link capacities

Top PDF link capacities:

On Secure Network Coding with Unequal Link Capacities and Restricted Wiretapping Sets

On Secure Network Coding with Unequal Link Capacities and Restricted Wiretapping Sets

unit capacity is made without loss of generality, since links of larger capacity can be modeled as multiple unit capacity links in parallel. However, in the secure communication problem, such an assumption cannot be made without loss of generality. Indeed, we show in this paper that there are significant differ- ences between the equal capacity and unequal capacity cases. For the case of equal link capacities, the secrecy capacity is given by the cut-set bound, whether or not the location of the k wiretapped links is known. The cut-set bound can be achieved by injecting k random keys at the source which are decoded at the sink along with the message [3]. However, we show that if the network has unequal link capacities and the wiretapper has access to an unrestricted set of links in the network the cut-set bound is not achievable in general by any linear or nonlinear coding scheme. We further show that this also holds in the case of an unrestricted wiretapping set and equal unit link capacities in the network. Finally, we address the complexity of determining the secrecy capacity if the location of the wiretapper is unknown. We show that this problem, which is closely related to network interdiction, is NP-hard.
Show more

5 Read more

Scope Of Physical Link Capacities Using Markov Decision Process Routing And Grade Of Service Constraints

Scope Of Physical Link Capacities Using Markov Decision Process Routing And Grade Of Service Constraints

The problem of Network Dimensioning [14] is divided into two sub problems. First the design of the topological structure (location of the nodes and interconnection among them and determine the optimal size of the network physical links given the end to end traffic and GoS constraints of each service class. There are two approaches used in the dimensioning problem[1]. The first approach to use link capacities as optimization variables and the second approach uses link performance characteristics as optimization variables. In the first approach the application of the general optimization methods is practical only when the continuous gradients of the constraint functions with respect to the CAC and routing parameters can be obtained. This is feasible only when the CAC and routing strategy is defined by a set of continuous parameters, as in the case of load sharing routing and MDP routing. In fact, in these cases the inequality constraints can be replaced with equality constraints which can simplify the solution. The first approach is preferred in this case.
Show more

13 Read more

Network Coding for Resource Optimization and Error Correction

Network Coding for Resource Optimization and Error Correction

Lastly, we study the capacity of single-source single-sink noiseless networks under adversarial attack on no more than z edges. In this work, we allow arbitrary link capacities, unlike prior papers. We propose a new cut-set upper bound for the error- correction capacity for general acyclic networks. This bound tightens previous cut- set upper bounds. For example networks where the bounds are tight, we employ both linear and nonlinear coding strategies to achieve the capacity. We present a method for upper bounding the linear coding capacity of an arbitrary network and prove the insufficiency of linear network codes to achieve the capacity in general. We also show by example that there exist single-source and single-sink networks for which intermediate nodes must perform coding, nonlinear error detection or error correction in order to achieve the network capacity. This is unlike the equal link capacity case, where coding only at the source suffices to achieve the capacity of any single-source and single-sink network. A new strategy, guess-and-forward is then introduced. We first find the capacity of the two-node network by employing guess- and-forward. Guess-and-forward is also applied to the proposed family of four-node acyclic networks, showing it achieves the network capacity. Finally, for a class of so called zig-zag networks, we derive achievable rate of guess-and-forward and present conditions under which that bound is tight.
Show more

167 Read more

Coding for Wireless Broadcast and Network Secrecy

Coding for Wireless Broadcast and Network Secrecy

In Chapter 5, we consider the problem of secure transmission in the presence of a wiretapper. Secure multicast network coding over erasure networks with unequal link capacities is studied in the presence of a wiretapper that can wiretap any subset of k links. Existing results show that for the case of equal (unit) link capacities, the secrecy capacity is the same whether or not the location of the wiretapped links is known, and can be achieved by injecting k random keys at the source which are decoded at the sink along with the message. In contrast, we show that for unequal link capacities, the secrecy capacity is not the same in general when the location of the wiretapped links is known as when it is unknown. We give achievable strategies where random keys are canceled at intermediate non-sink nodes, or injected at intermediate non-source nodes. Furthermore, we show that computing the secrecy rate is NP-complete both when the location of the wiretapped links is known and when it is unknown.
Show more

178 Read more

Collaborative Hierarchical Caching with Dynamic Request Routing for Massive Content Distribution

Collaborative Hierarchical Caching with Dynamic Request Routing for Massive Content Distribution

We have now obtained a cache cooperation mechanism that fully explores the potential of downstream content retrieval. The assignment is in a distributed fashion while both asym- metric link capacities and heterogeneous user demands are considered. Note that the capacity of the middle level server is not involved in making a decision, which allows us to further explore the opportunity of middle level cache cooperation in the next subsection. Compared to cache cooperation with static routing, our exploration of indirect bottom level cooperation can be beneficial in the scenario of heterogenous user demands as servers can fulfill others’ requests through downstream content retrieval, while the exploration of the middle level cooperation can be beneficial in the scenario of homogeneous user demands, as middle level servers do not have to store nearly duplicated contents with our dynamic routing scheme.
Show more

9 Read more

Joint Traffic Routing and Distribution of Security Services in High Speed Networks

Joint Traffic Routing and Distribution of Security Services in High Speed Networks

The performance of F IDRAN was assessed on the Cyber De- fense Technology Experimental Research testbed (DETER) [2], [7] which is a shared infrastructure designed for medium- scale repeatable experiments in computer security. The testbed provides a pool of over 300 computers of varying hardware which can be used to emulate networks. As scenario we chose the Abilene network—depicted in Figure 2—which is a research IP backbone connecting multiple universities across the US. For this network real world data—traffic flows and link capacities—is available on the project’s web-site [1].
Show more

5 Read more

Download
			
			
				Download PDF

Download Download PDF

The general Multiprotocol Label Switch (MPLS) topology optimisation problem is complex and concerns the optimum selection of links, the assignment of capacities to these links and the routing requirements on these links. Ideally, all these are jointly optimised, leading to a minimum cost network which continually meets given objectives on network delay and throughput. In practice, these problems are often dealt with separately and a solution iterated. In this paper, we propose an algorithm that computes the shortest routes, assigns optimal flows to these routes and simultaneously determines optimal link capacities. We take into account the dynamic adaptation of optimal link capacities by considering the same Quality of Service (QoS) measure used in the flow assignment problem in combination with a blocking model for describing call admission controls (CAC) in multiservice broadband telecommunication networks. The main goal is to achieve statistical multiplexing advantages with multiple traffic and QoS classes of connections that share a common trunk present. We offer a mathematical programming model of the problem and proficient solutions which are founded on a Lagrangean relaxation of the problem. Experimental findings on 2-class and 6-class models are reported.
Show more

21 Read more

Characterizing Residential Broadband Networks

Characterizing Residential Broadband Networks

In this paper, we present the first large-scale measurement study of major cable and DSL providers in North America and Europe. We describe and evaluate the measurement tools we developed for this purpose. Our study character- izes several properties of broadband networks, including link capacities, packet round-trip times and jitter, packet loss rates, queue lengths, and queue drop policies. Our analysis reveals important ways in which residential networks differ from how the Internet is conventionally thought to operate. We also discuss the implications of our findings for many emerging protocols and systems, including delay-based con- gestion control (e.g., PCP) and network coordinate systems (e.g., Vivaldi).
Show more

14 Read more

Analysis and Modeling of Variable Bitrate Video Traffic.

Analysis and Modeling of Variable Bitrate Video Traffic.

Using the proposed model, we can determine the packet arrival process for different types of networks by varying the number of nodes, link capacities, background traffic utilization and [r]

198 Read more

Goodwill Hunting? : Debates on the 'meaning' of lower palaeolithic handaxe form revisited

Goodwill Hunting? : Debates on the 'meaning' of lower palaeolithic handaxe form revisited

Penny Spikins is a lecturer in Early Prehistory at the Department of Archaeology, York. She has published several volumes on the Mesolithic (including Mesolithic Europe (CUP) co-edited with Geoff Bailey, and Re-thinking the Mesolithic: Environment, Population and Settlement (BAR)) as well as more recent papers on the significance of evolving emotional capacities in early prehistory (on the dynamics of collaboration and competition (in Journal of World Prehistory) on the origins and role of autism (in Cambridge Archaeological Journal) and, with Holly Rutherford and Andrew Needham, on the evolution of compassion (in Time and Mind)).
Show more

21 Read more

Constructional Tools as the Origin of Cognitive Capacities

Constructional Tools as the Origin of Cognitive Capacities

At the very least, we need to have tools that can create agents that correspond to significant elements of the sensory world, and can link these back again so as to reflect back on elements in the sensory world, e.g. to repeat a represented action or to identify a represented object. They must also have a capacity to link together these systems representing aspects of the sensory world in ways that can be used imply important relationships in the sensory world. Thus there can come the ability to abstract out and import into the supportive system phenomena in the sensory world, and then later export them again so that events such as pulling on something to make a noise can be repeated. Such an elementary process provides a very simple paradigm of support of activity by the representing system, and one can then go on binding together agents in the supportive system in ways that have more complex implications in the sensory world. For this to be of relevance there needs to be some process which can switch between a connected mode and a disconnected mode, so that constructs created in the disconnected mode can be tested in the connected mode.
Show more

5 Read more

Therapeutic Jurisprudence, Coercive Interventions, and Human Dignity

Therapeutic Jurisprudence, Coercive Interventions, and Human Dignity

Consider three potential subjects of parens patriae intervention. Davis is a competent adult who manifests no psychological disorder. He refuses surgery that has been recommended as necessary for a potentially lethal tumor in his brain. He has spent his adult life as a professor translating ancient Chinese texts, and he has been informed that the side effects of the surgery include a serious risk of impaired capacities that would prevent him from completing a translation that he pursues as the crowning achievement of his life’s work. He concludes that the potential side effects would prevent him from completing his lifelong project, resulting in a wasted life. He explains, ‘I would rather live fully for a shorter period than drag out a failed life.’ East has an extended history of chronic schizophrenia. 16 He refuses surgery considered necessary to resolve a potentially life-ending physical illness. He refuses the surgery because the hallucinatory voice of God warns him that the surgeons are agents of Satan who conspire to send him to hell.
Show more

17 Read more

Constructional Tools as the Origin of Cognitive Capacities

Constructional Tools as the Origin of Cognitive Capacities

directly with what is perceptible to the senses, but less clear how higher cognitive capacities might be encompassed within such a framework. To see how this might be done, let us postulate that besides the systems concerned directly with action and perception there exist support systems containing agents concerned with representations that do not have to refer to the immediate situation. These systems have to derive their activity in the first instance from something and we assume (apart from possible innate routines) that they derive initially from action and perception but they can subsequently become temporarily divorced from action and perception. (Temporarily is the key word here; if they were to remain permanently divorced from action and perception they would have no value.)
Show more

5 Read more

Progress to European Union - A Challenge for the Public Service. EIPAScope 1992(3):pp. 1-8

Progress to European Union - A Challenge for the Public Service. EIPAScope 1992(3):pp. 1-8

The EC's management deficit is due to a large extent to weaknesses and deficiencies in the capacities and linkages in the networks through which EC policies are administered. In a way, this is not surprising because in many, if not most, cases the organizations involved were not created to administer EC policies. They were formed with different purposes in view and there is therefore a 'management of change' problem in adapting them to serve EC objectives. In addition, there is no reason to suppose that the relationships among the organizations will develop naturally to establish a basis for effective cooperation. Just as an effort is needed to redesign organizations to fit them to different purposes so is an effort also needed to develop the linkages and establish coordination procedures that are essential to the smooth and effective operation of a network of organizations. To have a basic insight into the size of the task and the possible scale of the management deficit, one only has to recall that coordination requires good, reliable communication which, in the EC, means communication through many different organizations embedded in twelve different administrative systems and encoded in nine official languages.
Show more

8 Read more

Relationship between maturity levels and neuromuscular capacity among youth soccer players and individuals not practicing soccer

Relationship between maturity levels and neuromuscular capacity among youth soccer players and individuals not practicing soccer

Mendez-Villanueva et al. [21] where the authors found that maturation may not be related to speed. Our work corroborates the findings of Ré et al. [11], where no sig- nificant differences were found between young people with advanced maturation and young people of lesser maturation when physical capacities were analyzed. Matu- ration can influence performance in some physical abili- ties and not others [6-8,21-23].

5 Read more

Inactivation of T Antigen-Forming Capacities of Simian Virus 40 and Adenovirus 12 by Ultraviolet Irradiation

Inactivation of T Antigen-Forming Capacities of Simian Virus 40 and Adenovirus 12 by Ultraviolet Irradiation

The present communication describes the UV inactivation of T antigen-forming capacities of SV40 and Adl2, showing that the capacities were inactivated at the same rate as their infectivi[r]

7 Read more

The change and effect of endothelial progenitor cells in pig with multiple organ dysfunction syndromes

The change and effect of endothelial progenitor cells in pig with multiple organ dysfunction syndromes

injuries. The angiogenesis function would, however, still be stronger than normal even until death. The results showed that the occurrence of the decrease of the number and function of EPCs was prior to the occurrence of MODS, so the sharp decrease in the number and function of EPCs in the progres- sion of MODS may be one of the main pathogenic factors of MODS. In the present study, the migratory, adhesive and ang- iogenesis capacities of EPCs were detected on the EPCs that had been cultured for 7 days in vitro because we could not isolate EPCs directly. We found that these functions of EPCs would remain stable after short-time culturation. The functions of EPCs were therefore deemed able to reflect the functions of EPCs in vivo.
Show more

10 Read more

Link Services or Link Agents?

Link Services or Link Agents?

The server received details from the DLS client of the user’s selection, the document in which the selection was made, and the current context. The followlink module determined which link databases were required, and gathered these together to satisfy the request. The editlink module provided an HTML form that allowed the user to select from the available link databases and edit the individual links. The createlink module accepted details of end points for a link and entered the new link into a specified link database or into the user’s personal link database. The context module provided a list of the different context link databases available on the server and was used by the client to present a menu to the user. All of these modules were driven by an explicit command coded as a URL and sent to the link server as a normal HTTP request. Alternatively the server could return a form to the browser, and the user would fill in the fields to support a particular action. However, form-filling was never a convenient option for actions like creating a link or editing a large link database, simply because there were too many pieces of information to be entered manually (e.g. source and destination URLs, link title).
Show more

10 Read more

New sampling method for routine monitoring of selected pharmaceuticals in surface water

New sampling method for routine monitoring of selected pharmaceuticals in surface water

Degree of contamination determined by proposed sampling method is shown in Fig. 8. Units selected for evaluation of possible contamination were ng/g/24h according to used sampling method based on adsorption and due to impossibility of determination of exact volume of water to which the sampling bags were exposed. Data from Fig. 8 show that only tens ng of studied pharmaceuticals were adsorbed at the sorbent in sampling bags per 24 hours. These values are much lower than sorption capacities determined for used sorbent. Therefore, it could be stated that developed sampling bag method is suitable for routine monitoring of contamination in the natural environment.
Show more

11 Read more

The Link

The Link

I’m keen to work for a company with a great reputation and high profile like Kenyatta University. I have excellent references and would be delighted to discuss any possible vacancy wi[r]

11 Read more

Show all 10000 documents...