Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

October 1990

Comments

University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-90-74.

Abstract

Mirage is a research effort which attempts to provide a basis for analysis and design of gigabit communications networks. As part of the overall Mirage project, we develop here the Mirage model, a formal model for the design and analysis of high-speed wide-area network protocols. The primary goal of this research is to understand the effects of moving to the gigabit domain in wide-area networks, verifying or disproving the predicted failure of existing protocols, and anticipating potential solutions. A derivative and more fundamental goal is to provide a framework for understanding the effects of latency on communication. In the high-speed, wide-area domain, network inefficiencies are caused by the combined effect of increased channel capacity, without a corresponding decrease in communication latency (due to finite propagation delays). Mirage proposes a view where latency can be compensated by accepting information imprecision (a controlled form of error), thus inverting the problem.

This research is based on suggestions derived from analogies in physics, using a model of state space volume transformations, in an attempt to incorporate the imprecision evident in quantum models into communication protocol analysis. It proposes to extend Shannon's communication theory by accounting for the effects of latency, just as Shannon's accounts for communication errors.

The dissertation we propose will consist of a three phase development of the formal model, providing for its synthesis and examples of its use. The first phase uses the description of a simple, existing protocol, clock synchronization via the Network Time Protocol, to assist in the development of the formal model. In the second phase, we will consider the application of the Mirage model principles towards the analysis of a new protocol, specifically a flow protocol, and the accumulation resetting mechanisms contained therein.

Finally, we will show how Mirage can be useful in the design of new protocols. In particular, we can apply this model toward the design of new distributed cache management protocols. Mirage suggests interesting tradeoffs and optimizations in the protocols used to maintain caches in a distributed shared memory.

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Date Posted: 11 October 2007