When forwarding in opportunistic networks, the higher contact probability that the destination node has, the more likely it is to forward the message to the destination. Moreover, the higher the betweenness centrality that a node has, the more likely it is to act as a bridge node toward the destination in the network. Each of these two metrics is exploited in existing forwarding schemes. Nevert...

The performance of today’s email anti-spam systems is primarily measured by the percentage of false positives (non-spam messages detected as spam) rather than by the percentage of false negatives (real spam messages left unblocked). One reliable anti-spam technique is the Universal Resource Locator (URL)-based filter, which is utilized by most collaborative signature-based filters. URL-based fi...

Finding central nodes is a fundamental problem in network analysis. Betweenness centrality is a well-known measure which quantifies the importance of a node based on the fraction of shortest paths going though it. Due to the dynamic nature of many today’s networks, algorithms that quickly update centrality scores have become a necessity. For betweenness, several dynamic algorithms have been pro...

Measuring and predicting the human mobility along the links of a transportation network has always been of a great importance to researchers in the field. Hitherto, producing such data relied heavily on expensive and time consuming surveying and on-field observational methods. In this work we propose an efficient estimation method for the assessment of the flow through links in transportation n...

We study the response of complex networks subject to attacks on vertices and edges. Several existing complex network models as well as real-world networks of scientific collaborations and Internet traffic are numerically investigated, and the network performance is quantitatively measured by the average inverse geodesic length and the size of the largest connected subgraph. For each case of att...

Betweenness centrality is a metric that seeks to quantify a sense of the importance of a vertex in a network graph in terms of its ‘control’ on the distribution of information along geodesic paths throughout that network. This quantity however does not capture how different vertices participate together in such control. In order to allow for the uncovering of finer details in this regard, we in...

The goal of this paper is to estimate the top k central nodes in a network through parsimonious sampling, in an online fashion. We consider three centrality metrics: degree, betweenness, and closeness centrality. We identify and investigate through simulations the contributions of two sources of error in finding central nodes: (1) sampling (collection) error and (2) identification error. Sampli...

In a paper examining informal networks and organizational crisis, Krackhardt and Stern (1988) proposed a measure assessing the extent to which relations in a network were internal to a group as opposed to rokerage roles ategorical attributes external. They called their measure the E–I index. The measure is now in wide use and is implemented in standard network packages such as UCINET (Borgatti ...