Larry L. Peterson

TCP Vegas: end to end congestion avoidance on a global Internet

Vegas is an implementation of TCP that achieves between 37 and 71% better throughput on the Internet, with one-fifth to one-half the losses, as compared to the implementation of TCP in the Reno distribution of BSD Unix. This paper motivates and describes the three key techniques employed by Vegas, and presents the results of a comprehensive experimental performance study, using both simulations and measurements on the Internet, of the Vegas and Reno implementations of TCP. >

TCP Vegas: new techniques for congestion detection and avoidance

Vegas is a new implementation of TCP that achieves between 40 and 70% better throughput, with one-fifth to one-half the losses, as compared to the implementation of TCP in the Reno distribution of BSD Unix. This paper motivates and describes the three key techniques employed by Vegas, and presents the results of a comprehensive experimental performance study—using both simulations and measurements on the Internet—of the Vegas and Reno implementations of TCP.

PlanetLab: an overlay testbed for broad-coverage services

PlanetLab is a global overlay network for developing and accessing broad-coverage network services. Our goal is to grow to 1000 geographically distributed nodes, connected by a disverse collection of links. PlanetLab allows multiple service to run concurrently and continuously, each in its own slice of PlanetLab. This paper discribes our initial implementation of PlanetLab, including the mechanisms used to impelment virtualization, and the collection of core services used to manage PlanetLab.

Container-based operating system virtualization: a scalable, high-performance alternative to hypervisors

Hypervisors, popularized by Xen and VMware, are quickly becoming commodity. They are appropriate for many usage scenarios, but there are scenarios that require system virtualization with high degrees of both isolation and efficiency. Examples include HPC clusters, the Grid, hosting centers, and PlanetLab. We present an alternative to hypervisors that is better suited to such scenarios. The approach is a synthesis of prior work on resource containers and security containers applied to general-purpose, time-shared operating systems. Examples of such container-based systems include Solaris 10, Virtuozzo for Linux, and Linux-VServer. As a representative instance of container-based systems, this paper describes the design and implementation of Linux-VServer. In addition, it contrasts the architecture of Linux-VServer with current generations of Xen, and shows how Linux-VServer provides comparable support for isolation and superior system efficiency.

Fbufs: a high-bandwidth cross-domain transfer facility

We have designed and implemented a new operating system facility for I/O buffer management and data transferacross protection domain boundaries on shared memory machines. This facility, called fast buffers (fbufs), combines virtual page remapping with shared virtual memory, and exploits locality in I/O traffic to achieve high throughput without compromising protection, security, or modularity. goal is to help deliver the high bandwidth afforded by emerging high-speed networks to user-level processes, both in monolithic and microkernel-based operating systems.This paper outlines the requirements for a cross-domain transfer facility, describes the design of the fbuf mechanism that meets these requirements, and experimentally quantifies the impact of fbufs on network performance.

Preserving and using context information in interprocess communication

When processes in a network communicate, the messages they exchange define a partial ordering of externally visible events. While the significance of this partial order in distributed computing is well understood, it has not been made an explicit part of the communication substrate upon which distributed programs are implemented. This paper describes a new interprocess communication mechanism, called Psync, that explicitly encodes this partial ordering with each message. The paper shows how Psync can be efficiently implemented on an unreliable communications network, and it demonstrates how conversations serve as an elegant foundation for ordering messages exchanged in a distributed computation and for recovering from processor failures.

Making paths explicit in the Scout operating system

This paper makes a case for paths as an explicit abstraction in operating system design. Paths provide a unifying infrastructure for several OS mechanisms that have been introduced in the last several years, including fbufs, integrated layer processing, packet classifiers, code specialization, and migrating threads. This paper articulates the potential advantages of a path-based OS structure, describes the specific path architecture implemented in the Scout OS, and demonstrates the advantages in a particular application domain---receiving, decoding, and displaying MPEG-compressed video.

A dynamic network architecture

Network software is a critical component of any distributed system. Because of its complexity, network software is commonly layered into a hierarchy of protocols, or more generally, into a protocol graph. Typical protocol graphs—including those standardized in the ISO and TCP/IP network architectures—share three important properties; the protocol graph is simple, the nodes of the graph (protocols) encapsulate complex functionality, and the topology of the graph is relatively static. This paper describes a new way to organize network software that differs from conventional architectures in all three of these properties. In our approach, the protocol graph is complex, individual protocols encapsulate a single function, and the topology of the graph is dynamic. The main contribution of this paper is to describe the ideas behind our new architecture, illustrate the advantages of using the architecture, and demonstrate that the architecture results in efficient network software.

Understanding TCP Vegas: a duality model

We view congestion control as a distributed primal--dual algorithm carried out by sources and links over a network to solve a global optimization problem. We describe a multilink multisource model of the TCP Vegas congestion control mechanism. The model provides a fundamental understanding of delay, fairness and loss properties of TCP Vegas. It implies that Vegas stabilizes around a weighted proportionally fair allocation of network capacity when there is sufficient buffering in the network. It clarifies the mechanism through which persistent congestion may arise and its consequences, and suggests how we might use REM active queue management to prevent it. We present simulation results that validate our conclusions.

A routing underlay for overlay networks

We argue that designing overlay services to independently probe the Internet--with the goal of making informed application-specific routing decisions--is an untenable strategy. Instead, we propose a shared routing underlay that overlay services query. We posit that this underlay must adhere to two high-level principles. First, it must take cost (in terms of network probes) into account. Second, it must be layered so that specialized routing services can be built from a set of basic primitives. These principles lead to an underlay design where lower layers expose large-scale, coarse-grained static information already collected by the network, and upper layers perform more frequent probes over a narrow set of nodes. This paper proposes a set of primitive operations and three library routing services that can be built on top of them, and describes how such libraries could be useful to overlay services.