5,224 research outputs found
IP Fast Reroute with Remote Loop-Free Alternates: the Unit Link Cost Case
Up to not so long ago, Loop-Free Alternates (LFA)
was the only viable option for providing fast protection in pure
IP and MPLS/LDP networks. Unfortunately, LFA cannot provide
protection for all possible failure cases in general. Recently, the
IETF has initiated the Remote Loop-Free Alternates (rLFA)
technique, as a simple extension to LFA, to boost the fraction
of failure cases covered by fast protection. Before further stan-
dardization and deployment, however, it is crucial to determine
to what extent rLFA can improve the level of protection in a
general IP network, as well as to find optimization methods to
tweak a network for 100% rLFA coverage. In this paper, we take
the first steps towards this goal by solving these problems in the
special, but practically relevant, case when each network link is
of unit cost. We also provide preliminary numerical evaluations
conducted on real IP network topologies, which suggest that rLFA
significantly improves the level of protection, and most networks
need only 2 − 3 new links to be added to attain 100% failure
case coverage
Optimizing IGP Link Costs for Improving IP-level Resilience
Recently, major vendors have introduced new router
platforms to the market that support fast IP-level failure pro-
tection out of the box. The implementations are based on the
IP Fast ReRoute–Loop Free Alternates (LFA) standard. LFA
is simple, unobtrusive, and easily deployable. This simplicity,
however, comes at a severe price, in that LFA usually cannot
protect all possible failure scenarios. In this paper, we give new
graph theoretical tools for analyzing LFA failure case coverage
and we seek ways for improvement. In particular, we investigate
how to optimize IGP link costs to maximize the number of
protected failure scenarios, we show that this problem is NP-
complete even in a very restricted formulation, and we give exact
and approximate algorithms to solve it. Our simulation studies
show that a deliberate selection of IGP costs can bring many
networks close to complete LFA-based protection
Experimental L-band SST satellite communications/surveillance terminal study. Volume 1 - Study summary
Study of design for experimental L band supersonic transport communications/surveillance termina
Study of fault-tolerant software technology
Presented is an overview of the current state of the art of fault-tolerant software and an analysis of quantitative techniques and models developed to assess its impact. It examines research efforts as well as experience gained from commercial application of these techniques. The paper also addresses the computer architecture and design implications on hardware, operating systems and programming languages (including Ada) of using fault-tolerant software in real-time aerospace applications. It concludes that fault-tolerant software has progressed beyond the pure research state. The paper also finds that, although not perfectly matched, newer architectural and language capabilities provide many of the notations and functions needed to effectively and efficiently implement software fault-tolerance
A cross impact methodology for the assessment of US telecommunications system with application to fiber optics development, volume 2
The appendices for the cross impact methodology are presented. These include: user's guide, telecommunication events, cross impacts, projection of historical trends, and projection of trends in satellite communications
Design of the Electronics Subsystem for a High-Resolution Electro-Optical Payload Using Systems Engineering Approach
Satellite imagers, in contrast to commercial imagers, demand exceptional performance and operate under harsh conditions. The camera is an essential part of an Earth Observation Electro Optical (EO) payload that is designed in response to needs such as military demands, changes in world politics, inception of new technologies, operational requirements and experiments. As one of the key subsystems, the Imager Electronics Subsystem of a high-resolution EO payload plays very important role in the accomplishment of mission objectives and payload goals. Hence, these Electronics Subsystems require a special design approach optimised for their needs and meticulous characterizations of high-resolution space applications. This dissertation puts forward the argument that the system being studied is a subsystem of a larger system and that systems engineering principles can be applied to the subsystem design process also. The aim of this dissertation is to design the Imager Electronics Subsystem of a high-resolution Electro Optical Payload using a systems engineering approach to represent a logical integration and test flow using the space industry guidelines. The Imager Electronics Subsystem consists of group of elements forming the functional chain from the Image Sensors on the Focal Plane down to electrical interface to the Data Handling Unit and power interface of the satellite. This subsystem is responsible for collecting light in different spectral bands, converting this light to data of different spectral bands from image sensors for high-resolution imaging, performing operations for aligning, tagging and multiplexing along with incorporating internal and external interfaces
Experimental L-band SST satellite communications/surveillance terminal study. Volume 5 - Aircraft terminal definition
Aircraft terminal designs for experimental and operational supersonic transport for L band satellite air traffic contro
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