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The abstraction of a shared memory is of growing importance in distributed computing systems. Traditional memory consistency ensures that all processes agree on a common order of all operations on memory. Unfortunately, providing these guarantees entails access latencies that prevent scaling to large systems. This paper weakens such guarantees by(More)
We present a new protocol for maintaining replicated data that can provide both high data availability and low response time. In the protocol, the nodes are organized in a logical grid. Existing protocols are designed primarily to achieve high availability by updating a large fraction of the copies which provides some (although not signiicant) load sharing.(More)
Shared memories that provide weaker consistency guarantees than the traditional sequentially consistent or atomic memories have been claimed to provide the key to building scalable systems. One influential memory model, processor considency, has been cited widely in the literature but, due to the lack of a precise and formal definition, contradictory claims(More)
The growing popularity of IP telephony systems has made them attractive targets for spammers. Voice call spam, also known as Spam over Internet Telephony (SPIT), is potentially a more serious problem than email spam because of the real time processing requirements of voice packets. We explore a novel mechanism that uses duration of calls between users to(More)
As computing technology becomes more pervasive and broadband services are deployed into residential communities , new applications will emerge for the home and community environment. These applications will assist people in a variety of daily activities by enabling them to create, access, and manipulate information about the residents and resources in their(More)
We describe an approach to building security services for context-aware environments. Specifically, we focus on the design of security services that incorporate the use of security-relevant " context " to provide flexible access control and policy enforcement. We previously presented a generalized access control model that makes significant use of(More)
Ordering and time are two different aspects of consistency of shared objects in a distributed system. One avoids conflicts between operations, the other addresses how quickly the effects of an operation are perceived by the rest of the system. Consistency models such as sequential consistency and causal consistency do not consider the particular time at(More)
Interactive (or Synchronous) groupware is increasingly being deployed in widely distributed environments. Users of such applications are accustomed to direct manipulation interfaces that require fast response time. The state that enables interaction among distributed users can be replicated to provide acceptable response time in the presence of high(More)