Layer 7, the Application layer, is the interface to the user and provides services that deal with the communication portion of an application. It identifies the desired recipient of the communication and ensures that the recipient is available for a transmission session. Protocols associated with the Application layer include the following:
- File Transfer Protocol (FTP) – Provides for authenticated transfer of files between two computers and access to directories; it cannot execute a remote file as a program.
- Trivial File Transfer Protocol (TFTP) – Reduced version of FTP; does not provide authentication or accessing of directories.
- Domain Name Service (DNS) – A distributed database system that matches host names to IP addresses and vice versa. A popular DNS implementation is the Berkeley Internet Name Domain (BIND).
- Simple Mail Transfer Protocol (SMTP) – Supports the transmission and reception of e-mail.
- Secure File Transfer Protocol (SFTP) – A protocol that is replacing FTP. It provides increased security because it includes strong encryption and authentication. FTP is a client that is similar to FTP and uses SSH or SSH-2 to provides secure file transfer.
- Simple Network Management Protocol (SNMP) – Supports the exchange of management information among network devices through a management entity that polls these devices. It is a tool for network administrators used to manage the network and detect problem areas.
- Remote login (Rlogin) – A command in UNIX that begins a terminal session between an authorized user and a remote host on a network. The user can perform all functions as if he or she were actually at the remote host. Rlogin is similar to the Telnet command.
- BootP – Provides a diskless workstation with its IP address based on its MAC address; this information comes from a BootP server.
- Multipurpose Internet Mail Extensions (MIME) – Enables the use of non-US-ASCII textual messages, nontextual messages, multipart message bodies, and non–US-ASCII information in message headers in Internet mail.