Computer Networks and Communication Fundamentals

Network layer is responsible for packet forwarding, including routing through intermediate routers. Hence, routing is a concern of this layer.

Gopher protocol is a TCP/IP application layer protocol designed for distributing, searching, and retrieving documents over the Internet. Gopher ecosystem is often regarded as the effective predecessor of the World Wide Web.

Network News Transfer Protocol (NNTP) is an application protocol,  used for transporting Usenet news articles (netnews) between news servers and for reading and posting articles by end user client applications.

The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e.,  a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications.

Synchronous Optical Networking (SONET) is a standardised protocol that transfers multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs).

3G telecommunication networks support services that provide an information transfer rate of at least 200 kbit/s. However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service.

In half duplex mode, data can flow in both directions but only one at a time. Hence, a walkie talkie is half duplex.