5895699
Addressing reality: an architectural response to real-world demands on the evolving Internet
A system as complex as the Internet can only be designed effectively if it is based on a core set of design principles, or tenets, that identify points in the architecture where there must be common understanding and agreement. The tenets of the original Internet architecture [6] arose as a response to the technical, governmental, and societal environment of internetworking's earliest days, but have remained central to the Internet as it has evolved. In light of the increasing integration of the Internet into the social, economic, and political aspects of our lives, it is worth revisiting the underlying tenets of what is becoming a central element of the world's infrastructure.This paper examines three key tenets that we believe should guide the evolution of the Internet in its next generation and beyond. They are: design for change, controlled transparency, and the centrality of the tussle space. [8] Our purpose is not to present these ideas as new, but rather to propose that they should be elevated to central tenets of the evolving architecture of the Internet, and explore the ramifications of doing so. The paper first examines the tenets somewhat abstractly, and then in more detail by studying their relation to several design choices needed for a complete architecture. We conclude with a discussion of the relationship between the network architecture and the applications it serves.
6156615
The design philosophy of the DARPA internet protocols
The Internet protocol suite, TCP/IP, was first proposed fifteen years ago. It was developed by the Defense Advanced Research Projects Agency (DARPA), and has been used widely in military and commercial systems. While there have been papers and specifications that describe how the protocols work, it is sometimes difficult to deduce from these why the protocol is as it is. For example, the Internet protocol is based on a connectionless or datagram mode of service. The motivation for this has been greatly misunderstood. This paper attempts to capture some of the early reasoning which shaped the Internet protocols.
10720036
Evaluating multi-port frame buffer designs for a mesh-connected multicomputer
Multicomputers can be effectively used for interactive graphics rendering only if there are mechanisms available to rapidly composite and transfer images to an external display device. One method for achieving the necessary bandwidth for this operation is to provide multiple high-bandwidth ports into a frame buffer. In this paper, we evaluate the design space of a multiport frame buffer design for the Intel Paragon mesh routing network. We use an instrumented rendering system to capture the graphics operations needed for rendering a number of three-dimensional scenes; we then use those workloads as input to test programs running on the Paragon to estimate the performance of our hardware. Our experiments consider three major design questions: how many network ports the frame buffer needs, whether Z-buffering should be done in hardware on the frame buffer or in software on the computing nodes, and whether the design alternatives are scalable.
11325567
Design choices in the SHRIMP system: an empirical study
The SHRIMP cluster-computing system has progressed to a point of relative maturity; a variety of applications are running on a 16-node system. We have enough experience to understand what we did right and wrong in designing and building the system. In this paper we discuss some of the lessons we learned about computer architecture, and about the challenges involved in building a significant working system in an academic research environment. We evaluate significant design choices by modifying the network interface firmware and the system software in order to empirically compare our design to other approaches.
15573543
Invariant-Based Synthesis of Fault-Tolerant Systems
Statecharts are a very widely used formalism for reactive system development, however there are problems in using them as a fully formal specification notation because of the conflicting variants of statechart semantics which exist. In this paper a modular subset of statechart notation is defined which has a simple semantics, and permits compositional development and verification. Techniques for decomposing specifications in this notation, design strategies for incorporating fault tolerance, and translation to the B formal language, are also described, and illustrated with extracts from a case study of a fault tolerant system.
14082519
Structuring and Design of Reactive Systems Using RSDS and B
With the advent of comprehensive safety standards for software intensive safety related systems, such as IEC 61508 and its speciali-sations for particular industry sectors (medical, machinery, process, etc), there is a need to establish combinations of techniques which can be used by industry to demonstrate conformance to these standards for particular developments. In this paper we describe one such combination of techniques, involving statecharts and B, which is aimed at reactive control system development. 
 
We define strategies for controller decomposition which allow safety invariants to be distributed into subcontroller requirements, and define techniques for the automatic synthesis of controllers from invariants. A case study of a train control system is used to illustrate the ideas.
19812651
A Lattice of Abstract Graphs
This paper concerns the abstract interpretation of Term Graph Rewriting systems. We introduce a new lattice of abstract graphs; this improves over previous work in that the ordering is defined directly on the graph structure rather than via unravelling into trees. We use the lattice in sketching the correctness of Nocker's abstract reduction algorithm; an efficient strictness analysis used in the Concurrent Clean system.