38950443
Mechanical Verification of Distributed Algorithms in Higher-Order Logic
The only practical way to verify the correctness of distributed algorithms with a high degree of confidence is to construct machine-checked, formal correctness proofs. In this paper we explain how to do so using HOL an interactive proof assistant for higher order logic developed by Gordon and others. First, we describ how to build an infrastructure in HOL that supports reasoning about distributed algorithms,including formal theories of predicates, temporal logic, labeled transitions systems, simulation of programs, translation of properties, and graphs. Then we demonstrate, via an exemple, how to use the powerful intuition about eventsand causality to guide and structure correctness proofs of distributed algorithms. The example used is the verification of PIF (propagation of information with feedback), which is a simple but typical distributed algorithm due to Segall.
33219681
Linear Broadcast Routing
17395638
A Simple Method for Parameterized Verification of Cache Coherence Protocols
We present a simple method for verifying the safety properties of cache coherence protocols with arbitrarily many nodes. Our presentation begins with two examples. The first example describes in intuitive terms how the German protocol with arbitrarily many nodes can be verified using a combination of Murphi model checking and apparently circular reasoning. The second example outlines a similar proof of the FLASH protocol. These are followed by a simple theory based on the classical notion of simulation proofs that justifies the apparently circular reasoning. We conclude the paper by discussing what remains to be done and by comparing our method with other approaches to the parameterized verification of cache coherence protocols, such as compositional model checking, machine-assisted theorem proving, predicate ion, invisible invariants, and cut-off theorems.
14479349
Understanding and verifying distributed algorithms using stratified decomposition
Designers of autonomous distributed algorithms ( i.e., algorithms whose complete input is available before the start of execution) customarily refer to temporal ordering in describing the behavior of their algorithms-statements like “after A, task B is performed.” In the absence of an explicit termination detection for A built into the algorithm such a statement should be puzzling. However, the available proof methodologies do not seem to hinge on such statements. This paper provides firm theoretical ground for such as*Supported by NSF Presidential Young Investigators Award under grant DCR84-51396 and matching funds from IBM Faculty Development Award under grant D840622. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/ or specific permission.
29521519
Linear Broadcast Routing
Abstract In this paper we examine the problem of performing broadcasts in networks where the messages are constrained to follow linear paths. Many high speed networks, where routing is done in specialized hardware, have this characteristic. We show that the general problem is NP-complete but find a polynomial time approximation algorithm which is guaranteed to provide a solution which is within twice the optimal. We also suggest some generalizations of this work and propose several open problems.
12857629
Simple Proof Techniques for Property Preservation via Simulation
Let s1 and s2 be two reactive systems related by simulation. For what kind of properties φ can one infer s1 ≒ φ (s1 satisfies φ) from s2 ≒ φ, or vice versa? This problem has been treated in the literature for various logics in which to express φ. In this paper we make two simple observations by which such results can be proved very easily: 
1. 
(1) proofs of property preservation can be made compositional, and 
 
2. 
(2) infinitary logics are very expressive. Neither observation is new, but together they yield modular proofs of nontrivial results.
13565274
Optimized allocation of distributed applications across local area networks
Enterprise-wide distributed computing systems are inherently stochastic and the performance management of distributed applications running on the top of DCS is a complex and computationally hard task, in this paper, we define the enterprise distributed application and provide queueing analysis on the relationship between the application level performance parameters and the network and computer system parameters. We also provide a binary integer programming (BIP) model and a case study on how to allocate application components across an enterprise local area network.
41218825
Relaxed game chromatic number of graphs
This paper discusses a coloring game on graphs. Let k, d be non-negative integers and C a set of k colors. Two persons, Alice and Bob, alternately color the vertices of G with colors from C, with Alice having the first move. A color i is legal for an uncolored vertex x if by coloring x with color i, the subgraph of G induced by those vertices of color i has maximum degree at most d. Each move of Alice or Bob colors an uncolored vertex with a legal color. The game is over if either all vertices are colored, or no more vertices can be colored with a legal color. Alice's goal is to produce a legal coloring which colors all the vertices of G, and Bob's goal is to prevent this from happening. We shall prove that if G is a forest, then for k = 3, d ≥ 1, Alice has a winning strategy. If G is an outerplanar graph, then for k = 6 and d ≥ 1, Alice has a winning strategy.
6876063
Popularity-wise proxy caching for interactive streaming media
Most of the current proxy caching algorithms for streaming video media assume that users favor the beginning of the media object. However, this assumption is questionable in highly interactive scenarios, such as e-learning, where some parts of the video other than the prefix can also be popular. A new segment-based proxy caching algorithm, named popularity-wise caching, is proposed for highly interactive streaming. It is designed to deal with arbitrary popularity distribution of media content. Simulations are performed using synthetic traces with different kinds and levels of user interactivity. The results show that the performance of current segment-based caching (such as exponential caching and soccer caching) degrade with increasing user interactivity, while popularity-wise caching can provide the lowest user startup latency for interactive requests and highest bandwidth saving for the backbone network.
38703217
Design of Scalable Continuous Media Servers
Multimedia applications place high demands for quality-of-service (QoS), performance, and reliability on systems. These stringent requirements make design of cost-effective and scalable systems difficult. Therefore efficient adaptive and dynamic resource management techniques in conjunction with data placement techniques can be of great help in improving performance, scalability, and reliability of such systems. This is the focus of our paper.
16192278
A distributed location service for reducing query failures in geographic ad hoc routing
Location service support is required for mobile nodes using geographic ad hoc routing. The mobile nodes need location information of destinations for sending data packets. Due to mobility or node failures, queries to the location servers may not always succeed. This paper presents a distributed location service (DLS) that employs dual servers to maintain position information of mobile nodes and to achieve efficient performance. With the scheme, the number of failed queries, including no response and erroneous results, can be reduced. DLS has been implemented and evaluated using the ns2 simulator. The experimental results show that DLS not only improved service availability but also location query latency.