Installation guide

Network Infrastructure for EtherNet/IP™
Understanding the Basics of Network Protocols
2-5
2 Understanding the Basics of Network
Protocols
The following discussion includes information on the TCP/IP suite, focusing on the
Transmission Control Protocol (TCP), the Internet Protocol (IP) and the User Datagram
Protocol (UDP).
The OSI Model provides a conceptual framework for communication between computers, but the model
itself is not a method of communication. Actual communication is made possible by using
communication protocols. In the context of data networking, a
protocol is a formal set of rules and
conventions that govern how computers exchange information over a network medium. A protocol
implements the functions of one or more of the OSI Model layers. (See Appendix B for more
information.)
A wide variety of communication protocols exist. Some of these protocols include Local Area Network
(LAN) protocols, Wide Area Network (WAN) protocols, network protocols, and routing protocols.
LAN
and WAN protocols
operate at the physical layer (Layer 1) and data link layer (Layer 2) of the OSI
Model and define communication over the various LAN media.
Routing protocols are network-layer
protocols that are responsible for exchanging information between routers, so the routers can select the
proper path for network traffic. Finally,
network protocols are the various upper-layer protocols that
exist in a given protocol suite. (See Figure 2-1.)
Figure 2-1 Relationship of the Internet Protocol Suite to the OSI Reference Model.
Many protocols rely on the existence of others for operation. For example, CIP uses Internet Protocol
(IP), UDP, and TCP. This concept of building upon other existing layers is the foundation of the OSI
Model.
7
4
3
2
1
IP
TCP
Application
UDP
FTP SMTP Telnet TFTPSNMP HTTP
ARP RARP ICMP
LAP
X.21 ISDN
IBSEthernet
OSI Layer