The Application Layer gives applications access to the services of the other layers and defines the protocols that applications use to send and receive information. This layer is the first step in getting information onto the network. There are numerous Application Layer protocols and new ones come out all the time. Some of the most widely used Application Layer protocols are Hypertext Transfer Protocol (HTTP), which is used to send and receive files that make up the World Wide Web, File Transfer Protocol (FTP), which is implemented for interactive file transfers, Simple Mail Transfer Protocol (SMTP), which is used to send mail messages/attachments, and finally Telenet, which is a terminal emulation protocol implemented for remote logging of network hosts.
Many problems can arise with the Application Layer. Software bugs can occur, which is where an application crashes when sending data too fast. Incorrect settings are another issue and usually happen when host addresses or names may have been changed, however not documented. Services can also be set to an incorrect port. Lastly, client or server components that one uses might not follow published protocol standards. Many changes have been made to this since technology advances and require additional security measures and increased functionality.
“How TCP/IP Works.” Technet. Technet.microsoft.com. Web. 29 Mar 2003. Accessed 16 Jun 2017.