What I understand is:
So, is the difference the length of cable used to form a network or does it depend if it's formed in a city, state or between countries?
Many Answers here have given textbook-like definitions that have touched on this, but there are certain practical, real-world distinctions worth underscoring:
A LAN is typically something completely within your own premises (your organization's campus, or building, or office suite, or your home), so it's something you build and own yourself, all the way down to the physical cabling. In contrast, a WAN is something that connects between geographically separated locations, so you generally have to lease access to lines or data transmission services from telecommunications carriers to create your WAN.
Because of the shorter distances needed for on-premises networks, and because of the focus on connecting PCs and servers, LANs tend to be built on Ethernet and other 802.3-family (and 802.11-family) physical layers and data links. 1000BASE-T, 1000BASE-SX, 1000BASE-LX, etc.
Because off-premises network links usually need to go longer distances and work over the telecommunication carriers' existing infrastructure, they tend to use physical and data-link standards that are more common in the telecom industry. Then again, for your convenience, telecom carriers usually hand off to you using an 802.3-family link, even if what they're using behind the scenes is, say, OC-3 and SONET/SDH.
Because of the technical hurdles associated with moving lots of data long distances reliably, WAN links tend to be lower bandwidth and higher latency than LAN links. Also, because you're usually paying a separate telecom carrier for the service, to keep costs down, most organizations try to limit (or at least not go crazy with) how much data they move over WAN links.
The differences between LANs and WANs tend to be at the physical and data-link layers. At the network layer (Layer 3 in the old-but-still-helpful-for-some-discussions OSI layering model), most people use IP (Internet Protocol) nowadays. Because it all uses IP, applications that use IP don't have to know what physical and data-link layers are in use, so anything you can do on a LAN you can potentially do on a WAN as well, if you have high enough bandwidth and low enough latency for whatever it is you're trying to do, and as long as you haven't blocked it at your firewall (or via the accidentally firewall-like properties of a NAT).
While LAN and WAN are both two branches of networking and share many similarities, there’s a very fine line between them as well
There are differences on the basis of scope and connections. When I was doing my Cisco qualifications I seem to recall that a WAN was typically over a large geographical area, like a huge private network (mini internet [intranet])
http://www.computer-realm.net/lan-wan/
Difference on the basis of scope: WAN is considered to be more vast and widespread. WAN is meant for networking between wide geographical regions like between two cities or even across different time zones while LAN is mainly used for private connectivity among residential offices or a single edifice. Hence a small scale WAN can be developed by creating many LANs.
Difference on the basis of connections: In case of LAN, Ethernet is the main device which is used for connecting the workstations or the computers. Ethernet is a bus based protocol device in which cables and wires and permanent. Ethernet helps is the interconnection of the different types of LANs. While in the case of WAN, common carriers are usually used and most people opt in for service providers. When it comes to the speed of both the network technologies, a LAN is usually faster as it is confined to a small space with servers in a nearby location.
Networks are often classified by their physical or organizational extent or their purpose. Usage, trust level, and access rights differ between these types of networks.
Computer network types by area:
Body (BAN)
Personal (PAN)
Near-me (NAN)
Local (LAN)
Home (HAN)
Storage (SAN)
Campus (CAN)
Backbone
Metropolitan (MAN)
Wide (WAN)
Global (GAN)
Internet
Interplanetary Internet
LAN: A local area network (LAN) is a computer network that connects computers and devices in a limited geographical area such as home, school, computer laboratory or office building.
WAN: A wide area network (WAN) is a telecommunication network that covers a broad area (i.e., any network that links across metropolitan, regional, or national boundaries).
Here's a description of some of the differences...
LAN LAN (Local Area Network) is a computer network covering a small geographic area. Home, office, or schools ar typical examples.
WAN WAN (Wide Area Network) is a computer network that covers a broad area and whose communications links cross over other WANs. Metropolitan, regional, national and international networks are an example.
LAN Usually uses networking technologies like Ethernet.
WAN Uses technologies like Frame Relay or X.25
LAN Typically runs across user-owned network infrastructure. Cables, modems, computers, routers.
WAN Typically run across leased lines, and expensive equipment (like satellites, communications towers and communications centres) and ownership may be distributed among several organizations.
LAN Typically offers high data transfers rates with good quality cables and small distances between endpoints.
WAN Usually slower transfer rates. Distances usually impact on data transfer rates even if these are equal to LAN (10/100/1000 Mbps). Latency is much more visible in WANs due to the distances sometimes involved and the number of devices (or hops) a data packet has to travel through.
LAN Cheap to setup and maintain.
WAN Expensive to setup and maintain. Only at the reach of large communication corporations and governments.
In addition there's also MAN (Metropolitan Area Network). These are usually smaller than WANs and larger than LANs (although there's really no size restrictions). Their purpose is to provide higher quality service or differentiated service to a smaller geographical area like a town, city, or university campus and to establish a connection between the several LANs it may serve and the WAN it may be served with.
The confusion stems from the fact that networking has evolved greatly since the ARPANET. In the past, yes, location and distance were the predominant factors in the distinction between LAN and WAN; however today, it is both blurred, and somewhat re-defined. Today, the distinction is more in terms of addressing and administration, particularly for “LAN”.
A LAN no longer needs to be in a single location. Yes, a home, school, or company-network is considered a LAN, but the term also applies to ISPs. That is, your ISP may provide Internet access to thousands of houses across a large city, and it is still considered a LAN (for example, consider warnings of how someone using the same ISP may be able to sniff your traffic because they are on the same network). In this case, the addresses of the systems on the network are confined to the IPs that the ISP owns, and the network is administered by the same entity (the ISP).
A WAN, on the other hand, is usually defined more closely to what it was in the past: a collection of disparate networks connected to each other. In this regard, your home-network connected to my home-network forms a WAN, even if they are both on the same ISP. In this case, each sub-network in the WAN is administered by a different entity (you and me), and likely has different addressing (your router may use different addresses, network masks, etc. than mine).
Another definition for a WAN that falls in line with what it used to be does in fact use the location. For example, a company can have a LAN in their office building, but when it connects to their LAN in another building in another city/country, it forms a WAN.
It’s sort of a matter of perspective; two small LANs form a small WAN, which itself is a LAN that connects to other small LANs which form a larger WAN, and so on.
Another distinction for LAN and WAN that is easy to remember is the makeup of the networks. A LAN is usually just individual systems/devices connected to each other, while a WAN is usually networks connected to each other. That is, you don’t usually have a sub-network in a LAN, and you don’t usually have a single computer attached to a WAN all by itself.
Also, the networking hardware usually plays a role in the distinction. For example, routers in LANs and switches in WANs; CAT5 cables and little wireless antennae for LANs and giant under-sea cables and satellites in orbit for WANs.
One way to think about the difference is not in terms of size or geographical location, but control:
Your company may have routers in Chicago and LA, but since they're under one company's control, they're part of one LAN. You probably route traffic between them publicly, over the WAN.
Computer networks are bunch of interconnected PC or computers that facilitate the exchange of data or some other purposeful work. The first computer network to be designed was the "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense in the late 1960s and early 1970s. From then on, numerous new network technologies have been developed.
Computer networks can be classified into different types based on their scale of operation. They include: LAN: Local Area Networks cover a small physical area, like a home, office, or a small group of buildings, such as a school or airport.
WLAN: Wireless Local Area Networks enable users to move around within a larger coverage area, but still be wirelessly connected to the network.
WAN: Wide Area Networks cover a broad area, like communication links that cross metropolitan, regional, or national boundaries. The Internet is the best example of a WAN.
MAN: Metropolitan Area Networks are very large networks that cover an entire city.
SAN: Storage Area Networks help attach remote computer storage devices, such as disk arrays, tape libraries, and optical jukeboxes, to servers in such a manner that that they appear to be locally attached to the operating system.
CAN: Controller Area Networks allow micro controllers and devices to communicate with each other without a host computer.
PAN: Personal Area Networks are used for communication among various devices, such as telephones, personal digital assistants, fax machines, and printers, that are located close to a single user.
GAN: Global Area Networks support mobile communications across an arbitrary number of wireless LANs and satellite coverage areas.
INTERNETWORK: Internetworking is the process of connecting two or more distinct computer networks or network segments through a common routing technology.
Computer networks are an integral part of our lives. It is only because of networking that telephones, televisions, radios, and the Internet are at our fingertips.
A LAN is a group of computers in a single location or group (i.e. a school or a business).
A WAN is typically multiple networks connected in multiple locations.
Technically there is not much difference... they are both packet transporting networks.
The different names are for human comprehension of different parts of a big network.
For practical purposes, a WAN is routed, and packets passed between devices in the network go through routers which direct them to their destination. A LAN is not routed, and the devices in the network communicate with each other directly (they will probably go through one or more hubs or switches, but not routers).
So, after several answers have been tabled for your question... As far as a small home/office router is concerned:
The WAN port connects to the rest of the Internet via your ISP. The LAN port separates your hosts from your ISP so that your ISP nominally only sees one device connected to it.
The WAN port receives DHCP from your ISP, or acts as a DHCP client. The LAN port provides DHCP services to all devices connected to it, usually passing along parameters it picked up from the WAN port. The LAN port acts as a DHCP server. It is usually not a good idea to plug your LAN port into your ISP's device.
The WAN port in its most simple form usually has a public IP address. The LAN port, in its default configuration, is usually configured to serve a private IP network. (10.x.x.x, 192.168.x.x, 172.16.x.x-172.31.x.x).
The WAN port does Network Address Translation for devices that make requests (clients) to the Internet from the LAN port. Devices on the LAN port, unless specially configured on the router, cannot receive client requests from the Internet or any device connected to the WAN port. (The LAN port devices need special configuration to act as servers).
The WAN port, unless configured otherwise, usually drops any connection attempt made to its IP address. If a client connected to the LAN port originates a request (say, to view a web page), the router keeps track of the outbound request, and when the server replies, the Network Address Translation feature of the router makes sure the requesting client gets the response from the server.
