Protocols and Devices
Telnet, HTTP, FTP, SMTP
POP3, VoIP, SNMP
Firewall, Intrusion Detection System
Ethernet (IEEE 802.3), HDLC
Frame Relay, PPP
LAN switch, wireless access point
cable modem, DSL modem
RJ-45, EIA/TIA-232, V.35,
Ethernet (IEEE 802.3)
LAN Hub, Repeater
The International Standards Organisation (ISO
) defined a seven layer model to standardise
networking processes. The Open System Interconnection (OSI)
model facilitates the understanding of the complexities of
networking by defining what happens at each stage of the process.
Each of the seven layers in the model communicates with the layers above and below; using standardised coding at the
beginning of the message that can be interpreted by another device regardless of who made it.
The seven different layers break up the process of networking, making it easier to understand and to troubleshoot problems.
It is possible to test the functionabilty of each layer in sequence, to determine where the problem is, and where to