ARP is used to translate IPv4 addresses (OSI layer 3) into Ethernet MAC addresses (OSI layer 2).

Domain Name Service is an Application Layer service which is used to look up the IP address of a given domain name.

 

In computer networking, encapsulation is a method of designing modular communication protocols in which logically separate functions in the network are abstracted from their underlying structures by inclusion or information hiding within higher level objects.

Application LayerWhat is the OSI model, and how does it impact on the operation of your network?

The Open Systems Interconnection model is a conceptual model which standardises the communication functions of computing and networking systems.
It's aim is to encourage the interoperability of complex systems in a way which allows communications between each device using common protocols and instructions.

The Internet protocol suite is the computer networking model and set of communications protocols used on the Internet and similar computer networks.

It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) were the first networking protocols defined during its development.

It is occasionally known as the Department of Defense (DoD) model, because the development of the networking model was funded by DARPA, an agency of the United States Department of Defense.