Thermodynamics is a framework for explaining the behavior of large-scale systems in the natural world. Many systems in nature and the biological world are an open system that exchanges energy with an outside system, and their steady-state properties can be described by using the basic laws of thermodynamics. These systems are known to have inherent fluctuations due to perturbing elements. The Internet, which is an artificial large system, can be viewed as an open system where the behavior of the system and its surrounding environment have mutual influence. It is also known that the Internet experiences performance fluctuations such as delay jitter. Focusing on this analogy, we thermodynamically interpret the network system to explain the behavior of the network system from the point of view of thermodynamics. We derive some thermodynamic quantities of information networks from specific micro and macro models of information networks. We present that the temperature in the network means the degree of their fluctuations (uncertainty).