There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We will review some of the major results in random graphs and some of the more challenging open problems. We will cover algorithmic and structural questions. We will touch on newer models, including those related to the WWW.

Random graphs

"Grid" computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high performance orientation. In this article, the authors define this new field. First, they review the "Grid problem," which is defined as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources--what is referred to as virtual organizations. In such settings, unique authentication, authorization, resource access, resource discovery, and other challenges are encountered. It is this class of problem that is addressed by Grid technologies. Next, the authors present an extensible and open Grid architecture, in which protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing. The authors describe requirements that they believe any such mechanisms must satisfy and discuss the importance of defining a compact set of intergrid protocols to enable interoperability among different Grid systems. Finally, the authors discuss how Grid technologies relate to other contemporary technologies, including enterprise integration, application service provider, storage service provider, and peer-to-peer computing. They maintain that Grid concepts and technologies complement and have much to contribute to these other approaches.

The Anatomy of the Grid: Enabling Scalable Virtual Organizations

Cloud Computing, the long-held dream of computing as a utility, has the potential to transform a large part of the IT industry, making software even more attractive as a service and shaping the way IT hardware is designed and purchased. Developers with innovative ideas for new Internet services no longer require the large capital outlays in hardware to deploy their service or the human expense to operate it. They need not be concerned about overprovisioning for a service whose popularity does not meet their predictions, thus wasting costly resources, or underprovisioning for one that becomes wildly popular, thus missing potential customers and revenue. Moreover, companies with large batch-oriented tasks can get results as quickly as their programs can scale, since using 1000 servers for one hour costs no more than using one server for 1000 hours. This elasticity of resources, without paying a premium for large scale, is unprecedented in the history of IT. Cloud Computing refers to both the applications delivered as services over the Internet and the hardware and systems software in the datacenters that provide those services. The services themselves have long been referred to as Software as a Service (SaaS). The datacenter hardware and software is what we will call a Cloud. When a Cloud is made available in a pay-as-you-go manner to the general public, we call it a Public Cloud; the service being sold is Utility Computing. We use the term Private Cloud to refer to internal datacenters of a business or other organization, not made available to the general public. Thus, Cloud Computing is the sum of SaaS and Utility Computing, but does not include Private Clouds. People can be users or providers of SaaS, or users or providers of Utility Computing. We focus on SaaS Providers (Cloud Users) and Cloud Providers, which have received less attention than SaaS Users. From a hardware point of view, three aspects are new in Cloud Computing.

/pdf/above-the-clouds-a-berkeley-view-of-cloud-computing-tkj3etim13.pdf

Above the Clouds: A Berkeley View of Cloud Computing

A 2001 IBM manifesto observed that a looming software complexity crisis -caused by applications and environments that number into the tens of millions of lines of code - threatened to halt progress in computing. The manifesto noted the almost impossible difficulty of managing current and planned computing systems, which require integrating several heterogeneous environments into corporate-wide computing systems that extend into the Internet. Autonomic computing, perhaps the most attractive approach to solving this problem, creates systems that can manage themselves when given high-level objectives from administrators. Systems manage themselves according to an administrator's goals. New components integrate as effortlessly as a new cell establishes itself in the human body. These ideas are not science fiction, but elements of the grand challenge to create self-managing computing systems.

The vision of autonomic computing

We propose a radical re-architecture of the traditional operating system storage stack to move the kernel off the data path. Leveraging virtualized I/O hardware for disk and flash storage, most read and write I/O operations go directly to application code. The kernel dynamically allocates extents, manages the virtual to physical binding, and performs name translation. The benefit is to dramatically reduce the CPU overhead of storage operations while improving application flexibility.

/pdf/towards-high-performance-application-level-storage-27gjwkj67a.pdf

Towards high-performance application-level storage management

Modern production operating systems are large and complex systems developed over many years by large teams of programmers, containing many hundreds of thousands of lines of code. Consequently, it is extremely difficult to add significant new functionality to these systems. In response to this problem, a number of recent research projects have addressed the issue of extensible operating systems; these include SPIN, VINO, Exokernel, Lipto, and Fluke. This paper addresses the problem of providing extensibility for existing production operating systems such as Solaris, through the technique of interposition on existing kernel interfaces. Interposition is useful for extensions because it is transparent, it permits the incremental addition of functionality to an interface, and it enables the easy composition of multiple extensions. We have designed and implemented a prototype extension mechanism, SLIC, which utilizes interposition to efficiently insert trusted extension code into a production operating system kernel. We have used SLIC to implement a number of useful operating system extensions, such as a patch to fix a security hole described in a CERT advisory, an encryption file system, and a restricted execution environment for arbitrary untrusted binaries. Performance measurements of the SLIC prototype show that interposition on existing kernel interfaces can be accomplished efficiently.

/pdf/interposition-as-an-operating-system-extension-mechanism-5efhnduego.pdf

Interposition as an Operating System Extension Mechanism

Web applications are a frequent target of successful attacks. In most web frameworks, the damage is amplified by the fact that application code is responsible for security enforcement. In this paper, we design and evaluate Radiatus, a shared-nothing web framework where application-specific computation and storage on the server is contained within a sandbox with the privileges of the end-user. By strongly isolating users, user data and service availability can be protected from application vulnerabilities. To make Radiatus practical at the scale of modern web applications, we introduce a distributed capabilities system to allow fine-grained secure resource sharing across the many distributed services that compose an application. We analyze the strengths and weaknesses of a shared-nothing web architecture, which protects applications from a large class of vulnerabilities, but adds an overhead of 60.7% per server and requires an additional 31MB of memory per active user. We demonstrate that the system can scale to 20K operations per second on a 500-node AWS cluster.

Radiatus: a Shared-Nothing Server-Side Web Architecture

Talek is a private group messaging system that sends messages through potentially untrustworthy servers, while hiding both data content and the communication patterns among its users. Talek explores a new point in the design space of private messaging; it guarantees access sequence indistinguishability, which is among the strongest guarantees in the space, while assuming an anytrust threat model, which is only slightly weaker than the strongest threat model currently found in related work. Our results suggest that this is a pragmatic point in the design space, since it supports strong privacy and good performance: we demonstrate a 3-server Talek cluster that achieves throughput of 9,433 messages/second for 32,000 active users with 1.7-second end-to-end latency. To achieve its security goals without coordination between clients, Talek relies on information-theoretic private information retrieval. To achieve good performance and minimize server-side storage, Talek introduces new techniques and optimizations that may be of independent interest, e.g., a novel use of blocked cuckoo hashing and support for private notifications. The latter provide a private, efficient mechanism for users to learn, without polling, which logs have new messages.

https://dl.acm.org/doi/pdf/10.1145/3427228.3427231

Talek: Private Group Messaging with Hidden Access Patterns

A fundamental characteristic of the Internet, and increasingly other networked systems, is that it is controlled by many independent parties that act in their own interests. These parties, known as Internet service providers (ISPs), cooperate to provide global connectivity even though they often have competing interests. With current routing protocols, this competition induces each ISP to select paths that are optimal within its own network. The result is that paths across multiple networks can be poor from a global perspective. 
I present Wiser, a protocol that shows it is possible to achieve efficient global routing in practice even when ISPs select paths in their own interests. Wiser is based on "barter" between pairs of adjacent ISPs: each ISP selects paths that respect the concerns of the neighboring ISP as well as its own in return for the neighbor doing the same. To encourage ISPs to adopt Wiser, it is designed to maintain their autonomy, e.g., it does not require sensitive internal information to be disclosed, and individual ISPs do not lose compared to routing in the Internet today. Wiser can be implemented as an extension to current Internet routing protocols and deployed incrementally. 
To evaluate Wiser, I experiment with measured ISP topologies and a router-level prototype. I find that, unlike Internet routing today, the efficiency of Wiser is close to that of an ideal routing that globally optimizes network paths for metrics such as path length or band width provisioning. I further show that these benefits come at a low cost: the overhead of Wiser is similar to that of the current Internet routing protocol in terms of routing messages and computation.

/pdf/practical-and-efficient-internet-routing-with-competing-2zfrfpx93q.pdf

Thomas Anderson

Papers

Towards high-performance application-level storage management

Interposition as an Operating System Extension Mechanism

Radiatus: a Shared-Nothing Server-Side Web Architecture

Talek: Private Group Messaging with Hidden Access Patterns

Practical and efficient internet routing with competing interests