  We present FLIC, a distributed software data caching framework for fogs that
reduces network traffic and latency. FLICis targeted toward city-scale
deployments of cooperative IoT devices in which each node gathers and shares
data with surrounding devices. As machine learning and other data processing
techniques that require large volumes of training data are ported to low-cost
and low-power IoT systems, we expect that data analysis will be moved away from
the cloud. Separation from the cloud will reduce reliance on power-hungry
centralized cloud-based infrastructure. However, city-scale deployments of
cooperative IoT devices often connect to the Internet with cellular service, in
which service charges are proportional to network usage. IoT system architects
must be clever in order to keep costs down in these scenarios. To reduce the
network bandwidth required to operate city-scale deployments of cooperative IoT
systems, FLIC implements a distributed cache on the IoT nodes in the fog. FLIC
allows the IoT network to share its data without repetitively interacting with
a simple cloud storage service reducing calls out to a backing store. Our
results displayed a less than 2% miss rate on reads. Thus, allowing for only 5%
of requests needing the backing store. We were also able to achieve more than
50% reduction in bytes transmitted per second.
