A proposed group management scheme for XTP multicast

The purpose of a group management scheme is to enable its associated transfer layer protocol to be responsive to user determined reliability requirements for multicasting. Group management (GM) must assist the client process in coordinating multicast group membership, allow the user to express the subset of the multicast group that a particular multicast distribution must reach in order to be successful (reliable), and provide the transfer layer protocol with the group membership information necessary to guarantee delivery to this subset. GM provides services and mechanisms that respond to the need of the client process or process level management protocols to coordinate, modify, and determine attributes of the multicast group, especially membership. XTP GM provides a link between process groups and their multicast groups by maintaining a group membership database that identifies members in a name space understood by the underlying transfer layer protocol. Other attributes of the multicast group useful to both the client process and the data transfer protocol may be stored in the database. Examples include the relative dispersion, most recent update, and default delivery parameters of a group

Issues in designing transport layer multicast facilities

Multicasting denotes a facility in a communications system for providing efficient delivery from a message's source to some well-defined set of locations using a single logical address. While modem network hardware supports multidestination delivery, first generation Transport Layer protocols (e.g., the DoD Transmission Control Protocol (TCP) (15) and ISO TP-4 (41)) did not anticipate the changes over the past decade in underlying network hardware, transmission speeds, and communication patterns that have enabled and driven the interest in reliable multicast. Much recent research has focused on integrating the underlying hardware multicast capability with the reliable services of Transport Layer protocols. Here, we explore the communication issues surrounding the design of such a reliable multicast mechanism. Approaches and solutions from the literature are discussed, and four experimental Transport Layer protocols that incorporate reliable multicast are examined

A reliable multicast for XTP

Multicast services needed for current distributed applications on LAN's fall generally into one of three categories: datagram, semi-reliable, and reliable. Transport layer multicast datagrams represent unreliable service in which the transmitting context 'fires and forgets'. XTP executes these semantics when the MULTI and NOERR mode bits are both set. Distributing sensor data and other applications in which application-level error recovery strategies are appropriate benefit from the efficiency in multidestination delivery offered by datagram service. Semi-reliable service refers to multicasting in which the control algorithms of the transport layer--error, flow, and rate control--are used in transferring the multicast distribution to the set of receiving contexts, the multicast group. The multicast defined in XTP provides semi-reliable service. Since, under a semi-reliable service, joining a multicast group means listening on the group address and entails no coordination with other members, a semi-reliable facility can be used for communication between a client and a server group as well as true peer-to-peer group communication. Resource location in a LAN is an important application domain. The term 'semi-reliable' refers to the fact that group membership changes go undetected. No attempt is made to assess the current membership of the group at any time--before, during, or after--the data transfer

The multidriver: A reliable multicast service using the Xpress Transfer Protocol

A reliable multicast facility extends traditional point-to-point virtual circuit reliability to one-to-many communication. Such services can provide more efficient use of network resources, a powerful distributed name binding capability, and reduced latency in multidestination message delivery. These benefits will be especially valuable in real-time environments where reliable multicast can enable new applications and increase the availability and the reliability of data and services. We present a unique multicast service that exploits features in the next-generation, real-time transfer layer protocol, the Xpress Transfer Protocol (XTP). In its reliable mode, the service offers error, flow, and rate-controlled multidestination delivery of arbitrary-sized messages, with provision for the coordination of reliable reverse channels. Performance measurements on a single-segment Proteon ProNET-4 4 Mbps 802.5 token ring with heterogeneous nodes are discussed

Issues in providing a reliable multicast facility

Issues involved in point-to-multipoint communication are presented and the literature for proposed solutions and approaches surveyed. Particular attention is focused on the ideas and implementations that align with the requirements of the environment of interest. The attributes of multicast receiver groups that might lead to useful classifications, what the functionality of a management scheme should be, and how the group management module can be implemented are examined. The services that multicasting facilities can offer are presented, followed by mechanisms within the communications protocol that implements these services. The metrics of interest when evaluating a reliable multicast facility are identified and applied to four transport layer protocols that incorporate reliable multicast

A case series of familial ARID1B variants illustrating variable expression and suggestions to update the ACMG criteria

ARID1B is one of the most frequently mutated genes in intellectual disability (~1%). Most variants are readily classified, since they are de novo and are predicted to lead to loss of function, and therefore classified as pathogenic according to the American College of Medical Genetics and Genomics (ACMG) guidelines for the interpretation of sequence variants. However, familial loss-of-function variants can also occur and can be challenging to interpret. Such variants may be pathogenic with variable expression, causing only a mild phenotype in a parent. Alternatively, since some regions of the ARID1B gene seem to be lacking pathogenic variants, loss-of-function variants in those regions may not lead to ARID1B haploinsufficiency and may therefore be benign. We describe 12 families with potential loss-of-function variants, which were either familial or with unknown inheritance and were in regions where pathogenic variants have not been described or are otherwise challenging to interpret. We performed detailed clinical and DNA methylation studies, which allowed us to confidently classify most variants. In five families we observed transmission of pathogenic variants, confirming their highly variable expression. Our findings provide further evidence for an alternative translational start site and we suggest updates for the ACMG guidelines for the interpretation of sequence variants to incorporate DNA methylation studies and facial analyses

Abstract Towards an Efficient, Scalable Replication Mechanism for the I2-DSI Project

This paper presents the development of new functionality for the open-source rsync utility aimed at producing an efficient, scalable solution for multiple-site file synchronization. The context of our work is the Internet2 Distributed Storage Infrastructure (I2-DSI) project, which is developing a reliable, scalable, high performance storage service infrastructure for advanced applications in research and education. Specifically, the I2-DSI project is working on middleware software to enable the replication of applications across a set of geographically distributed hosts. This paper presents a new mechanism for replicating filesystems, rsync+, which is a modification of an open-source rsync file synchronization utility. Using rsync+ for file updates, a flexible, powerful replication mechanism can be developed for publishing source objects into the I2-DSI replication service, and the approach enables scalable network distribution through multicast-based solutions. The paper presents the technical details behind the rsync+ tool, its use as a replication solution within I2-DSI, and performance results from a large-scale (multi-gigabyte) WWW mirroring experiment using rsync+ that demonstrate correct operation and efficiency gains with actual data from an active WWW document archive

An Interactive WWW Search Engine for User-Defined Collections

Given the dynamic nature and the quantity of information on the WWW, many individual users and organizations compile and use focused WWW resource lists related to a particular topic or subject domain. The IRISWeb system extends this concept such that any user-defined set of WWW pages (a virtual collection) can be retrieved, indexed, and searched using a powerful full-text search engine with a relevance-feedback interface. This capability adds full-text searching to highly customized subsets of the WWW. Here we describe the IRISWeb software and an experiment that highlights its potential. KEYWORDS: Search engines, WWW, virtual collection, LIBClient, subject gateway, IRISWeb. INTRODUCTION Under the guidance of Professor William Shaw, a research group within the School of Information and Library Science has been investigating various aspects of operationalizing relevance feedback for the past three years[1]. Earlier versions of IRIS were successfully used to perform TREC experiments[2]..

On Retransmission-Based Error Control for Continuous Media Traffic in Packet-Switching Networks

Distribution of continuous media traffic such as digital audio and video over packet-switching networks has become increasingly feasible due to a number of technology trends leading to powerful desktop computers and high-speed integrated services networks. Protocols supporting the transmission of continuous media are already available. In these protocols, transmission errors due to packet loss are generally not recovered. Instead existing protocol designs focus on preventive error control techniques that reduce the impact of losses by adding redundancy, e.g., forward error correction, or by preventing loss of important data, e.g., channel coding. The goal of this study is to show that retransmission of continuous media data often is, contrary to conventional wisdom, a viable option in most packet-switching networks. If timely retransmission can be performed with a high probability of success, a retransmission-based approach to error control is attractive because it imposes little overh..