2,167 research outputs found
Distributed Failure Restoration for Asynchronous Transfer Mode (ATM) Tactical Communication Networks
Asynchronous Transfer Mode (A TM) is an attractive choice for future military
communication systems because it can provide high throughput and support multi-service
applications. Furthermore its use is consistent with the 'off the shelf technology
policy that is currently operated by the Defence Engineering Research Agency of Great
Britain. However, A TM has been developed as a civil standard and is designed to
operate in network infrastructures with very low failure rates. In contrast, tactical
networks are much less reliable. Indeed tactical networks operate on the premise that
failures, particularly node failures, are expected. Hence, efficient, automatic failure
restoration schemes are essential if an A TM based tactical network is to remain
operational. The main objective of this research is the proposal and verification of one
or more new restoration algorithms that meet the specific requirements of tactical
networks.
The aspects of ATM networks that influence restoration algorithms' implementation are
discussed. In particular, the features of A TM networks such as the concept of Virtual
Paths Virtual Channels and OAM (Operation And Maintenance) mechanisms that
facilitate implementation of efficient restoration techniques. The unique characteristics
of tactical networks and their impact on restoration are also presented.
A significant part of the research was the study and evaluation of existing approaches to
failure restoration in civil networks. A critical analysis of the suitability of these
approaches to the tactical environment shows no one restoration algorithm fully meets
the requirements of tactical networks. Consequently, two restoration algorithms for
tactical A TM networks, DRA-TN (Dynamic Restoration Algorithm for Tactical
Networks) and PPR-TN (Pre-planned Restoration Algorithm for Tactical Networks), are
proposed and described in detail. Since the primary concern of restoration in tactical
networks is the recovery of high priority connections the proposed algorithms attempt to
restore high-priority connections by disrupting low-priority calls. Also, a number of
additional mechanisms are proposed to reduce the use of bandwidth, which is a scarce
resource in tactical networks.
It is next argued that software simulation is the most appropriate method to prove the
consistency of the proposed algorithms, assess their performance and test them on
different network topologies as well as traffic and failure conditions.
For this reason a simulation software package was designed and built specifically to
model the proposed restoration algorithms. The design of the package is presented in
detail and the most important implementation issues are discussed. The proposed
restoration algorithms are modelled on three network topologies under various traffic
loads, and their performance compared against the performance of known algorithms
proposed for civil networks. It is shown that DRA-TN and PPR-TN provide better
restoration of higher priority traffic. Furthermore, as the traffic load increases the
relative performance of the DRA-TN and PPR-TN algorithms increases. The DRA-TN
and PPR-TN algorithms are also compared and their advantages and disadvantages
noted.
Also, recommendations are given about the applicability of the proposed algorithms,
and some practical implementation issues are discussed. The number of problems that
need further study are briefly described.Defence Engineering Research Agency of Great Britai
A Survey of Network Optimization Techniques for Traffic Engineering
TCP/IP represents the reference standard for the implementation of interoperable communication networks. Nevertheless, the layering principle at the basis of interoperability severely limits the performance of data communication networks, thus requiring proper configuration and management in order to provide effective management of traffic flows. This paper presents a brief survey related to network optimization using Traffic Engineering algorithms, aiming at providing additional insight to the different alternatives available in the scientific literature
Applications of satellite technology to broadband ISDN networks
Two satellite architectures for delivering broadband integrated services digital network (B-ISDN) service are evaluated. The first is assumed integral to an existing terrestrial network, and provides complementary services such as interconnects to remote nodes as well as high-rate multicast and broadcast service. The interconnects are at a 155 Mbs rate and are shown as being met with a nonregenerative multibeam satellite having 10-1.5 degree spots. The second satellite architecture focuses on providing private B-ISDN networks as well as acting as a gateway to the public network. This is conceived as being provided by a regenerative multibeam satellite with on-board ATM (asynchronous transfer mode) processing payload. With up to 800 Mbs offered, higher satellite EIRP is required. This is accomplished with 12-0.4 degree hopping beams, covering a total of 110 dwell positions. It is estimated the space segment capital cost for architecture one would be about 250M. The net user cost is given for a variety of scenarios, but the cost for 155 Mbs services is shown to be about $15-22/minute for 25 percent system utilization
A Bypass-Ring Scheme for a Fault Tolerant Multicast
We present a fault tolerant scheme for recovery from single or multiple node failures in multi-directional multicast trees. The scheme is based on cyclic structures providing alternative paths to eliminate faulty nodes and reroute the traffic. Our scheme is independent of message source and direction in the tree, provides a basis for on-the-fly repair and can be used as a platform for various strategies for reconnecting tree partitions. It only requires an underlying infrastructure to provide a reliable routing service. Although it is described in the context of a message multicast, the scheme can be used universally in all systems using tree-based overlay networks for communication among components
Resource and Application Models for Advanced Grid Schedulers
As Grid computing is becoming an inevitable future, managing, scheduling and monitoring dynamic, heterogeneous resources will present new challenges. Solutions will have to be agile and adaptive, support self-organization and autonomous management, while maintaining optimal resource utilisation. Presented in this paper are basic principles and architectural concepts for efficient resource allocation in heterogeneous Grid environment
Design of a fast and resource-efficient fault management system in optical networks to suit real-time multimedia applications
Today\u27s telecommunications networks are relying more and more on optical fibers as their physical medium. Currently the Wavelength Division Multiplexing technology enables hundreds of wavelengths to be multiplexed on a single fiber. Using this technology capacity can be dramatically increased, even to the order of Terabits per second. While WDM technology has given a satisfactory answer to the ever-increasing demand for capacity, there is still a problem which needs to be handled efficiently: survivability.
Our proposed fault restoration system optimized between restoration cost and speed. We extended the concept of Forward Equivalence Class (FEC) in Multi Protocol Label switching (MPLS) to our proposed fault restoration system. Speed was found to be in the order of 1 to 3 microseconds using predesigned protection, depending on the configuration of the system. Optimization was done between restoration speed and cost by introducing a priority field in the packet header
TOPOLOGICAL PLANNING OF COMMUNICATION NETWORKS
In this paper, we concentrate on topological planning process of large-scale communication networks such as those used by telecom operators. Such networks are usually spread over large geographical area, and finding an optimal topology is very important part of the planning process. Network equipment used in such network is very expensive, and two connection points can be hundreds of kilometers apart. These networks, in most cases, form a backbone network of telecom operator, meaning that majority of traffic is carried through high-speed communication links of such network. Any cable cuts or equipment malfunctions could result in huge data losses. Therefore, such networks require high degree of availability and fault resistance, which must be considered during the planning process. Network topology providing fault resistance should offer at least two separate communication paths between any pair of network nodes. Most important issue in network topology planning is finding topology with lowest possible overall network price, while keeping all requirements (such as fault tolerance, availability, maximal number of hops, maximal blocking probability etc.) satisfied. Network design process can be divided into three stages. First step is making decisions about which network elements (nodes, existing edges) should be included in a backbone network (for instance, one of sub-problems appearing in this phase is facility location problem). Second step includes selection of network topology, so that all elements selected in first step will be interconnected satisfying given requirements. Last phase is used to determine node and link capacities needed for successful traffic transport as well as routings of traffic demands, including protection. Depending on technologies used in network, different routing and protection mechanisms, as well as specific topology models, can be used (e.g. SDH/WDM SHR, mesh, dual-homing etc.)
Biologically Inspired Self-Healing Software System Architecture
Self-healing capabilities have begun to emerge as an interesting and potentially valuable
property of software systems. Self-healing characteristic enables software systems to
continuously and dynamically monitor, diagnose, and adapt itself after a failures has
occur in their components. Adding such characteristic into existing software systems is
immensely useful and valuable for allowing them to recover from failures. However,
developing such self-healing software systems is a significant challenge.
The nature introduces to us unforeseen concepts in terms of presenting biological
systems that have the ability to handle its abnormal conditions. Based on this observation,
this thesis presents self healing architecture for software system based on one of the
biological processes that have the ability to heal by itself (the wound-healing process).
The self-healing architecture provides software systems the ability to handle anomalous
conditions that appear among its components. The presented architecture is divided into
to layers, functional and healing layer. In the functional layer, the components of the
system provide its services without any disruptions. The component is considered as
faulty component if it fails to provide its services. The healing layer aims to heal the
faulty component and return it to the running system without the awareness of the user.
The presented self-healing software system is formally described to prove its
functionality. Set-theoretic and Finite State Machine (FSM) is introduced. A prototype
for the presented architecture has been implemented using Java language. Java objects
are considered as the system components. The modules of the healing layer in the selfhealing
architecture have been implemented into Java classes. An object from the module
class will be created to perform its task for the healing process. The thesis concludes with
recommendations for future works in this area and enhancement of the presented
architecture
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