No abstract

Until now, censorship research has largely focused on highly centralized networks that rely on government-run technical choke-points, such as the Great Firewall of China. Although it was previously thought to be prohibitively difficult, large-scale censorship in decentralized networks are on the rise. Our in-depth investigation of the mechanisms underlying decentralized information control in Russia shows that such large-scale censorship can be achieved in decentralized networks through inexpensive commodity equipment. This new form of information control presents a host of problems for censorship measurement, including difficulty identifying censored content, requiring measurements from diverse perspectives, and variegated censorship mechanisms that require significant effort to identify in a robust manner. By working with activists on the ground in Russia, we obtained five leaked blocklists signed by Roskomnadzor, the Russian government's federal service for mass communications, along with seven years of historical blocklist data. This authoritative list contains domains, IPs, and subnets that ISPs have been required to block since November 1st, 2012. We used the blocklist from April 24 2019, that contains 132,798 domains, 324,695 IPs, and 39 subnets, to collect active measurement data from residential, data center and infrastructural vantage points. Our vantage points span 408 unique ASes that control ≈ 65% of Russian IP address space. Our findings suggest that data centers block differently from the residential ISPs both in quantity and in method of blocking, resulting in different experiences of the Internet for residential network perspectives and data center perspectives. As expected, residential vantage points experience high levels of censorship. While we observe a range of blocking techniques, such as TCP/IP blocking, DNS manipulation, or keyword based filtering, we find that residential ISPs are more likely to inject blockpages with explicit notices to users when censorship is enforced. Russia's censorship architecture is a blueprint, and perhaps a forewarning of what and how national censorship policies could be implemented in many other countries that have similarly diverse ISP ecosystems to Russia's. Understanding decentralized control will be key to continuing to preserve Internet freedom for years to come.

No abstract

Vegetation composition, soil morphology, and hydrology were characterized along wetland-toupland gradients at six forested sites in north-central Florida to compare results of Federal wetland delineation methods with 3-5 yr of hydrologic data. Wetland and non-wetland identifications were supported by hydrology data in eight of nine plant communities. Lack of hydric soil indicators and hydrophytic vegetation in two upland communities (scrub and mixed mesic hardwoods) agreed with a deep water table. Six wetland communities (cypress dome, cypress strand, bayhead, cypress/bayhead, red maple/oak swamp, and cedar swamp) with field indicators of wetland hydrology, hydrophytic vegetation, and hydric soils were inundated or had water tables at or near the ground surface at least 5% of the growing season in most years. Flatwoods communities, however, occurred at intermediate positions on the moisture gradient and could not be consistently identified as wetland or upland communities. Identification of flatwoods as wetlands depended on wetland delineation method and was not usually supported by hydrologic measurements. In the flatwoods community, soil properties aad vegetation composition were correlated with the mean and standard deviation of water-table depths, as well as the depth continuously exceeded by the water table at least 5% of the growing season in most years. Various hydrologic parameters need to be considered in addition to the 5% exceedence level currently used in Federal wetland delineation guidance when characterizing wetland conditions in low-gradient areas such as flatwoods.