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OSI Networking Model
The OSI Networking Model is used as a reference point to describe how the various "layers" of networking interoperate.
It is also called the OSI seven layer model.
Here is a summary of the model with Layers, Topics and Methods with a short description for each method.
Presented by Abbe Vallipour, ASL Consulting
1- Physical layer
2- Data Link layer
3- Network layer
4- Transport layer
5- Session layer
6- Presentation layer
7- Application layer
A summary table starting with the bottom layer (1)
| OSI Layer |
Topics |
Methods |
| 1-Physical |
Connection types |
Point-to-Point |
| -Bits & Packets. |
|
Multipoint |
| |
Physical topology |
Bus |
| .Concentrators |
|
Ring |
| .Hubs |
|
Star |
| .Repeaters |
|
Mesh |
| .Connectors |
|
Cellular |
| .Modems |
Digital signaling |
Current state |
| .Codecs |
|
State transition |
| |
Analog signaling |
Current state |
| |
|
State transition |
| |
Bit synchronization |
Asynchronous |
| |
|
Synchronous |
| |
Bandwidth use |
Broadband (thick ethernet) |
| *Implementations of Physical layer |
|
Baseband (thin ethernet) |
| protocols are transmission media- |
Multiplexing |
Frequency-Division (FDM) |
| specific. |
|
Time-Division (TDM) |
| |
|
Stat.Time-Division (StatTDM) |
|
OSI Layer |
Topics |
Methods |
|
2-Data Link-MAC |
Logical Topology |
Bus |
|
(Media Access Control) |
|
Ring |
|
-Frames & Packets. |
Media access |
Contention (802.2 & 802.3) |
|
.Bridges |
|
Token passing (802.4 & 802.5) |
|
.Intelligent hubs |
|
Polling |
|
.NICs |
Addressing |
Physical device |
|
2-Data Link-LLC |
Transmission |
Asynchronous |
|
(Logical Link Control) |
Synchronization |
Synchronous |
|
*Organize first layer's bits to frames, |
|
Isochronous |
|
& identify computers on the network. |
Connection services |
LLC-level flow control |
|
>Operates on a single network. |
|
Error control |
|
OSI Layer |
Topics |
Methods |
|
3-Network |
Addressing |
Logical network |
|
-Datagrams & Packets. |
|
Service |
|
|
Switching |
Circuit |
|
.Routers |
|
Message |
|
|
|
Packet |
|
|
Route discovery |
Distance vector (RIP, RIP II) |
|
|
|
Link-state (OSPF, NLSP) |
|
*Move data to specific network |
Route selection |
Static |
|
locations. Ensure correct data routes |
|
Dynamic |
|
through an internetwork of decimilar |
Connection services |
Network-layer flow control |
|
networks |
|
Error control |
|
|
|
Packet sequence control |
|
>Operates on multiple (inter)networks. |
Gateway services |
Network-layer translation |
|
OSI Layer |
Topics |
Methods |
|
4-Transport |
Address/name resolution |
Service-requestor-initiated |
|
-Segments & Packets. |
|
Service-provider-initiated |
|
|
Addressing |
Connection identifier |
|
*Organizes higher level messages |
|
Transaction identifier |
|
into segments & delivers to session, |
Segment development |
Division and combination |
|
or higher, layer processes. |
Connection services |
Segment sequencing |
|
>two connections (conversations) |
|
Error control |
|
on end-nods |
|
End-to-end flow control |
|
OSI Layer |
Topics |
Methods |
|
5-Session |
Dialog control |
Simplex |
|
-Packets |
|
Full-duplex |
|
|
|
Half-duplex |
|
*Facilitates communications |
Session administration |
Connection establishment |
|
(& places the "calls") between |
|
Data transfer |
|
service requestors & providers |
|
Connection release |
|
OSI Layer |
Topics |
Methods |
|
6-Presentation |
Translation |
Bit order |
|
-Packets |
|
Byte order |
|
*Transforms data into a mutually |
|
Character code |
|
agreed-upon format (syntax) |
|
File syntax |
|
understood by app.& computer. |
Encryption |
Public key |
|
also encrypt or decrypt data |
Transpos. Subst. Algebraic |
Private key |
|
OSI Layer |
Topics |
Methods |
|
7-Application |
Network services |
|
|
-Messages & Packets |
Service advertisement |
Active |
|
|
|
Passive |
|
*Provides the protocols necessary to |
Service use |
OS call interception |
|
perform the specific network service |
|
Remote operation |
|
function for other 6 layer's services. |
|
Collaborative |
> Download the complete OSI model cheat sheet document in MS Excel format
> Here is an excelent on-line reading for those interested in the subject.
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