3,135 research outputs found
Agile-SD: A Linux-based TCP Congestion Control Algorithm for Supporting High-speed and Short-distance Networks
Recently, high-speed and short-distance networks are widely deployed and
their necessity is rapidly increasing everyday. This type of networks is used
in several network applications; such as Local Area Networks (LAN) and Data
Center Networks (DCN). In LANs and DCNs, high-speed and short-distance networks
are commonly deployed to connect between computing and storage elements in
order to provide rapid services. Indeed, the overall performance of such
networks is significantly influenced by the Congestion Control Algorithm (CCA)
which suffers from the problem of bandwidth under-utilization, especially if
the applied buffer regime is very small. In this paper, a novel loss-based CCA
tailored for high-speed and Short-Distance (SD) networks, namely Agile-SD, has
been proposed. The main contribution of the proposed CCA is to implement the
mechanism of agility factor. Further, intensive simulation experiments have
been carried out to evaluate the performance of Agile-SD compared to Compound
and Cubic which are the default CCAs of the most commonly used operating
systems. The results of the simulation experiments show that the proposed CCA
outperforms the compared CCAs in terms of average throughput, loss ratio and
fairness, especially when a small buffer is applied. Moreover, Agile-SD shows
lower sensitivity to the buffer size change and packet error rate variation
which increases its efficiency.Comment: 12 Page
Spacelab system analysis: A study of the Marshall Avionics System Testbed (MAST)
An analysis of the Marshall Avionics Systems Testbed (MAST) communications requirements is presented. The average offered load for typical nodes is estimated. Suitable local area networks are determined
Improving the Performance of Wireless LANs
This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids
Spacelab system analysis: A study of communications systems for advanced launch systems
An analysis of the required performance of internal avionics data bases for future launch vehicles is presented. Suitable local area networks that can service these requirements are determined
Multimedia Networks: Fundamentals and Future Directions
Multimedia has become an integral part of computing and communications environment, and networks are carrying ever-increasing volume of multimedia information. The main characteristics of multimedia information are high-volume and bursty traffic, with low tolerance to delay and delay variance. The legacy networks (designed in 70s and 80s) are not able to meet these requirements. Enhancements to the older networking technologies have been developed to convert these into multimedia networks. Enhancements to LANs include Switched Ethernet, Isochronous Ethernet, Fast Ethernet, 100VGAnyLAN, FDDI-II, and Synchronous FDDI. WAN options for multimedia networking include digital leased lines and ISDN. The Internet has revolutionized business and personal communications, but falls short of being a genuine multimedia network. To make the Internet capable of carrying multimedia traffic, new protocols such as MBone, ST-II, RTP, and RSVP have been developed. Internet2 is a new initiative that is aimed at overcoming the problems of throughput, delay and jitter encountered on the original Internet. One technology that was developed with multimedia networking as one of its main applications, is the Asynchronous Transfer Mode (ATM) technology. Upcoming Gigabit Ethernet technology will provide a path for upgrading current Ethernet networks into multimedia networks
GUIDELINES FOR THE DESIGN OF ENHANCED, COST EFFECTIVE NETWORKS IN A MANUFACTURING ENVIRONMENT
Investigations into the transmission of real-time interactive speech over local area
networks (LAN) in an industriai/commerciai environment to eventually obviate the
need for a private automatic branch exchange and ultimately prepare the way for a
single interactive integrated information system (PS) that provides work stations, which
are networked via a LAN, with a fully interactive speech and graphics facility
commensurate with the future requirements in computer integrated manufacturing
(CIM).
The reasons for conducting this programme of research were that existing LANs do not
offer a real time interactive speech facility. Any verbal communication between
workstation users on the LAN has to be carried out over a telephone network (PABX).
This necessitates the provision of a second completely separate network with its
associated costs. Initial investigations indicate that there is sufGcient capacity on
existing LANs to support both data and real-time speech provided certain data packet
delay criteria can be met.
Earlier research work (in the late 1980s) has been conducted at Bell Labs and MIT.
[Ref 25, 27 & 28], University of Strathclyde [Ref 24] and at BTRL [Ref 22 and 37].
In all of these cases the real time implementation issues were not fijlly addressed. In
this thesis the research work reported provides the main criteria for the implementation
of real-time interactive speech on both existing and newly installed networks.
With such enhanced communication facilities, designers and engineers on the shop
floor can be projected into their suppliers, providing a much greater integration
between manufacturer and supplier which will be beneficial as Concurrent and
Simultaneous Engineering Methodologies are further developed.
As a result, various LANs have been evaluated as to their suitability for the
transmission of real time interactive speech. As LANs, in general, can be separated
into those with either deterministic or stochastic access mechanisms, investigations were
carried out into the ability of both the:
(i) Token Passing Bus LANs supporting the Manufacturing and
Automation Protocol (MAP)—Deterministic
and
(u) Carrier Sense Multiple Access/Collision Detection (CSMA/CD) LANs
supporting the Technical Office Protocol (TOP)— Stochastic
to support real time interactive speech, as both are used extensively in commerce and
manufacturing.
The thesis that real time interactive speech can be transmitted over LANs employed in
a computer integrated manufacturing environment has to be moderated following the
tests carried out in this work, as follows:-
The Token Passing LAN presents no serious problems under normal
traffic conditions, however, the CSMA/CD LAN can only be used in
relatively light traffic conditions i.e. below 30% of its designed
maximum capacity, providing special arrangements are made to
minimise the access, transmission and processing delays of speech
packets.
Given that a certain amount of delay is inevitable in packet switched systems (LANs),
investigations have been carried out into techniques for reducing the subjective efifect
of speech packet loss on real-time interactive systems due to the unacceptable delays
caused by the conditions mentioned above
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