What is a Network?
A network consists of 2 or more computers connected together, and they can communicate and share resources .
How many kinds of Networks?
• Depending on one’s perspective, we can classify networks in different ways
• Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless
• Based on network size: LAN and WAN (and MAN)
• Based on management method: Peer-to-peer and Client/Server
• Based on topology (connectivity): Bus, Star, Ring …
Network Management Method :
Peer to Peer Network
• Peer-to-peer network is also called workgroup
• No hierarchy among computers Þ all are equal
• No administrator responsible for the network
• Network Clients (Workstation)
• Computers that request network resources or services
• Network Servers
• Computers that manage and provide network resources and services to clients
• Usually have more processing power, memory and hard disk space than clients
• Run Network Operating System that can manage not only data, but also users, groups, security, and applications on the network
• Servers often have a more stringent requirement on its performance and reliability
Networks are common in financial services. Perfect competition does not decentralize optimality on a network, and coordination of participants expectations and investments is crucial for success.
Financial exchange networks exhibit two kinds of externalities: liquidity enhancement by size expansion, and underpriced provision of market price information to outside rivals. We discuss .. the interaction of these externalities in alternative exchange network structures .
A crucial feature of networks is that they exhibit network externalities, i.e., production or consumption positive size externalities. In a typical network, the addition of a new customer (or network node) increases the willingness to pay for network services by all participants. When a new node is added to a network, new goods are created. Consumers demand these goods that were unavailable before. Thus, consumers are better off after the new node was added. The benefits of the addition of an extra node (or an extra customer) exceed the private benefits
accruing to the particular node (or customer).
networks are common in the modern economy as well as in the financial
services sector. Perfect competition does not decentralize optimality on a network, and coordination of participants expectations and investments is crucial for success. Financial networks exhibit two kinds of externalities: liquidity enhancement by size expansion, and underpriced provision of market price information to outside rivals. Both externalities can produce significant welfare distortions. However, markets structures can be established and fine tuned so as to realize more fully the positive externality of liquidity enhancement (for example through interspersing call and continuous markets). Further, the negative effects of the second externality can be diminished by pricing market information appropriately when used in commercial exchange transactions.
declining communication costs :
A multi-hop network of wireless sensors can be used to gather spatio-temporal samples of a physical phenomenon and transmit these samples to a processing center. This paper addresses the important issue of minimizing the number of transmissions required to gather one sample from each sensor. The technique used to minimize communication costs combines analytical results from stochastic geometry with a distributed, randomized algorithm for generating clusters of sensors. The minimum communication energy achieved by this approach is significantly lower than the energy costs incurred in non-clustered networks and in clustered networks produced by such algorithms as the Max–Min d-cluster algorithm
A lower bound on the number of processors and finish time for the problem of scheduling precedence graphs with communication costs is presented. The notion of the earliest starting time of a task is formulated for the context of lower bounds. A lower bound on the completion time is proposed. A task delay which does not increase the earliest completion time of a schedule is defined. Each task can then be scheduled within a time interval without affecting the lower bound performance on the finish time. This leads to definition of a new lower bound on the number of processors required to process the task graph. A derivation of the minimum time increase over the earliest completion time is also proposed for the case of a smaller number of processors. A lower bound on the minimum number of inter processor communication links required to achieve optimum performance is proposed. Evaluation had been carried out by using a set of 360 small graphs. The bound on the finish time deviates at most by 5% from the optimum solution in 96% of the cases and performs well with respect to the minimum number of processors and communication links
The Impact of Hurricane Katrina on Communications Infrastructure :
Communications infrastructure is critical to managing the complex, dynamic operations that evolve in disaster environments. The impact of Hurricane Katrina destroyed the communications infrastructure within the New Orleans metropolitan region, leaving emergency response personnel and the public with little capacity to exchange information vital for coordinating response actions. The loss of communications proved especially damaging, given the size of the geographic region and the number of people affected. The authors used content analysis of news reports to identify the network of organizations that emerged in response to Hurricane Katrina, and network analysis to examine patterns of interaction among the organizations. The patterns reveal significant asymmetry in information among organizations at different levels of authority and responsibility in the disaster response system, a condition that contributed to the collapse of coordination in disaster operations. Conversely, well-designed communications and information infrastructure can contribute significantly to the resilience of communities exposed to recurring risk
References:
