- Introduction to Networking -
What is a Network?
A network is defined as devices connected together to share information
and services. The types of data/services that can be shared on a network is
endless - documents, music, email, websites, databases, printers, faxes,
telephony, videoconferencing, etc.
Protocols are “rules” that govern the method by which devices share data
and services. Protocols are covered in great detail in subsequent sections.
Basic Network Types
Networks are generally broken down into two types:
LANs (Local Area Networks) - a high-speed network that covers a
relatively small geographic area, usually contained within a single building
or campus. A LAN is usually under the administrative control of a single
WANs (Wide Area Networks) – The book definition of a WAN is a
network that spans large geographical locations, usually to interconnect
A more practical definition describes a WAN as a network that traverses a
public network or commercial carrier, using one of several WAN
technologies. Thus, a WAN can be under the administrative control of
several entities or organizations, and does not need to “span large
A host refers to any device that is connected to your network. Some define a
host as any device that has been assigned a network address.
A host can serve one or more functions:
• A host can request data (often referred to as a client)
• A host can provide data (often referred to as a server)
• A host can both request and provide data (often referred to as a peer)
Because of these varying functions, multiple network “architectures” have
been developed, including:
• Peer-to-Peer networks
• Client/Server networks
• Mainframe/Terminal networks
When using a peer-to-peer architecture, all hosts on the network can both
request and provide data and services. For example, configuring two
Windows XP workstations to share files would be considered a peer-to-peer
Though peer-to-peer networks are simple to configure, there are several key
disadvantages to this type of architecture. First, data is spread across
multiple devices, making it difficult to manage and back-up that data.
Second, security becomes problematic, as you must configure individual
permissions and user accounts on each host.
When using a client/server architecture, hosts are assigned specific roles.
Clients request data and services stored on Servers. Connecting Windows
XP workstations to a Windows 2003 domain controller would be considered
a client/server network.
While client/server environments tend to be more complex than peer-to-peer
networks, there are several advantages. With data now centrally located on
a server or servers, there is only one place to manage, back-up, and secure
that data. This simplified management allows client/server networks to scale
much larger than peer-to-peer. The key disadvantage of client/server
architecture is that it introduces a single point of failure.
When using a mainframe/terminal architecture, often referred to as a thinclient
environment, a single device (the mainframe) stores all data and
services for the network. This provides the same advantage as a client/server
environment – centralized management and security of data.
Additionally, the mainframe performs all processing functions for the dumb
terminals (or thin-clients) that connect to the mainframe. The thin clients
perform no processing whatsoever, but serve only as input and output
devices into the mainframe. Put more simply, the mainframe handles all the
“thinking” for the thin-clients.
A typical hardware thin-client consists of a keyboard/mouse, a display, and
an interface card into the network. Software thin-clients are also prevalent,
and run on top of a client operating system (such as Windows XP or Linux).
Windows XP’s remote desktop is an example of a thin-client application.