On using content addressable memory for packet classification

Packet switched networks such as the Internet require packet classification at every hop in order to ap-ply services and security policies to traffic flows. The relentless increase in link speeds and traffic volume imposes astringent constraints on packet classification solutions. Ternary Content Addressable Memory (TCAM) devices are favored by most network component and equipment vendors due to the fast and de-terministic lookup performance afforded by their use of massive parallelism. While able to keep up with high speed links, TCAMs suffer from exorbitant power consumption, poor scalability to longer search keys and larger filter sets, and inefficient support of multiple matches. The research community has responded with algorithms that seek to meet the lookup rate constraint with greater efficiency through the use of com-modity Random Access Memory (RAM) technology. The most promising algorithms efficiently achieve high lookup rates by leveraging the statistical structure of real filter sets. Due to their dependence on filter set characteristics, it is difficult to provision processing and memory resources for implementations that support a wide variety of filter sets. We show how several algorithmic advances may be leveraged to im-prove the efficiency, scalability, incremental update and multiple match performance of CAM-based packet classification techniques without degrading the lookup performance. Our approach, Label Encoded Content Addressable Memory (LECAM), represents a hybrid technique that utilizes decomposition, label encoding, and a novel Content Addressable Memory (CAM) architecture. By reducing the number of implementation parameters, LECAM provides a vehicle to carry several of the recent algorithmic advances into practice. We provide a thorough overview of CAM technologies and packet classification algorithms, along with a detailed discussion of the scaling issues that arise with longer search keys and larger filter sets. We also provide a comparative analysis of LECAM and standard TCAM using a collection of real and synthetic filter sets of various sizes and compositions

Models, Algorithms, and Architectures for Scalable Packet Classification

The growth and diversification of the Internet imposes increasing demands on the performance and functionality of network infrastructure. Routers, the devices responsible for the switch-ing and directing of traffic in the Internet, are being called upon to not only handle increased volumes of traffic at higher speeds, but also impose tighter security policies and provide support for a richer set of network services. This dissertation addresses the searching tasks performed by Internet routers in order to forward packets and apply network services to packets belonging to defined traffic flows. As these searching tasks must be performed for each packet traversing the router, the speed and scalability of the solutions to the route lookup and packet classification problems largely determine the realizable performance of the router, and hence the Internet as a whole. Despite the energetic attention of the academic and corporate research communities, there remains a need for search engines that scale to support faster communication links, larger route tables and filter sets and increasingly complex filters. The major contributions of this work include the design and analysis of a scalable hardware implementation of a Longest Prefix Matching (LPM) search engine for route lookup, a survey and taxonomy of packet classification techniques, a thorough analysis of packet classification filter sets, the design and analysis of a suite of performance evaluation tools for packet classification algorithms and devices, and a new packet classification algorithm that scales to support high-speed links and large filter sets classifying on additional packet fields

Adopting Virtualized 10GBE Ethernet ISCSI SAN for Mission Critical Applications

The presentation will provide insight into the decision to move from a fibre channel SAN solution, the resulting performance metrics and financial savings seen by Marshall University. Presented at The Ohio Higher Education Computing Council (OHECC) March 23, 2011

CURIOS: Connecting Community Heritage through Linked Data

Peer reviewedPostprin

Vesivirus 2117 capsids more closely resemble sapovirus and lagovirus particles than other known vesivirus structures

Vesivirus 2117 is an adventitious agent that in 2009, was identified as a contaminant of CHO cells propagated in bioreactors at a pharmaceutical manufacturing plant belonging to Genzyme. The consequent interruption in supply of Fabrazyme and Cerezyme (drugs used to treat Fabry and Gaucher disease respectively), caused significant economic losses. Vesivirus 2117 is a member of the Caliciviridae; a family of small icosahedral viruses encoding a positive sense RNA genome. We have used cryo-electron microscopy and three dimensional image reconstruction to calculate a structure of vesivirus 2117 virus like particles as well as feline calicivirus and a chimeric sapovirus. We present a structural comparison of several members of the Caliciviridae, showing that the distal P domain of vesivirus 2117 is morphologically distinct from that seen in other known vesivirus structures. Furthermore, at intermediate resolutions we found a high level of structural similarity between vesivirus 2117 and Caliciviridae from other genera, such as sapovirus and rabbit haemorrhagic disease virus. Phylogenetic analysis confirms vesivirus 2117 as a vesivirus closely related to canine vesiviruses. We postulate that morphological differences in virion structure seen between vesivirus clades may reflect differences in receptor usage

Enantioselective NHC-catalyzed redox [4+2]-hetero-Diels-Alder reactions using α,β-unsaturated trichloromethyl ketones as amide equivalents

The authors thank the Royal Society for a University Research Fellowship (A.D.S.) and the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) ERC Grant Agreement No. 279850 (N.A. and J.E.T.).α,β-Unsaturated trichloromethyl ketones are suitable α,β-unsaturated amide and ester equivalents in N-heterocyclic carbene (NHC)-catalyzed redox hetero-Diels-Alder reactions with azolium enolates generated from α-aroyloxyaldehydes. The initially formed syn-dihydropyranone products can be isolated, or can undergo ring-opening with benzylamine followed by aminolysis of the resulting CCl3 ketone to form a range of diamides with high diastereo- and enantioselectivity (up to >95:5 dr and >99% ee).PostprintPeer reviewe

An examination of skill deterioration and retraining in the United States Navy

http://archive.org/details/examinationofski00taylLieutenant, United States NavyApproved for public release; distribution is unlimited

A qualitative process evaluation of a randomised controlled trial of a parenting intervention in community (school) settings for children at risk of attention deficit hyperactivity disorder (ADHD)

Background: Interventions for parents of children experiencing emotional and/or behavioural difficulties can help to improve their children’s health, educational and social outcomes. However, the desirability and acceptability of screening and offering such interventions for attention-deficit hyperactivity disorder (ADHD)-type problems are currently unclear. This article is a qualitative process evaluation of a pragmatic cluster randomised controlled trial (Trial registration: ISRCTN87634685; reported elsewhere) to assess the feasibility and acceptability of a school-based parenting intervention programme for parents and teachers of children with high levels of ADHD symptoms. Methods: Parents (n = 22) and teaching staff (n = 29) took part in semi-structured group or individual interviews, either by telephone or face-to-face, following the main trial. Interviews were digitally-recorded, transcribed verbatim and subjected to thematic analysis. Results: The parenting intervention was acceptable to parents and teachers, and they were enthusiastic about the need for parenting groups in the school environment and stressed the importance of parent-school collaboration. Parents generally stated a preference for universal recruitment approaches to such programmes whilst teachers described the need to target specific parents. Most parents who took part in the parenting intervention described it favourably and many saw benefits, at least in the short-term. Parents differed in their preferred group size, with some desiring one-to-one sessions and others favouring a larger group. Non-attending parents reported barriers to attendance such as fear of attending in a group, previous use of the programme, work and other commitments. Suggestions to improve the programme included: clearer communication; offering booster sessions; and greater collaboration with teachers. Conclusions: It is feasible to deliver parenting intervention programmes within or near schools. The intervention was acceptable to the majority of parents, thus retention was high, but recruitment was difficult and reaching the parents with the most need was challenging. The findings of the process evaluation identified greater benefits to families than were apparent in the main trial. Recommendations identified by parents and teaching staff may be used to inform service delivery and future research to enhance recruitment to parenting interventions in the school environmen