Understanding which node failures in a network have more impact is an important problem. Current understanding, motivated by the scale free models of network growth, places emphasis on the degree of the node. This is not a satisfactory measure; the number of connections a node has does not capture how redundantly it is connected into the whole network. Conversely, the structural entropy of a graph captures the resilience of a network well, but is expensive to compute, and, being a global measure, does not attribute any specific value to a given node. This lack of locality prevents the use of global measures as a way of identifying critical nodes. In this paper, we introduce local vertex measures of entropy which do not suffer from such drawbacks. In our theoretical analysis, we establish the possibility that our local vertex measures approximate global entropy, with the advantage of locality and ease of computation. We establish properties that vertex entropy must have in order to be useful for identifying critical nodes. We have access to a proprietary event, topology, and incident dataset from a large commercial network. Using this dataset, we demonstrate a strong correlation between vertex entropy and incident generation over events.

From Definition 2 in the above-named work, we have for a simple graph$G=(V,E)$, the following expression for the chromatic entropy$I_{C}(G)$of a graph:\begin{equation*} I_{C}\left ({G}\right) = \min _{\left \{{C_{i}}\right \}} - \sum _{i=1}^{N_{c}} \frac {|C_{i}|}{n} \log _{2} \frac {|C_{i}|}{n} \tag{1}\end{equation*}

Modern data centres provide large aggregate network capacity and multiple paths among servers. Traffic is very diverse; most of the data is produced by long, bandwidth hungry flows but the large majority of flows, which commonly come with strict deadlines regarding their completion time, are short. It has been shown that TCP is not efficient for any of these types of traffic in modern data centres. More recent protocols such MultiPath TCP (MPTCP) are very efficient for long flows, but are ill-suited for short flows. In this paper, we present Maximum MultiPath TCP (MMPTCP), a novel transport protocol which, compared to TCP and MPTCP, reduces short flows' completion times, while providing excellent goodput to long flows. To do so, MMPTCP runs in two phases; initially, it randomly scatters packets in the network under a single congestion window exploiting all available paths. This is beneficial to latency-sensitive flows. After a specific amount of data is sent, MMPTCP switches to a regular MultiPath TCP mode. MMPTCP is incrementally deployable in existing data centres as it does not require any modifications outside the transport layer and behaves well when competing with legacy TCP and MPTCP flows. Our extensive experimental evaluation in simulated FatTree topologies shows that all design objectives for MMPTCP are met.

A key objective of monitoring networks is to identify potential service threatening outages from events within the network before service is interrupted. Identifying causal events, Root Cause Analysis (RCA), is an active area of research, but current approaches are vulnerable to scaling issues with high event rates. Elimination of noisy events that are not causal is key to ensuring the scalability of RCA. In this paper, we introduce vertex-level measures inspired by Graph Entropy and propose their suitability as a categorization metric to identify nodes that are a priori of more interest as a source of events. We consider a class of measures based on Structural, Chromatic and Von Neumann Entropy. These measures require NP-Hard calculations over the whole graph, an approach which obviously does not scale for large dynamic graphs that characterise modern networks. In this work we identify and justify a local measure of vertex graph entropy, which behaves in a similar fashion to global measures of entropy when summed across the whole graph. We show that such measures are correlated with nodes that generate incidents across a network from a real data set.

With the proliferation of smartphones and their advanced connectivity capabilities, opportunistic networks have gained a lot of traction during the past years; they are suitable for increasing network capacity and sharing ephemeral, localised content. They can also offload traffic from cellular networks to device-to-device ones, when cellular networks are heavily stressed. Opportunistic networks can play a crucial role in communication scenarios where the network infrastructure is inaccessible due to natural disasters, large-scale terrorist attacks or government censorship. Geocasting, where messages are destined to specific locations (casts) instead of explicitly identified devices, has a large potential in real world opportunistic networks, however it has attracted little attention in the context of opportunistic networking. In this paper we propose Geocasting Spray And Flood (GSAF), a simple but efficient and flexible geocasting protocol for opportunistic, delay-tolerant networks. GSAF follows a simple but elegant and flexible approach where messages take random walks towards the destination cast. Messages that follow directions away from the cast are extinct when the device buffer gets full, freeing space for new messages to be delivered. In GSAF, casts do not have to be pre-defined; instead users can route messages to arbitrarily defined casts. Our extensive evaluation shows that GSAF is efficient, in terms of message delivery ratio and latency as well as network overhead.

In this paper, we introduce MMPTCP, a novel transport protocol which aims at unifying the way data is transported in data centres. MMPTCP runs in two phases; initially, it randomly scatters packets in the network under a single congestion window exploiting all available paths. This is beneficial to latency-sensitive flows. During the second phase, MMPTCP runs in Multi-Path TCP (MPTCP) mode, which has been shown to be very efficient for long flows. Initial evaluation shows that our approach significantly improves short flow completion times while providing high throughput for long flows and high overall network utilisation.

In order to understand the evolution of online identities, we measured the correlation between past and the current representations of self on MySpace social network. We applied several techniques and proposed a personality classifier to calculate the level of honesty and accountability for over 2 million users. We formulized a transformation algorithm to measure both static and dynamic features of identity traits over time. This experiment provides evidence of the dynamic nature of profilespsila information, the social network structure and the group similarities. In this paper, we will discuss how online identities progress during one year time frame and what impact it may have to determine user's characteristics. This analysis can be used to develop a technology to predict the taxonomy of identities and the direction of online social representation.

Dynamic pages and the increasing number of functions that websites can perform are changing users' relations with the Web. Little has been reported on how the experience of using this kind of interactive site differs from the ‘point and click’ interactivity of the early Web. This paper reports on a qualitative study of users who entered text while visiting a website of their choice. It shows how the process brought with it two levels of awareness: that of the interface, and that of the social context beyond the interface. The paper goes on to describe the perception of audience that emerged from analysing users' accounts. It also gives details of the data collection method, which is based on the work of Vermersch and has not been widely used outside France for analysing interaction with computers. The implications for website design are considered.

We describe an abstract architecture of adaptive applications, and indicate where we believe crucial design decisions must be made.We illustrate the use of the abstract model in the design and implementation ofan image proxy, and describe the studies required in determining the appropriate design points.In particular, even though adaptation to resource constraints is generally considered a systems probleu the adaptation is visible to the user in changes in utility, and so the user must be involved in designing the application.Finally, we discuss the politics that creep in when dwigners change the semantics of applications. Adapting to Constraints: Choices in Application Design An adaptive application is one in which the application changes its behaviour according to the perceived constraints in Ille envitnnnlent, so fl,rto nlaintain the semantics of the application for the lise~If we take the above definition as our starting point, then we 133 -----..-. . ... . . . .

This paper presents the Conference Control Channel Protocol (CCCP), a new scheme intended for controlling conferences ranging from small, tightly coupled meetings, to extremely large loosely coupled seminars. We describe the requirements of such a scheme, and present a framework for building systems that connect together new and existing applications.

We describe a mechanism for scalable control of multicast continuous media streams. The mechanism uses a novel probing mechanism to solicit feedback information in a scalable manner and to estimate the number of receivers. In addition, it separates the congestion signal from the congestion control algorithm, so as to cope with heterogeneous networks.

In this paper we analyse the requirements that the user and a packet network have of compressed video. From these, we produce a synthesis of the characteristics of an ideal video compression coding. Using this dialectic, we then examine the currently available compression schemes and determine which is closet to the ideal.