some questions about OSI reference model

[ITlover]

I had some questions about OSI reference model, can we say that OSI reference model refers to the layers on which the entire computer and network system works?

A very important question, when we copy a file or a folder from 1 partition to another, then on which layer are we basically working?

I hope its clear

[ktkendall]

I was taught that the OSI model is for data transmission between computers and not necessarily within 1 computer.

[DynamicTech]

The OSI model consists of 7 layers and is used for (like ktkendall said) for data transmission between computers. As data propegates up the stack, each layer "translates" the data that it recieves so it can ultimately be "understood" by the application, or protocol, that is requesting the data.

[mbossman2]

the OSI model is for data networking not internal PC functions.

if you want to hammer that round peg into a square hole, the answer is this would occur at the Application layer but that is not 100% correct as the moving from partition A to partition B does not require any network activity.

[ktkendall]

I was also taught to:

Please Do Not Throw Sausage Pizza Away

[ITlover]

what about data-link, dont you think that data-link layer can also be working when we copy or move data from 1 partition to another?

[mbossman2]

no...the data link layer is where the MAC "layer" (how a PC gains access to the network) and the LLC "layer" which is where flow control and synchronization takes place...

unless data is headed to/from a network, the OSI model really doesn't apply

[ITlover]

I was studying OSI reference Model Yesterday and understood each layer to some extent but I think their is still several things about it that are not clear. Would you guys mind If I ask you about each layer?

Please correct me if I am wrong ,if their is something wrong with network of computers, the layer that fails ,each layer above that layer also fails because the data travels from 1st layer to
7th layer and if their is something wrong with layer 4, then most probably the chances are that layer 1,2 and 3 also have problem since if layer 1 doesnot work, then definitely the data will not travel to its destination.

I hope this understanding of mine is correct.

[mbossman2]

correct...

[ITlover]

mbossman, is it also true that a network engineer or admin should have good grasp over the working of OSI reference model inorder to become successful network engineer or admin?

[mbossman2]

Originally Posted by ITlover mbossman, is it also true that a network engineer or admin should have good grasp over the working of OSI reference model inorder to become successful network engineer or admin?

the OSI model helps understand the processing of network packets and an understanding of it helps especially when confronted with a new technology....knowing where it fits on the stack can help understanding by providing analogous technologies as a comparison.

However, in day to day situations, I have never heard someone say: "Bob, we definitely have a layer 2 problem". Usually they say "Bob, switch 5 in closet 6 is down, take care of it!"

now, if I were a network asics designer or networking software (the stuff that goes in switches and routers and makes them go) programmer and working on or developing cutting edge technology, I would want more than just knowing what fits where.

[option44]

You can also use the osi model in trouble shooting. But also be aware that the layers can blur, but it can be used as a process of elimination for some tougher cases.

Physical Layer- Please
Cabling, Hubs

Data Link Layer -Do
(MAC and LLC sub layers)
Nics, Switches

Network Layer- Not
Routers

Transport Layer- Throw

Session Layer- Salty

Presentation Layer- Pretzels

Application Layer- Away

Anyway here is a link to check out http://searchnetworking.techtarget.c...523729,00.html

You can also google it and find some very in depth stuff on tcp/ip and the osi model.

[Floppyman]

I agree with mbossman2. Anyone who does any sort of network programming should probably understand this model pretty well. I was taught most of this information from a Computer Networking course that was part of a computer science curriculum. Otherwise, a more general knowledge is probably just fine. HTH

[ITlover]

Originally Posted by mbossman2 the OSI model helps understand the processing of network packets and an understanding of it helps especially when confronted with a new technology....knowing where it fits on the stack can help understanding by providing analogous technologies as a comparison. However, in day to day situations, I have never heard someone say: "Bob, we definitely have a layer 2 problem". Usually they say "Bob, switch 5 in closet 6 is down, take care of it!" now, if I were a network asics designer or networking software (the stuff that goes in switches and routers and makes them go) programmer and working on or developing cutting edge technology, I would want more than just knowing what fits where.

So by switch 5 in closet 6, you are refering to 2nd layer (data-link) ,right?
I know nobody uses such technical terms and simply talk about the devices that are used in networking?

[ktkendall]

Originally Posted by ITlover I was studying OSI reference Model Yesterday and understood each layer to some extent but I think their is still several things about it that are not clear. Would you guys mind If I ask you about each layer? Please correct me if I am wrong ,if their is something wrong with network of computers, the layer that fails ,each layer above that layer also fails because the data travels from 1st layer to 7th layer and if their is something wrong with layer 4, then most probably the chances are that layer 1,2 and 3 also have problem since if layer 1 doesnot work, then definitely the data will not travel to its destination. I hope this understanding of mine is correct.

If layer 4 is the problem then 5,6,7 are not going to function either but 1,2,3 probably are functional. Your right though that if layer 1 isn't functioning then you are not sending or receiving any data at all. This problem will be quite evident as you will not have a link light on your nic card and/or your switch port for this PC if layer 1 is down.

[mbossman2]

Originally Posted by ITlover So by switch 5 in closet 6, you are refering to 2nd layer (data-link) ,right? I know nobody uses such technical terms and simply talk about the devices that are used in networking?

most switches operate of the MAC address and MAC addresses are in Layer 2 of the model.

[Great_One]

Originally Posted by mbossman2 most switches operate of the MAC address and MAC addresses are in Layer 2 of the model.

unless its a layer 3 switch.

[option44]

Originally Posted by option44 You can also use the osi model in trouble shooting. But also be aware that the layers can blur, but it can be used as a process of elimination for some tougher cases. Physical Layer- Please Cabling, Hubs Data Link Layer -Do (MAC and LLC sub layers) Nics, Switches Network Layer- Not Routers Transport Layer- Throw Session Layer- Salty Presentation Layer- Pretzels Application Layer- Away Anyway here is a link to check out http://searchnetworking.techtarget.c...523729,00.html You can also google it and find some very in depth stuff on tcp/ip and the osi model.

Let me clarify on this also. If you are getting into networking, you will hear other terms that refer to TCP/IP that sound very similar to the OSI model. This can be confusing at first, especially after you have been introduced to OSI, then going into TCP/IP.

The TCP layers are:

Application Layer: Compare to Layers 7,6,5 in OSI
Transport Layer: Compare to Layer 4.
Internet Layer: Compare to Layer 3
Network Access Layer: Compare to layers 2,1

[ITlover]

Originally Posted by ktkendall If layer 4 is the problem then 5,6,7 are not going to function either but 1,2,3 probably are functional. Your right though that if layer 1 isn't functioning then you are not sending or receiving any data at all. This problem will be quite evident as you will not have a link light on your nic card and/or your switch port for this PC if layer 1 is down.

Well, if you find out that layer 4 is down or having problem, then how can it be possible that layer 5,6 and 7 are having problem? If their is a blockage on a rubber pipe at one end, can the water reach the other end of the pipe crossing the blockage without any problem?

It can also be possible as far as I understand ,that the layer 1,2, 3,5,6 and 7 are working fine but their is a problem at layer 4 because I think blockage or problem at any 1 layer can prevent data from reaching layer 7.

Oh, I think you are talking about whether you find data traveling from 5th layer to 7th layer, well if their is a problem at layer 4 then ,definitely the data wont be able to reach layer 5,6 and 7, because data travels from layer 1 to 7 layer. The layer 5,6 and 7 will be functional but the data wont reach their because of problem with layer 4.

I hope I am right.