Trading Throughput for Freshness: Freshness-Aware Traffic Engineering and In-Network Freshness Control

In addition to traditional concerns such as throughput and latency, freshness is becoming increasingly important. To stay fresh, applications stream status updates among their components. Existing studies propose the metric age of information (AoI) to gauge the freshness and design systems to achieve low AoI. Despite active research in this area, existing results are not applicable to general wired networks for two reasons. First, they focus on wireless settings where AoI is mostly affected by interference and collision while queueing is more dominant in wired settings. Second, the legacy drop-adverse flows are not taken into account in the literature. Scheduling mixed flows with distinct performance objective is not yet addressed. In this paper, we study wired networks shared by two classes of flows, aiming for high throughput and low AoI respectively, and achieve a good trade-off between their throughput and AoI. Our approach to the problem consists of two layers: freshness-aware traffic engineering (FATE) and in-network freshness control (IFC). FATE derives sending rate/update frequency for flows via optimization, and its solution is then enforced by IFC through efficient scheduling mechanisms at each outport of in-network nodes. We also present efficient Linux implementation of IFC and demonstrate the effectiveness of FATE/IFC through extensive emulations. Our results show that it is possible to trade a little throughput (5 % lower) for much shorter AoI (49 to 71% shorter) compared to state-of-the-art traffic engineering.