What is the relationship of a NIC to the OSI model?

MrAhmedSalah

What is the relationship of a NIC to the OSI model?

can someone explain the answer for this question for me please...

I'm new BTW!

markzab

The NIC would reside at the Physical layer, or layer 1, of the OSI model.

markzab

Found this online as well. Gives a little bit more detail:

"Layer 1 of the 7 layer Model is the Physical Layer and defines the physical and electrical characteristics of the network. The NIC cards in your PC and the interfaces on your routers all run at this level since, eventually, they have to pass strings of ones and zeros down the wire."

MrAhmedSalah

thanks for that, i thought it was in the 2nd layer, because of the MAC address...

dynamik

OMG.. Look what link I found when I googled "nic osi layer"

http://www.techexams.net/technotes/ccna/osimodel.shtml

The reason it's not layer 2 is because it doesn't make any decisions based on the MAC address.

That's why hubs are layer 1 and switches are layer 2. Hubs just mindlessly repeat the signal out of each port while switches inspect the data to see which MAC address it is going to and sends the data out only the port that is associated with that MAC address.

Webmaster

We've discussed this in our forum many many times over the past 5 years, if you'd do a search I'm sure you'll find them. I thought did was a dead issue by now (it's layer 2 according to Cisco, even in one of the Academy course materials.)

Instead of the link above, check out the Network+ version:
http://www.techexams.net/technotes/networkplus/osimodel.shtml
( yes, that means I forgot to update the CCNA OSI notes, which I'll do today.)

But instead of the OSI notes, check out the http://www.techexams.net/technotes/networkplus/networkcomponents.shtml
in particular:

I wrote:

A NIC provides operations up to layer 2 of the OSI model. The NIC's interface itself is a Physical layer (layer 1) device, the physical address (also known as MAC address) of the adapter as well as the drivers to control the NIC are located at the Data Link layer's MAC sub-layer. In an Ethernet network for example, every NIC attached to the same segment receive every ‘frame’ to discover the MAC address. Frames that do not match the local NIC’s MAC address are discarded; frames that do match the local NIC’s address are forwarded up the OSI model to the next layer to be processed by the network layer protocol. Obviously, a NIC must be able to interpret the MAC address, hence operate up to the MAC sub-layer of layer 2 of the OSI model.

In short it's a layer 1/2 device, if you need to choose 1 pick the highest. In other words layer 2 . The interface (pins, signalling etc) on the NIC is a physical layer thing, but an 'Ethernet' NIC for example needs to work up to layer 2 to even know the Ethernet 'frames' are destined to its MAC address. So it does "make decisions based on the MAC address". The decision to make is whether the NIC should pass it up to OSI layer to the software (IP stack for example) or just ignore it.

Remember that the Ethernet NIC is used to connect to an Ethernet network which are defined in the 802.3 layer1/2 specifications. Without layer 2, it would be merely a connector, which is not the case because that Ethernet NIC's while purpose is to feed the PC with layer 2 frames.

dynamik

That means... you lied to me... you lied to all of us

I'm JK. Thanks for the clarification.

MrAhmedSalah

dynamik wrote:

OMG.. Look what link I found when I googled "nic osi layer"

http://www.techexams.net/technotes/ccna/osimodel.shtml

how do u think i found this site!


thanks for explanation Webmaster & Dynamik.

Slowhand

From the mouth of a CCIE at a recent get-together with another company and my own:

Think of it this way: the part of the NIC that plugs into a PCI slot, the actual circuitry, is a layer 2 device. The RJ-45 port that connects to the wire, is a layer 1 device. Now, if you'll excuse me, there's a blonde over there in need of a drink.

He was a nice guy, but I get the feeling he wasn't up for talking shop at the party.

dynamik

MrAhmedSalah wrote:

dynamik wrote:

OMG.. Look what link I found when I googled "nic osi layer"

http://www.techexams.net/technotes/ccna/osimodel.shtml

how do u think i found this site!


thanks for explanation Webmaster & Dynamik.

Yea.. I actually found it by googling "ccna forum" because I was having problems connecting to my 2520 lol

JDMurray

The physical electronics of the NIC is the layer 1 side and the microcode (firmware) programming on the NIC's processor is where layer 2 resides. Layer 2 itself is split between the NIC (MAC) and the software of the TCP/IP stack (LLC).

Megadeth4168

I understand and agree with the final verdict, it's just interesting that the CCNA classes I had 6-7 years ago left no room for discussion on this... In my class NIC was layer 1, end of story.

JDMurray

Megadeth4168 wrote:

In my class NIC was layer 1, end of story.

This is most likely because the people who designed the course materials used by your class didn't understand what functionality came from hardware and what came from firmware--or that firmware even existed in a NIC.

keatron

We have to remember the OSI model is an abstract theoretical model. Many devies, applications, protocols and software actually "sit" or "operate" on the border line of two layers. That's what confuses most people being introduced.

jeorge_kabbi

keatron wrote: »

We have to remember the OSI model is an abstract theoretical model. Many devies, applications, protocols and software actually "sit" or "operate" on the border line of two layers. That's what confuses most people being introduced.

yes , or even worse they can span more than one layer . on what layer(s) a deep packet inspection firewall work ?

DevilWAH

What about running TCP off loading on the NIC does this change things ??

cyberguypr

Whoah, 7 year respawn! This must be on the top 10 "thread brought back from the dead" list.

xnx

Old thread but Layer 1 and Layer 2..