OSI layers

Oh man! Ad-blocking software has been detected! :'(

This website is run by the community, for the community... and it needs advertisements in order to keep running. Blocking our ads means your killing our stats!
Please disable your ad-block, or become a premium member to hide all advertisements and this notice.

Ok does anyone have an easy way to remeber the OSI layers and what happens where within them? Im having problems rembering what connects where on the osi and what protocols go with what layer... its driving me nuts. If i can crack this i might just pass the exam.

 

Oh man! Ad-blocking software has been detected! :'(

This website is run by the community, for the community... and it needs advertisements in order to keep running. Blocking our ads means your killing our stats!
Please disable your ad-block, or become a premium member to hide all advertisements and this notice.

Have you tried searching our site for "OSI"? I know we've tackled this one before.

 

something like Please Do Not Throw Sausage Pizza Away...

Remember,layer 1 is at the bottom,7 at the top.From bottom to top...PDNTSPA


7.Application
6.Presentation
5.Session
4.Transport
3.Network
2.Data Link
1.Physical

 

I learned it the other way around:

All People Seem To Need Data Processing

And I keep this link on my little homepage

OSI Model

Hope this helps

 

Thats my favourite!

Harry.

 

I honestly don't think I'd have remembered it if it wasn't for this.

Although I vaguely recall one which involved Australian ladies of ill repute.............

 

Hey Twizzle,

Im studying for the Network + as well, and the OSI just throws me every time.

What I'm currently doing is reading everything I can on it, and building up a spreadsheet. For each OSI level, Im writing a breif explanation of what each level is / does (which most wesbites seem to have) and I'm also using a column where im accumulating the protocols and processes (Ie tcp - ip - spx - hubs - routers) in the OSI level they should be in.

I hope to finish it in the next few days (Hopefully soon anyway, as Id ment to take the N+ This week . . . cant let it drag on too long) so if it would help, you are welcome to a copy of it. Obviously don't use any one piece of material as your only study guide, but it all helps.

 

One of the problems with OSI which you should bear in mind is that it is more of a theoretical thing than anything else. Many popular protocol stacks have approximate mappings to OSI layers, and sometimes books will differ as to where things go.

In addition also remember that a layer can sometimes be split into sublayers in the real world. ADSL is a classic example of this!

Harry.

 

One way to familiarise yourself with the OSI is to learn what protocols and devices function at which layer and why. As previously mentioned the OSI is an industry standard that was formed to define industry wide compatability for networking devices from different vendors.

A very important networking function that is well illustrated by the OSI concept is encapsulation and decapsulation. As information travels down the OSI model (or any other protocol stack) each layer encapsulates the information it recieves with it's own specific header (and sometimes footer as well). When information travels back up the stack the headers (and sometimes footers) are stripped away or decapsulated.

You may have heard of units of information being referred to as bits, packets, frames, segments- these terms aren't interchangeable. They are descriptive of the layer at which the information is at that time. Example;- At layer 3 (network layer) the information is in a layer 3 packet, as it is passed down to layer 2 it becomes a layer 2 frame.

Another acronym to remember for encapsulation is Don't Some People Fry Bacon. This stands for Data, Segments, Packets, Frames, Bits. They map to the 7 layers like so:

Application-----------------Data
Presentation---------------Data
Session--------------------Data
Transport------------------Segments
Network--------------------Packets
Data Link------------------Frames
Physical-------------------Bits

Not wanting to confuse you further by adding more stuff to remember but hopefully. Here's a very good page explaining encapsulation and decapsulation it's even got a little movie illustrating it!:

http://www.firewall.cx/osi-encap-decap.php

Some more OSI links as well if you want:

http://www.firewall.cx/osi-intro.php

http://www.firewall.cx/protocols.php

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/osi_prot.htm

Hope this helps!

 

Great Stuff Pete!

 

as a N+ student i have to say that this page is packed full of help, thanks to all who have contributed

 

Well thanks for all the tips guys. Im hoping if i try all of em something might stick. I just cant seem to get my head around what fits where within the OSI model.... Im even getting the same questions wrong using Exam cram tests (im trying not to learn the questions but learn what thier about), and its all on the OSI layers.. If i can just squeeze 2 or 3 marks outta this i would pass more often.

 

Hi All

With all the exams I've done on OSI I could never find one document that held ALL the info needed about it - so did a web page to help me. It may help you.

http://www.sandygarrity.org.uk/files/osi.htm

 

lol - Sandy, that's still pinned to the wall above my desk since I did the N+. It remains one of the best summaries of OSI I have seen to date.

To anyone doing the N+ or looking for OSI info - print that page off and keep it handy. Priceless.

Nice work, Sandy.

 

nice website Sandy.