The Domain Name System (DNS) is a distributed, hierarchical database for converting DNS names into IP addresses. The key-value store can be used for more than just IP address information. The DNS protocol runs in two different modes:
The Open Systems Interconnection (OSI) model was created to standardize the language used to describe networking protocols. It defines the manner in which systems communicate with one another using abstraction layers. Each layer communicates with the layer directly above and below. Not all layers are used at all times.