Lorenzo Vicisano

TCP-like congestion control for layered multicast data transfer

We present a novel congestion control algorithm suitable for use with cumulative, layered data streams in the MBone. Our algorithm behaves similarly to TCP congestion control algorithms, and shares bandwidth fairly with other instances of the protocol and with TCP flows. It is entirely receiver driven and requires no per-receiver status at the sender, in order to scale to large numbers of receivers. It relies on standard functionalities of multicast routers, and is suitable for continuous stream and reliable bulk data transfer. In the paper we illustrate the algorithm, characterize its response to losses both analytically and by simulations, and analyse its behaviour using simulations and experiments in real networks. We also show how error recovery can be dealt with independently from congestion control by using FEC techniques, so as to provide reliable bulk data transfer.

Replacement policies for a proxy cache

In this paper, we analyze access traces to a Web proxy, looking at statistical parameters to be used in the design of a replacement policy for documents held in the cache. In the first part of this paper, we present a number of properties of the lifetime and statistics of access to documents, derived from two large trace sets coming from very different proxies and spanning over time intervals of up to five months. In the second part, we propose a novel replacement policy, called LRV, which selects for replacement the document with the lowest relative value among those in cache. In LRV, the value of a document is computed adaptively based on information readily available to the proxy server. The algorithm has no hardwired constants, and the computations associated with the replacement policy require only a small constant time. We show how LRV outperforms least recently used (LRU) and other policies and can significantly improve the performance of the cache, especially for a small one.

RMDP: an FEC-based reliable multicast protocol for wireless environments

In this paper we present a Reliable Multicast data Distribution Protocols (RMDP), and discuss its performance. The protocol is based on the use of FEC techniques to drastically reduce the impact of independent losses for different receivers, which make ARQ-based protocols perform very poorly as the number of receivers grows. The protocol is well-suited to the use with mobile equipment because of its simplicity, robustness to losses, moderate demand for feedback, and scalability.