362 research outputs found
Performance Studies of a Double-Layered All-Optical Network Architecture
Transmission in complete lightform is now realised with advancements in technology. These include new developments in fabricating the fiber carrier
medium, low loss fiber coupling devices, optical switching components for routing
lightwave trans mission; laser light sources and sensitive photonic detectors. The
in creasing speeds of new generation electronic microprocessors, is capable of
resolving the differences in processing and transmission speeds. Access to the
medium is regulate d by the medium access control protocol, that permits multiple
users to share limited transmission resources of the network. The double-layere dhierarchical all-optical network architecture is proposed, that consists of an upper
layer to inter connect sub-networks of the lower layer. The data packets are
differentiate d for the two layers . The architecture implements wavelength -space
trans mission of wavelength division multiplexed channels. The architecture affords spatial reuse of channels in the lower layer. A non-contentious token-passing
medium access protocol is utilised. The token-passing variant that uses one token to
provide access to multiple channels is introduced.
The performance of the arrayed transmitter of the access node is gauged to
determine the suitability of the architecture with the access protocol in supporting
multiple accesses. The transmitter can queue a number of data packets awaiting
transmission depending on the size of the buffer. Performance indication can be
obtained from probabilistic modelling of the changing event states of the
transmitter. Performance causal parameters which include the number of nodes,
channel allocation and buffer size are defined. The results from the probabilistic
models are then analysed and verified with simulation. The architecture provides an
inherent feature termed as the bypass that is capitalised to improve performance of
the lower layer. Performance indication shows that the architecture is capable of
supporting the two types of data packets effectively, and the access protocol is
suitable for its purpose. Performance indication of average packet delay improves
when the when the bypass feature is implemented. The probabilistic models are
found to provide a logical and systematic approach to study and gauge performance
of the token-passing access protocol. In conclusion, the double-layered hierarchical
AON architecture and the medium access protocol, together serve as a reference for
the study of similar scaleable network architectures and their performance
Ethernet - a survey on its fields of application
During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal
Performance study of packet-optical transport network protocols
This research is carried out in the field of Optical Transport Network (OTN), in particular, to investigate the performance of a new protocol called Packet Optical Network that was introduced as a successor to the legacy Synchronous Digital Hierarchy/Synchronous optical networking (SDH/SONET). The migration to IP/Ethernet application globally is forcing enterprises to address two major (Wide Area Network) WAN issues: converging Time Division Multiplexing (TDM) and packet networks to reduce expenses, and improving network and service management to support delay-sensitive, bandwidth-intensive applications. Optical Transport Network - ITU G.709 is a global standard to address these challenges by eliminating unnecessary layer, IP straight over optic without being encapsulated in ATM/SDH frames, and eventually reduce Optical-Electronic-Optical (OEO) conversion. The International Telecommunication Union Telecommunication Standardization Sector ITU-T defines an OTN as a set of Optical Network Elements (ONE) connected by optical fiber links, able to provide functionality of transport, multiplexing, switching, management, supervision, and survivability of optical channels carrying client signals. Packet Optical Network or often called Optical Channel Digital Wrapper added more functionalities to the legacy SONET/SDH such as the inclusion of stronger FEC, switching scalability, Transparency, and different frame rates. The Optical Channel Payload Envelope (OCh PE) can carry any type of data: SONET/SDH, GbE, 10GbE, ATM, IP, and so on. The objective of this research is to model an Optical Transport Network in the OMNeT++ simulation environment and OptiSystem Software, where the performance of Packet Optical Network protocols is compared with the legacy system in terms of delay and error correction capability. Simulation conducted in the metro/core optical network environment shows that the optical network performances in delay and error performance are improved when using the Packet optical network protocol, up to 30% decrease in delay can be achieved and longer distances can be reached by employing the new more powerful Forward Error Correction of the Digital Wrapper G.709
Cost-effective Information and Communication Technology (ICT) infrastructure for Tanziania
The research conducted an Information and Communication Technology (ICT) field
survey, the results revealed that Tanzania is still lagging behind in the ICT sector due to
the lack of an internationally connected terrestrial ICT infrastructure; Internet connectivity
to the rest of the world is via expensive satellite links, thus leaving the majority of the
population unable to access the Internet services due to its high cost. Therefore, an ICT
backbone infrastructure is designed that exploits optical DWDM network technology,
which un-locks bandwidth bottlenecks and provides higher capacity which will provide
ICT services such as Internet, voice, videos and other multimedia interactions at an
affordable cost to the majority of the people who live in the urban and rural areas of
Tanzania. The research analyses and compares the performance, and system impairments, in a DWDM system at data transmission rates of 2.5 Gb/s and 10 Gb/s per wavelength channel. The simulation results show that a data transmission rate of 2.5 Gb/s can be successfully transmitted over a greater distance than 10 Gb/s with minimum system impairments. Also operating at the lower data rate delivers a good system performance for the required ICT services. A forty-channel DWDM system will provide a bandwidth of 100 Gb/s.
A cost analysis demonstrates the economic worth of incorporating existing optical fibre
installations into an optical DWDM network for the creation of an affordable ICT
backbone infrastructure; this approach is compared with building a completely new optical
fibre DWDM network or a SONET/SDH network. The results show that the ICT backbone
infrastructure built with existing SSMF DWDM network technology is a good investment,
in terms of profitability, even if the Internet charges are reduced to half current rates. The
case for building a completely new optical fibre DWDM network or a SONET/SDH
network is difficult to justify using current financial data
Simulation and analytical performance studies of generic atm switch fabrics.
As technology improves exciting new services such as video phone become possible and economically viable but their deployment is hampered by the inability of the present networks to carry them. The long term vision is to have a single network able to carry all present and future services. Asynchronous Transfer Mode, ATM, is the versatile new packet -based switching and multiplexing technique proposed for the single network. Interest in ATM is currently high as both industrial and academic institutions strive to understand more about the technique. Using both simulation and analysis, this research has investigated how the performance of ATM switches is affected by architectural variations in the switch fabric design and how the stochastic nature of ATM affects the timing of constant bit rate services. As a result the research has contributed new ATM switch performance data, a general purpose ATM switch simulator and analytic models that further research may utilise and has uncovered a significant timing problem of the ATM technique.
The thesis will also be of interest and assistance to anyone planning on using simulation as a research tool to model an ATM switch
Ethernet Networks for Real-Time Use in the ATLAS Experiment
Ethernet became today's de-facto standard technology for local area networks. Defined by the IEEE 802.3 and 802.1 working groups, the Ethernet standards cover technologies deployed at the first two layers of the OSI protocol stack. The architecture of modern Ethernet networks is based on switches. The switches are devices usually built using a store-and-forward concept. At the highest level, they can be seen as a collection of queues and mathematically modelled by means of queuing theory. However, the traffic profiles on modern Ethernet networks are rather different from those assumed in classical queuing theory. The standard recommendations for evaluating the performance of network devices define the values that should be measured but do not specify a way of reconciling these values with the internal architecture of the switches. The introduction of the 10 Gigabit Ethernet standard provided a direct gateway from the LAN to the WAN by the means of the WAN PHY. Certain aspects related to the actual use of WAN PHY technology were vaguely defined by the standard. The ATLAS experiment at CERN is scheduled to start operation at CERN in 2007. The communication infrastructure of the Trigger and Data Acquisition System will be built using Ethernet networks. The real-time operational needs impose a requirement for predictable performance on the network part. In view of the diversity of the architectures of Ethernet devices, testing and modelling is required in order to make sure the full system will operate predictably. This thesis focuses on the testing part of the problem and addresses issues in determining the performance for both LAN and WAN connections. The problem of reconciling results from measurements to architectural details of the switches will also be tackled. We developed a scalable traffic generator system based on commercial-off-the-shelf Gigabit Ethernet network interface cards. The generator was able to transmit traffic at the nominal Gigabit Ethernet line rate for all frame sizes specified in the Ethernet standard. The calculation of latency was performed with accuracy in the range of +/- 200 ns. We indicate how certain features of switch architectures may be identified through accurate throughput and latency values measured for specific traffic distributions. At this stage, we present a detailed analysis of Ethernet broadcast support in modern switches. We use a similar hands-on approach to address the problem of extending Ethernet networks over long distances. Based on the 1 Gbit/s traffic generator used in the LAN, we develop a methodology to characterise point-to-point connections over long distance networks. At higher speeds, a combination of commercial traffic generators and high-end servers is employed to determine the performance of the connection. We demonstrate that the new 10 Gigabit Ethernet technology can interoperate with the installed base of SONET/SDH equipment through a series of experiments on point-to-point circuits deployed over long-distance network infrastructure in a multi-operator domain. In this process, we provide a holistic view of the end-to-end performance of 10 Gigabit Ethernet WAN PHY connections through a sequence of measurements starting at the physical transmission layer and continuing up to the transport layer of the OSI protocol stack
Design Related Investigations for Media Access Control Protocol Service Schemes in Wavelength Division Multiplexed All Optical Networks
All-optical networks (AON) are emerging through the technological
advancement of various optical components, and promise to provide almost unlimited
bandwidth. To realise true network utilisation, software solutions are required. An active
area of research is media access control (MAC) protocol. This protocol should address
the multiple channels by wavelength division mutiplexing (WDM) and bandwidth
management. Token-passing (TP) is one such protocol, and is adopted due to its
simplicity and collisionless nature. Previously, this protocol has been analysed for a
single traffic type. However, such a study may not substantiate the protocol's acceptance
in the AON design. As multiple traffic types hog the network through the introduction
multimedia services and Internet, the MAC protocol should support this traffic. Four
different priority schemes are proposed for TP protocol extension, and classified as static and dynamic schemes. Priority assignments are a priori in static scheme, whereas in the
other scheme, priority reassignments are carried out dynamically. Three different
versions of dynamic schemes are proposed. The schemes are investigated for
performance through analytical modelling and simulations. The semi-Markov process
(SMP) modelling approach is extended for the analyses of these cases. In this technique,
the behaviour of a typical access node needs to be considered. The analytical results are
compared with the simulation results. The deviations of the results are within the
acceptable limits, indicating the applicability ofthe model in all-optical environment.
It is seen that the static scheme offers higher priority traffic better delay and
packet loss performance. Thus, this scheme can be used beneficially in hard real-time
systems, where knowledge of priority is a priori. The dynamic priority scheme-l is more
suitable for the environments where the lower priority traffic is near real-time traffic and
loss sensitive too. For such a scheme, a larger buffer with smaller threshold limits
resulted in improved performance. The dynamic scheme-2 and 3 can be employed to
offer equal treatment for the different traffic types, and more beneficial in future AONs.
These schemes are also compared in their performance to offer constant QoS level. New
parameters to facilitate the comparison are proposed. It is observed that the dynamic
scheme-l outperforms the other schemes, and these QoS parameters can be used for
such QoS analysis. It is concluded that the research can benefit the design of the
protocol and its service schemes needed in AON system and its applications
Multi-ring SDH network design over optical mesh networks
Ankara : The Department of Electrical and Electronics Engineering and Sciences of Bilkent University, 2002.Thesis (Master's) -- Bilkent University, 2002.Includes bibliographical references leaves 84-87.The evolution of networks in telecommunications has brought on the
importance of design techniques to obtain survivable and cost-effective transportation
networks. In this thesis, we study Synchronous Digital Hierarchy (SDH) ring design
problem with an interconnected multi-ring architecture overlaid over an optical mesh
network. We decouple the problem into two sub-problems: the first problem is the
SDH ring selection, and the second problem is the mapping of these rings onto the
physical mesh topology. In this structure, the logical topology consists of SDH
Add/Drop Multiplexers (ADMs) and Digital Cross-Connects (DXCs), and the
physical topology consists of Optical Cross-Connects (OXCs).
The ring selection problem is to choose the rings that give minimum inter-ring
traffic in the network. Since inter-ring traffic increases the network cost and
complexity, we aim to minimize the inter-ring traffic. We propose a greedy heuristic
algorithm for this problem that finds a solution subject to the constraint that the
number of nodes on each ring is limited. Numerical results on the ring design problem
are presented for different topologies.
Once the logical topology is obtained, resilient mapping of SDH rings onto the
mesh physical topology is formulated as a Mixed Integer Linear Programming
(MILP) problem. In order to guarantee proper operation of SDH ring protection
against all single failures, each link on an SDH ring must be mapped onto a lightpath
which is link and node disjoint from all other lightpaths comprising the same ring.
The objective of this mapping is to minimize the total fiber cost in the network. We
also apply a post-processing algorithm to eliminate redundant rings. The postprocessing
algorithm is very useful to reduce the cost. We evaluate the performance
of our design algorithm for different networks.Tan, Tuba AkıncılarM.S
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