, which has similar message complexity as the search approach and similar acquisition delay as the update approach. Then, we present a channel selection algorithm and integrate it into our distributed acquisition algorithm. By a rigorous analysis in terms of delay and message complexity, we show that our channel acquisition algorithm performs significantly better than the update approach (Dong and Lai 1997) and the search approach (Prakash et al. 1995). Detailed simulation experiments are carried out in order to evaluate our proposed methodology. The performance of our algorithm is compared with those of the geometric strategy (Baiocchi et al. 1995), the search approach, and the update approach. Simulation results show that our algorithm outperforms all other approaches in terms of call blocking probability under uniform as well as non-uniform traffic View full abstract»

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  • Analysis of nonuniform traffic in a switching network

    Page(s): 668 - 672
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    This paper evaluates the performance of a switching network using nonuniform traffic models. The switching network is presented using the Benes (1965) topology and buffered switch elements. The nonuniform traffic refers to a traffic model with unevenly distributed routing and different intensity at certain output port destinations. The performance of the buffered network is analyzed applying nonuniform traffic in the form of hot-spot and community-of-interest. An analytical queueing model is developed for performance evaluation. Results of the performance evaluation on the network throughput and delay are presented View full abstract»

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  • Design issues of an efficient distributed database scheduler for telecom

    Page(s): 897 - 904
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    We optimize the speed of real-time databases by optimizing the scheduler. The performance of a database is directly linked to the environment it operates in, and we use environment characteristics as guidelines for the optimization. A typical telecom environment is investigated, and characteristics that are relevant to performance are derived. A theoretical study of database scheduler performance is combined with the characteristics of the telecom environment. Design issues are extracted from this combination. It turns out that the scheduler overhead, rather than the concurrency is the most important factor in database performance. With the derived issues in mind, a light-weight optimistic concurrency control (OCC-light) scheduler has been designed. The OCC-light is implemented in the Mnesia database. Experiments were conducted to compare OCC-light against the existing two phase locking (2PL) scheduler. The OCC-light compared favorably to 2PL, as was already suggested by our theoretical study View full abstract»

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  • All-optical multi-layer switching architectures: (I) M×N-gon prism switches

    Page(s): 502 - 511
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    All-optical multi-layer switching architectures are analysed by means of the average distance, the maximum distance and the diameter of their intersection graphs (IGs) and by the grid size of a 3-D network of directional couplers (DCs). The basic multi-layer switch, called the M×N-gon prism switch (M-1 prisms are embedded), is improved by increasing the connectivity between the prisms towards a complexity-O(1)-switch View full abstract»

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  • Design and analysis of queue control functions for explicit rate switch schemes

    Page(s): 780 - 786
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    The ABR rate allocation schemes can achieve high link utilizations by maintaining non-zero (small) queues in the steady state, and draining queues when the sources do not have data to send. The queue length (and queuing delays) can be controlled if part of the available bandwidth is used for draining queues in the event of queue build up. A simple threshold function can allocate such bandwidth to drain queues. Better control of the queues, and hence delay, can be achieved using more sophisticated queue control functions. We study the design and analysis of several such queue control functions: the step, linear, hyperbolic and inverse hyperbolic functions. Analytical explanation and simulation results consistent with analysis are presented. From the study, we conclude that the inverse hyperbolic is the best queue control function. To reduce complexity, the linear function can be used since it performs satisfactorily in most cases View full abstract»

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  • Comparison of two swap heuristics with a genetic algorithm for the design of an ATM network

    Page(s): 833 - 837
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    The challenge of a network topology design is to provide a configuration with minimum cost given specified constraints. Network topology design is NP-hard and known. Algorithms to solve these problems run in time that increases exponentially with the number of choices. The economic importance of determining the placement of switches in an ATM network justifies heuristic methods to find a good configuration within a reasonable amount of time. In this paper, two types of heuristic algorithms are compared. The first algorithm is based on swapping used switch locations with unused switch locations. The second algorithm is a genetic algorithm View full abstract»

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  • Characterize the minimum required resources for admission control of pre-recorded VBR video transmission by an O(n log n) algorithm

    Page(s): 674 - 681
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    Given a pre-recorded VBR video, we have proposed an O(n) algorithm to smooth the transmission schedule with the minimum required resources. N is the number of video frames. As n is usually very large and varying for different videos, it is not suitable for online computation. To facilitate resource management and admission control for QoS (quality-of-service) guarantees, we need to explore the relations among the required resources. Thus, whenever a new request is presented, the admission control procedure can easily check the required resources against the available resources and decides to admit this new request or not. To compute these relations (such as rate-buffer and rate-delay), a native algorithm takes O(n3) time complexity. An O(n log n) algorithm is proposed to characterize the low-bounds of resources allocated for transmitting a pre-recorded VBR video. Having these pre-computed functions, the admission control procedure is as simple as a chart look-up with O(1) time complexity to allocate the required resources View full abstract»

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  • A parallel-tree switch architecture for ATM networks

    Page(s): 654 - 659
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    We present a novel ATM switch called parallel-tree Banyan switch fabric (PTBSF) that consists of parallel Banyans arranged in a tree topology. Packets enter at the topmost Banyan. Internal conflicts are eliminated by using a conflict free 3×4 switching element which distributes conflicting cells over different Banyans. Thus, cell loss may occur only at the lowest Banyan. Increasing the number of Banyans leads to noticeable decrease in the cell loss rate. The switch can be engineered to provide arbitrarily high throughput and low cell loss rate without the use of input buffering nor cell pre-processing. The performance of the switch is evaluated analytically under uniform traffic load and by simulation under a variety of ATM traffic loads. Compared to other proposed architectures, the switch exhibited stable and excellent performance with respect to cell loss and switching delay for all studied conditions as required by ATM traffic sources. The advantages of PTBF are modularity, regularity, self-routing, low processing over head, high throughput and robustness under a variety of ATM traffic conditions View full abstract»

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  • Performance of multihop communications using logical topologies on optical torus networks

    Page(s): 494 - 501
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    We consider multihop communications on optical torus networks with time-division multiplexing where logical topologies are realized on top of the physical network to improve the communication performance. The logical topologies reduce the number of intermediate hops at the cost of a larger multiplexing degree. On the one hand, the larger multiplexing degree increases the packet communication time between hops. On the other hand, reducing the number of intermediate hops reduces the time spent at intermediate hops. We study the trade-off between the multiplexing degree and the number of intermediate hops. Specifically, we study four logical topologies ranging from the most dense logical all-to-all connections to the simplest logical torus topology on top of physical torus networks. We develop an analytical model that models the maximum throughput and the average packet delay of the multihop networks, verify the model through simulations, and study the performance and the impact of system parameters on the performance for these four topologies View full abstract»

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  • Improving the PIM routing protocol with adaptive switching mechanism between its two sparse sub-modes

    Page(s): 768 - 773
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    We present an extension of the classical PIM (protocol independent multicast) routing protocol, named PIM SWITCH, that allows PIM to dynamically switch between its shared tree sub-mode and shortest-path tree sub-mode. This extension enables PIM to better adapt to the changing networking environment. PIM SWITCH has been extensively, evaluated using our software tool MCS (multicast simulation) reported in a previous paper. Our simulation results reveal that PIM SWITCH performs well as expected with minimum overhead View full abstract»

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  • Comparative study of scalable batching policies in disk-array-based deterministic video-on-demand servers

    Page(s): 682 - 689
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    Presented is a comparative study of various batching policies in deterministic video-on-demand (DVoD) servers under realistic conditions including customers' behavior storage organization, and time variations in request arrival rates. DVoD servers provide video playback without any interaction support and customers' QoS is simply expressed in terms of average waiting time to receive service and defection rate caused by long waits. We focus on disk-array-based DVoD servers, whose movie selection and channel capacity are determined by cost and the underlying striping scheme. We analyze the well-known lack of scalability of on-demand batching, and introduce a methodology to measure scalability. We then compare various scalable batching policies and show that even the simplest batching policy may vastly improve on-demand channel allocation. Finally we study the feasibility of different storage organizations in which disks are partitioned into several clusters to reduce service disruptions during their reconfiguration. We also show that high service availability and scalable batching can be achieved in a cost-effective way View full abstract»

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  • A flexible architecture for multihop optical networks

    Page(s): 472 - 478
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    It is desirable to have low diameter logical topologies for multihop lightwave networks. Researchers have investigated regular topologies for such networks. Only a few of these (e.g., GEMNET) are scalable to allow the addition of new nodes to an existing network. Adding new nodes to such networks requires a major change in routing scheme. For example, in a multistar implementation a large number of retuning of transmitters and receivers anti/or renumbering nodes are needed for GEMNET. We present a scalable logical topology which is not regular but it has a low diameter. This topology is interesting since it allows the network to be expanded indefinitely and new nodes can be added with a relatively small change to the network. We present the new topology, an algorithm to add nodes to the network and two routing schemes View full abstract»

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  • Scheduling input-queued ATM switches with QoS features

    Page(s): 107 - 112
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    The input-queued switching architecture is becoming the alternative architecture for high speed switches owing to its scalability. Tremendous amount of effort has been made to overcome the throughput problem caused by head of line blocking and the contentions occurred at input and output sides of a switch. Existing algorithms only aim at improving throughput but inadvertently ignore undesired effects on the traffic shape and quality of service features such as delay and fairness. In this paper a new algorithm, referred to as longest normalized queue first, is introduced to improve upon existing algorithms in terms of delay, fairness and burstiness. The proposed algorithm is proven to be stable for all admissible traffic patterns. Simulation results confirm that the algorithm can smooth the traffic shape, and provide good delay property as well as fair service View full abstract»

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  • Label switching and IP version 6

    Page(s): 561 - 565
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    This paper discusses how the strict hierarchical address structure of IP version 6 and high levels of IP route aggregation will effect the operation of popular label switching techniques. We predict that the introduction of IP version 6 will cause significant problems with control driven label switching proposals such as MPLS and Tag Switching. We propose an alternate label switching solution that uses information in the IP version 6 address structure to classify and cut-through flows based on destination site address. Our simulation studies shown that over 96% of packets will be switched by ATM bypassing network layer forwarding using this technique View full abstract»

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  • Phase assignment algorithm based on traffic measurement for periodic VBR sources in ATM networks

    Page(s): 178 - 182
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    This paper proposes a novel phase assignment algorithm “silent wave algorithm (SWA)” for periodic VBR traffic in ATM networks. Our algorithm decides when a new periodic VBR connection should begin to transmit based on its notification parameters and traffic measurement of going connections. Simulation results showed that it is difficult to accommodate pseudo periodic VBR traffic effectively without any phase allocation but the SWA can provide better QOS and improve the network utilization View full abstract»

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  • Distinguishing congestion losses from wireless transmission losses: a negative result

    Page(s): 722 - 731
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    The TCP is a popular transport protocol used in the present-day Internet. When packet losses occur the TCP assumes that the packet losses are due to congestion, and responds by reducing its congestion window. When a TCP connection traverses a wireless link, a significant fraction of packet losses may occur due to transmission errors. The TCP responds to such losses also by reducing the congestion window. This results in unnecessary degradation in the TCP performance. We define a class of functions named loss predictors which may be used by a TCP sender to guess the actual cause of a packet loss (congestion or transmission error) and take appropriate actions. These loss predictors use simple statistics on round-trip times and/or throughput, to determine the cause of a packet loss. We investigate their ability to determine the cause of a packet loss. Unfortunately, our simulation measurements suggest that the three loss predictors do not perform too well View full abstract»

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  • A dynamic approach for efficient TCP buffer allocation

    Page(s): 817 - 824
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    The paper proposes local and global optimization schemes for efficient TCP buffer allocation in an HTTP server. The proposed local optimization scheme dynamically adjusts the TCP send-buffer size to the connection and server characteristics. The global optimization scheme divides a certain amount of buffer space among all active TCP connections. These schemes are of increasing importance due to the large scale of TCP connection characteristics. The schemes are compared to the static allocation policy employed by a typical HTTP server and shown to achieve considerable improvement to server performance and better utilization of its resources. The schemes require only minor code changes and only at the server View full abstract»

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  • Efficient scheduling algorithms for real-time service on WDM optical networks

    Page(s): 486 - 493
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    We study the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages in WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their time constraints View full abstract»

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  • Traffic load balancing in low Earth orbit satellite networks

    Page(s): 191 - 195
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    One of the unique traffic features of low Earth orbit (LEO) satellite networks is the time-variant and nonuniform load distribution. This feature results in a locally biased congestion problem for the LEO satellite systems. We propose a traffic load balancing scheme to resolve the congestion problem in such traffic scenarios. The proposing scheme makes use of near-neighbor residual bandwidth information to apportion excess bandwidth from congested satellites to their underloaded neighbors in the network. Each traffic load balancing process is performed on the domain basis. When the residual bandwidth of the path by way of the target satellite is less than a prespecified amount, calls routed over the path can be migrated to the alternative paths of the same balancing domain. By decreasing the size of the network graph being considered in load balancing process, balancing domains reduce the complexity of the process View full abstract»

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