Page 112 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Unit 6: Data Communication

under private administration usually by an enterprise, and is only accessible by authorized users Notes
(e.g. employees). Intranets do not have to be connected to the Internet, but generally
have a limited connection. An extranet is an extension of an intranet that allows secure
communications to users outside of the intranet (e.g. business partners, customers).
Unofficially, the Internet is the set of users, enterprises, and content providers that are
interconnected by Internet Service Providers (ISP). From an engineering viewpoint, the Internet
is the set of subnets, and aggregates of subnets, which share the registered IP address space and
exchange information about the reachability of those IP addresses using the Border Gateway
Protocol. Typically, the human-readable names of servers are translated to IP addresses,
transparently to users, via the directory function of the Domain Name System (DNS).
Over the Internet, there can be business-to-business (B2B), business-to-consumer (B2C)
and consumer-to-consumer (C2C) communications. Especially when money or sensitive
information is exchanged, the communications are apt to be secured by some form of
communications security mechanism. Intranets and extranets can be securely superimposed
onto the Internet, without any access by general Internet users, using secure Virtual Private
Network (VPN) technology.
6.1.2 Networking Methods

One way to categorize computer networks is by their geographic scope, although many real-
world networks interconnect Local Area Networks (LAN) via Wide Area Networks (WAN)
and wireless wide area networks (WWAN). These three (broad) types are:

6.1.2.1 Local Area Network (LAN)
A local area network is a network that spans a relatively small space and provides services
to a small number of people.

A peer-to-peer or client-server method of networking may be used. A peer-to-peer network
is where each client shares their resources with other workstations in the network. Examples
of peer-to-peer networks are: Small office networks where resource use is minimal and a
home network. A client-server network is where every client is connected to the server and
each other. Client-server networks use servers in different capacities. These can be classified
into two types:
1. Single-service servers

2. Print servers
The server performs one task such as file server, while other servers can not only perform in
the capacity of file servers and print servers, but also can conduct calculations and use them
to provide information to clients (Web/Intranet Server). Computers may be connected in
many different ways, including Ethernet cables, Wireless networks, or other types of wires
such as power lines or phone lines.
The ITU-T G.hn standard is an example of a technology that provides high-speed (up to
1 Gbit/s) local area networking over existing home wiring (power lines, phone lines and
coaxial cables).

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