The phrase network entity goes for every single thing that can be brought into connection with telecommunication services. The word entity should be used because various types of things can be categorized in the term network entity: equipments, systems, servers, clients, adapters, etc. They are the sources and destinations of communication, and also the access between the two. Everything that is necessary for you to communicate properly.
The articles under the following links will help you to navigate through the whole telecommunication process by presenting every device needed. You should check the information on network entities whether you simply would like to gain knowledge on them or more advisedly, you would like to check all the necessary requirements for building a stable and reliable communication system with Ozeki VoIP SIP SDK.