Computer networks
are continuously operating all over the globe supporting our 24/7/365 always on
and always connected lifestyles.
You are probably using several different networks right now
without even realizing it.
You might be using a school’s network to communicate with
teachers, a phone network to communicate with friends, and a cable network to
watch TV or listen to the radio.
Networks enable telecommunications or the exchange of
information (voice, text, data, audio, video).
The telecommunication industry has morphed from a
government-regulated monopoly to a deregulated market where many suppliers
ferociously compete.
Types of Networks
There are several different types of computer networks.
Computer networks can be characterized by their size as well as their purpose.
The size of a network can be expressed by the geographic
area they occupy and the number of computers that are part of the network.
Networks can cover anything from a handful of devices within a single room to
millions of devices spread across the entire globe.
Some of the different networks based on size are:
• Personal
area network, or PAN
• Local
area network, or LAN
• Metropolitan
area network, or MAN
• Wide area
network, or WAN
In terms of purpose, many networks can be considered general
purpose, which means they are used for everything from sending files to a
printer to accessing the Internet. Some types of networks, however, serve a
very particular purpose. Some of the different networks based on their main
purpose are:
• Storage
area network, or SAN
• Enterprise
private network, or EPN
• Virtual
private network, or VPN
• A network
service provider (NSP) is a business or organization that sells bandwidth or
network access by providing direct Internet backbone access to the Internet and
usually access to its network access points (NAPs)[citation needed]. For such a
reason, network service providers are sometimes referred to as backbone
providers or internet providers.
• Network service providers may
consist of telecommunicationscompanies, data carriers, wireless communications
providers, Internet service providers, and cable television operators offering
high-speed Internet access.
• A few information technology
companies are also emerging[when?] into the NSP market, notably IBM, EDS, CSC,
Vanco and Atos Origin. This is due to the technological convergence of
information and communications technology.
Network Access Technologies
Network access is a critical component of any organization’s
network infrastructure. Administrators have to dynamically enable and control
network access for employees, vendors, business partners, and entire branch
offices that are in a variety of physical locations and that are using many
different types of devices. Enabling network access, while maintaining
security, is an enormous challenge for administrators. You can use the
Microsoft Windows Server 2003 operating system to implement a comprehensive
network access solution that can include the following variety of technologies:
• Secure
access to wireless local area networks (WLANs)
• Secure
remote access to intranets over the Internet
• Services that provide centralized
network connection authentication, authorization, and accounting
• Tools and services that support the
creation and distribution of components to manage secure client-side network
access
Network Access Technologies Architecture
In Windows Server 2003, there are four network access
technology components:
• 802.11
wireless
• Virtual
private networks (VPNs)
• Internet
Authentication Service (IAS)
• Connection
Manager
The following figure shows the components of a network access
technology infrastructure. In this example, the Connection Manager service
profile initiates remote access client connections to dial-up or VPN-based
remote access servers. The remote access servers act as Remote Authentication
Dial-In User Service (RADIUS) clients and send the access requests to an IAS
server for authentication and authorization. Similarly, the 802.11 wireless
client requests access from the wireless access point, which sends the access
requests to an IAS server.
The IAS server receives and processes the access requests
and queries a user account database to verify access client credentials.
Network Access Technologies
Components
The following network access technologies provide a range of
options for secure client access to an organization’s network.
802.11 Wireless
The WLAN protocol, 802.11, and associated technologies, such
as the 802.1X protocol, are IEEE standards supported by Microsoft to provide
secure wireless networking that allows you to extend your core network
infrastructure to roaming wireless clients.
VPN
A VPN is the extension of a private network that encompasses
secure links across shared or public networks, such as the Internet, so that
remote clients can securely connect to an organization’s network resources.
IAS
IAS is the Microsoft implementation of the RADIUS standard
defined by the Internet Engineering Task Force (IETF) in RFCs 2138 and 2139.
IAS performs centralized authentication, authorization, auditing, and
accounting of users who are connecting to a wireless or wired local area
network (LAN), using a remote access connection to connect to a private
intranet. A server running IAS can be configured to perform a RADIUS server
role or a RADIUS proxy role.
What does Network Protocols mean?
Network protocols are formal standards and policies
comprised of rules, procedures and formats that define communication between
two or more devices over a network. Network protocols govern the end-to-end
processes of timely, secure and managed data or network communication.
Network convergence refers to the provision of telephone,
video and data communication services within a single network. In other words,
one pipe is used to deliver all forms of communication services. The process of
Network Convergence is primarily driven by development of technology and
demand. One main goal of such integration is to deliver better services and
lower prices to consumers. Users are able to access a wider range of services,
choose among more service providers. On the other hand, convergence allows
service providers to adopt new business models, offer innovative services, and
enter new markets.
A LAN (local area network) is a group of computers and
network devices connected together, usually within the same building. By
definition, the connections must be high speed and relatively inexpensive
(e.g., token ringor Ethernet). Most Indiana University Bloomington departments
are on LANs.
A MAN (metropolitan area network) is a larger network that
usually spans several buildings in the same city or town. The IUB network is an
example of a MAN.
A WAN (wide area network), in comparison to a MAN, is not
restricted to a geographical location, although it might be confined within the
bounds of a state or country. A WAN connects several LANs, and may be limited
to an enterprise (a corporation or an organization) or accessible to the
public. The technology is high speed and relatively expensive. The Internet is
an example of a worldwide public WAN.
The SABRE airline reservation system is a classic example of
a strategic information system that depends upon communication provided through
a network.
SABRE Airline Solutions pioneered technological advances for
the industry in areas such as revenue management, pricing, flight scheduling,
cargo, flight operations and crew scheduling.
In addition, not only did SABRE help invent e-commerce (now
referred to as ebusiness) for the travel industry, the company holds claim to
progressive solutions that defined — and continue to revolutionize — the travel
and transportation marketplace.
It is very important, for example, for managers to be able
to retrieve overall corporate sales forecasts from corporate databases to use
in developing spreadsheets (or any other program used for business analysis) to
project future activity.
In order to satisfy customers, automobile dealers need to be
able to locate particular vehicle models and colors with specific equipment
installed.
Managers at various points in a supply chain need to have
accurate, up-to-date data on inventory levels and locations.
Accountants at corporate headquarters need to be able to
retrieve summary data on sales and expenses from each of the company's
divisional computer centers.
The chief executive officer, using an executive information
system, needs to be able to access up-to-the-minute data on business trends
from the corporate network.
An organization has to be concerned about proper
identification of users and authorization of network access, the control of
access, and the protection of data integrity. Almost all networks require some
kind of logon, including user name and password. Many people are casual with
their passwords, making them easy to guess. A good password has both letters
and numbers along with a few punctuation marks for added security. Most
corporate security goes far beyond passwords such as using a "firewall," a computer that sits
between an internal network and the Internet. The firewall allows access to
internal data from specified incoming sites but tries to detect unauthorized
access attempts and prevent them from occurring.
Some companies, such as Best Buy, Circuit City, Office
Depot, and Sears, already have their physical and online stores integrated.
These companies have been the fast movers because they already had an area in
their stores for merchandise pickup (usually for big, bulky items such as TVs
and appliances), and because long before the web they had systems and processes
in place that facilitated the transfer of a sale from one store to another.
To take on the challenge of business integration, an
organization needs a secure and reliable network for mission-critical systems.
National ISPs
Another type of ISP is the national ISP. These include such
companies as Earthlink and MindSpring who offer Internet access in a broad
geographical area. Compared to local ISPs, these companies tend to offer
higher-speed connections and greater long-term stability. Many national
providers also offer a broad range of services, including long-distance
telephone service, web site hosting, and secure electronic transactions. They
are generally a good choice for small businesses that want employees to be able
to access the Internet while traveling. They may also be convenient for
businesses that operate in several locations and wish to use the ISP for all
locations. The main disadvantages of the larger ISPs are that they rarely offer
the level of personalized service available from smaller providers, and they
may have so many customers that a small business's employees could have trouble
gaining access during prime business hours.
Small ISPs
Small, independent ISPs operate in many local or regional
markets. These companies vary widely in size, stability, and quality of
service. On the plus side, their access lines may be less busy than national
ISPs. In addition, many smaller providers specialize in offering services to
small businesses. Some of these ISPs may visit a small business customer's work
site, evaluate the company's Internet access needs, and present different
service packages. They may even assign a personal account representative to
handle the small business's growing electronic needs.
FINDING AN ISP
The first step in selecting an Internet Service Provider for
your small business is to compile a list of potential vendors. According to
Vince Emery in How to Grow Your Business on the Internet, looking in the local
telephone directory is not the best place to start. ISPs are typically
classified under a variety of confusing headings in the yellow pages. In
addition, making a random selection based on a advertisement is no way to
guarantee good service.
Instead, Emery recommends beginning your search for an ISP
on the Internet. There are several sites that list ISPs by geographic region
and also include pricing and contact information. The oldest and best-known of
these sites is The List (www.thelist.com), a searchable site with information
on 8,300 providers worldwide. Another possible source of information is an
organization named "The Directory" (www.thedirectory.org), which
lists 13,000 ISPs. Yahoo! and other search engines also yield a great deal of
information about service providers. Those without access to the Internet can
obtain a printed guide to ISPs from Light Reading (www.lightreading.com).
Small business owners might also benefit from calling
business associates, professional organizations, chambers of commerce, and
local computer users groups to obtain suggestions and references for potential
ISPs. Another option is to hire a consultant to help you evaluate your
business's Internet access needs, sort through the various options, deal with
the telephone company and ISP candidates, and avoid unnecessary costs or
services. In any case, Emery recommends obtaining at least three quotes,
encompassing both price and services provided, before selecting an ISP for your
small business.
CONSIDERATIONS IN CHOOSING AN ISP
In choosing among the various ISP options, the most
important thing to consider is the needs of the business. How much work will be
done online and how dependent will the business's communications be on e-mail
and other online services? The answer to these questions will determine the
range of bandwidth needed—a simple dial-up connection or a broad band
connection capable of providing a number of people with high-speed connections
simultaneously. By determining the bandwidth or speed requirements for the
Internet connection one may help to limit the number of ISPs to consider.
The next step in choosing an ISP is eliminating those
providers that 1) cost too much, 2) do not offer the services you need, or 3)
cannot provide the right type of connection. One important factor for small
businesses to consider is the availability of technical support. According to
William Kilmer in Getting Your Business Wired, ISPs vary widely in the level of
support they offer to customers. Online services make it easy to set up an
Internet account, for example, but may not be able to provide the personal
assistance a small business owner needs. It may be helpful to check the hours
that customer support is offered by telephone, and also to inquire about the
average time it takes the ISP to respond to requests for assistance.
A Web site for the company is something that many firms hope
to establish while they get themselves connected to the Internet. Most ISPs are
able to provide assistance to users in setting up a web site, and many ISPs
provide space on their servers to host client Web sites. But Kilmer noted that
small businesses may need to work with national providers or local providers
that specialize in business services in order to establish a professional site
with its own domain name. Otherwise, the business may be limited as to the size
or usage of its site. Ideally, an ISP should be able to register a domain name,
offer web designers to help create the site, and provide statistics on the
number of people who access the site.
Another important factor to consider in choosing an ISP is
the provider's tier rating. ISPs are rated according to their proximity to the
backbone of the Internet, known as their point of presence (POP). Tier 1
providers—usually big companies like AT&T and Sprint—are linked directly to
the Internet. Tier 2 providers lease their connections from Tier 1 companies,
and so on down the line. The lower an ISP's tier rating, the further its
connections lie from the Internet and the slower its access is likely to be.
Kilmer recommends that small businesses work with ISPs rated Tier 3 or better.
Other technical considerations in choosing an ISP include
the speed and redundancy of its connections. Ideally, an ISP should maintain
several different connections to balance traffic and make sure that one is
always available in case another fails. Finally, small business owners may wish
to seek out an ISP that offers special packages for small businesses. For
example, some providers offer several dial-up accounts or mailboxes for a
reduced price. Others may offer special deals on registering a domain name and
hosting a company web site.
Network Access Technologies
Bandwidth - The
maximum amount of data that can pass from one point to another in a unit of
time. Bandwidth is defined as a range within a band of frequencies or
wavelengths. For digital devices, the bandwidth is usually expressed in bits
per second(bps) or bytes per second. For analog devices, the bandwidth is
expressed in cycles per second, or Hertz (Hz).
The bandwidth is particularly important for I/O devices. For
example, a fast disk drive can be hampered by a bus with a low bandwidth. This
is the main reason that new buses, such as AGP, have been developed for the PC
·
Bit, also known as a Shannon, is the basic unit
of information in computing and digital communications. A bit can have only one
of two values, and may therefore be physically implemented with a two-state
device. These values are most commonly represented as either a 0or1. The term
bit is a portmanteau of binary digit.
·
Bit rate is quantified using the bits per second
unit (symbol: "bit/s"), often in conjunction with an SI prefix such
as "kilo" (1 kbit/s = 1000 bit/s), "mega" (1 Mbit/s = 1000
kbit/s), "giga" (1 Gbit/s = 1000 Mbit/s) or "tera" (1
Tbit/s = 1000 Gbit/s). The non-standard abbreviation "bps" is often
used to replace the standard symbol "bit/s", so that, for example,
"1 Mbps" is used to mean one million bits per second.
·
Modem (modulator-demodulator) is a network
hardware device that modulates one or more carrier wave signals to encode
digital information for transmission and demodulates signals to decode the
transmitted information. The goal is to produce a signal that can be
transmitted easily and decoded to reproduce the original digital data. Modems
can be used with any means of transmitting analog signals, from light emitting
diodes to radio. A common type of modem is one that turns the digital data of a
computer into modulated electrical signal for transmission over telephone lines
and demodulated by another modem at the receiver side to recover the digital
data.
Broadband is a wide bandwidth data transmission with an
ability to simultaneously transport multiple signals and traffic types. The
medium can be coaxial cable, optical fiber, radio or twisted pair. Also a
high-speed Internet connection that is always connected
- Digital
subscriber line
- Internet cable
connection
- High speed
Internet cable connections
- Cable modem
- Telecommuting
- Broadband over
power line
Network Protocols
Protocols exist at several levels in a telecommunication
connection. For example, there are protocols for the data interchange at the
hardware device level and protocols for data interchange at the application
program level. In the standard model known as Open Systems Interconnection
(OSI), there are one or more protocols at each layer in the telecommunication
exchange that both ends of the exchange must recognize and observe. Protocols
are often described in an industry or international standard.
Transmission control protocol/Internet protocol (TCP/IP) -
Provides the technical foundation for the public Internet as well as for large
numbers of private networks
Domain name system – Converts IP addresses into domains
- Packet
- Standard packet
format
- Packet header
- Packet footer
- Traceroute
- Proxy
A network protocol defines rules and conventions for communication between network devices. Protocols for computer networking all generally use packet switching techniques to send and receive messages in the form of packets.Network protocols include mechanisms for devices to identify and make connections with each other, as well as formatting rules that specify how data is packaged into messages sent and received.
Example of TCP/IP
Defining TCP
As indicated
in the name, there are two layers to TCP/IP. The top layer, TCP, is responsible
for taking large amounts of data, compiling it into packets and sending them on
their way to be received by a fellow TCP layer, which turns the packets into
useful information/data.
Defining IP
The bottom
layer, IP, is the locational aspect of the pair allowing the packets of
information to be sent and received to the correct location. If you think about
IP in terms of a map, the IP layer serves as the packet GPS to find the correct
destination. Much like a car driving on a highway, each packet passes through a
gateway computer (signs on the road), which serve to forward the packets to the
right destination.
The Internet works by using a protocol called TCP/IP, or Transmission Control Protocol/Internet Protocol. TCP/IP is the underlying communication language of the Internet. In base terms, TCP/IP allows one computer to talk to another computer via the Internet through compiling packets of data and sending them to right location.
Internet Domains Domain
names are used in various networking contexts and application-specific naming
and addressing purposes. In general, a domain name represents an Internet
Protocol (IP) resource, such as a personal computer used to access
the Internet, a server computer hosting a web site,
or the web site itself or any other service communicated via the Internet. For
example, the domain name microsoft.com represents
about a dozen IP addresses.
Every domain name has a suffix that indicates which top level domain (TLD) it
belongs to. There are only a limited number of such domains. For example:
Network
Convergence
Network convergence is the efficient coexistence of
telephone, video and data communication within a single network. The use of
multiple communication modes in a single network offers convenience and
flexibility not possible with separate infrastructures. Network convergence is
also called media convergence.
- Unified
communication (UC)
The integration of communication channels
or tools into a single service that help people exchange ideas and do their
jobs more effectively.
Some communication tools, like IP telephony, presence technology and instant messaging, facilitate synchronous communication. Synchronous communication occurs in real-time and is sometimes referred to as "same time/different place" communication. Other communication tools, like email or Twitter, facilitate asynchronous communication.
Some communication tools, like IP telephony, presence technology and instant messaging, facilitate synchronous communication. Synchronous communication occurs in real-time and is sometimes referred to as "same time/different place" communication. Other communication tools, like email or Twitter, facilitate asynchronous communication.
§ Peer-to-peer (P2P)
In a P2P network, the
"peers" are computer systems which are connected to each other via
the Internet. Files can be shared directly between systems on the network
without the need of a central server. In other words, each computer on a P2P network
becomes a file server
as well as a client
Network Convergence :
- Voice over IP (VoIP)
- Network
that Uses IP technology to transmit telephone calls
- Internet Protocol TV (IPTV) - Distributes digital video content using
IP across the Internet and private IP networks
Numerous
vendors offer VoIP services; however, the service works differently depending
on the vendor’s IT infrastructure. The start-up Skype pairs P2P (peer-to-peer)
technology with a PC’s sound card to create a voice service, which the user can
use to call other Skype users, Vonage lets the user place calls to any person
who has a mobile or landline (regular telephone) number. Vonage sends the call
over a cable via a digital-to-analog converter
BENEFITS
OF A CONNECTED WORLD :
Before
networks, transferring data between computers was time-consuming and
labor-intensive.People had to physically copy data from machine to machine
using a disk. Networks offer many advantages for a business including:
•Sharing resources
•Providing opportunities
•Reducing travel
- Sharing resources , Shared resources, also known as network resources, refer to computer
data, information, or hardware devices that can be easily accessed from a
remote computer through a local area network (LAN) or enterprise intranet.
Successful shared resource access allows users to operate as if the shared
resource were on their own computer. The most frequently used shared network
environment objects are files, data, multimedia and hardware resources like
printers, fax machines and scanners.
- Providing opportunities, Many
people become easier to find a new job and increase the opportunities for the
business itself.
- Reducing
Travel, Network nowadays become much easier and can communicate with other
business people around the world with internet so they reduce to travel to
communicate with their business partner.
Sharing
Resources
- The
primary resources for sharing include :
§ Intranet - a computer network with restricted access, as
within a company, that uses software and protocols developed for the Internet.
§ Extranet - An extranet is a private network that uses Internet
technology and the public telecommunication system to securely share part of a
business's information or operations with suppliers, vendors, partners,
customers, or other businesses. An extranet can be viewed as part of a
company's intranet that is extended to
users outside the company. It has also been described as a "state of
mind" in which the Internet is perceived as a way to do business with
other companies as well as to sell products to customers.
§ Virtual private network - A virtual private network (VPN) is
a technology that creates an encrypted connection over a less secure network.
The benefit of using a VPN is that it ensures the appropriate level of security
to the connected systems when the underlying network infrastructure alone
cannot provide it. The justification for using a VPN instead of a private
network usually boils down to cost and feasibility: It is either not feasible
to have a private network (e.g., for a traveling sales rep) or it is too costly
to do so. The most common types of VPNs are remote-access VPNs and site-to-site
VPNs
Networking enables humans to
connect globally without having to meet face view and save time and costs
without the need for distance.
·
networks enable us to communicate
over long distances.
·
network provides many advantages
but it can negatively impact also for Internet users.
SSL Certificates are small data
files that digitally bind a cryptographic key to an organization’s details.
When installed on a web server, it activates the padlock and the https protocol
(over port 443) and allows secure connections from a web server to a browser.
Typically, SSL is used to secure credit card transactions, data transfer and
logins, and more recently is becoming the norm when securing browsing of social
media sites. SSL Certificates bind together:
• A
domain name, server name or hostname.
• An
organizational identity (i.e. company name) and location.
An organization needs to install
the SSL Certificate onto its web server to initiate secure sessions with
browsers. Depending on the type of SSL Certificate applied for, the organization
will need to go through differing levels of vetting. Once installed, it is
possible to connect to the website over https://www.domain.com, as this tells
the server to establish a secure connection with the browser. Once a secure
connection is established, all web traffic between the web server and the web
browser will be secure.
The term Digital divide describes a
gap in terms of access to and usage of information and communication
technology, including the skills to make use of those technology within a
geographic area, society or community. It was traditionally considered to be a
question of having or not having access, but with a global mobile phone
penetration of over 95%,it is becoming a relative inequality between those who
have more and those who have less
