bluuebunny/crossref_metadata_2025 huggingface dataset:
PREVENTION OF SINTERING DURING ANNEALING PROCESS OF FePt NANOPARTICLES COATED WITH ZnO SHELL
Authors: ZEYNALI HOSSEIN , AKBARI HOSSEIN , GHASABEH REYHANEH KARIMI , ARUMUGAM S. , CHAMANZADEH ZOHREH , KALAISELVAN G.
Published: September 2012

Monodispersed 4.1 nm FePt nanoparticles with narrow size distribution were successfully synthesized by the chemical polyol process with co-reduction of Fe (acac)3 and Pt (acac)2 in the presence of 1,2-hexadecanediol as a reducing agent. To achieve hard ferromagnetic behavior with L10 phase and face center tetragonal (fct) structure, high temperature annealing is performed. Annealing causes the surfactant surrounding particles to decompose and agglomeration of particles occurs. In the present work, chemically synthesized FePt nanoparticles were coated with nonmagnetic ZnO oxide shell to prevent them from sintering. Coercivity of FePt and FePt/ZnO nanoparticles increases from 5 kOe to 10 kOe and 1.8 kOe to 6 kOe respectively, with the increasing annealing temperatures from 650 to 750°C.
HYDROGEN STORAGE ENHANCEMENT VIA TRANSITION METAL DECORATION ON METAL ORGANIC FRAMEWORKS: A FIRST-PRINCIPLES STUDY
Authors: HWANG JEONGWOON , PARK CHANGWON , CHOI KEUNSU , CHA MOON-HYUN , AHUJA RAJEEV , KIM DONG WOOK , KIM DONG OK , SAGONG KIL , JOUNG UI GAB , JEONG HOGYUN , IHM JISOON
Published: September 2012

We investigate the hydrogen storage capacity of the light transition metal (TM)-decorated metal organic frameworks (MOFs) by performing ab initio density functional theory calculations. We find that among all the light TM elements, divalent Ti and Fe are suitable for decorating MOFs to enhance the hydrogen uptake, considering the H2 binding energy on the TM atom and the reversibly usable number of H2 molecules attached to the metal site. In general, the magnetization of metal atoms undergoes a high-spin to low-spin state transition when H2 molecules are adsorbed, which helps to stabilize the system energetically. By analyzing the projected density of states on each TM atom, it is shown that the d-level shift induced by the ligand field of the adsorbed H2 molecules contributes substantially to the H2 binding strength. We also study the stability of selected TM-decorated nanostructures against the attack of foreign molecules by examining the energetics of those contaminating molecules around the metal sites.
CONTROLLABLE CHEMICAL VAPOR DEPOSITION SYNTHESIS OF SINGLE-WALL CARBON NANOTUBES USING MIST FLOW METHOD
Authors: SUN YUN , KITAURA RYO , NAKAYAMA TAKUYA , MIYATA YASUMITSU , SHINOHARA HISANORI
Published: September 2012

The influences of synthesis parameters on the mean diameter and diameter distribution of as-grown single-wall carbon nanotubes (SWCNTs) with chemical vapor deposition (CVD) using the mist flow method have been investigated in detail with Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We found that CVD reaction temperature and flow rate play an essential role in controlling the mean diameter and the quality of as-grown SWCNTs. Furthermore, we found that the carbon supply kinetics can be a dominant factor to determine the diameter of as-grown SWCNTs in the present mist flow method. Under a different combination of various parameters, the mean diameter of SWCNTs can be varied from 0.9 nm to 1.5 nm controllably.
GLOBAL ASYMPTOTIC STABILITY FOR A TWO-SPECIES DISCRETE RATIO-DEPENDENT PREDATOR–PREY SYSTEM
Authors: ZHUO XIANGLAI
Published: September 2012

The dynamical behaviors of a two-species discrete ratio-dependent predator–prey system are considered. Some sufficient conditions for the local stability of the equilibria is obtained by using the linearization method. Further, we also obtain a new sufficient condition to ensure that the positive equilibrium is globally asymptotically stable by using an iteration scheme and the comparison principle of difference equations, which generalizes what paper [G. Chen, Z. Teng and Z. Hu, Analysis of stability for a discrete ratio-dependent predator–prey system, Indian J. Pure Appl. Math.42(1) (2011) 1–26] has done. The method given in this paper is new and very resultful comparing with papers [H. F. Huo and W. T. Li, Existence and global stability of periodic solutions of a discrete predator–prey system with delays, Appl. Math. Comput.153 (2004) 337–351; X. Liao, S. Zhou and Y. Chen, On permanence and global stability in a general Gilpin–Ayala competition predator–prey discrete system, Appl. Math. Comput.190 (2007) 500–509] and it can also be applied to study the global asymptotic stability for general multiple species discrete population systems. At the end of this paper, we present an open question.
NEIGHBOR SUM DISTINGUISHING COLORING OF SOME GRAPHS
Authors: DONG AIJUN , WANG GUANGHUI
Published: September 2012

A proper [k]-edge coloring of a graph G is a proper edge coloring of G using colors of the set [k] = {1, 2,…,k}. A neighbor sum distinguishing [k]-edge coloring of G is a proper [k]-edge coloring of G such that for each edge uv ∈ E(G), the sum of colors taken on the edges incident to u is different from the sum of colors taken on the edges incident to v. By ndiΣ(G), we denote the smallest value k in such a coloring of G. In this paper, we obtain that (1) ndiΣ(G) ≤ max {2Δ(G) + 1, 25} if G is a planar graph, (2) ndiΣ(G) ≤ max {2Δ(G), 19} if G is a graph such that mad(G) ≤ 5.
BOUNDS FOR CODES CORRECTING/DETECTING REPEATED LOW-DENSITY BURST ERRORS
Authors: DASS BAL KISHAN , GARG POONAM
Published: September 2012

This paper presents lower bound on the number of parity-check digits required for linear codes that correct m-repeated low-density burst errors of length b (fixed) with weight w or less (w ≤ b). An upper bound on the number of parity-check digits required for linear codes that are capable of detecting such m-repeated low-density bursts has also been derived.
ACYCLIC MATCHINGS IN SUBCLASSES OF BIPARTITE GRAPHS
Authors: PANDA B. S. , PRADHAN D.
Published: September 2012

A set M ⊆ E is called an acyclic matching of a graph G = (V, E) if no two edges in M are adjacent and the subgraph induced by the set of end vertices of the edges of M is acyclic. Given a positive integer k and a graph G = (V, E), the acyclic matching problem is to decide whether G has an acyclic matching of cardinality at least k. Goddard et al. (Discrete Math.293(1–3) (2005) 129–138) introduced the concept of the acyclic matching problem and proved that the acyclic matching problem is NP-complete for general graphs. In this paper, we propose an O(n + m) time algorithm to find a maximum cardinality acyclic matching in a chain graph having n vertices and m edges and obtain an expression for the number of maximum cardinality acyclic matchings in a chain graph. We also propose a dynamic programming-based O(n + m) time algorithm to find a maximum cardinality acyclic matching in a bipartite permutation graph having n vertices and m edges. Finally, we strengthen the complexity result of the acyclic matching problem by showing that this problem remains NP-complete for perfect elimination bipartite graphs.
ABSOLUTELY SECURE MESSAGE TRANSMISSION USING A KEY SHARING GRAPH
Authors: INDO YOSHIHIRO , MIZUKI TAKAAKI , NISHIZEKI TAKAO
Published: September 2012

Assume that there are players and an eavesdropper Eve of unlimited computational power and that several pairs of players have shared secret keys beforehand. In a key sharing graph, each vertex corresponds to a player, and each edge corresponds to a secret key shared by the two players corresponding to the ends of the edge. Given a key sharing graph, a player wishes to send a message to another player so that the eavesdropper Eve and any other player can get no information on the message. In this paper, we first give a necessary and sufficient condition on a key sharing graph for the existence of such a unicast protocol. We then extend the condition to the case where a multiple number of players other than the sender and receiver passively collude. We finally give a sufficient condition for the existence of a secure multicast protocol.
A REVIEW ON THE HEAT-TRANSFER PERFORMANCE AND PRESSURE-DROP CHARACTERISTICS OF VARIOUS ENHANCED TUBES
Authors: LAOHALERTDECHA S. , DALKILIC A. S. , WONGWISES S.
Published: September 2012

The enhanced tube is a kind of the passive technique for improving the thermal performance of the heat exchangers with a little increase of the friction penalty. They have stated to use instead of the common smooth tubes for designing of the heat exchangers. The size of these heat exchangers can be reduced considerably by using the enhanced tubes instead of smooth tubes. Normally, they are divided into four groups: the corrugated tube, ribbed tube, grooved tube, and fluted tube. Compared with the common smooth tube, many researchers reported that use of the enhanced tubes dramatically increases the heat-transfer performance, both theoretically and experimentally. Focusing on the advantages of the enhanced tubes, this article summarizes the published studies on the heat-transfer and pressure-drop characteristics of the enhanced tubes, both experimental and quantitative investigations.
TRANSCRITICAL CO2 REFRIGERATION SYSTEMS: COMPARISON WITH CONVENTIONAL SOLUTIONS AND APPLICATIONS
Authors: SARKAR JAHAR
Published: September 2012

Carbon dioxide (CO2) is one of the natural refrigerants which can be used as working fluid in various refrigeration applications along with the ammonia and hydrocarbons due to its eco-friendliness, higher volumetric capacity, good heat transfer properties, etc. The present article consists of two parts: A detailed comparative study of CO2 -based transcritical refrigeration systems with conventional refrigerants-based systems in terms of both thermodynamic and heat transfer performances, and review of both theoretical and experimental researches on transcritical CO2 vapor compression cycle for various refrigeration applications including commercial product status. Suitability of the CO2 system in specific refrigeration application is also discussed.
In-situ soil moisture sensing
Authors: Wu Xiaopei , Liu Mingyan , Wu Yue
Published: September 2012

We study the problem of optimal sensor placement in the context of soil moisture sensing. We show that the soil moisture data possesses some unique features that can be used together with the commonly used Gaussian assumption to construct more scalable, robust, and better performing placement algorithms. Specifically, there exists a coarse-grained monotonic ordering of locations in their soil moisture level over time, both in terms of its first and second moments, a feature much more stable than the soil moisture process itself at these locations. This motivates a clustered sensor placement scheme, where locations are classified into clusters based on the ordering of the mean, with the number of sensors placed in each cluster determined by the ordering of the variances. We show that under idealized conditions the greedy mutual information maximization algorithm applied globally is equivalent to that applied cluster by cluster, but the latter has the advantage of being more scalable. Extensive numerical experiments are performed on a set of three-dimensional soil moisture data generated by a state-of-the-art soil moisture simulator. Our results show that our clustering approach outperforms applying the same algorithms globally, and is very robust to lack of training and errors in training data.
Theory and algorithms for hop-count-based localization with random geometric graph models of dense sensor networks
Authors: Nath Swaprava , Ekambaram Venkatesan N. , Kumar Anurag , Kumar P. Vijay
Published: September 2012

Wireless sensor networks can often be viewed in terms of a uniform deployment of a large number of nodes in a region of Euclidean space. Following deployment, the nodes self-organize into a mesh topology with a key aspect being
self-localization
. Having obtained a mesh topology in a dense, homogeneous deployment, a frequently used approximation is to take the hop distance between nodes to be proportional to the Euclidean distance between them. In this work, we analyze this approximation through two complementary analyses. We assume that the mesh topology is a random geometric graph on the nodes; and that some nodes are designated as
anchors
with known locations. First, we obtain high probability bounds on the Euclidean distances of
all
nodes that are
h
hops away from a fixed anchor node. In the second analysis, we provide a heuristic argument that leads to a direct approximation for the density function of the Euclidean distance between two nodes that are separated by a hop distance
h
. This approximation is shown, through simulation, to very closely match the true density function.

Localization algorithms that draw upon the preceding analyses are then proposed and shown to perform better than some of the well-known algorithms present in the literature. Belief-propagation-based message-passing is then used to further enhance the performance of the proposed localization algorithms. To our knowledge, this is the first usage of message-passing for hop-count-based self-localization.
Redesigning the data center
Authors: Mone Gregory
Published: September 2012

Faced with rising electricity costs, leading companies have begun revolutionizing the way data centers work, from the hardware to the buildings themselves.
Computer science and the three Rs
Authors: Hoffmann Leah
Published: September 2012

A growing sense of crisis prevails as computer science searches for its place in the K--12 curriculum.
Reflecting on the Facebook IPO
Authors: Cusumano Michael A.
Published: September 2012

Exploring some factors that reflect a company's worth.
A nice piece of code
Authors: Neville-Neil George V.
Published: September 2012

Colorful metaphors and properly reusing functions.
Computing as if infrastructure mattered
Authors: Blanchette Jean-François
Published: September 2012

Understanding the technical and social fundamentals of the computing infrastructure is essential in the continuously evolving technological realm.
A fast solver for a class of linear systems
Authors: Koutis Ioannis , Miller Gary L. , Peng Richard
Published: September 2012

The solution of linear systems is a problem of fundamental theoretical importance but also one with a myriad of applications in numerical mathematics, engineering, and science. Linear systems that are generated by real-world applications frequently fall into special classes. Recent research led to a fast algorithm for solving symmetric diagonally dominant (SDD) linear systems. We give an overview of this solver and survey the underlying notions and tools from algebra, probability, and graph algorithms. We also discuss some of the many and diverse applications of SDD solvers.
Improving New Users’ Query Performance
Authors: Robb David A. , Bowen Paul L. , Borthick A. Faye , Rohde Fiona H.
Published: September 2012

As the volume of data in organizational databases grows, organizations are seeking to use this data to improve organizational success. To this end, users are being asked to query these databases to provide information to help answer questions posed by key management personnel. Users who have had extensive experience with an organization’s data can often detect the presence of errors in their queries when query results do not correspond to their ex ante expectations. New users, however, are less familiar with the data they will be querying. Having no, or limited, ex ante expectations for query results, new users may be unaware that the result produced by their query is incorrect. Unwarranted confidence in the correctness of their queries predisposes these users to stop looking for query errors even when their queries still contain errors. This behavior, premature stopping of query revision, prompts investigating whether new users’ query performance would improve if they were not only provided with, but used, readily available information to form ex ante expectations. Our results demonstrated a threshold effect in new users heeding information for forming ex ante expectations. That is, the mere availability of information for forming ex ante expectations made no difference in query performance. When admonishing users to heed ex ante information, however, there was an associated increase in the accuracy of their queries. These results suggest that users unfamiliar with a particular database might make fewer query errors if they not only received readily available information but were then prompted to use the information to form ex ante expectations for query results.
Ubiquity symposium: Evolutionary computation and the processes of life
Authors: Schwefel Hans-Paul
Published: September 2012

In this second article in the ACM Ubiquity symposium on evolutionary computation Hans-Paul Schwefel explores the effects of simulating evolutionary mechanisms.
Picasso
Authors: Hong Steven S. , Mehlman Jeffrey , Katti Sachin
Published: September 2012

This paper presents the design, implementation and evaluation of Picasso, a novel radio design that allows simultaneous transmission and reception on separate and arbitrary spectrum fragments using a single RF frontend and antenna. Picasso leverages this capability to flexibly partition fragmented spectrum into multiple slices that share the RF frontend and antenna, yet operate concurrent and independent PHY/MAC protocols. We show how this capability provides a general and clean abstraction to exploit fragmented spectrum in WiFi networks, handle coexistence in dense deployments as well as many other applications. We prototype Picasso, and demonstrate experimentally that a Picasso radio partitioned into four slices, each concurrently operating four standard WiFi OFDM PHY and CSMA MAC stacks, can achieve the same sum throughput as four physically separate radios individually configured to operate on the spectrum fragments. We also demonstrate experimentally how Picasso's slicing abstraction provides a clean mechanism to enable multiple diverse networks to coexist and achieve higher throughput, better video quality and latency than the best known state of the art approaches.
Efficient and reliable low-power backscatter networks
Authors: Wang Jue , Hassanieh Haitham , Katabi Dina , Indyk Piotr
Published: September 2012

There is a long-standing vision of embedding backscatter nodes like RFIDs into everyday objects to build ultra-low power ubiquitous networks. A major problem that has challenged this vision is that backscatter communication is neither reliable nor efficient. Backscatter nodes cannot sense each other, and hence tend to suffer from colliding transmissions. Further, they are ineffective at adapting the bit rate to channel conditions, and thus miss opportunities to increase throughput, or transmit above capacity causing errors.

This paper introduces a new approach to backscatter communication. The key idea is to treat all nodes as if they were a single virtual sender. One can then view collisions as a code across the bits transmitted by the nodes. By ensuring only a few nodes collide at any time, we make collisions act as a
sparse code
and decode them using a new customized compressive sensing algorithm. Further, we can make these collisions act as a
rateless code
to automatically adapt the bit rate to channel quality --i.e., nodes can keep colliding until the base station has collected enough collisions to decode. Results from a network of backscatter nodes communicating with a USRP backscatter base station demonstrate that the new design produces a 3.5× throughput gain, and due to its rateless code, reduces message loss rate in challenging scenarios from 50% to zero.
Network-aware service placement in a distributed cloud environment
Authors: Steiner Moritz , Gaglianello Bob Gaglianello , Gurbani Vijay , Hilt Volker , Roome W.D. , Scharf Michael , Voith Thomas
Published: September 2012

We consider a system of compute and storage resources geographically distributed over a large number of locations connected via a wide-area network. By distributing the resources, latency to users can be decreased, bandwidth costs reduced and availablility increased. The challenge is to distribute services with varying characteristics among the data centers optimally. Some services are very latency sensitive, others need vast amounts of storage, and yet others are computationally complex but do not require hard deadlines on execution. We propose efficient algorithms for the placement of services to get the maximum benefit from a distributed cloud systems. The algorithms need input on the status of the network, compute resources and data resources, which are matched to application requirements.

This demonstration shows how a network-aware cloud can combine all three resource types - computation, storage, and network connectivity - in distributed cloud environments. Our dynamic service placement algorithm monitors the network and data center resources in real-time. Our prototype uses the information gathered to place or migrate services to provide the best user experience for a service.
Blockmon
Authors: Huici Felipe , di Pietro Andrea , Trammell Brian , Gomez Hidalgo Jose Maria , Martinez Ruiz Daniel , d'Heureuse Nico
Published: September 2012

Passive network monitoring and data analysis, crucial to the correct operation of networks and the systems that rely on them, has become an increasingly difficult task given continued growth and diversification of the Internet. In this demo we present Blockmon, a novel composable measurement system with the flexibility to allow for a wide range of traffic monitoring and data analysis, as well as the necessary mechanisms to yield high performance on today's modern multi-core hardware. In this demo we use Blockmon's GUI to show how to easily create Blockmon applications and display data exported by them. We present a simple flow meter application and a more involved VoIP nomaly detection one.
Signposts
Authors: Chaudhry Amir , Madhavapeddy Anil , Rotsos Charalampos , Mortier Richard , Aucinas Andrius , Crowcroft Jon , Eide Sebastian Probst , Hand Steven , Moore Andrew W. , Vallina-Rodriguez Narseo
Published: September 2012

This demo presents Signposts, a system to provide users with a secure, simple mechanism to establish and maintain communication channels between their personal cloud of named devices. Signpost names exist in the DNSSEC hierarchy, and resolve to secure end-points when accessed by existing DNS clients. Signpost clients intercept user connection intentions while adding privacy and multipath support. Signpost servers co-ordinate clients to dynamically discover routes and overcome the middleboxes that pervade modern edge networks. The demo will show a simple scenario where an individual's personal devices (phone, laptop) are interconnected via Signposts while sitting on different networks behind various middleboxes. As a result they will be able to fetch and push data between each other, demonstrated by, e.g., simple web browsing, even as the network configuration changes.
Towards SmartFlow
Authors: Németh Felicián , Stipkovits Ádám , Sonkoly Balázs , Gulyás András
Published: September 2012

The limited capabilities of the switches renders the implementation of unorthodox routing and forwarding mechanisms as a hard task in OpenFlow. Our high level goal is therefore to inspect the possibilities of slightly smartening up the OpenFlow switches. As a first step in this direction we demonstrate (with Bloom filters, greedy routing and network coding) that a very limited computational capability enables us to natively support experimental technologies while preserving performance. We distribute the demos in source files and as a ready-to-experiment VM image to promote further improvements and evaluations.
Reduction-based analysis of BGP systems with BGPVerif
Authors: Wang Anduo , Gurney Alexander J.T. , Han Xianglong , Cao Jinyan , Talcot Carolyn , Loo Boon Thau , Scedrov Andre
Published: September 2012

Today's inter-domain routing protocol, the Border Gateway Protocol (BGP), is increasingly complicated and fragile due to policy misconfiguration by individual autonomous systems (ASes). Existing configuration analysis techniques are either manual and tedious, or do not scale beyond a small number of nodes due to the state explosion problem. To aid the diagnosis of misconfigurations in real-world large BGP systems, this paper presents BGPVerif , a reduction based analysis toolkit. The key idea is to reduce BGP system size prior to analysis while preserving crucial correctness properties. BGPVerif consists of two components, NetReducer that simplifies BGP configurations, and NetAnalyzer that automatically detects routing oscillation. BGPVerif accepts a wide range of BGP configuration inputs ranging from real-world traces (Rocketfuel network topologies), randomly generated BGP networks (GT-ITM), Cisco configuration guidelines, as well as arbitrary user-defined networks. BGPVerif illustrates the applicability, efficiency, and benefits of the reduction technique, it also introduces an infrastructure that enables networking researchers to interact with advanced formal method tool.
A demonstration of ultra-low-latency data center optical circuit switching
Authors: Farrington Nathan , Porter George , Sun Pang-Chen , Forencich Alex , Ford Joseph , Fainman Yeshaiahu , Papen George , Vahdat Amin
Published: September 2012

We designed and constructed a 24x24-port optical circuit switch (OCS) prototype with a programming time of 68.5 μs, a switching time of 2.8 μs, and a receiver electronics initialization time of 8.7 μs [1]. We demonstrate the operation of this prototype switch in a data center testbed under various workloads.
AutoNetkit
Authors: Knight Simon , Jaboldinov Askar , Maennel Olaf , Phillips Iain , Roughan Matthew
Published: September 2012

We present a methodology that brings simplicity to large and complex test labs by using abstraction. The networking community has appreciated the value of large scale test labs to explore complex network interactions, as seen in projects such as PlanetLab, GENI, DETER, Emulab, and SecSI. Virtualization has enabled the creation of many more such labs. However, one problem remains: it is time consuming, tedious and error prone to setup and configure large scale test networks. Separate devices need to be configured in a coordinated way, even in a virtual lab.

AutoNetkit, an open source tool, uses abstractions and defaults to achieve both configuration and deployment and create such large-scale virtual labs. This allows researchers and operators to explore new protocols, create complex models of networks and predict consequences of configuration changes. However, our abstractions could also allow the discussion of the broader configuration management problem. Abstractions that currently configure networks in a test lab can, in the future, be employed in configuration management tools for real networks.
Bulk of interest
Authors: Wählisch Matthias , Schmidt Thomas C. , Vahlenkamp Markus
Published: September 2012

The paradigm of information-centric networking subsumes recent approaches to integrate content replication services into a future Internet layer. Current concepts foster either a dynamic mapping that directs content requests to a nearby copy, or an immediate routing on content identifiers. In this paper, we evaluate in practical experiments the performance of content routing, which we analyze with a focus on conceptual aspects. Our findings indicate that the performance of the content distribution system is threatened by a heavy management of states that arise from the strong coupling of the control to the data plane in the underlying routing infrastructure.
Towards detecting BGP route hijacking using the RPKI
Authors: Wählisch Matthias , Maennel Olaf , Schmidt Thomas C.
Published: September 2012

Prefix hijacking has always been a big concern in the Internet. Some events made it into the international world-news, but most of them remain unreported or even unnoticed. The scale of the problem can only be estimated.

The Resource Publication Infrastructure (RPKI) is an effort by the IETF to secure the inter-domain routing system. It includes a formally verifiable way of identifying who owns legitimately which portion of the IP address space. The RPKI has been standardized and prototype implementations are tested by Internet Service Providers (ISPs). Currently the system holds already about 2% of the Internet routing table.

Therefore, in theory, it should be easy to detect hijacking of prefixes within that address space. We take an early look at BGP update data and check those updates against the RPKI---in the same way a router would do, once the system goes operational. We find many interesting dynamics, not all can be easily explained as hijacking, but a significant number are likely operational testing or misconfigurations.
Choice as a principle in network architecture
Authors: Wolf Tilman , Griffioen James , Calvert Kenneth L. , Dutta Rudra , Rouskas George N. , Baldine Ilia , Nagurney Anna
Published: September 2012

There has been a great interest in defining a new network architecture that can meet the needs of a future Internet. One of the main challenges in this context is how to realize the many different technical solutions that have developed in recent years in a single coherent architecture. In addition, it is necessary to consider how to ensure economic viability of architecture solutions. In this work, we discuss how to design a network architecture where choices at different layers of the protocol stack are explicitly exposed to users. This approach ensures that innovative technical solutions can be used and rewarded, which is essential to encourage wide deployment of this architecture.
Detecting third-party addresses in traceroute IP paths
Authors: Marchetta Pietro , de Donato Walter , Pescapé Antonio
Published: September 2012

Traceroute is probably the most famous computer networks diagnostic tool, widely adopted for both performance troubleshooting and research. Unfortunately, traceroute is not free of inaccuracies.

In this poster, we present our ongoing work to address the inaccuracy caused by
third-party addresses
.We discuss the impact of third-party addresses on traceroute applications and present a novel active probing technique able to identify such addresses in traceroute traces. Finally, we detail preliminary results suggesting how this phenomenon has been largely underestimated.
Deadline-aware datacenter tcp (D2TCP)
Authors: Vamanan Balajee , Hasan Jahangir , Vijaykumar T.N.
Published: September 2012

An important class of datacenter applications, called Online Data-Intensive (OLDI) applications, includes Web search, online retail, and advertisement. To achieve good user experience, OLDI applications operate under soft-real-time constraints (e.g., 300 ms latency) which imply deadlines for network communication within the applications. Further, OLDI applications typically employ tree-based algorithms which, in the common case, result in bursts of children-to-parent traffic with tight deadlines. Recent work on datacenter network protocols is either deadline-agnostic (DCTCP) or is deadline-aware (D3) but suffers under bursts due to race conditions. Further, D3 has the practical drawbacks of requiring changes to the switch hardware and not being able to coexist with legacy TCP. We propose Deadline-Aware Datacenter TCP (D2TCP), a novel transport protocol, which handles bursts, is deadline-aware, and is readily deployable. In designing D2TCP, we make two contributions: (1) D2TCP uses a distributed and reactive approach for bandwidth allocation which fundamentally enables D2TCP's properties. (2) D2TCP employs a novel congestion avoidance algorithm, which uses ECN feedback and deadlines to modulate the congestion window via a gamma-correction function. Using a small-scale implementation and at-scale simulations, we show that D2TCP reduces the fraction of missed deadlines compared to DCTCP and D3 by 75% and 50%, respectively.
Finishing flows quickly with preemptive scheduling
Authors: Hong Chi-Yao , Caesar Matthew , Godfrey P. Brighten
Published: September 2012

Today's data centers face extreme challenges in providing low latency. However, fair sharing, a principle commonly adopted in current congestion control protocols, is far from optimal for satisfying latency requirements.

We propose Preemptive Distributed Quick (
PDQ
) flow scheduling, a protocol designed to complete flows quickly and meet flow deadlines. PDQ enables flow preemption to approximate a range of scheduling disciplines. For example, PDQ can emulate a shortest job first algorithm to give priority to the short flows by pausing the contending flows. PDQ borrows ideas from centralized scheduling disciplines and implements them in a fully distributed manner, making it scalable to today's data centers. Further, we develop a multipath version of PDQ to exploit path diversity.

Through extensive packet-level and flow-level simulation, we demonstrate that PDQ significantly outperforms TCP, RCP and D
3
in data center environments. We further show that PDQ is stable, resilient to packet loss, and preserves nearly all its performance gains even given inaccurate flow information.
Inferring visibility
Authors: Gürsun Gonca , Ruchansky Natali , Terzi Evimaria , Crovella Mark
Published: September 2012

Consider this simple question: how can a network operator identify the set of routes that pass through its network? Answering this question is surprisingly hard: BGP only informs an operator about a limited set of routes. By observing traffic, an operator can only conclude that a particular route passes through its network -- but not that a route does not pass through its network. We approach this problem as one of statistical inference, bringing varying levels of additional information to bear: (1) the existence of traffic, and (2) the limited set of publicly available routing tables. We show that the difficulty depends critically on the position of the network in the overall Internet topology, and that the operators with the greatest incentive to solve this problem are those for which the problem is hardest. Nonetheless, we show that suitable application of nonparametric inference techniques can solve this problem quite accurately. For certain networks, traffic existence information yields good accuracy, while for other networks an accurate approach uses the "distance" between prefixes, according to a new network distance metric that we define. We then show how solving this problem leads to improved solutions for a particular application: traffic matrix completion.
It's not easy being green
Authors: Gao Peter Xiang , Curtis Andrew R. , Wong Bernard , Keshav Srinivasan
Published: September 2012

Large-scale Internet applications, such as content distribution networks, are deployed across multiple datacenters and consume massive amounts of electricity. To provide uniformly low access latencies, these datacenters are geographically distributed and the deployment size at each location reflects the regional demand for the application. Consequently, an application's environmental impact can vary significantly depending on the geographical distribution of end-users, as electricity cost and carbon footprint per watt is location specific. In this paper, we describe FORTE: Flow Optimization based framework for request-Routing and Traffic Engineering. FORTE dynamically controls the fraction of user traffic directed to each datacenter in response to changes in both request workload and carbon footprint. It allows an operator to navigate the three-way tradeoff between access latency, carbon footprint, and electricity costs and to determine an optimal datacenter upgrade plan in response to increases in traffic load. We use FORTE to show that carbon taxes or credits are impractical in incentivizing carbon output reduction by providers of large-scale Internet applications. However, they can reduce carbon emissions by 10% without increasing the mean latency nor the electricity bill.
Flashback
Authors: Cidon Asaf , Nagaraj Kanthi , Katti Sachin , Viswanath Pramod
Published: September 2012

Unlike their cellular counterparts, Wi-Fi networks do not have the luxury of a dedicated control plane that is decoupled from the data plane. Consequently, Wi-Fi struggles to provide many of the capabilities that are taken for granted in cellular networks, including efficient and fair resource allocation, QoS and handoffs. The reason for the lack of a control plane with designated spectrum is that it would impose significant overhead. This is at odds with Wi-Fi's goal of providing a simple, plug-and-play network.

In this paper we present Flashback, a novel technique that provides a decoupled low overhead control plane for wireless networks that retains the simplicity of Wi-Fi's distributed asynchronous operation. Flashback allows nodes to reliably send short control messages
concurrently
with data transmissions, while ensuring that data packets are decoded correctly without harming throughput. We utilize Flashback's novel messaging capability to design, implement and experimentally evaluate a reliable control plane for Wi-Fi with rates from 175Kbps to 400Kbps depending on the environment. Moreover, to demonstrate its broad applicability, we design and implement a novel resource allocation mechanism that utilizes Flashback to provide efficient, QoS-aware and fair medium access, while eliminating control overheads including data plane contention, RTS/CTS and random back offs.
TUBE
Authors: Ha Sangtae , Sen Soumya , Joe-Wong Carlee , Im Youngbin , Chiang Mung
Published: September 2012

The two largest U.S. wireless ISPs have recently moved towards usage-based pricing to better manage the growing demand on their networks. Yet usage-based pricing still requires ISPs to over-provision capacity for demand at peak times of the day. Time-dependent pricing (TDP) addresses this problem by considering
when
a user consumes data, in addition to how much is used. We present the architecture, implementation, and a user trial of an end-to-end TDP system called TUBE. TUBE creates a price-based feedback control loop between an ISP and its end users. On the ISP side, it computes TDP prices so as to balance the cost of congestion during peak periods with that of offering lower prices in less congested periods. On mobile devices, it provides a graphical user interface that allows users to respond to the offered prices either by themselves or using an "autopilot" mode. We conducted a pilot TUBE trial with 50 iPhone or iPad 3G data users, who were charged according to our TDP algorithms. Our results show that TDP benefits both operators and customers, flattening the temporal fluctuation of demand while allowing users to save money by choosing the time and volume of their usage.
namehelp
Authors: Otto John S. , Sánchez Mario A. , Rula John P. , Stein Ted , Bustamante Fabián E.
Published: September 2012

The Domain Name System (DNS) is a fundamental component of today's Internet. Recent years have seen radical changes to DNS with increases in usage of remote DNS and public DNS services such as OpenDNS. Given the close relationship between DNS and Content Delivery Networks (CDNs) and the pervasive use of CDNs by many popular applications including web browsing and real-time entertainment services, it is important to understand the impact of remote and public DNS services on users' overall experience on the Web. This work presents a tool, namehelp, which comparatively evaluates DNS services in terms of the web performance they provide, and implements an end-host solution to address the performance impact of remote DNS on CDNs. The demonstration will show the functionality of namehelp with online results for its performance improvements.
RaptorStream
Authors: Eittenberger Philipp M.
Published: September 2012

As mobile devices and cellular networks become ubiquitous, first apps for popular P2P video streaming networks emerge. We have observed that when these applications operate in cellular networks, they don't upload video traffic back to other peers. This paper presents a reason for this behavior and proposes a viable solution to exploit the uplink capacity of mobile devices more efficiently. To the best of our knowledge, this paper is the first to propose the usage of Raptor codes to increase the upload throughput of mobile P2P applications.
Predicting location using mobile phone calls
Authors: Zhang Daqiang , Vasilakos Athanasios V. , Xiong Haoyi
Published: September 2012

Location prediction using mobile phone traces has attracted increasing attention. Owing to the irregular user mobility patterns, it still remains challenging to predict user location. Our empirical study in this paper shows that the call patterns are strongly correlated with co-locate patterns (
i.e., visiting the same cell tower at the same period
), and the call patterns mainly affect user short-time mobility. On top of these findings, we propose
NextMe
--- a novel scheme to enhance the location prediction accuracy by leveraging the social interplay revealed in the cellular calls. To identify when the social interplay will affect user mobility, we introduce the concepts of the Critical Call Pattern (CCP), and the Critical Call (CC). We validate
NextMe
with the MIT Reality Mining dataset, involving 350,000-hour activity logs of 106 persons, and 112,508 cellular calls. Experimental results show that the social interplay significantly improves the accuracy.
SmartDiet
Authors: Saarinen Aki , Siekkinen Matti , Xiao Yu , Nurminen Jukka K. , Kemppainen Matti , Hui Pan
Published: September 2012

Offloading computation to cloud has been widely used for extending battery life of mobile devices. However, little effort has been invested in applying the offloading techniques to communication-related tasks. We propose SmartDiet, a toolkit to identify the constraints that reduce offloading opportunities and to calculate the energy-saving potential of offloading communication-related tasks. SmartDiet traces the method-level application execution and estimates the allocation of communication energy cost from traffic traces. We discuss key features of SmartDiet and show some preliminary results using a prototype implementation.
Revealing contact interval patterns in large scale urban vehicular ad hoc networks
Authors: Li Yong , Jin Depeng , Hui Pan , Su Li , Zeng Lieguang
Published: September 2012

Contact interval between moving vehicles is one of the key metrics in vehicular ad hoc networks (VANETs), which is important to routing schemes and network capacity. In this work, by carrying out an extensive experiment involving tens of thousands of operational taxis in Beijing city, we find an invariant character that the contact interval can be modeled by a three-segmented distribution, and there exists a characteristic time point, up to which the contact interval obeys a power law distribution, while beyond which it decays as an exponential one. This property is in sharp contrast to the recent empirical data studies based on
Shanghai
vehicular mobility, where the contact interval exhibits only exponential distribution.
Perspectives on network calculus
Authors: Ciucu Florin , Schmitt Jens
Published: September 2012

ACM Sigcomm 2006 published a paper [26] which was perceived to unify the deterministic and stochastic branches of the network calculus (abbreviated throughout as DNC and SNC) [39]. Unfortunately, this seemingly fundamental unification---which has raised the hope of a straightforward transfer of all results from DNC to SNC---is invalid. To substantiate this claim, we demonstrate that for the class of stationary and ergodic processes, which is prevalent in traffic modelling, the probabilistic arrival model from [26] is quasi-deterministic, i.e., the underlying probabilities are either zero or one. Thus, the probabilistic framework from [26] is unable to account for statistical multiplexing gain, which is in fact the raison d'être of packet-switched networks. Other previous formulations of SNC can capture statistical multiplexing gain, yet require additional assumptions [12], [22] or are more involved [14], [9] [28], and do not allow for a straightforward transfer of results from DNC. So, in essence, there is no free lunch in this endeavor.

Our intention in this paper is to go beyond presenting a negative result by providing a comprehensive perspective on network calculus. To that end, we attempt to illustrate the fundamental concepts and features of network calculus in a systematic way, and also to rigorously clarify some key facts as well as misconceptions. We touch in particular on the relationship between linear systems, classical queueing theory, and network calculus, and on the lingering issue of tightness of network calculus bounds. We give a rigorous result illustrating that the statistical multiplexing gain scales as Ω(√
N
), as long as some small violations of system performance constraints are tolerable. This demonstrates that the network calculus can capture actual system behavior tightly when applied carefully. Thus, we positively conclude that it still holds promise as a valuable systematic methodology for the performance analysis of computer and communication systems, though the unification of DNC and SNC remains an open, yet quite elusive task.
Private and verifiable interdomain routing decisions
Authors: Zhao Mingchen , Zhou Wenchao , Gurney Alexander J.T. , Haeberlen Andreas , Sherr Micah , Loo Boon Thau
Published: September 2012

Existing secure interdomain routing protocols can verify validity properties about individual routes, such as whether they correspond to a real network path. It is often useful to verify more complex properties relating to the route decision procedure - for example, whether the chosen route was the best one available, or whether it was consistent with the network's peering agreements. However, this is difficult to do without knowing a network's routing policy and full routing state, which are not normally disclosed. In this paper, we show how a network can allow its peers to verify a number of nontrivial properties of its interdomain routing decisions without revealing any additional information. If all the properties hold, the peers learn nothing beyond what the interdomain routing protocol already reveals; if a property does not hold, at least one peer can detect this and prove the violation. We present SPIDeR, a practical system that applies this approach to the Border Gateway Protocol, and we report results from an experimental evaluation to demonstrate that SPIDeR has a reasonable overhead.
On-chip networks from a networking perspective
Authors: Nychis George P. , Fallin Chris , Moscibroda Thomas , Mutlu Onur , Seshan Srinivasan
Published: September 2012

In this paper, we present network-on-chip (NoC) design and contrast it to traditional network design, highlighting similarities and differences between the two. As an initial case study, we examine
network congestion
in bufferless NoCs. We show that congestion manifests itself differently in a NoC than in traditional networks. Network congestion reduces system throughput in congested workloads for smaller NoCs (16 and 64 nodes), and limits the scalability of larger bufferless NoCs (256 to 4096 nodes) even when traffic has locality (e.g., when an application's required data is mapped nearby to its core in the network). We propose a new source throttling-based congestion control mechanism with application-level awareness that reduces network congestion to improve system performance. Our mechanism improves system performance by up to 28% (15% on average in congested workloads) in smaller NoCs, achieves linear throughput scaling in NoCs up to 4096 cores (attaining similar performance scalability to a NoC with large buffers), and reduces power consumption by up to 20%. Thus, we show an effective application of a network-level concept, congestion control, to a class of networks -- bufferless on-chip networks -- that has not been studied before by the networking community.