Comparison of LANs and WANs
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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.
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| 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. |
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.
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