We propose a Progressive Email Classifier (PEC) for high-speed classification of message patterns that are commonly associated with unsolicited bulk email (UNBE). PEC is designed to operate at the network access point, the ingress between the Internet Service Provider (ISP) and the enterprise network; so that a surge of UNBE containing fresh patterns can be detected before they spread into the enterprise network. A real-time scoreboard keeps track of detected feature instances (FI) based on a scoring and aging engine, until they are considered either from valid or UNBE sources. A FI of a valid email is discarded, but an anomalous one is passed to a blacklist to control (e.g., block or defer) subsequent emails containing the FI.

This paper studies a fundamental problem, the termination detection problem, in distributed systems. Under a wireless network environment, we show how to handle the host mobility and disconnection problems. In particular, when some distributed processes are temporarily disconnected, we show how to capture a weakly terminated state where silence has been reached only by those currently connected processes. A user may desire to know such a state to tell whether the mobile distributed system is still running or is silent because some processes are disconnected. Our protocol tries to exploit the network hierarchy by combining two existing protocols together. It employs the weight-throwing scheme on the wired network side, and the diffusion-based scheme on each wireless cell. Such a hybrid protocol can better pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Analysis and simulation results are also presented.

Incorporating mobile components into a distributed system has posed new challenges to the design of distributed computation. This paper studies a fundamental problem in distributed computing, the termination detection problem, in a mobile environment. Two types of termination detection protocols already exist: the diffusion-based schemes and the weight-throwing schemes, that are designed for traditional static distributed systems. We propose a hybrid scheme by combining these two protocols together. The scheme can better exploit the communication hierarchy (in terms of wired and wireless bandwidths) and can pave the gaps of computation and communication capability between static and mobile hosts, thus more scalable to larger distributed systems. Simulation results are presented, which show the advantage of the hybrid scheme over existing schemes.