This article has coverd a great detail...
Just a little addition, The pullup resistor value can not be reduced after a lmit which is decided by one of the two factors. 1) The least value of maximum allowed power dissipation among all the ICs on Bus which again depends on thermal limitations of the IC.
2) Least value of Maximum allowed current through the I2C terminals among all the ICs on bus.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Are the design challenges the same as with embedded systems, but with a little developer- and IT-skills added in? What do engineers need to know? Rick Merritt talks with two experts about the tools and best options for designing IoT devices in 2016. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.