What is a hierarchical communication protocol?

Question

What is a hierarchical communication protocol? I came across so many topics on hierarchical routing, hierarchical protocol and the basic idea of this hierarchical structure is to provide anonymity over a network. Does it have anything to do with "Hierarchical communication networks"? There is no reference of hierarchical communication protocol anywhere! At another place, I saw that the entire network is divided into zones, like clusters and different protocols are used inside and outside the clusters. That was called something hierarchical as well! So, coming back to the question, what exactly is a "hierarchical communication protocol"? [ I have a paper with me named "Energy Efficient Hierarchical Cluster Based Communication Protocol for Wireless Sensor Networks with Base Station Mobility". That is why the question.

Answer 1

A hierarchical protocol is just a protocol where nodes form a hierarchy, i.e. different nodes have different roles (cf. peer-to-peer protocol). A client-server protocol is a trivial example. The 'hierarchy' could be about different behaviour of the nodes, or it could be about altogether different network layers with their own protocols, as you mentioned.