OSI MODEL
Has anyone got any good hints in remembering the OSI model?. 
I remember what order it goes in, but having real trouble remembering what runs on each layer. Want to give myself a 5 week study period. Do you think this enough?
I remember what order it goes in, but having real trouble remembering what runs on each layer. Want to give myself a 5 week study period. Do you think this enough? Comments
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Transatlantic
Member Posts: 120
What I found really worked for me to remember it was writing it down on flash cards, with examples of what each layer was, and what ran over it. Then took them with me everywhere and read them any time I had spare, until it was stuck in my head. Painful I know, but it worked for me."Mistakes have been made, others will be blamed." -
Ricka182
Member Posts: 3,359
I agree with the flashcards. I used them and they helped a lot, mainly with ports, and the OSI. 5 weeks should be enough, if you've some understanding of basic networking to begin with. The Net+ exam isn't very diffcult right now, but will be harder with the new objectivews in 2005. Here's a great set of flashcards for Network+.i remain, he who remains to be....
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Webmaster
Admin Posts: 10,292 Admin
I agree also
Remember that one of the main reasons the OSI model is created to simplify teaching and learning networking concepts. Don't try to memorize the order of the layers, instead try to understand them and the entire models as a whole.
Apart from the All People Seem To Need Data Processing and other funny phrases to remember the layer order, start with dividing them into the upper and lower layers. (http://www.techexams.net/technotes/networkplus/osimodel.shtml)
Visualize the model and see it as a host on the network, and visualize another host on the network also as an OSI model.
Than realize that the Application layer is closest to the user, it refers to the software (ie. some client). The data from the first client travels down the OSI model until it reaches the Physical layer which puts the signal (bits) on the medium (wire or ether), the target host picks up the bits from the wire and processes it up the OSI model until it reaches the Application layer (i.o.w. the software on the target host). Note that each layer communicates only with the layer directly above it and directly below it (and via the other layers it communicates with the same layer on the target host)
The client needs the present the data in a format recognized by the target host, so they need to use a common format (ie. GIF file, Word file, HTML file). This is where the Presentation layer comes in, it presents the data received from the Application layer into a standard format that can be recognized by the Presentation layer on the target host (so it can be passed on to the Application layer on the target host.)
The idea of the OSI model is that a manufacturer of some software (application layer) is not obligated to code/develop file formats. The layers are independent of each other (although the Physical and Data Link layer are often combined into a single standard or device, and the Transport and Network Layers are often combined into a single protocol suite such as TCP/IP and IPX/SPX). Also the manufacturer of the software can spend its time creating the software (i.e. a browser) without having to worry about how it will communicate over TCP/IP(transport/network layer stuff), or how bits are put on the cable (physical layer task).
But, sometimes software needs to be able to create its own type of connection over several different types of network/transport layer protocols. Here's where the Session layer kicks in, it manages session/connections between two applications (not per definition between two TCP/IP hosts for example). A typical example is an SQL connection. Those who created SQL did not worry about which 'underlying' network protocols were used. They cared only about the connection between the applications (ie. SQL client and database server).
The Application layer, Presentation layer, and Session layer are the 'upper layers', they always refer to the software, and do not care about the hardware at all. They actually have little to do with 'networking' and therefore in the Net+ exam, but especially in Cisco networking exams, the focus is on the lower 4 layers.
I hope my OSI rambling is of some use... I'd be happy to continue with the lower layers though
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gbagirl73
Member Posts: 7 ■□□□□□□□□□
Thanx for the flash cards they really helped a lot. I guess its a matter of repetition!!
.Also has anyone done Security+?. Thinking of doing that cert after N+! -
Ricka182
Member Posts: 3,359
A lot of people have done Sec+, and I've heard it's not easy. I would think you should get some experience with security, or read a lot, a real lot, before going for Sec+.i remain, he who remains to be....
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cliffjag
Member Posts: 20 ■□□□□□□□□□
Please
>Physical
Layer 1
Do
>Data Link
Layer 2
Not
>Network
Layer 3
Throw
>Transport
Layer 4
Sauzage
>Session
Layer 5
Pizza
>Presentation
Layer 6
Away
>Application
Layer 7
On the exam that was the first thing i wrote down??
Isn't that a good ideaAlway try,never give up to easy.
Ok
Deal , -
lazyart
Member Posts: 483
Well, after writing that down, I would add the devices that are used on the specific levels... like layer 1 is for NICs, cabling, and any device that blasts bits across the medium without thought (hubs and repeaters-- dumb devices). Layer 2 gets a bit better with bridges and switches, but when you get to routing data across different network types you have found layer 3.
Now if I can get the protocols straight I might be on to something!
Getting my mind around that model seems to be the roughest part. I have put the technotes on a USB key and look it over when I have time at work (it takes 40 minutes to put a ghost image onto a laptop... good study time).I'm not a complete idiot... some parts are missing.
