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The following table summarizes the characteristics of PANs, LANs, MANs and WANs.
Parameter PAN LAN MAN WAN
Area covered Small area A building or campus A city (up to 100 km Entire country, continent
(up to 10 m radius) (up to 10 km) radius) or globe
Networking cost Negligible Inexpensive Expensive Very expensive
Transmission High speed High speed Moderate speed Low speed
speed
Error rate Lowest Lowest Moderate Highest
Network devices WLAN, USB Dongle LAN/WLAN, Hub/ Switch, Router, Gateway Router, Gateway
used Repeater, Modem
Technology/ Infrared, Bluetooth Ethernet, Wi-Fi Optical fibre, Radio- Microwave Satellite
media used wave, Microwave

CTM: LAN and WAN are the two primary and best-known categories of area networks; the others have
emerged with technological advances.

Comparing LAN and WAN

As we have seen, computer networks can be classified into LAN, MAN and WAN categories on the
basis of their geographical domains. A WAN extends over a large geographical area, such as states
or countries. A LAN is confined to relatively smaller areas, such as an office, a building, etc. A MAN
usually covers an entire city. It uses the LAN technology. The most common example of MAN is the
cable television network. Thus, the basic points of difference between LAN and WAN are as follows:
1. The distance between the nodes in a LAN connection is limited to a specific range. The upper
limit is approximately 10 kilometres and the lower limit is one metre. On the other hand, WANs
are spread across thousands of kilometres in different countries or regions.
2. LANs operate between speeds of 1 mega bit per second (mbps) and 10 mbps while WANs
operate at speeds of less than 1 mbps. To achieve speeds of several hundred mbps, it is advisable
to use the optical fibre technology.

3. The error rate in LANs is lower than that in WANs because of the short distances involved in
LANs. The error rate in LANs is approximately one thousand times less than that in WANs.
4. As LANs are limited by distance, an entire LAN is usually under the control of a single entity,
such as an organization. On the other hand, WANs are usually operated and controlled by
multiple organizations.
Thus, we can say that in comparison to WANs, LANs cover a limited area but they operate with high
speed and low error rates.

8.11 NETWORK TOPOLOGIES

Topology is a way of connecting devices with each other either physically or logically. Two or
more devices make a link and two or more links form a topology. It is basically a geometrical
representation of how a network is laid out.
Computer Networks
CTM: Topology is a way of connecting several devices with each other on a network.

8.17