The Application/Process Layer is where TCP/IP applications and services reside. You’re more than likely familiar with many of these, since you probably interact with many TCP/IP applications on a daily basis – a web browser using HTTP, or your email client connecting to a POP3 server are but two simple examples.
The list below outlines some of the more common Application layer protocols that you should be familiar with.
- Telnet. Telnet is used to create a terminal session with a remote host, providing command-line access to the target system running a telnet server (daemon).
- FTP. The File Transfer Protocol is used to reliably transfer files between an FTP client and server using TCP.
- SMTP. The Simple Mail Transfer Protocol is used for the exchange of email between systems.
- DNS. The Domain Name Service is a distributed database that is queried to resolve (or translate) names such as www.2000trainers.com to an IP address.
- SNMP. The Simple Network Management Protocol is a lightweight network protocol that allows information to be gathered about network devices. Examples include information about utilization, hardware configuration, and so forth.
- TFTP. The Trivial File Transfer Protocol is used to transfer files between a client and a TFTP server over UDP. You’ll learn more about TFTP later, since it’s the protocol used to transfer files to and from a Cisco router.