This paper considers the average consensus problem on a network of digital links, and proposes a set of algorithms based on pairwise "gossip" communications and updates. We study the convergence properties of such algorithms with the goal of answering two design questions, arising from the literature: whether the agents should encode their communication by a deterministic or a randomized quantizer, and whether they should use, and how, exact information regarding their own states in the update. (C) 2009 Elsevier Ltd. All rights reserved.