Rumor Spreading with Bounded In-Degree

In the gossip-based model of communication for disseminating information in a network, in each time unit, every node u can contact a single random neighbor v but can possibly be contacted by many nodes. In the present paper, we consider a restricted model where at each node only one incoming call can be answered in one time unit. We study the implied weaker version of the well-studied pull protocol, which we call restricted pull.

We prove an exponential separation of the rumor spreading time between two variants of the protocol (the answered call among a set of calls is chosen adversarial or uniformly at random). Further, we show that if the answered call is chosen randomly, the slowdown of restricted pull versus the classic pull protocol can w.h.p. be upper bounded by O(Δ/δ⋅logn)
, where Δ and δ are the largest and smallest degree of the network.