The Age of Gossip in Networks

TL;DR

This paper analyzes how information ages in a network where nodes share updates via gossip protocols, providing a method to evaluate average age and demonstrating that age grows logarithmically with network size.

Contribution

It introduces a novel method for calculating average version age in networks using gossip protocols and applies it to simple network models.

Findings

Average age grows logarithmically with network size in complete graphs.

Method effectively evaluates age in networks with memoryless gossip.

Analysis provides insights into information freshness in network protocols.

Abstract

A source node updates its status as a point process and also forwards its updates to a network of observer nodes. Within the network of observers, these updates are forwarded as point processes from node to node. Each node wishes its knowledge of the source to be as timely as possible. In this network, timeliness is measured by a discrete form of age of information: each status change at the source is referred to as a version and the age at a node is how many versions out of date is its most recent update from the source. This work introduces a method for evaluating the average version age at each node in the network when nodes forward updates using a memoryless gossip protocol. This method is then demonstrated by version age analysis for a collection of simple networks. For gossip on a complete graph with symmetric updating rates, it is shown that each node has average age that grows as the logarithm of the network size.