Characterizing a Meta-CDN

CDNs have reshaped the Internet architecture at large. They operate (globally) distributed networks of servers to reduce latencies as well as to increase availability for content and to handle large traffic bursts. Traditionally, content providers were mostly limited to a single CDN operator. However, in recent years, more and more content providers employ multiple CDNs to serve the same content and provide the same services. Thus, switching between CDNs, which can be beneficial to reduce costs or to select CDNs by optimal performance in different geographic regions or to overcome CDN-specific outages, becomes an important task. Services that tackle this task emerged, also known as CDN broker, Multi-CDN selectors, or Meta-CDNs. Despite their existence, little is known about Meta-CDN operation in the wild. In this paper, we thus shed light on this topic by dissecting a major Meta-CDN. Our analysis provides insights into its infrastructure, its operation in practice, and its usage by Internet sites. We leverage PlanetLab and Ripe Atlas as distributed infrastructures to study how a Meta-CDN impacts the web latency

A First Look at QUIC in the Wild

For the first time since the establishment of TCP and UDP, the Internet transport layer is subject to a major change by the introduction of QUIC. Initiated by Google in 2012, QUIC provides a reliable, connection-oriented low-latency and fully encrypted transport. In this paper, we provide the first broad assessment of QUIC usage in the wild. We monitor the entire IPv4 address space since August 2016 and about 46% of the DNS namespace to detected QUIC-capable infrastructures. Our scans show that the number of QUIC-capable IPs has more than tripled since then to over 617.59 K. We find around 161K domains hosted on QUIC-enabled infrastructure, but only 15K of them present valid certificates over QUIC. Second, we analyze one year of traffic traces provided by MAWI, one day of a major European tier-1 ISP and from a large IXP to understand the dominance of QUIC in the Internet traffic mix. We find QUIC to account for 2.6% to 9.1% of the current Internet traffic, depending on the vantage point. This share is dominated by Google pushing up to 42.1% of its traffic via QUIC

The outer-membrane export signal of Porphyromonas gingivalis type IX secretion system (T9SS) is a conserved C-terminal β-sandwich domain

Iñaki de Diego et al.In the recently characterized Type IX Secretion System (T9SS), the conserved C-terminal domain (CTD) in secreted proteins functions as an outer membrane translocation signal for export of virulence factors to the cell surface in the Gram-negative Bacteroidetes phylum. In the periodontal pathogen Porphyromonas gingivalis, the CTD is cleaved off by PorU sortase in a sequence-independent manner, and anionic lipopolysaccharide (A-LPS) is attached to many translocated proteins, thus anchoring them to the bacterial surface. Here, we solved the atomic structure of the CTD of gingipain B (RgpB) from P. gingivalis, alone and together with a preceding immunoglobulin-superfamily domain (IgSF). The CTD was found to possess a typical Ig-like fold encompassing seven antiparallel β-strands organized in two β-sheets, packed into a β-sandwich structure that can spontaneously dimerise through C-terminal strand swapping. Small angle X-ray scattering (SAXS) revealed no fixed orientation of the CTD with respect to the IgSF. By introducing insertion or substitution of residues within the inter-domain linker in the native protein, we were able to show that despite the region being unstructured, it nevertheless is resistant to general proteolysis. These data suggest structural motifs located in the two adjacent Ig-like domains dictate the processing of CTDs by the T9SS secretion pathway.This study was financially supported in part by grants from European, US American, Polish, Spanish, and Catalan agencies (UMO-2012/04/A/NZ1/00051, UMO-2012/05/B/NZ6/00581, UMO-2013/08/W/NZ1/00696, UMO-2011/01/D/NZ1/01169, 2975/7.PR/13/2014/2, NIH NIDCR DE09761; FP7-PEOPLE-2011-ITN-290246 “RAPID”; FP7-HEALTH-2012-306029-2 “TRIGGER”; BFU2012-32862; BIO2013-49320-EXP; MDM-2014-0435; 1306/MOB/IV/2015/0 (“Mobilność Plus” MK) and 2014SGR9). The Department of Structural Biology of IBMB is a “María de Maeztu” Unit of Excellence from the Ministry of Economy and Competitiveness. Funding for data collection was provided in part by ESRFPeer Reviewe

Makna Shajarah Dalam Alqur’an Qs. Al-Baqarah: 35 (Studi Komparatif Tafsir Al-Tabari Dan Hamka)

Sebab diturunkannya Nabi Adam ke bumi, dikalangan mufasir masih menjadi pertanyaan, dan diantara pertanyaan yang muncul, benarkah Adam melakukan salah? lupa? ataukah memang rencana besar Tuhan kepada Adam agar Adam menjadi manusia yang sempurna. Selain itu, yang menjadi perbincangan mufasir adalah mengenai pohon yang didekati oleh Nabi Adam. Apakah pohon tersebut hanya merupakan sifat, pohon layaknya di dunia, ataukah hanya Tuhan yang mengerti mengenai makna pohon tersebut? Selanjutnya, skripsi ini membahas penafsiran al-Tabari dan Hamka dalam menafsirkan shajarah QS. al-Baqarah:35, sekaligus menjelaskan metode yang digunakan dalam menafsirkan ayat tersebut. Meski dikalangan mufasir, menyebutkan bahwa bukan merupakan hal yang penting mengetahui pohon tersebut, tetapi setidaknya akan memberikan wahana baru bagi penulis ataupun pembaca yang dalam kaitannya dengan pemaknaan shajarah dalam QS. al-Baqarah:35. Kedua mufasir tersebut, mempunyai karakteristik yang berbeda, selain berbeda dalam segi corak, juga berbeda dalam produk penafsirannya, yang tentunya dipengaruhi oleh kondisi sosial saat itu, dan masalah zaman menjadi faktor utama yang menyebabkan produk tafsir tersebut berubah. Hamka dan Al-Tabari mempunyai kesamaan dalam memberikan penjelasan mengani ayat shajarah tersebut, yakni sama-sama tidak menganggap penting. Hanya saja, bedanya jika Hamka sejak awal memang tidak menafsirakan shajarah tersebut, sedangkan Al-T{abari sedikit menjelaskan mengenai pohon tersebut sesuai kondisi Arab. Meski pada akhirnya tidak menganggap penting

Cybersecurity and information assurance in Information Science curricula

As a newly emerging and one of the fastest growing fields of study, cybersecurity/information assurance has plenty to offer in terms of teaching and research. If Library and Information Science (LIS) schools are to take advantage of this fast growth in the field by expanding their program and/or course offerings, thereby increasing their enrollments, and, indeed, provide their students with opportunities to be able to take advantage of the demand for skilled manpower in cybersecurity/information assurance, it is imperative for them to systematically approach the inclusion of courses and/or programs to their curricula. A component of this systematic approach is a closer examination of programs, concentrations, and courses in cybersecurity/information assurance currently offered at similar or peer LIS schools in order to identify best practices and gaps. The study reported here is a small but important part of this effort

Structure of the catalytic domain of the Tannerella forsythia matrix metallopeptidase karilysin in complex with a tetrapeptidic inhibitor

5 páginas, 1 figura, 1 tabla.-- et al.Karilysin is the only metallopeptidase identified as a virulence factor in the odontopathogen Tannerella forsythia owing to its deleterious effect on the host immune response during bacterial infection. The very close structural and sequence-based similarity of its catalytic domain (Kly18) to matrix metalloproteinases suggests that karilysin was acquired by horizontal gene transfer from an animal host. Previous studies by phage display identified peptides with the consensus sequence XWFPXXXGGG (single-letter amino-acid codes; X represents any residue) as karilysin inhibitors with low-micromolar binding affinities. Subsequent refinement revealed that inhibition comparable to that of longer peptides could be achieved using the tetrapeptide SWFP. To analyze its binding, the high-resolution crystal structure of the complex between Kly18 and SWFP was determined and it was found that the peptide binds to the primed side of the active-site cleft in a substrate-like manner. The catalytic zinc ion is clamped by the α-amino group and the carbonyl O atom of the serine, thus distantly mimicking the general manner of binding of hydroxamate inhibitors to metallopeptidases and contributing, together with three zinc-binding histidines from the protein scaffold, to an octahedral-minus-one metal-coordination sphere. The tryptophan side chain penetrates the deep partially water-filled specificity pocket of Kly18. Together with previous serendipitous product complexes of Kly18, the present results provide the structural determinants of inhibition of karilysin and open the field for the design of novel inhibitory strategies aimed at the treatment of human periodontal disease based on a peptidic hit molecule. © 2013.This study was supported in part by grants from European, American, Polish, Spanish, Danish and Catalan agencies (2012/04/A/NZ1/00051, 2011/03/N/NZ1/00586, 2137/7.PR-EU/2011/2, DE09761, FP7-HEALTH-F3-2009-223101 ‘AntiPathoGN’, FP7-HEALTH-2010-261460 ‘Gums&Joints’, FP7-PEOPLE-2011-ITN-290246 ‘RAPID’, BIO2009-10334, BFU2012-32862, CSD2006-00015, Lundbeck Foundation grant R54-A5291 and Fundació ‘La Marató de TV3’ grants 2009-100732 and 2009SGR1036). The Faculty of Biochemistry, Biophysics and Biotechnology of the Jagiellonian University in Kraków (Poland) is a beneficiary of structural funds from the European Union (grant No POIG.02.01.00-12-064/08 ‘Molecular Biotechnology for Health’).Peer Reviewe