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. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.