– USER INTERACTIONS WITH PACKAGE…
Process & Applications Provide applications services to users and programs+application specific protocols
An application layer specifies the shared communications protocols and interface methods used by hosts in a communications network.
The application layer abstraction is used in both of the standard models of computer networking: the Internet Protocol Suite (TCP/IP) and the OSI model.
In TCP/IP, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client-server or peer-to-peer networking model.
In the OSI model, the definition of the application layer is narrower in scope. The OSI model defines the application layer as the user interface responsible for displaying received information to the user.
(Session Layer under OSI model) The IETF definition document for the application layer in the Internet Protocol Suite is RFC 1123. It provided an initial set of protocols that covered the major aspects of functionality of the early Internet.
Remote login to hosts: Telnet
File transfer: File Transfer Protocol (FTP), Trivial File Transfer Protocol (TFTP)
Electronic mail transport: Simple Mail Transfer Protocol (SMTP)
Networking support: Domain Name System (DNS)
Host initialization: BOOTP
Remote host management: Simple Network Management Protocol (SNMP), Common Management Information Protocol over TCP (CMOT)