2. A computer network, often simply referred to as a
network, is a collection of computers and devices
interconnected by communications channels that facilitate
communications and allows sharing of resources and
information among interconnected devices. Put more simply,
a computer network is a collection of two or more
computers linked together for the purposes of sharing
information, resources, among other things. Computer
networking or Data Communications (Datacom) is the
engineering discipline concerned with computer networks.
Computer networking is sometimes considered a subdiscipline of electrical engineering, telecommunications,
computer science, information technology and/or
computer engineering since it relies heavily upon the
theoretical and practical application of these scientific and
engineering disciplines
3. Networks may be classified according to a wide variety of
characteristics such as medium used to transport the data,
communication protocol used, scale, topology,
organizational scope, etc.
A communications protocol defines the formats and rules for
exchanging information via a network. Well-known
communications protocols are Ethernet, which is a family of
protocols used in LANs, the Internet Protocol Suite, which is used
not only in the eponymous Internet, but today nearly ubiquitously in
any computer network
4. LocaL area network
A local area network (LAN) is a computer network
that connects computers and devices in a limited
geographical area such as home, school, computer
laboratory or office building. The defining
characteristics of LANs, in contrast to
wide area networks (WANs), include their usually
higher data-transfer rates, smaller geographic area,
and lack of a need for leased telecommunication lines.
ARCNET, Token Ring and other technology standards
have been used in the past, but Ethernet over
twisted pair cabling, and Wi-Fi are the two most
common technologies currently in use.
5.
The development and proliferation of CP/Mbased personal computers from the late
1970s and then DOS-based
personal computers from 1981 meant that a
single site began to have dozens or even
hundreds of computers. The initial attraction
of networking these was generally to share
disk space and laser printers, which were
both very expensive at the time. There was
much enthusiasm for the concept and for
several years, from about 1983 onward,
computer industry pundits would regularly
declare the coming year to be “the year of
the LAN”.
6.
7. ethernet
Ethernet is a family of connectionless protocols used in LANs,
described by a set of standards together called IEEE 802 published
by the Institute of Electrical and Electronics Engineers. It has a
flat addressing scheme and is mostly situated at levels 1 and 2 of
the OSI model. For home users today, the most well-known
member of this protocol family is IEEE 802.11, otherwise known
as Wireless LAN (WLAN). However, the complete protocol suite
deals with a multitude of networking aspects not only for home
use, but especially when the technology is deployed to support a
diverse range of business needs. MAC bridging (IEEE 802.1D)
deals with the routing of Ethernet packets using a
Spanning Tree Protocol, IEEE 802.1Q describes VLANs, and
IEEE 802.1X defines a port-basedNetwork Access Control protocol
which forms the basis for the authentication mechanisms used in
VLANs, but also found in WLANs - it is what the home user sees
when they have to enter a "wireless access key".
8.
campus network
A campus network is a computer network made up of an
interconnection of LANs within a limited geographical area.
The networking equipment (switches, routers) and
transmission media (optical fiber, copper plant, Cat5 cabling
etc.) are almost entirely owned (by the campus tenant /
owner: an enterprise, university, government etc.).
In the case of a university campus-based campus network,
the network is likely to link a variety of campus buildings
including, for example, academic colleges or departments, the
university library, and student residence halls.
14. internet
The Internet is a global system of interconnected governmental,
academic, corporate, public, and private computer networks. In
other words, the Internet is a worldwide interconnection of
computers and networks which are either owned privately or
publicly. It is based on the networking technologies of the
Internet Protocol Suite. It is the successor of the
Advanced Research Projects Agency Network(ARPANET)
developed by DARPA of the
United States Department of Defense. The Internet is also the
communications backbone underlying the World Wide Web
(WWW).
Participants in the Internet use a diverse array of methods of
several hundred documented, and often standardized, protocols
compatible with the Internet Protocol Suite and an addressing
system (IP addresses) administered by the
Internet Assigned Numbers Authority and address registries.
Service providers and large enterprises exchange information
about the reachability of their address spaces through the
Border Gateway Protocol (BGP), forming a redundant worldwide
23. how-to Protect against
coMPuter Viruses
1. Avoid Unknown
AttAchments .
Nowadays, most viruses are spread via email attachments which, thankfully, can
only become active when the attachment is
opened or unzipped. While you cannot
contract a virus just by receiving e-mail, it
is a good idea to delete messages
containing attachments if you do not
know the sender.
24.
2. Avoid Bootleg or PirAted
softwAre.
With popular software packages running
upwards of $200, it can be hard to resist
the lure of the bootleg versions freely
available on Internet file sharing utilities
such as FreeNet and Gnutella.
Virus writers take advantage of the
insatiable market for bootlegs to
disseminate their creations across the
Internet and around the world.
25.
3. TreaT Floppy Disks anD CDs WiTh
suspiCion.
Prior to the mid-1990s, most computer viruses
were spread via infected floppy disks. While
floppy disks aren't inherently evil, as they
pass through many hands and many computers,
they have an increasingly greater chance of
becoming infected by a virus - one that will then
infest your system. New technologies such as CD
burners (recorders) also open new doors for viruses
to slip through. Homemade CD-RW disks (CDs
which can be re-written using a burner) with
unknown pedigrees can also be a source of
26.
4. BaCk iT up.
Along with hardware failure, theft and acts of God or
Nature, the possibility of viral infection is just one more
reason to back up your data regularly. For Windows users,
once you have chosen a backup medium (floppy disk, zip
disk, CD-RW, tape drive), you can set up the Task
Scheduler in Windows 95/98 to perform automatic backups
on a daily, weekly or monthly basis. Still, you should
always keep the last and the next-to-the-last backups in case
you need to restore files that have been corrupted.
27.
5. purChase anTivirus
soFTWare.
Most antivirus software packages offer an
automatic background protection mode,
which will detect and clean out infections
as they appear. If you don’t have this
option, be sure to use the software to scan
any and all Internet downloads, e-mail
attachments and foreign disks before you
open or run them. (More information on
antiviral software is coming up in the next
sections.)
28.
6. CheCk sysTem requiremenTs.
The last thing you need is to trek out, buy the
software, trek back, try to install it and get a
nasty error message saying "Unable to install
program. You need Windows version XYZ." For
example, the Windows 98 version of Symantec's
Norton AntiVirus may not work on an NT 2000
system. Make sure you check the minimum
system requirements and platform on the package
before you buy to make sure you get the right
version.
29.
7. sCan all Drives .
Once you've purchased and installed the software, schedule
regular scans. Most virus scan programs are set to
automatically scan the C: Drive first. It's easy to think
you're home free when no viruses are found. Make sure you
set the program to check all drives, including e-mail
programs, as many viruses are delivered through e-mail
attachments and Internet files, and spread through shared
documents.
30.
8. upDaTe oFTen.
For optimum protection, antivirus software
must be updated on a monthly basis so that
it can recognize and eradicate new bugs as
they make the rounds. The updates can
usually be found on the software
company’s Web site, but if you need
reminding, many packages will allow you
to schedule automatic updates. Still, you
should never assume that your antiviral
software offers complete protection from
infection, and you should continue to take
basic safe computing precautions