OSI Model
The open systems interconnection (OSI) model was created to standardize the rules of networking in order for all systems to be able to communicate. In order for communication to occur on a networking using different device drivers and protocol stacks, the rules for communication must be explicitly defined. The OSI model deals with the following issues;
How a device on a network sends it's data, and how it knows when are where to send it
How a device on a network receives it's data, and how to know where to look for it.
How devices using different languages communicate with each other.
How devices on a network are physically connected to each other.
How protocols work with devices on a network to arrange data.
The OSI model is broken down into the following 7 layers.
| Layer | Function | Protocols/Standards | Data Component | Network Component | |
| 7) Application | This layer offers the user interface and
specifies what's being done on the network and how.
|
Telnet, HTTP, FTP, and SMTP. | Messages | Gateway | |
| 6) Presentation | The sixth layer is concerned with extracting data from the application layer and putting the data in a format that can be read based on various file standards. | JPEG, GIF, MPEG, and ASCII. | Messages | Gateway | |
| 5) Session | Controls the beginning, middle, and end of individual networking "sessions." | DECnet, RPC, NFS and SQL. | Messages | Gateway | |
| 4) Transport | Layer 4 is involved primarily as a gateway between the upper application-oriented layers and the lower network-oriented protocols. | TCP, UDP, and SPX. | Segments | Brouter/Gateway | |
| 3) Network | Defines end-to-end delivery of information. This includes such functions as routing and routing protocols. Ex: this layer defines the addressing and routing structure of the Internet. | IP,RIP,ICMP IPX,
NWLink NetBEUI |
Packets or datagrams | Router
ATM Switch
|
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| 2) Data Link | Logical Link Control |
Specifies a direct means of communication on the network. It's best thought of as a one-hop protocol.
|
HDLC, SDLC, Frame Relay, PPP, FDDI, and ATM,LAPB, | Frames | Bridge
Switch ISDN Router Intelligent Hub NIC
|
| Media Access Contro | |||||
| 1) Physical | Defines the physical components that make the network function. This includes cabling standards and electrical or light communication methods. Standards in the Physical layer are usually defined by international standards committees. | UTP,STP, Fiber, V.35, X.21,RS-232 | Bits | Repeater
Multiplexer Hubs
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Partial list of TCP/IP protocols in relation to the
seven-layer model