Wiretapping the Internet

With network security threats and vulnerabilities increasing, solutions based on online detection remain attractive. A complete, durable record of all activity on a network can be used to evaluate and train intrusion detection algorithms, assist in responding to an intrusion in progress, and, if properly constructed, serve as evidence in legal proceedings. This paper describes the Advanced Packet Vault, a technology for creating such a record by collecting and securely storing all packets observed on a network, with a scalable architecture intended to support network speeds in excess of 100 Mbps. Encryption is used to preserve users' security and privacy, permitting selected traffic to be made available without revealing other traffic. The Vault implementation, based on Linux and OpenBSD, is open-source. A Vault attached to a heavily loaded 100 Mbps network must capture, process, and store about a terabyte each day, so we have to be very sensitive to the recurring cost of operation and the reliability issues of 24x7 operation. We must also be sensitive to the admissibility of information collected by the Vault in support of legal proceedings; the legal ramifications of operating a vault, particularly at a public institution; and the public perception of its use.http://deepblue.lib.umich.edu/bitstream/2027.42/107911/1/citi-tr-00-9.pd

Multi-level Caching in Distributed File Systems

We are investigating the potential for intermediate file servers to address scaling problems in increasingly large distributed file systems. To this end, we have run trace-driven simulations based on data from DEC-SRC and our own data collection to determine the potential of caching-only intermediate servers. The degree of sharing among clients is central to the effectiveness of an intermediate server. This turns out to be quite low in the traces available to us. All told, fewer than 10% of block accesses are to files shared by more than one file system client. Trace-driven simulation shows that even with an infinite cache at the intermediate, cache hit rates are disappointingly low. For client caches as small as 20 MB, we observe hit rates less than 19%. As client cache sizes increase, the hit rate at the intermediate approaches the degree of sharing among all clients. On the other hand, the intermediate does appear to be effective in reducing the peak load presented to upstream file servers.http://deepblue.lib.umich.edu/bitstream/2027.42/107967/1/citi-tr-91-3.pd

Peephole Log Optimization

The log files generated while operating a file system in disconnected mode grow to substantial sizes. Eliminating redundant or useless operations in these logs can free up scarce disk space on laptops, reduce replay times, and reduce the frequency of data conflict. Our approach uses a rule-based portable peephole optimizer for compilers. This work suggests a general method of optimization for any system that performs logging at the vnode layer.http://deepblue.lib.umich.edu/bitstream/2027.42/107933/1/citi-tr-95-3.pd

On-farm Examples of Alternative Winter Farrowing Systems

There is growing demand in Iowa for pigs raised outdoors or in deep-bedded systems without the use of antibiotics, growth promotants, or animal by-products. Currently many producers selling naturally-raised pork market their animals to a company that requires adherence to the Animal Welfare Institute’s (AWI) Animal Welfare Standards. One of the key components of these standards is the requirement for bedding and the prohibition of farrowing crates. While a pasture farrowing system is effective during most of the spring, summer, and fall, an alternative system is needed in order to farrow pigs in the winter for the naturally-raised pork market. There are a variety of farrowing systems currently being used during cold weather to farrow pigs for the natural pork market. In general, all rely upon a primary heat source capable of maintaining a room temperature of at least 50º F and auxiliary heat sources (heat lamps, bedding pack, confined space) to create a warmer microclimate for the young pigs. The use of adequate bedding and a design in harmony with the natural instincts of the hogs are key to the success of the example systems. A final critical consideration is a breeding program that insures sows in a particular room farrow within a short time frame (7 days or less). Three unique systems, detailed in this report are free stalls in retrofitted buildings, the Swedish system, and greenhouse with radiant tube heater. A relative comparison of the three winter farrowing alternatives is shown in table 1. No system has a clear advantage over the others, but each system has its own unique strengths and management requirements. Producers interested in capitalizing on the growing demand for natural pork born in the winter should consider their individual resources and goals as they adopt a system to meet their needs

Alternative Winter Farrowing Demonstration Project: A Progress Report

There is growing demand in Iowa for pigs raised outdoors or in a deep-bedded system without the use of antibiotics, growth promotants, or animal by-products. Currently, most producers selling naturally-raised pork, market their animals to a company that requires adherence to the Animal Welfare Institute’s (AWI) Animal Welfare Standards. One of the key components of these standards is the prohibition of farrowing crates. While a pasture farrowing system is effective during most of the spring, summer, and fall, an alternative system is needed in order to farrow pigs in the winter for the naturally-raised pork market. There are a variety of farrowing systems currently being used during cold weather to farrow pigs for the natural pork market. In general, all rely upon a primary heat source capable of maintaining a room temperature of at least 50ºF and auxiliary heat sources (heat lamps, bedding pack, confined space) to create a warmer microclimate for the young pigs. The use of adequate bedding and a design in harmony with the natural instincts of the hogs is key to the success of the example systems. A final critical consideration is a breeding program that insures sows in a particular room farrow within a short time frame (7 days or less) of each other. With an increasing interest in winter farrowing to meet the naturally-raised pork market, Iowa State University embarked on a project funded by the Leopold Center to demonstrate alternative farrowing systems in cold weather. In 2002, a 62 ft 150,000 Btu/hr radiant heater tube was purchased and installed in an existing building on the Allee Demonstration Farm near Newell, IA. Modified A-frame farrowing huts designed for pasture farrowing were set-up in a double row down the center of the building. In the winter of 2002/2003, 36 litters were farrowed in this system. A total of 293 pigs were weaned for an average of 8.14 pigs/litter. Total energy expense for producing those 293 pigs was $4.94/pig weaned

COST OF ORGANIC PORK PRODUCTION: A SEASONAL ANALYSIS AND NEEDED PRICE PREMIUM FOR CONTINUOUS PRODUCTION

Niche markets of agricultural products are experiencing rapid growth. One such market is organic pork. Organic production typically demands specific production conditions that can be cost increasing. This study evaluates the cost of organic pork production, seasonal differences in costs, and premiums necessary to induce continuous organic pork production. In the past few years, niche marketing has been a rapidly growing phenomenon in agriculture. One area that has experienced dramatic growth is the production of organic products. Organic production typically brings with it specific conditions on how the product is produced. These can impact the cost structure of the business and in turn, needed premiums for economic production. One of these niche markets that are growing rapidly is the market for organic pork. A major issue in organic pork production is the differing cost structures across the seasons of the year which relates, in part, to the types of production systems allowed or disallowed. Studies have shown that consumers are very conscientious of product price, freshness, and availability. In the production of organic pork, we are able to demonstrate that there are cost savings to the producer by producing a seasonal product over a continuous product. While this allows for a lower cost for the producer, it causes an uneven pig flow problem throughout the vertical chain which affects packers, marketers, and consumers. The packers are affected by having their plants at full capacity only part of the year. For the consumer, there are certain times of the year when the product is in surplus and other times when it is in shortage causing prices to fluctuate greatly. This implies that both the consumer and the packer may have an incentive to induce the producer to provide a continuous supply of organic pork to the market. This study has two objectives. The first is to provide a detailed analysis of the producer's cost of producing organic pork in a seasonal and continuous production system. The second objective is to develop a premium structure that could induce a producer to adopt a continuous production system. The study addresses the issue by examining the increase of costs involved in expanding a seasonal (summer only farrowing) organic pork production system to continuous production of organic hogs. Production costs differ by production system and season of the year. Organic pork production cost per hundred pounds is projected to be $59.45 for the seasonal system. The seasonal system consists of farrowing in the summer time only. This cost can be compared to a continuous system of organic pork production with a cost of$63.88 per hundred pounds. The continuous system has farrowing occurring in both the winter and summer seasons. With the current premium structures for organic pork, there are more hogs being produced using summer farrowing than by winter farrowing. Consumers prefer a more uniform supply of fresh pork. To foster a more uniform supply of fresh organic pork throughout the year, premiums received by producers need to reflect the seasonal production costs differences. Our results show that if the producer is paid the continuous system's cost of production of $63.88, the producer would have an incentive to produce only seasonal hogs. To induce the producer to provide a continuous flow of hogs, a minimum premium of$7.47 beyond the seasonal price must be paid to the producer for producing hogs in the winter, and a premium of $1.66 must be paid in the summer. An alternative is that the producer would receive no premium for summer production and a premium of$9.13 per hundred pounds over the seasonal production costs to induce the producer to produce a continuous supply of hogs.Marketing,

A Brownian-pumping model for oceanic trace metal scavenging: Evidence from Th isotopes

Two observed characteristics of Th isotope and stable metal sorption in natural aquatic systems are seemingly at odds with physico-chemical adsorption theory: (1) characteristic sorption times of days to weeks and (2) Kds which are inversely related in magnitude to particle concentrations. In addition, sorption rate constants are positiveiy correlated with particle concentrations and Kd. This paper presents a conceptual and mathematical model with which it is proposed that these metal sorption characteristics have the same underlying physical process in common: the coagulation of colloidal (nonfilterable) particles onto larger (filterable) particles. “Brownian pumping” (the transfer of truly dissolved metal species to filterable particles through a colloidal intermediate) consists of two rate steps: (1) rapid formation of metal/colloid surface site complexes (adsorption) and (2) slow coagulation of colloids with filterable particles. The Brownian-pumping model is tested against field and laboratory data. The field data, obtained from the literature, covers different regions of the oceans: deep ocean environments, euphotic zone, coastal and estuarine systems. The laboratory data involved 228Th sorption in suspensions of goethite and polystyrene latexes. Although the model has general applicability, results and discussions herein emphasize thorium isotope behavior. The Brownian-pumping model suggests that Th or other strongly sorbing elements may be useful as in situ “coagulometers” either at relatively high (e.g., greater than 5–10 mg/l) particle concentrations or when the mass ratio of colloids (C*p) to filterable particles (Cp) is known. The model also indicates that the ratio of colloids to filterable particles in marine systems, may be, by a first approximation, described by the relationship log C*p = 0.7 log Cp – 2.6 (in units of kg/l)

Evaluating Delayed Write in a Multilevel Caching File System

Delayed write in a multilevel file system cache hierarchy offers a way to improve performance in diverse client/server scenarios, such as integrating mass store into a distributed file system or providing distributed file system access over low-speed links. Using file system traces and cache simulations, we explore extensions and modifications to the traditional client caching model employed in such file systems as AFS, Sprite, and DFS. High cache hit rates at an intermediate cache server—a machine logically interposed between clients and servers that provides cached file service to the clients—combined with high client cache hit rates lend practicality to an integrated mass storage file system. In such a system, magnetic tape or optical-based mass storage devices may be used as a first-class data repository, fronted by disk and RAM caches to offer acceptable access times to the large, but slow, mass storage system. Similarly, a high cache hit rate is necessary for users accessing file systems via low-speed links, where a delayed write intermediate caching server can mediate traffic to make better use of available bandwidth. In an example taken from mobile computing, an intermediate server might be used as a docking station at a user's home. This arrangement would be convenient for users of mobile computers who upload large amounts of data generated while operating in disconnected mode. Simulations of delayed write caching strategies are applicable to both the mass storage and low-speed link scenarios.http://deepblue.lib.umich.edu/bitstream/2027.42/107940/1/citi-tr-95-9.pd

Access Control in a Workstation-Based Distributed Computing Environment

This paper describes the mechanisms employed to control access to system services on the IFS project. We base our distributed computing environment on systems that we trust, and run those systems in physically secure rooms. From that base, we add services, modifying them to interoperate with existing access control mechanisms. Some weaknesses remain in our environment; we conclude with a description of present vulnerabilities and future plans.http://deepblue.lib.umich.edu/bitstream/2027.42/107869/1/citi-tr-90-2.pd