1. 1. What is computer internet?
• A means of connecting a computer to any other computer anywhere in the world via
dedicated routers and servers. When two computers are connected over the Internet,
they can send and receive all kinds of information such as text, graphics, voice, video,
and computer programs.
• The Internet is a global system of interconnected computer networks that use the standard
Internet protocol suite (TCP/IP) to link several billion devices worldwide. It is an international
network of networks that consists of millions of private, public, academic, business, and
government packet switched networks, linked by a broad array of electronic, wireless, and
optical networking technologies. The Internet carries an extensive range of information
resources and services, such as the inter-linked hypertext documents and applications of the
World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks for
file sharing and telephony.
2.what are the advantages of internet

2. 3. things needed to access the internet
- needed to access the Internet (1) an ISP, (2) a modem, (3) a Web browser and (4) an e-mail
program.
The Internet Service Provider (ISP)
Your access to the Internet is through an Internet service provider (ISP), which can be a large
company such as America Online or MSN, or any of hundreds of smaller ISPs throughout the
country. You are offered unlimited access for a fixed rate per month.
The Modem
Depending on the kind of service you have, you will need a unit of hardware called a "modem"
for connection. Slow-speed dial-up telephone access uses an analog modem, which may already
be installed in your computer. If not, one can be plugged into the USB port.
If you sign up for cable or DSL service, which is from 40 to 100 times faster than telephone dial-
up, your provider may send you the appropriate modem, or you can purchase it at your local
electronics store. Quite simply, opt for the high-speed service if you can. Dial-up modems are an
exercise in extreme patience.
Browsing the Web
A Windows PC comes with the Internet Explorer Web browser. The Mac comes with Safari.
Windows and Mac users quite often choose a different browser such as Firefox
(www.mozilla.org) or Chrome (www.google.com/chrome), which offer additional features and
are not as subject to attack by hackers.
The first time you hook up to a new ISP, you may need their assistance to configure the dial-up
or networking software in your computer. After that, all you do is launch the browser to "surf the
Web."
Sending E-Mail
Although e-mail can be sent and received using your Web browser (see e-mail interfaces), your
computer may come with a dedicated e-mail program like the ones found in smartphones. For
example, the Mac comes with Mail, while Windows has renamed its free program many times:
Outlook Express, Windows Mail, Windows Live Mail and Mail. However, many users prefer
Eudora, Thunderbird and other e-mail clients.
The first time you connect to a new ISP, you may need help in configuring your e-mail program
to use their mail servers. From then on, you launch the mail program as you would any other
application.

3. Switching ISPs
If you only browse the Web, there is little lost in starting with one ISP and switching to another.
However, switching your e-mail address is not like switching your street address. The U.S.
Postal Service will forward your letters for a while, but if you close your account with an ISP,
they may not be as accommodating. It would be a good idea to find out, if you plan on heavily
promoting your e-mail address.
Get Your Own Domain Name
There are two ways around this problem. First is to register your own domain name and use an
ISP that supports third-party names. For example, had Alan Freedman, editor of this
encyclopedia, wanted to secure the alanfreedman.com domain name, his e-mail address could
have been alan@alanfreedman.com. If you have your own domain name and switch ISPs, you
keep your e-mail address because it belongs to you.
Use an Alternate E-Mail Provider
A second way to keep your e-mail address is to establish an account with an Internet e-mail
provider that you stay with no matter which ISP you use for Internet access. There are sites on
and off the Web that provide free e-mail and e-mail forwarding. See how to register a domain
name.

6. 4. what is computer communication?
- Computer network is a collection of nodes, where the computing stations (resources) reside. The
nodes communicate to each other via communication network. Transmission, and switching
accomplishes the course of communications.
-using a computing device while in transit. Mobile computing implies wireless transmission, but
wireless transmission does not necessarily imply mobile computing. Fixed wireless applications use
satellites, radio systems and lasers to transmit between permanent objects such as buildings and
towers.
5. Uses of computer communication
- the purpose of a computer communications network is to allow moving information
from one point to another inside the network. The information could be stored on a
device, such as a personal computer in the network, it could be generated live outside the network,
such as speech, or could be generated by a process on another piece of information, such
as automatic sales transactions at the end of a business day. The device does not necessarily have to
be a computer; it could be a har d disk, a camera or even a printer on the network.
Due to a lar ge variety of information to be moved, and due to the fact that each type of
information has its own conditions for intelligibility, the computer network has evolved into a highly
complex system. Specialized knowledge from many areas of science and engineering goes into
the design of networks. It is practically impossible for a single area of science or
engineering to be entirely responsible for the design of all the components. Therefore, a study of
computer networks branches into many areas as we go up from fundamentals to advanced levels.
6. what is computer network?
- A computer network or data network is a telecommunications network that allows computers to
exchange data. In computer networks, networked computing devices pass data to each other along
data connections (network links). Data is transferred in the form of packets.
- Network computer devices that originate, route and terminate the data are called network nodes.[1]
Nodes can include hosts such as personal computers, phones, servers as well as networking hardware.
Two such devices are said to be networked together when one device is able to exchange information
with the other device, whether or not they have a direct connection to each other.

7. 7. define the following:
• WAN
A wide area network (WAN) is a network that covers a broad area (i.e., any
telecommunications network that links across metropolitan, regional, national or international
boundaries) using leased telecommunication lines. Business and government entities utilize
WANs to relay data among employees, clients, buyers, and suppliers from various geographical
locations. In essence, this mode of telecommunication allows a business to effectively carry
out its daily function regardless of location. The Internet can be considered a WAN as well, and
is used by businesses, governments, organizations, and individuals for almost any purpose
imaginable.[1]
• LAN
A local area network (LAN) is a computer network that interconnects computers within a
limited area such as a home, school, computer laboratory, or office building, using network
media.[1]
The defining characteristics of LANs, in contrast to wide area networks (WANs),
include their smaller geographic area, and non-inclusion of leased telecommunication lines
• WLAN
A wireless local area network (WLAN) is a wireless distribution method for two or more
devices that use high-frequency radio waves and often include an access point to the
Internet. A WLAN allows users to move around the coverage area, often a home or small
office, while maintaining a network connection.
A WLAN is sometimes call a local area wireless network (LAWN).
• MAN
A metropolitan area network (MAN) is a network that interconnects users with
computer resources in a geographic area or region larger than that covered by even a
large local area network (LAN) but smaller than the area covered by a wide area
network (WAN).
8. What are the different network architecture? Define each
- Network architecture is the design of a communications network. It is a framework for the
specification of a network's physical components and their functional organization and configuration, its
operational principles and procedures, as well as data formats used in its operation.
- Network architectures are sometimes classified into two broad categories:
· client-server architectures,

8. · peer-to-peer architectures.
In the client-server architectural model, a system is decomposed into client and server processors
or processes. Servers provide computational resources (or services), which clients consume.
Typically a server provides services to many clients. It is also common for clients to consume
services from multiple services. Stated otherwise, there is generally a 1:M relationship between a
server and its clients, and it is sometimes the case that there is a 1:M relationship between a
client and the servers that it uses. The client-server architectural model supports the separation of
functionality based on the service concept.
Client-server architectures are commonly organized into layers referred to as “tiers”.
Tiered Architectures
· Two-tier architectures. The system architecture consists of a data server layer and an
application client layer. Data access computation is associated with the data server layer, and the
user interface is associated with the client application layer. If most of the application logic is
associated with the client application logic, it is sometimes referred to as a “fat client.” If it is
associated with the data access server, the application client layer is sometimes referred to as a
“thin client.”
· Three-tier architecture. The system architecture consists of data server layer, an application
server layer and a client application layer. The application server layer facilitates the separation
of application logic from presentation, and promotes distributed processing.
· Multi-tier architecture. The system architecture is a superset of a three-tier architecture, and
includes additional layers for data and/or application servers.
Peer-to-Peer Architectures
In a peer-to-peer architecture model, a system is decomposed into computational nodes that have
equivalent capabilities and responsibilities. This division is in contrast to a client-server
architectural model, where client and server nodes are divided into server and client roles.
An example of a peer-to-peer architecture is a system of intelligent agents that collaborate to
collect, filter, and correlate information.
Sometimes layered (“tiered”) and peer-to-peer architectures are combined, where the nodes in
particular layers are in peer-to-peer relationships. For example, a multi-tiered architecture might
include an enterprise management layer, consisting of peer nodes for such things as network
management, event management, database management, Web sever management, and workload
balancing.
9. types of networking devices

9. List of network devices
Connectivity network devices
• Network hub
A hub is a small Network Device. A hub joins multiple computers (or other
network devices) together to form a single network segment. On this network
segment, all computers can communicate directly with each other. Ethernet hubs
are by far the most common type, but hubs for other types of networks such as
USB also exist.
A hub includes a series of ports that each accept a network cable, one port is
reserved for "uplink" connections to another hub or similar device.
Main Features
■ Operate at Layer 1 devices ( Physical layer ) in the OSI model .
■ Hubs do not read any of the data passing through them and are not aware of
their source or destination.
■ Hub simply receives incoming packets, possibly amplifies the electrical signal,
and broadcasts these packets out to all devices on the network - including the one
that originally sent the packet!
Types of Hub
■ Passive Hub
■ Active Hub
■ Intelligent Hub
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.
Intelligent hubs add extra features to an active hub that are of particular
importance to businesses. An intelligent hub typically is stackable (built in such a
way that multiple units can be placed one on top of the other to conserve space).
It also typically includes remote management capabilities via SNMP and virtual
LAN (VLAN) support.

10. • Network repeater
Network repeaters regenerate incoming electrical, wireless or optical signals.
With physical media like Ethernet or Wi-Fi, data transmissions can only span a
limited distance before the quality of the signal degrades. Repeaters attempt to
preserve signal integrity and extend the distance over which data can safely
travel.
Actual network devices that serve as repeaters usually have some other name.
Active hubs, for example, are repeaters. Active hubs are sometimes also called "
Multiport Repeaters " but more commonly they are just "hubs." Other types of
"passive hubs" are not repeaters. In Wi-Fi, access points function as repeaters
only when operating in so-called " Repeater mode ."
• Network bridge
A Network Bridge reads the outermost section of data on the data packet, to tell
where the message is going.only the outermost hardware address of the packet.
Main Features
■ It reduces the traffic on other network segments, since it does not send all
packets.
■ Bridges can be programmed to reject packets from particular networks.
■ Bridging occurs at the data link layer of the OSI model.
■ Bridge cannot read IP addresses .
■ Bridge can read the ethernet data which gives the hardware address of the
destination address.
■ Bridges forward all broadcast messages.
Only a special bridge called a translation bridge will allow two networks of different
architectures to be connected. Bridges do not normally allow connection of
networks with different architectures. The hardware address is also called the MAC
(media access control) address. To determine the network segment a MAC
address belongs to, bridges use one of:
■ Transparent Bridging - They build a table of addresses (bridging table) as
they receive packets. If the address is not in the bridging table, the packet is
forwarded to all segments other than the one it came from. This type of bridge is
used on ethernet networks.
■ Source route bridging - The source computer provides path information inside
the packet. This is used on Token Ring networks.

11. -
• Network router
Network Router is a network device with interfaces in multiple networks whose
task is to copy packets from one network to another. Router gives path to data
packet to destination. Routers provide connectivity inside enterprises, between
enterprises and the Internet, and within an Internet Service Provider (ISP).
Main Features
■ Operates at Layer 3 (Network Layer) of the OSI Model.
■ Router works with Static Routing manully configure by Network Administrator.
■ Router works with Dynamic Routing which routers calculate automatically by
different methods.
■ Router stores calculate path in his Routing Table.
■ The network router will then use its routing table to make intelligent decisions
about which packets to copy to which of its interfaces .
■ The router will use this information to create a routing table.
■ This process is known as routing.
Types of Router
■ Wired Router
■ Wireless Router
Types of Router by Placement
■ Internal Routers (Access)
Routers are used to connect two LAN's.
■ Edge Routers
Router used to connect LAN with WAN, means at the end of your network.
■ Core Routers
Core Router provides a stepdown backbone , interconnecting the distribution
routers from multiple building of a campus ( LAN), or Large enterprise Location
(WAN).
■ Security Routers
for Interconnecting ISPs.
■ Inter-provider Border Routers
considered as part of the overall security strategy, firewall & VPN.

12. • Network switch
Network Switch is a small hardware device that joins multiple computers
together within one local area network (LAN).
Main Features
■ Network Switches operate at layer two (Data Link Layer) of the OSI model .
■ Network switches appear nearly identical to network hubs, but a switch
generally contains more intelligence (and a slightly higher price tag) than a hub.
■ Unlike hubs, Switches are capable of inspecting data packets as they are
received, determining the source and destination device of each packet, and
forwarding them appropriately.
■ By delivering messages only to the connected device intended.
■ Switch conserves network bandwidth and offers generally better performance
than a hub.
■ Switch supports different bandwidth either 10/100 Mbps Fast Ethernet or Gigabit
Ethernet (10/100/1000) standards.
■Switches can be connected to each other, a so-called daisy chaining method to
add progressively larger number of devices to a LAN.
■ Switch Reduce the Collision Domain.
Types of Switches by Forms
■ Rack Mounted Switches.
■ Chassis Switches.
■ Catalyst Switches.
■ DIN Rail Switches.
Types of Switches by Configuration
Unmanaged Switches
■ Switches are not configured.
■ Commonly used in home networks and small businesses.
■ Switches does not need to be monitored or configured using external software
applications.
■ They are easy to set up and require only cable connections.
Managed Switches
■ Can be configured with SNMP.

13. ■ Console Cable.
■ secure shell.
■ This types of Switches will be configured.
Check cisco for Managed Switches
Types of Managed Switches
Smart Managed Switches
■ Operates in Managed and Unmanaged.
■ Configure virtual LANs ports.
■ Set up for trunking with other Switches.
■ Fast LANs to support gigabit data transfer.
Enterprise Managed Switches
■ Fully Managed.
■ Support web interface.
■ Support SNMP agent.
■ Support command-line interface.
■ Restore, Backup, Modify & Display Configurations.
Types of Switches by Placement or Function
■ Access Switches.
■ Distribution Switches.
■ Core Switches.
• cdsu/dsu device
A CSU/DSU (Channel Service Unit/Data Service Unit) is a hardware device
about the size of an external modem that converts a digital data frame from the
communications technology used on a local area network (LAN) into a frame
appropriate to a wide-area network (WAN) and vice versa.
■ The Channel Service Unit (CSU) receives and transmits signals from and to the
WAN line and provides a barrier for electrical interference from either side of the
unit.
■ The CSU can also echo loopback signals from the phone company for testing
purposes.
■ The Data Service Unit (DSU) manages line control, and converts input and
output between RS-232C, RS-449, or V.xx frames from the LAN and the time-
division multiplexed (TDM) DSX frames on the T-1 line.
■ The DSU manages timing errors and signal regeneration.
■ The DSU provides a modem-like interface between the computer as Data
Terminal Equipment (DTE) and the CSU.

14. Hybrid network devices
• Protocol Conversion
■ A protocol converter is a mechanism that changes a standard protocol by one
device to a protocol that can be used to facilitate the function of another device.
Protocol converters also are referred to as protocol translators. Process.
■ Protocol converters are essentially software installed on routers that are used to
convert the data rate, or speed at which data is transmitted, and existing
protocols in one network to the protocols of the other network that is sending or
receiving the data. Protocol converters, much like a language translator, translate
messages, or data streams, between networks to enable both networks to easily
interpret the data. Applications.
■ Protocol converter software is used in a variety of industries for applications
such as building and process automation. Protocol converters also are used for
substation automation, or a system for managing and controlling equipment in an
electric power system
• Brouter
■ A Network brouter is a network device that works as a bridge and as a router.
Network brouter (pronounced BRAU-tuhr or sometimes BEE-rau-tuhr) is a
network bridge and a router combined in a single product. A bridge is a device
that connects one local area network (LAN) to another local area network that
uses the same protocol (for example, Ethernet or token ring).
■ If a data unit on one LAN is intended for a destination on an interconnected LAN,
the bridge forwards the data unit to that LAN; otherwise, it passes it along on the
same LAN. A bridge usually offers only one path to a given interconnected LAN. A
router connects a network to one or more other networks that are usually part of
a wide area network (WAN) and may offer a number of paths out to destinations
on those networks.
■A router therefore needs to have more information than a bridge about the
interconnected networks. It consults a routing table for this information. Since a
given outgoing data unit or packet from a computer may be intended for an
address on the local network, on an interconnected LAN, or the wide area
network, it makes sense to have a single unit that examines all data units and
forwards them appropriately.
Hardware or software components
• Proxy

15. Proxy: In communications, a proxy is something that acts as a server, but when
given requests from clients, acts itself as a client to the real servers. Analogy:
Consider talking to somebody who speaks a foreign language through a translator.
You talk to the translator, who receives your statements, then regenerates
something else completely to the other end. The translator serves as your proxy.
Key point: The communication terminates at the proxy. In other words, the proxy
doesn't forward data so much as it tears it completely apart.
For example, an HTTP proxy doesn't forward every request sent through it.
Instead, it first examines if it already has the requested web page in its cache. If
so, then it returns that page without sending another request to the destination
server. Because proxies completely terminate the communication channel, they
are considered a more secure firewall technology than packet filters, because they
dramatically increase the isolation between the networks. Key point: You will
occasionally be scanned for proxies.
• Network Firwall
A system designed to prevent unauthorized access to or from a private network.
Firewalls can be implemented in both hardware and software, or a combination of
both. Firewalls are frequently used to prevent unauthorized Internet users from
accessing private networks connected to the Internet, especially intranets. All
messages entering or leaving the intranet pass through the firewall, which
examines each message and blocks those that do not meet the specified security
criteria. There are several types of firewall techniques:
■ Packet filter: Looks at each packet entering or leaving the network and accepts
or rejects it based on user-defined rules. Packet filtering is fairly effective and
transparent to users, but it is difficult to configure. In addition, it is susceptible to
IP spoofing.
■ Application gateway: Applies security mechanisms to specific applications,
such as FTP and Telnet servers. This is very effective, but can impose a
performance degradation.
■ Circuit-level gateway: Applies security mechanisms when a TCP or UDP
connection is established. Once the connection has been made, packets can flow
between the hosts without further checking.
■ Proxy server: Intercepts all messages entering and leaving the network. The
proxy server effectively hides the true network addresses.
In practice, many firewalls use two or more of these techniques in concert. A
firewall is considered a first line of defense in protecting private information. For
greater security, data can be encrypted.