Download When you have two or more computers connected to each

Synopsis
T0 Applied Network and Operating System Concepts
By
Suman chintha ([email protected])
NETWORKS:
When you have two or more computers connected to each other, you have a network. The
purpose of a network is to enable the sharing of files and information between multiple
systems.
By definition a network is simply two or more computers communicating with each
other. By understanding the different kinds of networks and how they work you will be
able to determine which network will suit your organization's needs best. Some networks
are rather simple and easy to set up while others are much more complex and will require
the help of a trained professional
LAN: LAN stands for Local Area Network. These networks can consist of anywhere
from two to thousands of computers. Even a simple network of one computer connected
to one printer can be considered a LAN.


WAN:
Peer-to-Peer - Sometimes called P2P, these networks are the simplest and least expensive
networks to set up. P2P networks are simple in the sense that the computers are connected
directly to each other and share the same level of access on the network, hence the name.
Computer 1 will connect directly to Computer 2 and will share all files with the appropriate
security or sharing rights. If many computers are connected a hub may be used to connect all
these computers and/or devices.
Client/Server - Probably the most common LAN types used by companies today, they are called
"client/server" because they consist of the server (which stores the files or runs applications) and
the client machines, which are the computers used by workers. Using a client/server setup can
be helpful in many ways. It can free up disk space by providing a central location for all the files
to be stored. It also ensures the most recent copy of that file is available to all. A server can also
act as a mail server (which collects and sends all the e-mail) or a print server (which takes all the
print jobs and sends them to the printer, thus freeing computing power on the client machine to
continue working)
Wide Area Networks, or WANs are very large networks of computers. These networks span large
geographical areas, generally covering a couple miles, sometimes connecting computers thousands of miles
apart. A WAN can also be a collection of LANs, bringing together many smaller networks into one large
network. A WAN can constitute a very large corporate or government network, spanning the country or even
the world. In fact, the Internet is the largest and most common WAN in existence today.
OSI MODELS
The standard model for networking protocols and distributed applications is the International Standard
Organization's Open System Interconnect (ISO/OSI) model. It defines seven network layers.
Layer 1 - Physical
This layer defines the cable or physical medium itself, e.g. unshielded twisted pairs (UTP). All
media of transmission are functionally equivalent in this layer and the main difference is in
convenience and cost of installation and maintenance.
Layer 2 - Data Link
Data Link layer defines the format of data on the network ( a network data frame, packet and
destination address). The Maximum Transmission Unit (MTU) is defined by the largest packet that
can be sent through a data link layer.
Layer 3 - Network
This layer defines the protocols that are responsible for data delivery at the required destination,
and requires.
Layer 4 - Transport
This layer subdivides user-buffer into network-buffer sized datagrams and enforces desired
transmission control. Two transport protocols, Transmission Control Protocol (TCP) and User
Datagram Protocol (UDP), sits at the transport layer. Reliability and speed are the primary
difference between these two protocols.
Layer 5 - Session
This leyer defines the format of the data sent over the connections.
Layer 6 - Presentation
This layer converts local representation of data to its canonical form and vice versa. The canonical
uses a standard byte ordering and structure packing convention, independent of the host.
Layer 7 - Application
Provides network services to the end-users. e.g Mail.
OSI Model gives; Increased evolution, Modular engineering, Interoperable technology, Reduced complexity
Simplified teaching and learning, Standardised interfaces.
ADVANTAGES OF NETWORK
Speed. Sharing and transferring files within Networks are very rapid. Thus saving time, while
maintaining the integrity of the file.
Cost. Individually licensed copies of many popular software programs can be costly. Networkable
versions are available at considerable savings. Shared programs, on a network allows for easier
upgrading of the program on one single file server, instead of upgrading individual workstations
.
Security. Sensitive files and programs on a network are passwords protected (established for
specific directories to restrict access to authorized users) or designated as "copy inhibit," so that
you do not have to worry about illegal copying of programs
Centralized Software Management. Software can be loaded on one computer (the file server)
eliminating that need to spend time and energy installing updates and tracking files on independent
computers throughout the building.
Resource Sharing. Resources such as, printers, fax machines and modems can be shared.
Electronic Mail. E-mail aids in personal and professional communication. Electronic mail on a LAN
can enable staff to communicate within the building having tot to leave their desk.
Flexible Access. Access their files from computers throughout the firm.
Workgroup Computing. Workgroup software (such as Microsoft BackOffice) allows many users to
work on a document or project concurrently.
Server faults stop applications being available
DISADVANTAGES OF NETWORK







Network fault could lead to loss of resources
User work dependent upon network
System open to hackers
Decisions tend to become centralized
Could become inefficient
Could degrade in performance
Resources could be located too far from users