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IEEE conference on Open Architectures and network Programming

作者： T. Moors Aflliated with Defence Science Technology Organisation Australia

The paper proposes a functional architecture for protocol systems, as opposed to the conventional temporally layered one. Each block of information to be communicated is operated on by several organs, e.g. for routing, integrity and flow control. The architecture retains a skeleton protocol stack to determine the sequence of these operations. However, unlike conventional stacks, the operators themselves are separate from the layers of the stack. This functional architecture eliminates several shortcomings that plague layered systems. The architecture provides a path along which current systems can evolve to provide the performance and economy that will be required in the future.

关键词： Protocols Timing Object oriented modeling Communication system software Australia Routing Skeleton Operating systems Software systems internet

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A distributed multicast routing algorithm for delay-sensitive applications

A distributed multicast routing algorithm for delay-sensitiv...

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International conference on Parallel and Distributed systems (ICPADS)

作者： Yonjun Im Yanghee Choi Department of Computer Engineering Seoul National University Seoul South Korea

ISBN: (纸本)0818686030

We present a distributed multicast algorithm for constructing minimum cost multicast trees with delay constraints. The proposed algorithm, which provides multicasting and guaranteed end-to-end delay bound at the network layer, is also designed to find a reduced cost routing tree. The proposed algorithm requires limited network state information and the routing tree is computed through a single round of message exchanges between network nodes. We prove the algorithm's correctness by showing that it is always capable of constructing a delay constrained multicast tree, if one exists. The algorithm is verified by simulation, and it is shown that it exhibits superior performance compared to existing ones for the tree cost measure.

关键词： Routing Multicast algorithms Delay Costs Multicast protocols Resource management Web and internet services Application software Computer networks Communication system control

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Experimental TCP performance evaluation in an ABR access environment

Experimental TCP performance evaluation in an ABR access env...

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IEEE conference and Exhibition on Global Telecommunications (GLOBECOM)

作者： J. Nelissen A. Hendrikse Alcatel Bell Antwerp Belgium

The available bit rate (ABR) service category has a great potential in avoiding congestion in data communication networks. The ABR relies on a closed loop flow control mechanism, attempting to push buffer requirements towards the boundaries of the ABR aware network regions, be-it to the ATM end-systems in an ATM end-to-end environment or to the edge routers in a router based environment. On the other hand, internet traffic is most often flow controlled at layer 4 by means of the transmission control protocol (TCP). Consequently it is of great importance to investigate the potential of the ABR in carrying TCP traffic efficiently. Most work reported in the literature is based on simulation studies. As interesting these simulation studies are, they can never capture all the real-world effects. The availability of an ABR ATM multiplexer and ABR network interface cards (NIC) gave us the unique opportunity to acquire hands-on experience in dimensioning an ABR system for internet traffic. This paper studies the performance and buffer requirements of TCP traffic multiplexed with priority VBR background traffic in an ABR queue. We applied several modes of ABR responsiveness by changing the ABR connection parameters. We optimised the ABR node parameters, varied the amount of TCP sources and changed the VBR traffic profile. The outcome of this study is a set of guidelines for dimensioning an ABR access configuration for the efficient transport of internet TCP traffic.

关键词： Traffic control Asynchronous transfer mode Telecommunication traffic internet Communication system traffic control Bit rate Data communication Communication system control Protocols Availability

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performance of a distributed DCA algorithm under inhomogeneous traffic modelled from an operational GSM network

Performance of a distributed DCA algorithm under inhomogeneo...

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IEEE conference on Vehicular Technology (VTC)

作者： K. Kennedy E. de Vries P. Koorevaar KPN-Research Netherlands

This paper presents results obtained from two different dynamic channel allocation (DCA) algorithms, namely the timid and persistent polite aggressive (PPA) algorithms, simulated under both static homogeneous and dynamic inhomogeneous traffic. The dynamic inhomogeneous traffic is modelled upon real data collected from 49 cell sites in the PTT Telecom GSM network in Amsterdam. This paper shows that the DCA algorithms always outperform the FCA algorithm for low to medium traffic, with the gain increasing as the traffic becomes more inhomogeneous.

关键词： Traffic control Telecommunication traffic Channel allocation GSM Microcell networks Frequency Centralized control Land mobile radio cellular systems Electronic mail Web and internet services

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Exploring the performance impact of QoS support in TCP/IP protocol stacks

Exploring the performance impact of QoS support in TCP/IP pr...

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IEEE Annual Joint conference: INFOCOM, IEEE Computer and Communications Societies

作者： R. Engel D. Kandlur A. Mehra D. Saha J. Watson Research Center IBM Thomas J. Watson Research Center Yorktown Heights NY USA

This paper explores the performance impact of supporting QoS guarantees on communication in TCP/IP protocol stacks at Unix-like end hosts. We first demonstrate the efficacy of our RSVP-based QoS architecture in providing the desired QoS to individual connections via application-level experiments using UDP sessions and TCP connections on an ATM network. We then identify and measure, via detailed profiling, the overheads imposed by the individual components of the QoS architecture, such as traffic policing, traffic shaping, and buffer management. Our measurements reveal that traffic policing overheads are largely offset by savings due to per-session buffer pre-allocation, and, for ATM networks, a faster path through the network interface layer. In the latter case the data path latency for compliant packets can even be slightly smaller than the default best-effort data path latency. Traffic shaping presents more challenges, primarily because of interactions with the operating system CPU scheduler. We discuss the performance implications of traffic shaping and suggest techniques to reduce or mask some of the associated overheads.

关键词： TCPIP Protocols Telecommunication traffic Operating systems Web and internet services Intserv networks Delay Communication system traffic control Traffic control Multimedia systems

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A distributed computing environment for signal processing and systems health monitoring

A distributed computing environment for signal processing an...

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conference on Digital Avionics systems (DASC)

作者： L.C. Freudinger M.J. Miller K. Kiefer NASA Dryden Flight Research Center Edwards CA USA Creare Inc. Hanover NH USA Invocon Inc. Conroe TX USA

The evolution of systems health monitoring and signal processing is toward online automated techniques that improve performance, cost effectiveness, and safety associated with operating modern machines. The evolution of computing is toward distributed networks of dissimilar applications communicating through standard interfaces and tools. This papers gives an overview of a scaleable collaborative computing environment that routes real-time and non-real-time data via transaction control protocol/internet protocol (TCP/IP). A primary enabling technology is an object-oriented, Java/sup TM/-based, software data server and data management tool. A network composed of one or more of these data servers provides storage, data stream parsing and merging, and compatibility among similar and dissimilar applications running anywhere on the network. Connectivity to mobile platforms is accomplished through a wireless spread spectrum approach. Applications to flight research and aviation safety are discussed.

关键词： Distributed computing Signal processing Application software Protocols network servers Web server Computerized monitoring Condition monitoring Costs Health and safety

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Active reliable multicast

Active reliable multicast

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IEEE Annual Joint conference: INFOCOM, IEEE Computer and Communications Societies

作者： L.H. Lehman S.J. Garland D.L. Tennenhouse MIT Laboratory for Computer Science USA

This paper presents a novel loss recovery scheme, active reliable multicast (ARM), for large scale reliable multicast. ARM is "active" in that routers in the multicast tree play an active role in loss recovery. Additionally, ARM utilizes soft-state storage within the network to improve performance and scalability. In the upstream direction, routers suppress duplicate NACKs from multiple receivers to control the implosion problem. By suppressing duplicate NACKs, ARM also lessens the traffic that propagates back through the network, In the downstream direction, routers limit the delivery of repair packets to receivers experiencing loss, thereby reducing network bandwidth consumption. Finally, to reduce wide-area recovery latency and to distribute the retransmission load, routers cache multicast data on a "best effort" basis. ARM is flexible and robust in that it does not require all nodes to be active, nor does it require any specific router or receiver to perform loss recovery. Analysis and simulation results show that ARM yields significant benefits even when less than half the routers within the multicast tree can perform ARM processing.

关键词： Robustness Communication system traffic control Bandwidth Delay Large-scale systems Algorithm design and analysis internet performance loss Feedback Laboratories

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performance analysis of multi-code spread slotted ALOHA (MCSSA) system

Conference Record / IEEE Global Telecommunications Conferenc...

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conference Record / IEEE Global Telecommunications conference 1998年 3卷 1839-1847页

作者： Dastangoo, Siamak Vojcic, Branimir R. Daigle, John N. Bell Lab North Andover United States

In this paper, we present an analytical framework to investigate the dynamics of a medium access control (MAC) protocol which is governed by two distinct disturbing elements. The first element concerns the users' random selection from a finite number of resources (i.e., channels or spread spectrum (SS) codes). The second element is the simultaneous transmission of users' packets if the resources happen to be SS codes. These elements are realized through two stages of packet acquisition (Stage-I) and packet transmission (Stage-ii). Therefore, a successful transmission depends not only upon the success in Stage-I, but also success in Stage-ii. Simply stated, MCSSA combines two existing MAC protocols: multichannel ALOHA and CDMA. An earlier attempt to properly study this protocol in [5] was unsuccessful. The model developed in our paper is based on a finite-state discrete time Markov chain and a combinatorial approach. A key feature in our model is a recursive expression for the probability of successful channel or code acquisitions given so many simultaneous attempts by the users. Our analytical model is properly constructed and adequately parameterized to reduce to the special cases: slotted ALOHA, multichannel slotted ALOHA, and CDMA. To assess the performance of the MCSSA protocol, we evaluate two commonly used performance metrics: average packet delay and throughput. Preliminary results indicate that, depending on different loading regions (e.g., high offered load level), the MCSSA protocol surpasses that of its CDMA counterpart. This behavior is attributed to the controllability feature of Stage-I which performs similar to a traffic smoother in queueing systems.

关键词： network protocols

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internetwork traffic management enhancements: evaluation and experimental results

Internetwork traffic management enhancements: evaluation and...

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MILCOM, Military Communications conference

作者： J. Macker V. Park Information Technology Division Naval Research Laboratory Inc. Washington D.C. DC USA

There has been an increasing reliance on internetworking technology for military communication networks. As more diverse and mission critical applications begin to coexist within this shared infrastructure the need for improved network traffic and bandwidth management becomes apparent. Previous developments within the research community and within commercial products provide numerous candidate technologies that may be applied as solutions. This paper explores a set of such techniques while evaluating their relative merits and performance tradeoffs. A subset of empirical results from an actual testbed environment is also provided and discussed.

关键词： internet Telecommunication traffic Traffic control Wide area networks Military communication Bandwidth Resource management Mission critical systems Costs Protection

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Explicit window adaptation: a method to enhance TCP performance

Explicit window adaptation: a method to enhance TCP performa...

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IEEE Annual Joint conference: INFOCOM, IEEE Computer and Communications Societies

作者： L. Kalampoukas A. Varma K.K. Ramakrishnan Bell Laboratories Lucent Technologies Inc. Holmdel NJ USA Computer Engineering Department University of California Santa Cruz CA USA AT and T Research Laboratories Florham Park NJ USA

We study the performance of the TCP in an internetwork consisting of both rate-controlled and non-rate-controlled segments. A common example of such an environment occurs when the end systems are part of IP datagram networks interconnected by a rate-controlled segment, such as an ATM network using the ABR service. In the absence of congestive losses in either segment, the TCP keeps increasing its window to its maximum size. Mismatch between the TCP window and the bandwidth-delay product of the network will result in an accumulation of large queues and possibly buffer overflows in the devices at the edges of the rate-controlled segment, causing degraded throughput and unfairness. We develop an explicit feedback scheme, called explicit window adaptation based on modifying the receiver's advertised window in the TCP acknowledgments returning to the source. The window size indicated to the TCP is a function of the free buffer in the edge device. Results from simulations with a wide range of traffic scenarios show that this explicit window adaptation scheme can control the buffer occupancy efficiently at the edge device, and results in significant improvements in packet loss rate, fairness, and throughput over a packet discard policy such as drop-from-front or random early detection.

关键词： TCPIP Asynchronous transfer mode internet Throughput Degradation Traffic control Buffer overflow Feedback Propagation losses Protocols

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