Showing papers by "Michael Merritt published in 2008"

Group Renaming

Abstract: We study the group renaming task, which is a natural generalization of the renaming task. An instance of this task consists of n processors, partitioned into m groups, each of at most g processors. Each processor knows the name of its group, which is in { 1, ..., M }. The task of each processor is to choose a new name for its group such that processors from different groups choose different new names from {1, ..., ***}, where ***< M . We consider two variants of the problem: a tight variant, in which processors of the same group must choose the same new group name, and a loose variant, in which processors from the same group may choose different names. Our findings can be briefly summarized as follows: 1 We present an algorithm that solves the tight variant of the problem with ***= 2m *** 1 in a system consisting of g -consensus objects and atomic read/write registers. In addition, we prove that it is impossible to solve this problem in a system having only (g *** 1)-consensus objects and atomic read/write registers. 1 We devise an algorithm for the loose variant of the problem that only uses atomic read/write registers, and has $\ell = 3n - \sqrt{n} - 1$. The algorithm also guarantees that the number of different new group names chosen by processors from the same group is at most $\min\{g, 2m, 2\sqrt{n}\}$. Furthermore, we consider the special case when the groups are uniform in size and show that our algorithm is self-adjusting to have ***= m (m + 1) / 2, when $m , and $\ell = 3n / 2 + m - \sqrt{n}/2 - 1$, otherwise.

Interdomain network aware peer-to-peer protocol

Abstract: A method includes receiving network distance information, receiving a request from a client for an identity of a peer providing content, and identifying a first peer and a second peer providing the content. The network distance information includes a compilation of network distance information provided by a plurality of service providers. The method further includes determining that a network distance between the first peer and the client is less than a network distance between the second peer and the client based on the network distance information, and providing the identity of the first peer to the client.

Sequentially consistent versus linearizable counting networks

Abstract: We compare the impact of timing conditions on implementing sequentially consistent and linearizable counters using (uniform) counting networks in distributed systems. For counting problems in application domains which do not require linearizability but will run correctly if only sequential consistency is provided, the results of our investigation, and their potential payoffs, are threefold: First, we show that sequential consistency and linearizability cannot be distinguished by the timing conditions previously considered in the context of counting networks; thus, in contexts where these constraints apply, it is possible to rely on the stronger semantics of linearizability, which simplifies proofs and enhances compositionality. Second, we identify local timing conditions that support sequential consistency but not linearizability; thus, we suggest weaker, easily implementable timing conditions that are likely to be sufficient in many applications. Third, we show that any kind of synchronization that is too weak to support even sequential consistency may violate it significantly for some counting networks; hence, we identify timing conditions that are to be totally ruled out for specific applications that rely critically on either sequential consistency or linearizability.