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Just where do NICs and WAPs operate?

Discussion in 'Network+' started by iSiDiS, Jul 25, 2006.

  1. iSiDiS

    iSiDiS Bit Poster

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    Hi People

    Im studying for my Network+ at the minute, and using the Sybex (Groth) book (fourth edition). It says that a NIC operates at both the physical and data link layers of the OSI model, but in other texts I've red they say it only operates at the Physical level. This is also the case with WAPs (the Groth book states it only operates at the data link layer, but other texts say data link and physical).

    My question is simple - does anyone have a definitive answer - i know its only a small point, but thats me i'm afraid - i just dont like not being sure!

    Any help would be greatly appreciated!!!
     
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  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    In most cases these days both operate at the phy and Datalink level.

    Most modern NICs and APs have a processor on board, and as well as the hardware doing the physical bit that processor does a lot of the Datalink work as well. This helps to offload some work from the main machine.

    I'm at a loss to see how a AP *doesn't* operate at the physical layer. Are you sure you have quoted that right? (Page number? - I have that book)

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
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  3. Baba O'Riley

    Baba O'Riley Gigabyte Poster

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    Anything with a MAC address must operate at the MAC sublayer of the Datalink layer as this is the layer that deals with physical addressing.

    As for a plain and simple WAP, it's basically just a wireless bridge or switch so I would say they operate at the datalink layer in the same way (Harry, confirmed Groth says this is the case, page 66). How could it operate at the physical layer when there is no physical media involved?

    [EDIT] Once again, I'm talking out of my arse, of course there is physical media involved. What I meant was, it gets more involved with the way the data is encoded than just simply placing it on the wire like a physical device would.
     
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  4. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    As far as i can remember, a wired or wireless NIC operates at both layers.

    Remember that what Comptia want you to say isn't always the *perfect*.

    Si
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  5. hbroomhall

    hbroomhall Petabyte Poster Gold Member

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    This is always a problem deciding what the book says, and what the exam wants! :eek:

    In real life clearly these devices operate at layer 1 and 2. But the exam may be looking at what might be called the top layer, where a bridge is a layer 2 device and a router is layer 3.

    In my (admitedly limited) experience of the exam the actual questions are framed in a way as to make it clearer (a bit) what they are after.

    Harry.
     
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  6. Arroryn
    Honorary Member

    Arroryn we're all dooooooomed

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    As an add-on to the already great advice, I was reading about OSI in the MM All In One for N+.

    He explains about how the NIC operates at both layers, but if a question somehow pins you down to answering either Physical or Datalink, you should answer Physical.

    Try and grab his book (I picked it up for £7.00 off eBay) and use it as a cross-reference. I always find it useful to read about a topic from a different perspective. (ergo I'm also reading Tanenbaum's 'Computer Networks', amongst other books).
     
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  7. Boycie
    Honorary Member

    Boycie Senior Beer Tester

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    Me, too. I like to read several books on one topic, for this exact reason. Once i feel i *know* the topics, i refer to the *strictly facts* book (usually Sybex).

    Si
     
    Certifications: MCSA 2003, MCDST, A+, N+, CTT+, MCT
  8. r.h.lee

    r.h.lee Gigabyte Poster

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    iSiDiS,

    Since I have neither of the books you're citing, I'm going to give a reasonable answer.

    There are at least two elements in a network: 1) hosts/clients/server/computer/whatever and 2) networking. NICs are located on the hosts/clients/server/computer/whatever device itself. Which OSI layer it operates at, depends on your point of view.

    From a client/server perspective, in conjunction with the BIOS, drivers, operating system, applications, the NIC definitely operates on the Datalink layer because NICs have Media Access Control addresses, or MAC addresses for short.

    From the networking point of view, which may be relevant to the Network+ exam, it is the Physical layer. That's because networks are seen in terms of a cable. The network is the area between two clients/servers/hosts/computer/whatever. So if you have two clients connected by a cross-over cable, the "network" is the cross-over cable itself. Therefore, from the network or cable's perspective, the NIC is operating at the Physical Layer.

    Now, as far as WAPs, it depends on which side of the WAP you're talking about: 1) the radio antennae or 2) the networking port to connect the WAP to the rest of the network. As far as the radio antennae side of the WAP, that's the Physical Layer part. Just like electrical energy in the form of Ethernet Frames travel along ethernet cables, so does the electromagnetic energy of radio waves travel from the wireless laptop WIC to the WAP antennae. Once the electromagnetic energy from the WIC reaches the WAP antennae, it is converted from Physical Layer "bits" to an Ethernet Datalink Frame. Then that electrical frame is then sent to the nearest networking device. So from the Ethernet interface perspective, the WAP is operating at the Datalink Layer.

    I hope this helps.
     
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  9. iSiDiS

    iSiDiS Bit Poster

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    Thanks for the help - its straightened a few things out!
     
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  10. Baba O'Riley

    Baba O'Riley Gigabyte Poster

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    Just to add, Groth says (page 55):

     
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  11. Theprof

    Theprof Petabyte Poster Forum Leader

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    I agree with Baba
     
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  12. Baba O'Riley

    Baba O'Riley Gigabyte Poster

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    Blimey, that doesn't happen often. What's wrong with you Prof?:D
     
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