Cisco PIX 520 - PIX Firewall 520 Online Help Manual page 247

The Internet protocols consist of a suite of communication protocols, of which the two best known are the
Transmission Control Protocol (TCP) and the Internet Protocol (IP). The Internet protocol suite not only includes
lower-layer protocols (such as TCP and IP), but it also specifies common applications such as electronic mail,
terminal emulation, and file transfer.
Internet Protocols Application-Layer Protocols
The Internet protocol suite includes many application-layer protocols that represent a wide variety of applications,
including the following:
File Transfer Protocol (FTP)—Moves files between devices
Simple Network-Management Protocol (SNMP)—Primarily reports anomalous network conditions and
sets network threshold values
Telnet—Serves as a terminal emulation protocol
X Windows—Serves as a distributed windowing and graphics system used for communication between X
terminals and UNIX workstations
Network File System (NFS)—External Data Representation (XDR), and Remote Procedure Call
(RPC)—Work together to enable transparent access to remotenetwork resources
Simple Mail Transfer Protocol (SMTP)—Provides electronic mail services
Domain Name System (DNS)—Translates the names of network nodes into network addresses
Layers
Internet protocols span the complete range of OSI model layers which describe the function of network
protocols..