LAN & WAN -> Subjective VS Objective

[169.254.X.Y]

LAN is a local area network in which end devices can communicate each others, but cannot communicate outside of their network. WAN is a wide area network which is composed of at least two Local Area networks. It can cover the entire world. Let me know your subjective point and objective point regarding range of LAN and WAN. 

[Georg Pauwen]

Hello,

I wouldn't make it more complicated than it is: a LAN covers a small, local area, such as a campus, a building, a home, a hospital. A WAN covers a large geographical area, such as different cities or countries.

There is also a MAN, a metropolitan area network, which is, geographically, something in between.

The POTUS perspective is not a bad analogy, actually. He has administrative authority over the entire US, the LAN, so from his perspective, the US is the LAN. The rest of the world would be the WAN.

Check the link below for a pretty good (I think) explanation:

LAN vs. WAN

http://www.diffen.com/difference/LAN_vs_WAN

[169.254.X.Y]

Thank you very much. I think I understood around 80%. My thought is that I am an American and the president of the United State is also an American. That means we are in the same group. Doesn't that mean to me and to the president, American is a LAN? If I am an immigrant, obviouslly American is a WAN to me, but I am not an immigrant. So, my conclusion is that size of the LAN could be different depending on perspectives. For example, my friend A's perspective on a LAN is that it contains just the 3 or 4 buildings on the grounds of his factory. However, my friend B's perspetive on a LAN is much much larger and actually includes different technologies.

[Georg Pauwen]

Hello,

I would stay away from these analogies. Stick with: LAN is local (campus, building, home), WAN is a wider geographical area (cities in different locations, different countries) that usually requires a third party to connect.

Everybody in the networking world understands it that way. 

[Peter Paluch · Accepted solution]

Hi,

I can understand your confusion - I guess I would be confused, too.

The truth is that the terms LAN and WAN never had any exact definition, and they are understood mostly in intuitive ways. Therefore, I do not believe that there is a single correct way of explaining and understanding these terms.

When I was learning about networks myself, LAN and WAN were defined mostly in terms of size and speed. LANs were small networks in the size of at most one building. Their purpose was to attach and interconnect end hosts - computers, printers, servers, data storage, etc. The speeds were comparably high, the span of these networks, however, did not - by rule of a thumb - exceed a building. The typical LAN technologies were Ethernet and Token Ring. What was very important was that a LAN was owned by you - its user.

WANs were networks operated across large distances. Their speeds were comparably slower, but the distances could encompass cities, states, even countries. Typical technologies were leased lines, HDLC, PPP, ATM, Frame Relay to say the least. Importantly, a WAN was not owned by its user - a user only "rented" its use.

It seems that the aspect of the ownership plays a role. As a normal user, you do not own a WAN even though you might be using it - you own your LANs but you do not own the WAN that might be interconnecting them. However, even the service provider who operates the WAN would not call his own network a LAN simply because the technologies are different, and the geographical span is way beyond what a LAN is expected to cover.

Nowadays, the speeds and technologies of LANs and WANs are practically the same - tens and hudreds of Gbps, and Ethernet is the ubiquitous technology, with other technologies rapidly declining. The real distinction between LANs and WANs reduces to their geographical scope, and perhaps their ownership, but this makes the distinction even more blurred.

Quite frankly, the approach of your instructor would be confusing to me as well. I would not dare to talk about America as "a LAN" or "a WAN". The best I could say is that it contains multiple LANs and WANs, but that's as far as I could go. However, surely, it is not a single LAN, nor a single WAN, and I also do not agree with the notion that a single network could be a WAN to someone, and a LAN to someone else.

Quite a philosophical debate, truly. But what's more, I'd say it is largely irrelevant, as it is merely debating about two vague terms whose exact definition never existed.

Best regards,
Peter

[169.254.X.Y]

Thank you very much. Your explanation is clear and perfect like universitiy professors'. Thank you very very much for spending your time writing this awesome explanation to me :)

[Joseph W. Doherty]

For another take of LAN vs. WAN, let's consider what they mean.

LAN is a Local Area Network, while WAN is a Wide Area Network.

Of course, what is "Local" vs. Wide". Well, it's often just generally distance. LAN, as Peter notes, are often within a building networks, by often they are also so considered when between buildings, say within a campus.

WANs often span much larger geographic distances, such as links between cities.

As Peter notes the equipment used between LAN and WAN might differ (not as much today), but media often does. For example, a LAN might use copper links limited to 100m or fiber links limited to 300m (or a few K, when between buildings).

Besides LANs and WANs, there are also MANs, Metropolitan Area Networks. These tend to be same "city" networks.

Another factor that makes LANs different vs. MANs or WANs, wired LANs usually don't cross public property. Once you need to cross a public road, you often run into many government issues, which is why MANs and WANs are often provided by companies that provide public carriage of your traffic.

BTW, I agree with Peter, your instructor's usage of a President "seeing" the US as a network is a bit confusing. Here your instructor appears to be considering administrative control.

I work within a very large company, with a national footprint. We also provide public carriage. So we do have a large national network, and the technology, other than media (and capacity), is often similar whether the network is within a building or from one side of the country to the other. Yet, we think of networks within a building or campus as a LAN but the interconnections between sites as WAN links. (NB: we own both.)

[169.254.X.Y]

Thank you very much :) Really appreciate!!!