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I know the OSI model has seven layers. Can you consider a LAN to exist without layer 2 and just layer 1? The answers that I saw on Quora were not clear. Some of the answers on Quora came close to indicating that only the physical layer was needed.

I would think that a switch and the data link layer would be needed to have a local area network. A working LAN would need the transfer of data, and I do not see how that would be achievable without layer 2.

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  • Think of layer 1 as electrical signals, LAN operations require a mac address and thus happen at layer 2.
    – Gngogh
    Mar 9, 2021 at 18:33
  • Not all data-link protocols use MAC addressing. Some use other addressing, and some use no addressing.
    – Ron Maupin
    Mar 9, 2021 at 19:18
  • Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin
    Dec 23, 2021 at 17:05

5 Answers 5

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The OSI model is just a model. That means it describes an idealized concept, rather than anything in the real world. So the question is really hypothetical. If you create a network with only one layer, you are not conforming to the OSI model, so at that point, the question becomes moot. Also, there's no strict definition of a network, local or otherwise.

The OSI model describes the component functions of a packet-switched network. Information is divided into parts called packets, and these are individually sent to the destination. The layers of the model are used to control and route the packets.

There are other kinds of networks that don't use packets (although they are rapidly becoming obsolete). Because there are no packets, there is no need for the functions of the OSI model (framing, routing, etc.)

One example of this is the (wired) telephone network**. It is (was) a circuit-switched network, where a temporary data path is set up between the endpoints. The data is sent in a continuous stream -- no packets. After all the data is sent, the data path is removed.

** In truth, I'm describing the telephone network of at least 30 years ago. Today, most telephone networks have converted to packet-switched networks because of their efficiency.

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You have to define a 'local area network' before you can theoretically strip away 90% of the features of it and ask whether it still exists.

A 'layer 1 only network' is a simple electrical circuit with devices that modulate and interpolate the voltage on the circuit to some end. A radio with a speaker connected to it might qualify, depending on whether you want to consider the audio signal layer 2 or not.

Essentially this question is meaningless because you can't define something as 'layer 1' without a layer 2 or more. It would simply be 'all the layers' if there is only layer 1.

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Imagine a telegraph network carrying Morse Code as a layer-1 network. You can communicate to others in a point-to-point fashion.

If you want to communicate to more than one endpoint, queue up messages for asynchronous delivery (when the recipient isn't physically present at the telegraph office), have a billing scheme for messages, etc. you'll invent some additional, upper-layer(s).

An example upper-layer may be the framing of a message -- for example, how you signal (using Morse) the start & end of a message, and perhaps who is the sender and recipient. Some of this functionality is present at layer-2 and layer-3 of today's IP-over-Ethernet networks.

You could have a very simple telegraph line between your house and your neighbor's, but if you want to send messages across the world, you need message framing & routing!

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I think the question is poorly phrased. I don't believe you can have a "Local Area Network" without some upper levels. But if we phrase it instead as:

Is it possible to have network components with only level 1 of the OSI model?

Then I think the answer is certainly yes. I have one in my basement right now. It is an amplifier on the cable TV system.

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In addition to local addressing (see MAC address), L2 is doing the framing - so essentially, no, you can't get away without L2.

You can avoid addressing by using point-to-point links only - one interface per peer, and likely a lot of meshing (forwarding nodes), but there's no alternative to framing.

Of course, you can use different names in your network model but you can't do away vital functions.

Can you consider a LAN to exist without layer 2 and just layer 1?

You could put a switch in the middle of your bench and call it a "LAN". That's just physical layer and data link layer, but as soon as you connect hosts and begin to make use of that "LAN" you add higher layers, at least an application layer.

If you place a repeater hub or a coax cable on your desk as "LAN", that'd be just the physical layer, no data link layer. Again, when you connect hosts you add the same layers as above.

Effectively, it all boils down to your definition of "LAN". In my book, a hypothetical LAN requires at the very least the physical, data link, and application layers. The transport layer may be present but it might be barely noticeable. Practically, you'd also a network layer for commonly expected functionality - then you've got the full stack.

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    A "network" isn't necessarily packetized, so framing isn't strictly required. You could use RS-232, for example, or your own custom signaling.
    – Ron Trunk
    Mar 9, 2021 at 18:41
  • A "network" is a somewhat modern sense requires packetization for mulitplexing. Without it, you can only run a single application with a single data stream (voice, video, ...) between two points.
    – Zac67
    Mar 9, 2021 at 18:47
  • TDM and FDM are two examples of non-packetized multiplexing.
    – Ron Trunk
    Mar 9, 2021 at 18:49
  • I was referring to some kind of multi-use network. Multiplexing the physical signal doesn't help here. You still need some kind of addressing or application-level multiplexing to make some use of a network.
    – Zac67
    Mar 9, 2021 at 19:51

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