Comparison of LANs and WANs

LANs (Local Area Networks) and WANs (Wide Area Networks) are two basic types of networks used in digital communications. We try to distinguish between LAN and WAN by comparing both technologies.

As a case study, a college Aurobindo has several departments and a centralized applications server. Each department needs to access the central server to access any application such as Microsoft Word or Excel. These applications are bandwidth intensive, and require high band width over a shorter distance. What is required under these circumstances is a Local Area Network. A LAN may be confined to a small room, or a building, or a big campus depending on the requirement.

Now, that you want to provide email access to a school, Shanti situated in a different city. You can't provide a LAN connection, since it is typically limited to a fraction of a kilometer (or a few kilometers with signal conditioners). Another reason for unsuitability of LAN is that you can't lay cables over public property without explicit permissions. One feasible solution for this is to have a WAN connection. For example, both Aurobindo and Shanti can have a link to ISP at both ends, and setup a virtual LAN over the the WAN. By using WAN, you can have your LAN spread across a large geographical regions. Without WAN, it would have been impossible to provide email access to the school. Internet is an example of a Wide Area Network spreading across continents.

Property	LAN	WAN
Protocols commonly used	Ethernet, Token Ring, FDDI, etc.	X.25, Frame Relay, ISDN, Leased line etc.
Communication method	Shared Media	Point-to-point
Main Advantage	Offer high speeds over short distances. Since LANs spread over short distances (typically a fraction of a kilometer), they offer very high speeds. The signal strengths offered by LAN devices is good, and LANs typically require less expensive equipment for transmission, and reception of signals.	Offer relatively low speeds over longer distances. With WAN, the media becomes very expensive since it had to traverse over several kilometers (sometimes 100s or 1000s of Kilometers). Attenuation and noise become significant over such large distances. Hence, powerful transmitters, and receivers are used with WANs. These equipment tend to be very expensive. All these factors influence the protocols used for implementing WANs.
Common Usage	1. Within a building, campus, or city 2. Used to connect several host computers within a building or campus together.	1. Between cities or any points that are geographically separated by a large distance (several kilometers or more) 2. WAN is normally used for connecting LANs separated by a large distance (say, several hundred kilometers)
Speeds	Up to 1 Gbps typical. Normally, all of LAN bandwidth is available to a single user (or host) at any given time. The communication is burst in nature.	Up to several Gbps shared. Though todays WANs offer very high bandwidths, the bandwidth is typically shared among several customers.
Cost	Very low cost per Mbps	High cost per Mbps.
Comments	Both LAN and WAN are used in different circumstances, and they both complement each other.

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