Design BasicsDesign BasicsThe International Standards Organization created the Open Systems Interconnect Model, finalized in 1984, generally recognized as the "Bible" of networking protocol standards. All networking protocols are discussed using the OSI model as their point of reference, so understanding it is very important.
|
Name |
example |
||
| Layer 1 | Physical Layer | Cabling |
|
| Layer 2 | Data Link Layer | NIC address |
|
| Layer 3 | Network Layer | IP address |
|
| Layer 4 | Transport Layer | Transmission controls |
|
| Layer 5 | Session Layer | Telnet, FTP, SMTP |
|
| Layer 6 | Presentation Layer | ||
| Layer 7 | Application Layer | email, file transfer |
|
You'll notice that some examples don't fit nicely into the OSI Model.
This is because the OSI Model is a design criterion, and was developed after
many protocols were already established. It was also developed after
TCP/IP was established, the most important of all the networking protocols.
Consequently, OSI is something of an academic idea -- never actually implemented
in real life. Yet, because it was recognized as the design model from
whence all thought on protocols should be referenced, and also because at the time
which protocol would prevail was uncertain, it was
considered neutral ground.
There is less concern about this today, since TCP/IP is the
standard for large scale networking (and the Internet) recognized by all
proprietary protocol advocates (Novell, Microsoft, Apple, IBM, et cetera, et
cetera, et cetera)
