Page 96 - DCAP309_INFORMATION_SECURITY_AND_PRIVACY

Information Security and Privacy

Notes A typical use of MANs to provide shared access to a wide area network is shown in the figure
below:

Figure 7.3: The Functioning of MAN
Metropolitan Wide Area
Area Network To other
Network networks

Metropolitan Area
Network

Local Area Networks Local Area Networks

Notes There are three important features which distinguish MANs from LANs or WANs:

1. The network size falls in between LANs and WANs. A MAN typically covers an area
of between 5 and 50 km diameter. Many MANs cover an area the size of a city,
although in some cases MANs may be as small as a group of buildings.
2. A MAN, like a WAN, is not generally owned by a single organisation. The MAN, its
communications links and equipments are generally owned by either a group of
users or by a single network provider who sells the service to the users. This level of
service provided to each user must be negotiated with the MAN operator, and some
performance guarantees are normally specified.
3. A MAN often acts as a high-speed network to allow sharing of regional resources
(similar to a large LAN). It is also frequently used to provide a shared connection to
other networks using a link to a WAN.

7.2.4 Value Added Network (VAN)

VAN is also an acronym for virtual area network. A value-added network (VAN) is a private
network provider that is hired by a company to facilitate Electronic Data Interchange (EDI) or
provide other network services. VANs are public networks that add value by transmitting data
and by providing access to commercial databases and software. The use of VANs is usually sold
by subscription, with users paying for the amount of data they move. VANs are used for a
number of reasons. They can be considered as a way of transmitting computerized data, offering
a service similar to what the telephone networks do for telephone calls. VANs can send data
between computers in different cities or even different countries. They are often used in electronic
data interchange (EDI) systems because they reduce the complexity of connecting to the disparate
EDI systems of various trading partners.

7.2.5 Internet

The Internet is a worldwide network of computer networks. It is an interconnection of large and
small networks around the globe. In other words, it is a global network of networks connecting

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