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Distribution by Scientific Domains

Engineering	100%

Selected Abstracts

A study on a receiver-based management scheme of access link resources for QoS-controllable TCP connections

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2006
Kazuhiro Azuma
Abstract Although the bandwidth of access networks is rapidly increasing with the latest techniques such as DSL and FTTH, the access link bandwidth remains a bottleneck, especially when users activate multiple network applications simultaneously. Furthermore, since the throughput of a standard TCP connection is dependent on various network parameters, including round-trip time and packet loss ratio, the access link bandwidth is not shared among the network applications according to the user's demands. In this thesis, we present a new management scheme of access link resources for effective utilization of the access link bandwidth and control of the TCP connection's throughput. Our proposed scheme adjusts the total amount of the receive socket buffer assigned to TCP connections to avoid congestion at the access network, and assigns it to each TCP connection according to characteristics in consideration of QoS. The control objectives of our scheme are (1) to protect short-lived TCP connections from the bandwidth occupation by long-lived TCP connections, and (2) to differentiate the throughput of the long-lived TCP connections according to the upper-layer application's demands. One of the results obtained from the simulation experiments is that our proposed scheme can reduce the delay of short-lived document transfer perceived by the receiver host by up to about 90%, while a high utilization of access link bandwidth is maintained. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Network dimensioning at the call level for the always-on network

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 9 2004
Soracha Nananukul
Abstract It is becoming common for the network to provide always-on access services, where subscribers are guaranteed that their call requests will never be blocked. This paper studies the call-level link dimensioning for the always-on network with single-class traffic. The call-level QoS requirement is expressed in terms of the probability of a poor-quality call, which is the probability that a call experiences packet-level QoS violation at any time during its duration, as opposed to the probability of blocking in the network with call admission control (CAC). The system is modelled as the M/M/infinite system with finite population and an analytic expression for the probability of a poor-quality call is derived based on performability analysis. The effects of the call-level traffic characteristics on the required link resources are studied. It is also shown that the call-level link dimensioning for the always-on network needs more link resources than the network with CAC, and the call-level link dimensioning based on the analytic expression can be used to conservatively dimension the always-on network with arbitrarily distributed call holding time and inter-call time. The paper also studies the problem of estimating the call-level traffic characteristics when the knowledge of call boundaries is not available. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Performance evaluation of TCP-based applications over DVB-RCS DAMA schemes

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 3 2009
M. Luglio
Abstract Transmission Control Protocol (TCP) performance over Digital Video Broadcasting,Return Channel via Satellite (DVB-RCS) standard is greatly affected by the total delay, which is mainly due to two components, propagation delay and access delay. Both are significant because they are dependent on the long propagation path of the satellite link. The former is intrinsic and due to radio wave propagation over the satellite channel for both TCP packets and acknowledgements. It is regulated by the control loop that governs TCP. The latter is due to the control loop that governs the demand assignment multiple access (DAMA) signalling exchange between satellite terminals and the network control center, necessary to manage return link resources. DAMA is adopted in DVB-RCS standard to achieve flexible and efficient use of the shared resources. Therefore, performance of TCP over DVB-RCS may degrade due to the exploitation of two nested control loops also depending on both the selected DAMA algorithm and the traffic profile. This paper analyses the impact of basic DAMA implementation on TCP-based applications over a DVB-RCS link for a large set of study cases. To provide a detailed overview of TCP performance in DVB-RCS environment, the analysis includes both theoretical approach and simulation campaign. Copyright © 2009 John Wiley & Sons, Ltd. [source]