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fWe know that they only care about the first 3 layers of OSI-Model so when a node receive the data from a PC/Server, it goes up to layer 2 (Here is MAC address) and then it goes up to Network layer (3) where it's now IP. Then :

  • How this node knows the route to follow to the other node ?
  • How do they communicates ?
  • Do they use Ethernet ?
  • If yes, the internet is then considered as a local network ?

Further :

  • Can I consider my house and my equipment as a LAN ? And then I saw that nodes connections are known as Internet/Network but they use Ethernet and Ethernet is used in local network so should we consider the connections between nodes as a local network ?
  • And we know that Ethernet is asynchronous so the Internet is asynchronous because it uses Ethernet ?
  • This article series will explain everything that happens to move packets through a network. Included are how Switches work and how Routers work, which are the crux of your questions. – Eddie Jun 21 '17 at 22:56
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Feb 19 '18 at 5:06
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Let me try to unpack some of your questions.

First, many of the terms you use, like "local network" do not have precise definitions. They can mean different things depending on the context.

How this node knows the route to follow to the other node ?

The short answer -- it doesn't. Nodes (or hosts) only know if the other host is on its local network or not. If not, the sending host forwards the data to the configured gateway.

How do they communicate?

I'm not sure what you're asking here.

Do they use Ethernet?

Ethernet is by far the most common layer 2 protocol for local area networks and some wide area links, but there are others for longer distance links. Older technologies such as SONET, frame relay, TDM, are still in use. Also, consider that Wi-Fi, which is very common for local area networks, is not Ethernet.

If yes, the internet is then considered as a local network ?

Ethernet is a layer 2 protocol. It was originally designed for use in local area networks, but as the technology matured, other uses were found for it. Now it is used for some long-haul links. The protocol does not define whether a network is "local" or not.

Internet providers do not exclusively use Ethernet, especially on long distance links.

Finally, the definition of "local" is...well, there isn't a clear definition. Most would agree that your home network is a local network. Whether two connected nodes are "local" is dependent on the context.

  • In any case, the Internet isn't "local" - unless you look at it from an interplanetary perspective. ;-) – Zac67 Jun 21 '17 at 17:02
  • So is the communication between nodes of the internet consider as local ? (because it uses Ethernet) ? – Romain B. Jun 21 '17 at 17:33
  • Ok in my course it says that inter-node connections are considered as large network so it uses synchrone communication.. And I saw that they uses 3 layers of OSI including IP so do they communicate with IP or MAC ? – Romain B. Jun 21 '17 at 17:37
  • And how our PC communicates with DNS and ARP ? Do our packets travel through the 7 layers of OSI or is it logical dialopue ? – Romain B. Jun 21 '17 at 18:44
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For the follow up questions...

Can I consider my house and my equipment as a LAN ?

Yes.

And then I saw that nodes connections are known as Internet/Network but they use Ethernet and Ethernet is used in local network so should we consider the connections between nodes as a local network ?

Not sure I understand the question but I'll try to answer. The distinction between LAN and WAN can sometimes be a little fuzzy, which is why some people also use terms like Metropolitan Area Network (MAN). Typically though if devices are connected by Ethernet then they're considered in the LAN. The network would be considered a WAN once you bring WAN technologies into the mix (such as HDLC).

And we know that Ethernet is asynchronous so the Internet is asynchronous because it uses Ethernet ?

Synchronous and asynchronous describe protocols for transmitting data, not networks. For example, you would call Ethernet an asynchronous protocol but you would never call a LAN asyncrhonous.

There are synchronous and asynchronous LAN and WAN technologies. HDLC is an example of a WAN technology that is sychronous and Ethernet is an example of a LAN technology that is asynchronous.

  • Thanks a lot ! I saw that connections between nodes are considered as big network so data is transmit in a synchronous way ! But I saw that nodes communicates with each other using the first 3 layers (IP + Ethernet + Bits). I'm still a little bit confused but unfortunately my test is tomorrow.. – Romain B. Jun 21 '17 at 22:30
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Ethernet is a technology or protocol that operates at the data link layer meaning that it has no awareness or need for Internet Protocol (IP). Nodes on an Ethernet network are addressed with a world-wide unique ID (MAC address). If node gets a frame not addressed to itself, it drops/ignores that frame. That's it really. Local Area Network is a non-technical term that simply signifies the physical area or size of a network.

IP is software. There's a whole IP Suite of protocols. It exists for interoperability and is what the Internet is based off of. Way back in the day, there was actually competition in this interoperability game - Apple had 'Appletalk' Novell had IPX/SPX.

  • Yeah I saw that but I have also seen that nodes communicates using IP + MAC so I don't know why they use IP.. – Romain B. Jun 21 '17 at 22:53
  • where did you see that? a packet capture/sniffer or a book or article? – Ron Royston Jun 21 '17 at 22:56
  • google.fr/… – Romain B. Jun 21 '17 at 23:09
  • You can see that there is communications at level 1 2 3 – Romain B. Jun 21 '17 at 23:10
  • And in my course (on paper) we see clearly that the paquet reach a nodes, it de-encapsulate from 1 et 3; re-encapsulate from 3 to 1 and then sent to the other PC – Romain B. Jun 21 '17 at 23:11

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