Short description of LAN Network

2. NETWORK
A network consists of 2 or a lot of computers
that are coupled so as to share resources (such
as CDs and printers), exchange files, or enable
electronic communications. The computers on
a network are also coupled through cables,
telephone lines, radio waves, satellites, or
infrared radiation beams.

3. TYPES OF NETWORK
By depending upon the area covered by the network, networks are classified as
below:

4. LOCALAREA NETWORK
(LAN)
 A local area network (LAN) could be a cluster of computers and
associated devices that share a standard communications line or wireless
link to a server. Typically, a local area network encompasses computers
and peripherals connected to a server among a definite geographic
region like a workplace or a billboard institution. Computers and
different mobile devices use a local area network affiliation to share
resources like a printer or network storage.
 A local space network could function few as 2 or 3 users (for example,
in a very small-office network) or many hundred users in a very larger
workplace. Computer network networking contains cables, switches,
routers and different parts that allow users hook up with internal servers,
websites and different LANs via wide area networks.

5. DIAGRAMMATIC REPRESENTATION OF LAN

6. ADVANTAGES OF LAN
1. Resource Sharing
Sharing of resources such as hard disk drives, DVD drives and Printers are made easy in Local Area Network. For an
example all the resources can be connected to one single computer with a network so that whenever there is a need of
resources it can be shared with the connected computers.
2. Software Sharing
Another type of sharing made easy here is the Software sharing. A single computer with the licensed software can be
shared among other users in the network. There is no need to purchase individual license for each and every
computer in the network. All can be worked under one single license.
3. Convenient Communication
Using LAN users can exchange messages and data in a convenient way. Since the data is placed on the server it can
be accessed anytime by the LAN users. Every single LAN user can do this with others on the network. Hence, this
not only saves lots of time, it ensures that messages get delivered to the right people.
4. Centralized Data
As mentioned earlier data of the users are located at the centralized server. Any workstation in a particular network
can be used to access this information. Moreover users can access their own set of data by logging into their
respective accounts.
5. Internet Sharing
LAN has the capability to share internet connection among all the LAN users. One single computer with an internet
connection shares internet with all the connected computers. This type of infrastructure can be seen in Offices and
Netcafes.

7. DISADVANTAGES OF LAN
1. Implementation Cost
Even though LAN saves lots of money in terms of resource sharing, the initial cost involved in setting up the network is quite
high. This is mainly due to the requirement of a special software that is needed to make a server. In addition to that purchasing of
hardware equipments such as routers, hubs, switches and cables are required for the first time setup.
2. Policy Violations
Since all the data of the connected computers are stored inside a central server, unauthorized users can view all the browsing
history and downloads of all the connected computers. Especially the LAN administrator has the authority to check personal data
of each and every LAN user. Therefore, this can lead to Policy violations.
3. Security
Since it is rather easy to gain access to programs and other types of data, security concerns are a big issue in LAN. The sole
responsibility to stop unauthorized access is in the hands of LAN administrators. The LAN administrator has to make sure that the
centralized data is properly secured by implementing correct set of rules and privacy policies on the server.
4. Maintenance
LAN often faces hardware problems and system failure. Hence, it requires a special administrator to look after these issues. The
administrator needs to be well knowledgeable in the field of networking and needed at its full time job.
5. Area Coverage
LAN is usually made to cover up a limited distance (up to 10km). Most probably it is operated in small areas such as in offices,
banks and schools. This is because its cabling system cannot be extended more than a certain range.

8. FEATURES OF LAN
LAN’s will be either wired or wireless. Twisted pair, coax
or fiber optic cable will be utilized in wired LAN’s.
Every LAN uses a protocol –a set of rules that governs,
however, packets are designed and transmitted.
LANs are capable of terribly high transmission rates (100s
Mb/s to G b/s).
Nodes in a LAN are joined at the side of an exact
topology.

9. WHAT IS THE USE OF LAN ?
Not only LAN connects computers, it does the work
of communicating devices such as routers, hubs and
switches. It is no doubt that through LAN
communication has made much more efficient.
However LAN aren't flawless. LAN has certain pros
and cons that you need to know before network
installation.

10. Classification of LAN
LANs are classified as below according to the methods used for sharing data:

11. ETHERNET
 It is a network protocol that controls how data is transferred over a local area network.
 In this type of LAN, the user is able to transfer data at a rate of more than 10 megabits
per second.
 Firstly, the system checks the medium used for the transfer of data; if the medium is
available, then only the data transmission is done.
 It is used in wired local area networks.
 When a machine or machines want to communicate with each other on a network, they
detect the main wire connecting all the devices which will be used to carry the data. If
the main wire, which is referred to as the carrier, is available and free, which means no
other machine on the network is transmitting any data, then the sender machine initiates
sending the packets of data on the network.
 Whenever a packet is transmitted, the sender has to wait if there is already a data packet
in the queue. After that, all the devices on the network check that packet to see if they
are the recipients of that packet. The actual recipient then receives the packet.

12. TOKEN RING
 It is a type of local area network in which all devices are connected in a ring arrangement.
 All the devices are connected in a circle, and they receive a token as per their requirements. A token
keeps on rotating in the circular ring.
 A token is used to avoid collisions of data. It is of 3 bytes and keeps on traveling in the ring of servers
or workstations.
 The details of three 1-byte fields of a free token frame are:
 Starting Delimiter (SD): It signals the beginning of the token frame.
 Access Control (AC): Contains the priority field, reservation field, a token bit, and a monitor bit.
 Ending Delimiter (ED): It refers to the end of the token frame.
 A station can send data frames only if it has a token. After the data frame is received successfully, the
tokens are made free or released.
 The computers are connected by a ring or also called as a star topology.
 The token is passed over the physical ring, which is formed by the circular arrangement of stations and
the coaxial cable network.
 In this type of LAN, it is possible to calculate the maximum time for a token to reach a station.
 It was developed to solve a collision problem, i.e. when two stations transmit simultaneously at the
same time.
 A newer version called Fast Token Ring has been developed, which can transfer data up to a rate of
100Mbps.

13. TOKEN BUS
 This is also a type of Local Area Network developed by IBM.
 Token Bus standard uses copper cables which are coaxial for connecting multiple devices to the main large
computers or workstations. The coaxial cable acts as the common communication bus.
 In this protocol, also a token is created by this protocol to manage access for communication.
 Any computer that holds the token can transfer the data. The token is released when the station completes its
data transmission or when a higher priority device needs to transmit (such as the mainframe).
 Due to the token freeing mechanism, there is no collision, i.e. two or more devices can easily transmit
information on the bus at the same time, and the transmitted data is also saved from being destroying.
 It is similar to the token-ring network, but the difference is that the ends of the network do not meet each
other to form a ring. But the network gets terminated at both ends.
 In this protocol, the token or a small message which circulates among the devices of a computer network is
passed along the virtual ring of stations connected to a LAN.
 The topology which is used is a bus or tree type that connects the stations.
 Each and every device is aware of the address of its preceding and succeeding device to transmit token to.
 Data transmission cannot be performed without a token.
 In this type of LAN topology, it is not possible to calculate the time for the token transfer. The working
procedure of this token bus is the same as the token ring topology.

14. FIBER DISTRIBUTED DATA INTERFACE
(FDDI)
 It is a LAN standard used for data transmission via optical media.
 Used for long-distance networks.
 Uses optical fiber and copper cable.
 It provides communication with fiber optic cables up to 200 kilometers at a speed of 100 Mbps.
 FDDI has two token rings, primary and secondary communication rings. One ring is for backup in
the case when the primary one fails.
 The primary ring works, and the second one remains free and is available for backup.
 It is extended to FDDI-2 for long-distance voice and multimedia communication.
 It is used for huge and fast data transfer, such as in voice and video conferences, online lectures,
news, etc.
 It was displaced by fast Ethernet, which is cheaper and has a faster data transfer rate.
 It is used in a large geographical scenario with thousands of end-users.

15. Thank You