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The VersaKey Framework: Versatile Group Key Management
- IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 1999
"... Middleware supporting secure applications in a distributed environment faces several challenges. Scalable security in the context of multicasting or broadcasting is especially hard when privacy and authenticity is to be assured to highly dynamic groups where the application allows participants to jo ..."
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Cited by 130 (5 self)
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Middleware supporting secure applications in a distributed environment faces several challenges. Scalable security in the context of multicasting or broadcasting is especially hard when privacy and authenticity is to be assured to highly dynamic groups where the application allows participants to join and leave at any time. Unicast security is well-known and has widely advanced into production state. But proposals for multicast security solutions that have been published so far are complex, often require trust in network components or are inefficient. In this paper, we propose a framework of new approaches for achieving scalable security in IP multicasting. Our solutions assure that that newly joining members are not able to understand past group traffic, and that leaving members may not follow future communication. For versatility, our framework supports a range of closely related schemes for key management, ranging from tightly centralized to fully distributed and even allows switching between these schemes on-the-fly with low overhead. Operations have low complexity (O(log N) for joins or leaves), thus granting scalability even for very large groups. We also present a novel concurrency-enabling scheme, which was devised for fully distributed key management. In this paper we discuss the requirements for secure multicasting, present our flexible system, and evaluate its properties, based on the existing prototype implementation.
A model, analysis, and protocol framework for soft state-based communication
, 1999
"... "Soft state" is an often cited yet vague concept in network protocol design in which two or more network entities intercommunicate in a loosely coupled, often anonymous fashion. Researchers often define this concept operationally (if at all) rather than analytically: a source of soft state ..."
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Cited by 106 (7 self)
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"Soft state" is an often cited yet vague concept in network protocol design in which two or more network entities intercommunicate in a loosely coupled, often anonymous fashion. Researchers often define this concept operationally (if at all) rather than analytically: a source of soft state transmits periodic "refresh messages" over a (lossy) communication channel to one or more receivers that maintain a copy of that state, which in turn "expires" if the periodic updates cease. Though a number of crucial Internet protocol building blocks are rooted in soft state-based designs | e.g., RSVP refresh messages, PIM membership updates, various routing protocol updates, RTCP control messages, directory services like SAP, and so forth | controversy is building as to whether the performance overhead of soft state refresh messages justify their qualitative benefit of enhanced system "robustness". We believe that this controversy has risen not from fundamental performance tradeo s but rather from our lack of a comprehensive understanding of soft state. To better understand these tradeoffs, we propose herein a formal model for soft state communication based on a probabilistic delivery model with relaxed reliability. Using this model, we conduct queueing analysis and simulation to characterize the data consistency and performance tradeo s under a range of workloads and network loss rates. We then extend our model with feedback and show, through simulation, that adding feedback dramatically improves data consistency (by up to 55%) without increasing network resource consumption. Our model not only provides a foundation for understanding soft state, but also induces a new fundamental transport protocol based on probabilistic delivery. Toward this end, we sketch our design of the "Soft State Transport Protocol" (SSTP), which enjoys the robustness of soft state while retaining the performance benefit of hard state protocols like TCP through its judicious use of feedback.
FASTDash: A Visual Dashboard for Fostering Awareness
- in Software Teams. SIGCHI conference on Human Factors in computing systems
, 2007
"... Software developers spend significant time gaining and maintaining awareness of fellow developers ’ activities. FASTDash is a new interactive visualization that seeks to improve team activity awareness using a spatial representation of the shared code base that highlights team members ’ current acti ..."
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Cited by 99 (4 self)
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Software developers spend significant time gaining and maintaining awareness of fellow developers ’ activities. FASTDash is a new interactive visualization that seeks to improve team activity awareness using a spatial representation of the shared code base that highlights team members ’ current activities. With FASTDash, a developer can quickly determine which team members have source files checked out, which files are being viewed, and what methods and classes are currently being changed. The visualization can be annotated, allowing programmers to supplement activity information with additional status details. It provides immediate awareness of potential conflict situations, such as two programmers editing the same source file. FASTDash was developed through usercentered design, including surveys, team interviews, and in situ observation. Results from a field study show that FASTDash improved team awareness, reduced reliance on shared artifacts, and increased project-related communication. Additionally, the team that participated in our field study continues to use FASTDash.
SPORC: Group Collaboration using Untrusted Cloud Resources
- 9TH USENIX SYMPOSIUM ON OPERATING SYSTEMS SYSTEMS DESIGN AND IMPLEMENTATION (OSDI ’10)
, 2010
"... Cloud-based services are an attractive deployment model for user-facing applications like word processing and calendaring. Unlike desktop applications, cloud services allow multiple users to edit shared state concurrently and in real-time, while being scalable, highly available, and globally accessi ..."
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Cited by 80 (6 self)
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Cloud-based services are an attractive deployment model for user-facing applications like word processing and calendaring. Unlike desktop applications, cloud services allow multiple users to edit shared state concurrently and in real-time, while being scalable, highly available, and globally accessible. Unfortunately, these benefits come at the cost of fully trusting cloud providers with potentially sensitive and important data. To overcome this strict tradeoff, we present SPORC, a generic framework for building a wide variety of collaborative applications with untrusted servers. In SPORC, a server observes only encrypted data and cannot deviate from correct execution without being detected. SPORC allows concurrent, low-latency editing of shared state, permits disconnected operation, and supports dynamic access control even in the presence of concurrency. We demonstrate SPORC’s flexibility through two prototype applications: a causally-consistent key-value store and a browser-based collaborative text editor. Conceptually, SPORC illustrates the complementary benefits of operational transformation (OT) and fork* consistency. The former allows SPORC clients to execute concurrent operations without locking and to resolve any resulting conflicts automatically. The latter prevents a misbehaving server from equivocating about the order of operations unless it is willing to fork clients into disjoint sets. Notably, unlike previous systems, SPORC can automatically recover from such malicious forks by leveraging OT’s conflict resolution mechanism.
A Proxy Architecture for Reliable Multicast in Heterogeneous Environments
"... IP Multicast has proven to be an effective communication primitive for best effort, large-scale, multi-point audio/video conferencing applications. While the best-effort transport of real-time digital audio/video is a relatively straightforward and well understood problem, many other applications li ..."
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Cited by 51 (10 self)
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IP Multicast has proven to be an effective communication primitive for best effort, large-scale, multi-point audio/video conferencing applications. While the best-effort transport of real-time digital audio/video is a relatively straightforward and well understood problem, many other applications like multicast-based shared whiteboards and shared text editors are more challenging to design because their underlying media require reliable transport, i.e., a "reliable multicast" protocol. The design of scalable end-to-end reliable multicast protocols has unfortunately proven to be an especially hard problem, exacerbated by the enormous degree of network and system heterogeneity present in the Internet. In this paper, we propose to tackle the heterogeneity problem with a hybrid model for reliable multicast that relies in part on end-to-end loss recovery mechanisms and in part on intelligent and application-aware adaptation carried out within the network. In our framework, application-aware agents -- or proxies -- use detailed knowledge of application semantics to hide the effects of heterogeneity from the rest of the system. We present a general architecture for proxy-based reliable multicast called the Reliable Multicast proXy (RMX) model and describe a prototype implementation of an RMX for a shared whiteboard application for hand-held PDAs.
The Reliable Multicast Design Space for Bulk Data Transfer
- RFC
, 2000
"... Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. The design space for reliable multicast is ric ..."
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Cited by 36 (3 self)
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Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. The design space for reliable multicast is rich, with many possible solutions having been devised. However, application requirements serve to constrain this design space to a relatively small solution space. This document provides an overview of the design space and the ways in which application constraints affect possible solutions. 1.
Scalable Multimedia Communication with Internet Multicast, Light-weight Sessions, and the MBone
"... In this survey article we describe the roots of IP Multicast in the Internet, the evolution of the Internet Multicast Backbone or “MBone,” and the technologies that have risen around the MBone to support large-scale Internet-based multimedia conferencing. We develop the technical rationale for the d ..."
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Cited by 28 (6 self)
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In this survey article we describe the roots of IP Multicast in the Internet, the evolution of the Internet Multicast Backbone or “MBone,” and the technologies that have risen around the MBone to support large-scale Internet-based multimedia conferencing. We develop the technical rationale for the design decisions that underly the MBone tools, describe the evolution of this work from early prototypes into Internet standards, and outline the open challenges that remain and must be overcome to realize a ubiquitous multicast infrastructure. We and others in the MBone research community have implemented our protocols and methods in “real” applications and have deployed a fully operational system on a very large scale over the MBone. This infrastructure — including our audio, video, shared whiteboard tools and protocols — is now in daily use by the large and growing MBone user and research communities and the success and utility of this approach has resulted in commercialization of many of the underlying technologies.
MediaBoard: A Shared Whiteboard Application for the MBone
- UCB CS Masters Thesis
, 1997
"... In this thesis, we describe our comprehensive design and implementation of a multicast based shared drawing tool called MediaBoard. Like its predecessor, the LBL whiteboard application, wb, its design follows the principles of application level framing and lightweight sessions. Both applications ..."
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Cited by 25 (0 self)
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In this thesis, we describe our comprehensive design and implementation of a multicast based shared drawing tool called MediaBoard. Like its predecessor, the LBL whiteboard application, wb, its design follows the principles of application level framing and lightweight sessions. Both applications use the Scalable, Reliable Multicast protocol (SRM) to distribute data over the network. But unlike wb, which embeds the networking code in the application, MediaBoard uses a separate SRM framework library and customizes it to achieve application level semantics and thus performance gains. Based on actual deployment experiences --- MediaBoard was used in an "online classroom" at U.C. Berkeley --- we extended the design to improve its usability, provide increased awareness of remote participants, and integrate support for interactive browsing of the drawing space history. The application is also extremely flexible.
Using Multicast FEC to Solve the Midnight Madness Problem
, 1997
"... "Push" technologies to large receiver sets often do not scale due to large amounts of data replication and limited network bandwidth. Even with improvements from multicast communication, scaling challenges persist. Diverse receiver capabilities still result in a high degree of resends. To ..."
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Cited by 25 (1 self)
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"Push" technologies to large receiver sets often do not scale due to large amounts of data replication and limited network bandwidth. Even with improvements from multicast communication, scaling challenges persist. Diverse receiver capabilities still result in a high degree of resends. To combat this drawback, we combine multicast with Forward Error Correction. In this paper we describe an implementation of this approach that we call filecasting (Fcast) because of its direct application to multicast bulk data transfers. We discuss a variety of uses for such an application, focusing on solving the Midnight Madness problem, where congestion occurs at Web sites when a popular new resource is made available. Introduction When Microsoft released version 3.0 of the Internet Explorer (IE), the response was literally overwhelming. The number of people attempting to download the new product overloaded Microsoft web servers and saturated network links near Microsoft, as well as elsewhere. Not s...
Scalable Reliable Multicast Using Erasure-Correcting Re-sends
- In Microsoft Research Technical Report
, 1997
"... Reliable multicast schemes often cannot scale to large receiver sets due to the problems of state explosion and message implosion. In this paper we propose Erasure Correcting Scalable Reliable Multicast, ECSRM. ECSRM is based on the SRM framework proposed by Floyd et. al., which utilizes NACK suppre ..."
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Cited by 20 (6 self)
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Reliable multicast schemes often cannot scale to large receiver sets due to the problems of state explosion and message implosion. In this paper we propose Erasure Correcting Scalable Reliable Multicast, ECSRM. ECSRM is based on the SRM framework proposed by Floyd et. al., which utilizes NACK suppression to reduce message implosion. ECSRM makes a number of modifications to SRM to addressed enhanced scalability and rate control. Most notably, instead of resending lost packets, erasure-correcting encoded packets are sent in response to NACK messages. Introduction There are many instances in which it is desirable to deliver the same data to a number of receivers across a network. Popular "push" technology is focused on distributing news articles, stock quotes and the like to many subscribers. Other examples of applications that can utilize multipoint communication included multi-party video-conferencing, software updates, and multiplayer gaming. IP multicast is an excellent means of tra...
