TY - GEN

T1 - Gradient clock synchronization in dynamic networks

AU - Kuhn, Fabian

AU - Locher, Thomas

AU - Oshman, Rotem

PY - 2009

Y1 - 2009

N2 - Over the last years, large-scale decentralized computer networks such as peer-to-peer and mobile ad hoc networks have become increasingly prevalent. The topologies of many of these networks are often highly dynamic. This is especially true for ad hoc networks formed by mobile wireless devices. In this paper, we study the fundamental problem of clock synchronization in dynamic networks. We show that there is an inherent trade-off between the skew S guaranteed along sufficiently old links and the time needed to guarantee a small skew along new links. For any sufficiently large initial skew on a new link, there are executions in which the time required to reduce the skew on the link to O(S) is at least Ω(n/S). We show that this bound is tight for moderately small values of S. Assuming a fixed set of n nodes and an arbitrary pattern of edge insertions and removals, a weak dynamic connectivity requirement suffices to prove the following results. We present an algorithm that always maintains a skew of O(n) between any two nodes in the network. For a parameter S = Ω(√ρn), where ρ is the maximum hardware clock drift, it is further guaranteed that if a communication link between two nodes u, v persists in the network for Θ(n/S) time, the clock skew between u and v is reduced to no more than O(S).

AB - Over the last years, large-scale decentralized computer networks such as peer-to-peer and mobile ad hoc networks have become increasingly prevalent. The topologies of many of these networks are often highly dynamic. This is especially true for ad hoc networks formed by mobile wireless devices. In this paper, we study the fundamental problem of clock synchronization in dynamic networks. We show that there is an inherent trade-off between the skew S guaranteed along sufficiently old links and the time needed to guarantee a small skew along new links. For any sufficiently large initial skew on a new link, there are executions in which the time required to reduce the skew on the link to O(S) is at least Ω(n/S). We show that this bound is tight for moderately small values of S. Assuming a fixed set of n nodes and an arbitrary pattern of edge insertions and removals, a weak dynamic connectivity requirement suffices to prove the following results. We present an algorithm that always maintains a skew of O(n) between any two nodes in the network. For a parameter S = Ω(√ρn), where ρ is the maximum hardware clock drift, it is further guaranteed that if a communication link between two nodes u, v persists in the network for Θ(n/S) time, the clock skew between u and v is reduced to no more than O(S).

KW - Clock synchronization

KW - Distributed algorithms

KW - Dynamic networks

UR - http://www.scopus.com/inward/record.url?scp=70449670991&partnerID=8YFLogxK

U2 - 10.1145/1583991.1584059

DO - 10.1145/1583991.1584059

M3 - פרסום בספר כנס

AN - SCOPUS:70449670991

SN - 9781605586069

T3 - Annual ACM Symposium on Parallelism in Algorithms and Architectures

SP - 270

EP - 279

BT - SPAA'09 - Proceedings of the 21st Annual Symposium on Parallelism in Algorithms and Architectures

Y2 - 11 August 2009 through 13 August 2009

ER -