OSI Model question

infamous

I feel stupid for asking this, but does a NIC fall under Level 1 or 2 of the OSI model?

The reason I am asking is because the different resources I have used in my studying have listed it at either level 1 or 2 and I need some kind of definitive, comptia pleasing answer, that I can use when I write the test on Monday.


Thanks in advance!

RussS

See here http://www.techexams.net/technotes/networkplus/osimodel.shtml

infamous

Actually I have been doing some research on the net for this answer and it seems that a NIC is at level 2 of the OSI model. Comptia basically looks at the highest level of the OSI model that a device can operate on, and since a NIC also at level 2, that's what they want as the answer.

rentaghost

(as per the previous posts) Yes its Layer 2.

It was one of the first questions I remember asking my instructor at the start of CCNA 1.

The fact that the one card also defines the Layer 1 characteristics was confusing to me but the instructor pointed out that an application is a single entity too and will work at multiple layers of the OSI model. Also think MAC addresses, they are burned into the card and are used at Layer 2.

hc2ab

It should be layer 2 since it use the MAC address.

Not too sure if it is true for all OS, but for some it would have a driver which is responsible for handling the NIC driver and the physical interface. That is independent of the NIC you use though I think.

remyforbes777

I have heard it a couple of ways, but the one that seems to make the most sense to me is that , the NIC card itself operates on Layer 1 (Physical Layer) and the drivers for the NIC operate on Layer 2 (MAC Layer). The reason being is that the actual circuitry of the NIC is what is used to get the data onto the physical media but the drivers are what does the actual interaction with the other layers of the OSI.

Webmaster

Network Interface Card on Layer 1, Layer 2 or both?

If your NIC is broken, you're having a layer 1 problem, not layer 2.

Seriously though, a NIC 'has' a MAC address, but ‘that’ doesn't make it layer 2 device. A NIC puts data on the media, the drivers and network client software including a protocol suite decide what it put on the media. When it sees data on the media, it checks if its own MAC is in the data before it processes the data up the OSI model. ‘That’ is a layer-2 function. The connector, the pin functions, pin voltages, signaling and anything else related to the ‘physical’ aspects of the NIC is defined at layer 1 of the OSI model, regardless of where its "address type" (MAC addressing) is defined or on which layer the software (drivers) used to 'drive' the NIC and the corresponding functions reside.

As many other lower-layer network technologies, its functions are spread over layer 1 and 2. Although the layers in the OSI model allow a modular approach to networking, one layer is nothing without the others and functions of devices and protocols often overlap multiple layers, especially the lower two.

I’ve seen the same conflicts in the past in study material and other resources, and because of that, I spent more time on fact-checking (using non-certification study material) than usual when I wrote the OSI TechNotes (Net+ and CCNA) and practice exams. However, considering my previous comments above, I’m not entirely sure why I didn’t list it at the data link layer as well in the OSI model TechNotes, considering the more complete info in my Network Components TechNotes:

The NIC's interface itself is defined at the Physical layer (Layer 1) of the OSI model, the physical address (also known as Burned-In Address and commonly: 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. The reason the physical address is defined at the Data Link layer is that the Physical layer only handles bits.

Regardless of what CompTIA thinks or wants to hear, as long as there is only one possible answer, there is not a definite one (though one might be better).

I’ll try to write a TechNote/article soon, just about this topic.

jtfranks

Its in layer 1 the physical layer

Drakonblayde

It's actually both, hehe. The transceiver for the NIC resides at level 1 and the rest of it resides at Level 2.

But I think as far as CompTIA is concerned, it's layer 2.

Like someone else said, CompTIA considers the highest level a devide will operate it to be it's layer.

I mean, look at a router. It's got interfaces. The transceivers for those devices put stuff on the wire, that's a layer 1 function. Those same interfaces have MAC addresses which are used in the same way a NIC's is. And finally, the router makes decisions based on a logical network address, which is a layer 3 function. But you'll never hear anyone describe a router as a Layer 1 or 2 OSI device.