This paper studies a covering problem on graph which is a variant of facility location problem. In this research, constraints are considered to improve the previous model. These constraints have not considered previously. The first constraint limits the capacity of the facilities and the other one considers different coverage distances. The objective is to determine the optimal subset of candid...

We propose the so-called backup tree algorithm to compute a set of n-1 backup multicast delivery trees from the default multicast tree for application level multicast. For each backup multicast tree exactly one link of the default multicast tree is replaced by a backup link from the set of available links. The backup tree algorithm calculates the n-1 trees with a complexity of O (m log n).

We investigate multidimensional covering mechanism-design problems, wherein there are m items that need to be covered and n agents who provide covering objects, with each agent i having a private cost for the covering objects he provides. The goal is to select a set of covering objects of minimum total cost that together cover all the items. We focus on two representative covering problems: unc...

Network Function Virtualization (NFV) is a promising technique to greatly improve the effectiveness and flexibility of network services through a process named Service Function Chain (SFC) mapping, with which different network services are deployed over virtualized and shared platforms in data centers. However, such an evolution towards software-defined network functions introduces new challeng...

We consider a finite capacity queueing system with one main server who is supported by a backup server. We assume Markovian arrivals, phase type services, and a threshold-type server backup policy with two pre-determined lower and upper thresholds. A request for a backup server is made whenever the buffer size (number of customers in the queue) hits the upper threshold and the backup server is ...

In this paper, we show two process allocation schemes to tolerate multiple faults when the primary-backup replication method is used. The rst scheme, called multiple backup scheme, is running multiple backup processes for each process to tolerate multiple faults. The second scheme, called regenerative backup scheme, is running only one backup process for each process, but regenerates backup pro...

In this paper, we show two process allocation schemes to tolerate multiple faults when the primary-backup replication method is used. The first scheme, called multiple backup scheme, is running multiple backup processes for each process to tolerate multiple faults. The second scheme, called regenerative backup scheme, is running only one backup process for each process, but re-generates backup ...

We consider the indirect covering subtree problem (Kim et al., 1996). The input is an edge weighted tree graph along with customers located at the nodes. Each customer is associated with a radius and a penalty. The goal is to locate a tree-shaped facility such that the sum of setup and penalty cost is minimized. The setup cost equals the sum of edge lengths taken by the facility and the penalty...

This paper describes two similar user-initiated methods to backup and restore PC workstations over an ethernet network. The first method concerns ‘‘PC Hardware All Alike,’’ or the backup and restoring of sets of identical disk images across many identical systems. The second method is the backup and restoring of ‘‘PC Hardware All Different,’’ which manages unique disk images on individual syste...

In a primary-backup system, transaction processing takes place at the primary and the log records generated are propagated to the backup which uses them to reconstruct a recent state of the database. If the primary fails, the backup takes over transaction processing without causing users to observe a breach in service. Existing approaches can be broadly classi ed as 2-safe or 1-safe based on wh...