A network is any collection of computers connected together to share resources. When computers are connected in a network, users can share files, printers and other devices. As companies rely more on applications like email and databases, computer networking becomes increasingly important. Networks include computers, networking cards, connections like wires, and network operating systems. There are different types of networks like LANs, WANs, intranets and the Internet. Devices like repeaters, hubs, bridges, gateways and switches are used to connect network segments and devices.

1. NETWORKING
BASICS OF NETWORKING
A network is any collection of independent computers that communicate with one
another over a shared network medium.A computer network is a collection of two
or more connected computers. When these computers are joined in a network,
people can share files and peripherals such as modems, printers, tape backup
drives, or CD-ROM drives. When networks at multiple locations are connected
using services available from phone companies, people can send e-mail, share
links to the global Internet, or conduct video conferences in real time with other
remote users. As companies rely on applications like electronic mail and
database management for core business operations, computer networking
becomes increasingly more important.
Every network includes:
•At least two computers Server or Client workstation.
•Networking Interface Card's (NIC)
•A connection medium, usually a wire or cable, although wireless
communication between networked computers and peripherals is also
possible.
•Network Operating system software, such as Microsoft Windows NT or
2000, Novell NetWare, Unix and Linux.

2. TOPOLOGIES
Types of Networks
• LANs (Local Area Networks)
A network is any collection of independent computers that
communicate with one another over a shared network
medium. LANs are networks usually confined to a
geographic area, such as a single building or a college
campus.
• WAN’S(WIDE AREA NETWORK)
Wide area networking combines multiple LANs that are
geographically separate.
• INTERNET
The Internet is a system of linked networks that are
worldwide in scope and facilitate data communication
services such as remote login, file transfer, electronic mail,
the World Wide Web and newsgroups.

3. Intranet
With the advancements made in browser-based software for the
Internet, many private organizations are implementing intranets. An
intranet is a private network utilizing Internet-type tools, but available
only within that organization. For large organizations, an intranet
provides an easy access mode to corporate information for employees.
MANs (Metropolitan area Networks)
The refers to a network of computers with in a City.
VPN (Virtual Private Network)
VPN uses a technique known as tunneling to transfer data securely on the
Internet to a remote access server on your workplace network. Using a
VPN helps you save money by using the public Internet instead of making
long–distance phone calls to connect securely with your private network.
There are two ways to create a VPN connection, by dialing an Internet
service provider (ISP), or connecting directly to Internet.

4. CONNECTING DEVICES
• Repeaters
A repeater is an electronic device that receives a signal, cleans it of
unnecessary noise, regenerates it, and retransmits it at a higher power
level, or to the other side of an obstruction, so that the signal can cover
longer distances without degradation. In most twisted pair Ethernet
configurations, repeaters are required for cable that runs longer than 100
meters. Repeaters work on the Physical Layer of the OSI model.
• Hubs
A network hub contains multiple ports. When a packet arrives at one
port, it is copied unmodified to all ports of the hub for transmission. The
destination address in the frame is not changed to a broadcast address. It
works on the Physical Layer of the OSI model..
• Bridges
A network bridge connects multiple network segments at the data link
layer (layer 2) of the OSImodel. Bridges broadcast to all ports except the
port on which the broadcast was received. However, bridges do not
promiscuously copy traffic to all ports, as hubs do, but learn which MAC
addresses are reachable through specific ports. Once the bridge associates
a port and an address, it will send traffic for that address to that port only.

5. ACTIVE &PASSIVE HUBS
• Passive hubs do not amplify the electrical
signal of incoming packets before
broadcasting them out to the network.
• Active hubs, on the other hand, do perform
this amplification, as does a different type of
dedicated network device called a repeater.
Some people use the terms concentrator
when referring to a passive hub and multiport
repeater when referring to an active hub.

6. NETWORK GATEWAY
• A network gateway is an internetworking
system capable of joining together two
networks that use different base protocols. A
network gateway can be implemented
completely in software, completely in
hardware, or as a combination of both.
Depending on the types of protocols they
support, network gateways can operate at any
level of the OSI model.

7. NETWORK SWITCHES
• A network switch is a computer networking
device that connects network segments.
• The term commonly refers to a network
bridge that processes and routes data at the
data link layer (layer 2) of the OSI model.
Switches that additionally process data at the
network layer (layer 3 and above) are often
referred to as Layer 3 switches or multilayer
switches.