Determining the Solution Space of Vertex-Cover by Interactions and Backbones

To solve the combinatorial optimization problems especially the minimal Vertex-cover problem with high efficiency, is a significant task in theoretical computer science and many other subjects. Aiming at detecting the solution space of Vertex-cover, a new structure named interaction between nodes is defined and discovered for random graph, which results in the emergence of the frustration and long-range correlation phenomenon. Based on the backbones and interactions with a node adding process, we propose an Interaction and Backbone Evolution Algorithm to achieve the reduced solution graph, which has a direct correspondence to the solution space of Vertex-cover. By this algorithm, the whole solution space can be obtained strictly when there is no leaf-removal core on the graph and the odd cycles of unfrozen nodes bring great obstacles to its efficiency. Besides, this algorithm possesses favorable exactness and has good performance on random instances even with high average degrees. The interaction with the algorithm provides a new viewpoint to solve Vertex-cover, which will have a wide range of applications to different types of graphs, better usage of which can lower the computational complexity for solving Vertex-cover

‘Unfair’ Discrimination in Two-sided Peering? Evidence from LINX

‘Unfair’ Discrimination in Two-sided Peering? Evidence from LINX Abstract: Does asymmetry between Internet Providers affect the “fairness” of their interconnection contracts? While recent game theoretic literature provides contrasting answers to this question, there is a lack of empirical research. We introduce a novel dataset on micro-interconnection policies and provide an econometric analysis of the determinants of peering decisions amongst the Internet Service Providers interconnecting at the London Internet Exchange Point (LINX). Our key result shows that two different metrics, introduced to capture asymmetry, exert opposite effects. Asymmetry in “market size” enhances the quality of the link, while asymmetry in “network centrality” induces quality degradation, hence “unfairer” interconnection conditions

Expansion of the ligand knowledge base for chelating P,P-donor ligands (LKB-PP)

[Image: see text] We have expanded the ligand knowledge base for bidentate P,P- and P,N-donor ligands (LKB-PP, Organometallics2008, 27, 1372–1383) by 208 ligands and introduced an additional steric descriptor (nHe(8)). This expanded knowledge base now captures information on 334 bidentate ligands and has been processed with principal component analysis (PCA) of the descriptors to produce a detailed map of bidentate ligand space, which better captures ligand variation and has been used for the analysis of ligand properties

Private Peering Among Internet Backbone Providers

We develop a model, in which Internet backbone providers decide on private peering agreements, comparing the benefits of private peering relative to being connected only through National Access Points. Backbone providers compete by setting capacities for their networks, capacities on the private peering links, if they choose to peer privately, and access prices. The model is formulated as a multistage game. We examine the model from two alternative modelling perspectives - a purely non-cooperative game, where we solve for Subgame Perfect Nash Equilibria through backward induction, and a network theoretic perspective, where we examine pairwise stable and efficient networks. While there are a large number of Subgame Perfect Nash Equilibria, both the pairwise stable and the efficient network are unique and the stable network is not efficient and vice versa. The stable network is the complete network, where all the backbone providers choose to peer with each other, while the efficient network is the one, where the backbone providers are connected to each other only through the National Access Points.Subgame perfect Nash equilibrium, networks, pairwise stability, efficiency

Private Peering Among Internet Backbone Providers

We develop a model, in which Internet backbone providers decide on private peering agreements, comparing the benefits of private peering relative to being connected only through National Access Points. Backbone providers compete by setting capacities for their networks, capacities on the private peering links, if they choose to peer privately, and access prices. The model is formulated as a multistage game. We examine the model from two alternative modelling perspectives - a purely non-cooperative game, where we solve for Subgame Perfect Nash Equilibria through backward induction, and a network theoretic perspective, where we examine pairwise stable and efficient networks. While there are a large number of Subgame Perfect Nash Equilibria, both the pairwise stable and the efficient network are unique and the stable network is not efficient and vice versa. The stable network is the complete network, where all the backbone providers choose to peer with each other, while the efficient network is the one, where the backbone providers are connected to each other only through the National Access Points.Subgame perfect Nash equilibrium, networks, pairwise stability, efficiency

Large-scale topological and dynamical properties of Internet

We study the large-scale topological and dynamical properties of real Internet maps at the autonomous system level, collected in a three years time interval. We find that the connectivity structure of the Internet presents average quantities and statistical distributions settled in a well-defined stationary state. The large-scale properties are characterized by a scale-free topology consistent with previous observations. Correlation functions and clustering coefficients exhibit a remarkable structure due to the underlying hierarchical organization of the Internet. The study of the Internet time evolution shows a growth dynamics with aging features typical of recently proposed growing network models. We compare the properties of growing network models with the present real Internet data analysis.Comment: 13 pages, 15 eps figure

Asymmetry and Discrimination in Internet Peering Evidence from the LINX

Is the quality of interconnection between Internet operators affected by their asymmetry? While recent game theoretic literature provides contrasting answers to this question, there is a lack of empirical research. We introduce a novel dataset based on Internet routing policies, and study the interconnection decisions amongst the Internet Service Providers (ISPs) members of the London Internet Exchange Point (LINX). Our results show that interconnection quality degradation can be significantly explained by asymmetry between providers. We also show that Competition Authorities should focus more on the role played by the “centrality of an operatorâ€, rather than on its market share.Internet Peering, Two-sided Markets, Network Industries, Antitrust, Net Neutrality