TCP/IP Protocol Stack
In this lesson, you will:
List TCP/IP Process layer protocols.
Identify the functions handled by Process layer protocols in the TCP/IP stack.
TCP/IP is the most popular protocol used today to transmit and receive data throughout corporations
and the Internet. It is used in both LANs and WANs. TCP/IP is a suite of protocols: TCP operates at
Layer 4 and IP operates at Layer 3. In addition, various application protocols are included with
TCP/IP. These applications are discussed next. The figure below compares the OSI stack to the
TCP/IP model. There is no interrelation between the two, the comparison is provided for clarity,
since most people learn the concept of layers from OSI.
TCP/IP Layer 4 - Process Layer
The Process layer protocols provide the user interface for the various protocols and applications that
access the network. Process layer protocols in the TCP/IP stack handle file transfer, remote login to
other nodes, email functionality, and network monitoring.
File Transfer Protocol (FTP) provides the capability to transfer files between two computers. FTP is
actually a full-blown file transfer application. Other applications such as Web browsers also support
this protocol. Trivial File Transfer Protocol (TFTP) is a stripped-down version of FTP that provides a
way to move files without any type of authentication (meaning no user name or password). TFTP is
used to save router configuration files or to update the IOS of a router.
Simple Mail Transport Protocol (SMTP) is a protocol that provides mail delivery between two
computers. Email clients for sending and receiving email on the Internet use SMTP. Simple Network
Management Protocol (SNMP) is a protocol that provides the capability to collect network
information. SNMP uses agents (software watchdogs that monitor network processes) that collect
data on network performance. Software packages like CiscoWorks use SNMP to help network
administrators monitor the health of a network.
Telnet is a terminal emulation protocol that allows you to connect a local computer with a remote
computer (or other device such as a router). The local computer becomes a virtual terminal that has
access to applications and other resources on the remote computer. Network File Service (NFS) is a
service that allows network users to access shared files stored on computers of different types.
HyperText Transfer Protocol (HTTP) is the protocol used by the World Wide Web. It defines how
messages are formatted and transmitted, and what actions Web servers and browsers take in response
to these messages. Domain Name Service (DNS) is a service that translates domain names into IP
1. List at least three TCP/IP applications.
TCP/IP applications include: HTTP, FTP, telnet, SNMP, SMTP, DNS, and NFS
2. What functions do Process layer protocols in the TCP/IP stack handle?
File transfer, remote login to other nodes, email functionality, and network monitoring.