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Networking, IEEE/ACM Transactions on

Issue 1 • Date Feb 1993

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Displaying Results 1 - 12 of 12
  • Communication architectures and algorithms for media mixing in multimedia conferences

    Page(s): 20 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    The problem of media mixing that arises in teleconferencing applications such as teleorchestra is addressed. The mixing algorithm presented minimizes the difference between generation times of the media packets that are being mixed together in the absence of globally synchronized clocks, but in the presence of jitter in communication delays on packet switched networks. In order to support applications, such as teleorchestra, that involve a large number of participants, hierarchical mixing architectures are proposed, and it is shown that they are an order of magnitude more scalable than purely centralized or distributed architectures. Furthermore, mechanisms for minimizing the delays incurred by mixing in various communication architectures are presented. The mixing algorithms are implemented on a network of workstations connected by Ethernets, and the performance of various mixing architectures is experimentally evaluated. The results reveal the maximum number of participants that can be supported in a conference View full abstract»

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  • SCOQ: a fast packet switch with shared concentration and output queueing

    Page(s): 142 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    A space-division, nonblocking packet switch with data concentration and output buffering is proposed. The performance of the switch is evaluated with respect to packet loss probability, the first and second moments of the equilibrium queue length and waiting time, throughput, and buffer overflow probability. Numerical results indicate that the switch exhibits very good delay-throughput performance over a wide range of input traffic. The switch compares favorably with some previously proposed switches in terms of fewer basic building elements used to attain the same degree of output buffering View full abstract»

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  • On the generation of minimal-length conformance tests for communication protocols

    Page(s): 116 - 129
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    A technique for generating a test sequence for conformance testing of communication protocols is presented. This approach shows that it is possible to generate optimal-length test sequences which include multiple unique input/output (UIO) sequences and overlapping under certain conditions. In the absence of the above-mentioned conditions, a heuristic technique is used to obtain suboptimal solutions which show significant improvement over optimal solutions without overlapping. The technique is illustrated by the example of the NBS Class 4 Transport Protocol (TP4). The computational complexity of the algorithm is compared with that of previous techniques. A brief discussion of bounds on test sequence length is presented, and the results are compared with these bounds View full abstract»

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  • A simple scheme for slot reuse without latency for a dual bus configuration

    Page(s): 96 - 104
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    A simple scheme for slot reuse without latency for the dual bus configuration is studied. The scheme relies on information read in the previous slot and will be referred to as previous slot information (PSI) slot reuse. The scheme requires a minimal addition to the station hardware and its reliability is high. The efficiency of PSI is checked over a wide range of parameters and is found to be almost as good as destination release. The scheme can be implemented with or without the addition of erasure nodes View full abstract»

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  • A protocol for route establishment and packet forwarding across multidomain internets

    Page(s): 56 - 70
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    Internetworks that are global in scale, contain multiple administrative domains, and support a range of services present special requirements for routing. Multiple administrative domains introduce the need for policy-sensitive routing. Service heterogeneity intensifies the requirement for type of service (TOS) routing, as well as other protocol support for handling a range of services, from datagrams to multimedia streams. Key concepts and protocols developed as part of the interdomain policy routing (IDPR) architecture are summarized. Emphasis is placed on the route installation and packet forwarding mechanisms because they are critical to protocol performance and differ significantly from current practice in datagram wide area networks View full abstract»

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  • A language-based approach to protocol implementation

    Page(s): 4 - 19
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    Morpheus is a special-purpose programming language that facilitates the efficient implementation of communication protocols. Protocols are divided into three categories, called shapes, so that they can inherit code and data structures based on their category. The programmer implements a particular protocol by refining the inherited structure. Morpheus optimization techniques reduce per-layer overhead on time-critical operations to a few assembler instructions even though the protocol stack is not determined until run time. This supports divide-and-conquer simplification of the programming task by minimizing the penalty for decomposing complex protocols into combinations of simpler protocols View full abstract»

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  • Fault detection with multiple observers

    Page(s): 48 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    There is a pressing need for network management systems capable of handling faults. The use of a set of independent observers to detect faults in communication systems that are modeled by finite-state machines is proposed. An algorithm for constructing these observers and a fast real-time fault detection mechanism used by each observer are given. Since these observers run in parallel and independently, one immediate benefit is that of graceful degradation-one failed observer will not cause collapse of the fault management system. In addition, each observer has a simpler structure than the original system and can be operated at higher speed. This approach has the potential to be incorporated into the fault management system for a high-speed communication system View full abstract»

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  • Loop-free routing using diffusing computations

    Page(s): 130 - 141
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    A family of distributed algorithms for the dynamic computation of the shortest paths in a computer network or internet is presented, validated, and analyzed. According to these algorithms, each node maintains a vector with its distance to every other node. Update messages from a node are sent only to its neighbors; each such message contains a distance vector of one or more entries, and each entry specifies the length of the selected path to a network destination, as well as an indication of whether the entry constitutes an update, a query, or a reply to a previous query. The new algorithms treat the problem of distributed shortest-path routing as one of diffusing computations, which was first proposed by Dijkstra and Scholten (1980). They improve on a number of algorithms introduced previously. The new algorithms are shown to converge in finite time after an arbitrary sequence of link cost or topological changes, to be loop-free at every instant, and to outperform all other loop-free routing algorithms previously proposed from the standpoint of the combined temporal, message, and storage complexities View full abstract»

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  • Computing approximate blocking probabilities for large loss networks with state-dependent routing

    Page(s): 105 - 115
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    A reduced load approximation (also referred to as an Erlang fixed point approximation) for estimating point-to-point blocking probabilities in loss networks (e.g., circuit switched networks) with state-dependent routing is considered. In this approximation scheme, the idle capacity distribution for each link in the network is approximated, assuming that these distributions are independent from link to link. This leads to a set of nonlinear fixed-point equations which can be solved by repeated substitutions. The accuracy and the computational requirements of the approximation procedure for a particular routing scheme, namely least loaded routing, is examined. Numerical results for six-node and 36-node asymmetric networks are given. A novel reduced load approximation for multirate networks with state-dependent routing is also presented View full abstract»

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  • Analysis of the link error monitoring protocols in the common channel signaling network

    Page(s): 31 - 47
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    Motivated by the excessive link status changes observed in some field operations of the common channel signaling (CCS) network, the authors provide a detailed analysis of the signaling link error monitoring algorithms in the Signaling System No. 7 (SS7) protocol. These algorithms determine when to fail a link due to excessive error rates and when to put a failed link back into service. The analysis shows that, under current SS7 specifications of the error monitoring algorithms, the probability of a signaling link oscillating in and out of service could be high, depending on the traffic load, signal unit size, and the statistical nature of errors (bursty or random). The link oscillation phenomenon could become worse as longer Transaction Capability Application Part (TCAP) messages for transaction-based services (e.g., 800 Service) are carried in the CCS networks. While the risk to the existing network may not be high due to the light loads carried at present, there is still a need to study the error monitoring issues thoroughly View full abstract»

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  • Ballot theorems applied to the transient analysis of nD/D/1 queues

    Page(s): 81 - 95
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    The problem of transporting constant-bit-rate (CBR) traffic through a packet network is analyzed. In the system considered, CBR traffic is packetized and packets from several similar sources are multiplexed on a transmission link. The bit streams are recreated at the receiving end by demultiplexing the packets and then playing out the packets of each CBR stream. Traffic fluctuations may cause gaps to appear in the playout process. Their frequency can be reduced by adding a smoothing delay to each stream. The queueing system analyzed has periodic arrivals and deterministic service times. A method of analysis, based on the ballot theorems of Takacs (1967), is presented to provide steady-state delay distributions as well as a transient analysis of the system to predict the statistics of the time for a gap to develop in the CBR stream as a function of the smoothing delay View full abstract»

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  • Joint source/channel coding of statistically multiplexed real-time services on packet networks

    Page(s): 71 - 80
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    The interaction of congestion control with the partitioning of source information into components of varying importance for variable-bit-rate packet voice and packet video is investigated. High-priority transport for the more important signal components results in substantially increased objective service quality. Using a Markov chain voice source model with simple PCM speech encoding and a priority queue, simulation results show a signal-to-noise ratio improvement of 45 dB with two priorities over an unprioritized system. Performance is sensitive to the fraction of traffic placed in each priority, and the optimal partition depends on network loss conditions. When this partition is optimized dynamically, quality degrades gracefully over a wide range of load values. Results with DCT encoded speech and video samples show similar behavior. Variations are investigated such as further partition of low-priority information into multiple priorities. A simulation with delay added to represent other network nodes shows general insensitivity to delay of network feedback information. A comparison is made between dropping packets on buffer overflow and timeout based on service requirements View full abstract»

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Aims & Scope

The IEEE/ACM Transactions on Networking’s high-level objective is to publish high-quality, original research results derived from theoretical or experimental exploration of the area of communication/computer networking.

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Meet Our Editors

Editor-in-Chief
R. Srikant
Dept. of Electrical & Computer Engineering
Univ. of Illinois at Urbana-Champaign