Wireless Topologies / Internet and Networking

Wireless Topologies :- 
A wireless topology is one in which few cables are used to connect systems. The network is made up of transmitters that broadcast the packets using frequencies
A star - bus hybrid topology 

       The network contains special transmitters called calls,  or wireless access points,  which extend a radio sphere in the shape of a bubble around the transmitter.  This bubble can extend to multiple rooms and possibly floors in a building.  The PCs and network device have a special transmitter-receiver, which allows them to receive broadcasts and transmit requested data back to the access point.  The access point is connected to the physical network by a cable,  which allows it,  and any wireless clients,  to communicate with systems on the wired network.  A wireless network topology 

Wireless topologies that the wireless cells,  or access points,  are connected to the network by connecting into the hub or switch that has a connection to the rest of the wired network.  Also notice that the clients,  and they will get access to the network through the wireless cells (or access point). 

Another option for wireless networks is the use of a radio antenna on or near the building,  which allows one cell to cover the building and the surrounding area.  This approach is best in a campus-type arrangement, where many building that need to be included in the cell are in a clos3 geographical area.  This setup does not easily 

Hybrid Topologies / Internet and Networking

Hybrid Topologies :- 
It is important to note it is typical for networks to implement a mixture of topologies to from a hybrid topology.  For example,  a very popular hybrid topology is a star-bus topology,  in which a number of Star topologies are connected by a central bus, as shown in Figure 1-10. This is a popular topology because the bus will connect hubs that are spread over distance.
              Another very popular hybrid topology is the star-ring topology.  The star-rung topology is popular because it looks like a star but acts as a ring.  For example,  there is network architecture known as Token Ring (more on this later,  in the section "Network Architectures") that uses a central "hub" type device,  but the internal wiring makes a ring.  Physically it looks like a star,  but logically it acts as a ring topology. 

Disadvantages of a Ring Topology / Internet and Networking

Disadvantages of a Ring Topology :-
The biggest problem with ring topologies is that if one computer fails or the cable link is broken,  the entire network could go down.  With newer technology,  however,  this isn't always the case.  The concept of a ring topology today is that the ring will not be broken when a system is disconnected; only that system is dropped from the ring.  Isolating a problem can be difficult in some ring configurations. (With newer technologies,  a workstation or server will put out a beacon if it notices a break in the ring.) Another disconnection can interrupt or bring down the entire network. 

Advantages of a Ring Topology / Internet and Networking

Advantages of a Ring Topology :- 
A major advantage of a ring topology is that signal degeneration is low because each workstation is responsible for regenerating or boosting the signal.  With the other topologies,  as a result travel the wire,  it gets weaker and weaker as a result of outside interference: eventually,  it becomes unreadable if the destination system is too far away.  Because each workstation in a ring topology regenerates the signal,  the signal is stronger when it reaches it's destination and seldom needs to be transmitted. 

Ring Topologies / Internet and Networking

Ring Topologies :-
In a ring topology,  all computers are connected via a cable that loops in a ring or circle. As shown in Figure 1-9,  a ring topology is a circle that has no start and no end. Because there are no ends,  terminators are not necessary in a ring topology.  Signals travel in one direction on a ring while they are passed from one computer to the next,  with each computer regenerating the signal so that itay travel the distance required. 

Disadvantages of a Mesh topology / Internet and Networking

Disadvantages of a Mesh topology :-
A disadvantage of a mesh topology is the cost of the additional cabling and network interface to create the multiple pathways between each system.  A mesh topology is very hard to administer and manage because of the numerous connections.

Advantages of a Mesh Topology / Internet and Networking

Advantages of a Mesh Topology :-
The biggest advantage of a mesh topology is fault tolerance,  meaning that,  if there is a break in a cable segment,  traffic can be rerouted through a different pathway because there are multiple pathways to send data from one system to another.  This fault tolerance means that it is almost impossible for the network to go down due to cable fault. 

Mesh topologies / Internet and Networking

Mesh topologies :- 
A mesh topology is not very common in computer networking today,  but you must understand the concept for the exam. In a mesh topology,  every workstations has a connection to every other component of the network,  as illustrated in Figure :-
Computers in a mesh topology are all connected to every other computer on the network. 

Disadvantages of Star Topology / Internet and Networking

Disadvantages of Star Topologies :-
On the flip side,  if the hub fails in a star topology,  the entire network comes down, so we still have central point of failure.  But this is a much easier problem to troubleshoot than trying to find a cable break with a bus topology.  Another disadvantage of a star topology is cost.  To connect each workstation to the network,  you will need to ensure that there is a hub with an available ports,  and you will need to ensure you have a cable to go from the workstation to the hub.
Today,  the cost is increasingly less of a disadvantage because of the low prices of devices such as hubs and switches. 

Advantages of a Star Topology / Internet and Networking

Advantages of a Star Topology :- 
One advantage of a star topology is availability and ease of adding another system to the network.  If you need to add another workstation to the network with a star topology,  you simply connect that system to an unused port on the hub.  Another benefit is the fact that if there is a break in the cable it affects only the system that is connected can make an administrator's life much easier in the long run.  Centralized management and monitoring of network traffic can be vital to network success. 
With a star configuration,  it is also easy to add or charge configurations because all of the connections come to a central point.

Computers connected in a star topology are all connected to a central hub or switch. 

A five-port  hub with four available ports 

Star Topologies / Internet and Networking

Star Topologies :-
In a star topology,  all computers are connected through one central device known as a hub or a switch,  as illustrated in Figure 1-6. Each workstation has a cable that goes from the network card to the hub device.  One of the major benefits of a star topology is that a break in the cable causes only the workstation that is connected to the cable to go down,  not the entire network,  as with a bus topology. Star topologies are very popular topologies in today's networking environments.

Disadvantages of a Bus Topology / Internet and Networking

Disadvantages of a Bus Topology :-
The main disadvantage of a bus topology is the difficulty of troubleshooting it.  When the network goes down,  it is usually due to a break in the cable segment.  With a large network,  this problem can be tough to isolate.  Availability is an important consideration in the dynamic world of networking.  Being able to make changes easily within the size and layout of your network can be important in future productivity or downtime.  The bus topology is not very scalable. 

A break in the cable with the bus topology causes the entire network to fail / Internet and Networking

A break in the cable with bus topology causes the entire network to fail 
A bus is a passive topology,  which means that the workstation on the bus are not responsible for regenerating the signal as it passes by them.  Since the workstation do not play an active role,  the workstations are not a requirement of a functioning bus,  which means that if a workstations fails the bus does not fail.  But if there is an un-terminated end in the bus,  the entire network will fail.
Advantages of a Bus Topology :-
One advantage of a bus topology is cost.  A bus topology uses less cable than a star topology or a mesh topology,  and you do not need to purchase any additional devices such as hubs.  Another advantages of a bus topology is the ease of installation.  With a bus topology,  you simply connect the workstation to the cable segment or backbone.  You need only the amount of cable to connect the workstation to the backbone.  The most economical choice for a network topology is a bus topology,  because it is easy to work with and a minimal amount of additional devices as required.  Most importantly if a computer fails,  the network stays functional. 

Bus topologies / Internet and Networking

Bus topologies :- 
A bus topology uses one cable as a main trunk to connect all of the systems together . A bus topology is very easy to set up and requires on additional hardware such as a hub.  The cable is also called a trunk, a backbone,  or a segment.

With a bus topology,  when a computer sends out a signal travels the cable length in both directions from the sending computer.  When the signal reaches the end of the cable length bounces back and returns in the direction it came from.  This is known as signal bounce Signal bounce is a problem,  because if another signal is sent on the cable length at the signal time,  two signals will collide and be destroyed and then must be transmitted.  For this reason,  at each end of the cable there is a terminator.  The terminator is designed to absorb the signal when the signal reaches the end,  preventing signal bounce.  If there is no termination. The entire network fails because of signal bounce,  which also means that if there is ever a break in the cable,  you will have u terminated ends and the entire network will go down,  With a bus topology , all system,  are connected to one linear cable.

Identifying Network Topologies / Internet and Networking

Identifying Network Technologies :-
This section will introduce you to a number of different network topologies,  but this topic is a lead-in to a bigger topic introduced later in the chapter: network architectures.  A network architectures is made up of a Topology , a cable type,  and an access method.  Before we can discuss network architectures,  we need to specify what the different types of topologies,  cables,  and access methods are.

A network topology is the physical layout of computers,  cable, and other components on a network.  There are a number of different network topologies,  and a network may be using multiple topologies.  This different types of network layouts are.

•  Bus topology 
•  Star topology 
•  Mesh topology 
•  Ring topology 
•  Hybrid topology 
•  Wireless topology 

Internet, Intranet, and Extranet / Internet and Networking

Internet,  Intranet,and Extranet :-
Internet, intranet, and Extranet are three terms that describe "Internet-type" applications that are used by an organization,  but how do you know if web application is part of your intranet or part of the internet?

Internet :- If you wish to expose information to everyone in the world,  then you world build an internet-type application.  An internet -type application used internet protocols such as HTTP, FTP, or SMTP and is available to person's anywhere on the internet.  We use the internet and web application as ways to extend who the application can reach.  For example,  I no longer need to go to the bank to transfer funds.  Because the bank has built a web site on the internet,  I can do that from the comfort of my own home.

Intranet:- An applica7is considered to be on the company's intranet if is using Internet -type protocols such as HTTP or FTP but the application is available only within the company.  The information on a company's intranet would not be accessible to person's on the internet because it is not for public use.  For example,  adequate years ago I was sitting with my banking officer going over my account and noticed that the bank had moved all of its customer
Account information to a web site and that banking officer was using a web browser to retrieve my account details.  Although the application was being used by a wave browser,  it was still an "internal" application meant only for banking officers.

Extranet :-From time to time,  an application that has been built for the company's internet and used by internal employee's will need to be extended to select business partners or customers.  If you extend your intranet out to select business partners or customers,  you have created an Extranet.  An Extranet cannot be used by anyone else external to the company except for those selected individuals.  Figure 1-3 displays the basic configurations of internet,  intranet,  and Extranet.
This section has introduction you to some terms such as per-to-peer versus server-based networking , internet,  intranet,  and Extranet;  now let's look at how the network is out with the different network topologies!

Identifying Characteristics of a network / Internet and Networking

Identifying Characteristics of network :- More and more people are building home and small office networks now as a result of the low cost of networking devices such as hubs and home routers.  As a Network+ Certified Professional,  you will need to ensure that you can support these small,  medium,  and large networks , so you will start by learning some basic terms.
          A network is group of systems that are connected to allow sharing of resources-such as files or printers-or sharing of services - such as an internet connection.  There are two aspects of setting up a network : the hardware used to connect the systems together and the software installed on the computer to allow them to communicate.  This chapter is designed to give you an understanding of the hardware used to build a network,  and later chapters discuss the software needed.  The network hardware is made up of basic components: the entities that want to share the information or resources,  such as servers and workstation,  and the medium that enables the entities to communicate,  which is a cable or a wireless medium.
Internet,  Intranet,and Extranet :-
Internet, intranet, and Extranet are three terms that describe "Internet-type" applications that are used by an organization,  but how do you know if web application is part of your intranet or part of the internet? 

Type of account TCP/IP or sheli / Internet and Networking

Type of account TCP/IP or shell 
Username or login name :- This is the name by which you login to the internet.  You have to suggest this name while applying for connection.
Password :- This is necessary for accessing the internet.  Usually you are required to suggest this password while applying for the connection.  If no one else on the internet has this password this will assign to you.  Else,  the system administrator of the ISP will assign a suitable password to you at the time of granting of connection,  with an advice to change this password.  It is essential to keep changing password frequently.
E-mail address :- Since most ISPs support e-mail services,  you will also be ass8gned an e-mail address. The network provides the convenient system for users to send a message to each other; this use of a network is known as Electronic Mail (E-mail).  To avail of E-mail facility a user has to become a subscriber of an agency providing Email services. In E-mail system,  each user (subscriber)  is allotted an E-mail number and a mail box. A mail box is a memory which can store message and data.  Consider an example where two users have E-mail facility and wants to communicate with each other.  When the first user wants to send the message to other users,  he will send it on the E-mail number of the second user.  The message will be stored on his computer; he can issue appropriate command to read the message from the mail box.  Note that the message can be transmitted from one user to the other users in his absence.
           Thus the E-mail offers the speed and convenience of a phone call with out the frustration of telephone tag and with the option of communicating simultaneously with a number of person.  The message be of short size,  a single line or a copy of pages or a several hundred-page document.  The E-mail is becoming very popular this day.  E-mail services are cheaper and fast as compared to courier,  STD,  FAX or Telex.
               There are many E-mail service providers operating in India.  Some of them are provider by India. Government and other are provided by private sectors.  The commercial providers are clubbing other services along with E-mail.  The other services like stock market and hotel reservation are provided by the private network.  The Bucket is a satellite based communication network.  It is the biggest network under the control of the headquarters of National Informatics Center (NIC),  New Delhi. The E-mail facility is available to government agencies and members of the NIC family.
              Format of an E-mail message Like a formal letter e-mail also is divided into various sections.  In a good business letter,  you would have the name and address of the person to whom the letter is addressed,  salutation,  textatter, sender's name etc. Most of these you would find here too but with some difference.
Headers :- It is very important that your header must be loud and clear for it can be seen and read from a distance too.
To :- The To: field contains the e-mail address of the person to whom you are sending the e-mail. If you are sending e-mail to someone in your own domain,  you do not need to include @ domain.
From :- In most of the cases,  you would not be typing this,  since it would be taken from the system.  It in fact included your e-mail address.
Subject :- The Subject : field should contain a very short description (20-30 characters)  of what your message is about.  This field can also be called Subject of the Message : or simply message. Bit is not compulsory to have a subject.
Cc :- You can send the copy of the same e-mail to another person.  For this you have to mention the e-mail address of the second receipt.  The software would take care that the same message is sent to the second recipient too.
Bcc :- It is the short from of Blind Carbon Copy,  which gives you a way of copying along with this e-mail . In most of the cases while applying for a job,  the latter is typed in the e-mail text and the bio data which is mostly in some word processing mode,  attached to it. 
Data :- Data and time are usually taken from the system.  You need not type it.
I address :- Every connected computer to the internet will be assigned unique number called it's IP address.  This is actually a 33bit number,  but is more commonly represented as four numbers joined by dots,  like 202.54.1.18

Using a direct connection to an ISP / Internet and Networking

Using a direct connection to an ISP:-
                This uses a cable or a dedicated phone line to connect directly to your ISP.  An example of this mode is the widely used ISDN (integrated service digital network)  line,  which is a higher speed version of the slandered phone line and can handle upwards of 56.6 kbps.  The difference is mainly in speed and cost.
              Dial up connection is the more popular and conventional mode of connecting to your ISP.  At present VSNL is the predominant ISP in India, though many other ISPs are gaining recognition.  VSNL provides this service through its 'Gateway internet Access Service' (GIAS)  Two types of accounts are at present offered by VSNL shell account and TCP/IP account.
              The shell account is cheaper but it is restricted to text based internet access only.  That means,  you will not be able to see pictures,  graphics,  images etc.  This account is good for e-mail services and for beginners to get initiated into internet.  Access to the net is faster in shell account. The TCP/IP account is more expensive but allows you to access text,  graphics,  images,  video,  etc. That is available a plenty on internet. Access is slower as compared to shell account.
When you register with an internet services provider,  you will be given an internet account,  which consist of following informatio's

Using a dial up account / Internet and Networking

Using a dial account and :-
             In this mode of connection,  you use a modem and telephone line to connect to your ISP.  You can log on the internet by dialing your local ISP,  either by way of serial line internet protocol SLIP or point to print protocol (ppp), VSNL provides direct access by way of ppp. 

Internet service / Internet and Networking

Internet services:-
               Internet is used by millions of people throughout the world for various purpose such as communication,  business transaction,  education,  and referencing,  downloading shareware and freeware software.  Recreation and so on. Internet provides all these services and more at your convenience and at negligible cost.  Some of popular services provided by internet are :E-mail which allows you to send and receive massages commerce which allows you to visit virtual shops on the net and make purchase,  chat which let's you talk :live with your friends and relatives,  down loading popular software,  games and music take part in newspaper groups,  search for information of any kind and so on.  To avail an internet services,  you must have an internet Service provider connection.  There are two ways you can connect to your internet service provider. 

Browser / Internet and Networking

Browser:-
                 A browser is software which allows you get connected to the internet and browser it's contents . Browsers act as interface between you and internet.  When you ask for same information,  the browser sends the quarters the web server and on receipt of the same displays it on the screen.  A browser can either be text oriented or have a graphical interface,  the latter being more popular.  The most commonly used browser are the Microsoft INTRNET Explorer and Netscape Navigator. 

Internet service provider / Internet and Networking

Internet service provider 
               While the internet facility is free for all,  you just cannot avail of it directly.  You have to register with ISP,  an acronym for internet service provider's is an agency or an organization,  which provide the user an access to the internet.  In India,  VSNL (Codes sanchar Morgan limited)  is the prominent ISP,  while non government organization like Satan and others have started to make there presence felt in this expending field. 

What you require for internet connection / Internet and Networking

What you require for internet connection 
You require following to have internet connection.
Computer :- Minimum requirements for connecting to internet is a 486dx IIPC with 8MB RAM.  However,  a Pentium  with 32MB of RAM  would be ideal.  An Operating system (windows,  UNIX,  Macintosh)  are essentials.
Telephone connection:- A telephone connection is essential to get connected to the Internet.  When you are connected to the Internet,  your phone will be engaged and you will not able to place or receive a cell fro outside on that telephone.
Modem :- already discuss 

What is internet connection / Internet and Networking

What is internet connection 
               Computers are interconnected using many kinds of electronic transport media,  including optical fiber,  telephone lines,  satellite systems and local area networks.  Practically any kind of computer or operating system can be connected to internet. The communication with internet is usually implemented using international standards collectively called TCP\IP protocol.  The protocols are implemented in software running on the connected computer.  Most computers connected on the internet are called hosts.  Computers that route data to other computers are called router.  Networks and computers that are part of global internet possess unique registered addresses and obtain access from internet service provider.
There are four ways to connect to the public internet by host,  network,  and terminal or gateway access.  Host access is usually with done either with local area network or with the use of telephone lines and modems combined with internet software on a personal computer.  Host access allows the attached computer to fully interact with any other attached computer.  Limited only by bandwidth of the connection and the capability of the computer.  Network access is similar to host access , but it is usually done via a leased telephone line that connects to a local or wide area network.  All the attached computers can become internet hosts. The terminal access is usually done via telephone lines and modems combined with terminal emulation software on a personal computer.  It allows interaction with another computer that is an internet hosts.  Gateway access is similar to terminal access but is provided via on line or similar proprietary service, or other network such as Bitnet, Fidonets. Etc 

What can you do with Internet / Internet and Networking

What can you do with internet
The users of internet are a varied lot ranging from researchers to ten year old looking for entertainment.
Following is little significant service

• Using internet a business organization can wattch it's computer more closely. 
• New customers can be found and existing customers can be better supported .
• Many online shopping malls exists on the internet,  where one can place order something by pressing just a few keys and some mouse clicking 
• For individuals,  the internet is a great way to keep with friends or relatives around the world. 
• It can be used to keep up to data on any hobby or topic of interest. 
• As an educational resources,  the internet is virtually limitless.  It can also be used as an entertainment media. 
• You can send articles to newspapers for acceptance,  interact with the editors and other concerned people. 
• You can put up your own website for advertisement. 

WiFi (Wireless Fidelity) / Internet and Networking

WiFi (Wireless Fidelity) :
WiFi is the Nena of a popular wireless networking technology that uses radio waves to provide wireless high-speed internet and network connection. A common misconception is that the term Wi-Fi is short for "wireless fidelity, " however this is not the case.
          Wi-Fi works with no physical wired connection between sender and receiver by using radio frequency (RF)  technology,  a frequency within the electro-magnetic spectrum associated with radio wave propagation.  When an RF current is supplied to an antenna an electro-magnetic field is created that then is able to propagate through space.  The cornerstone of any wireless network is an access point (AP). The primary job of an access point is to broadcast a wireless signal that computers can detect and "tune" into.  In order to connect to an access point and join a wireless network,  computers and devices must be equipped with wireless network adapters. 

Dial -up Internet Access / Internet and Networking

Dial -up Internet Access 
Dial -up Internet access is a from of internet access that uses the facilities of the public switched telephone network (PSTW)  to establish a diaper connection to an internet Service provider (ISP)  via telephone lines.  The user's computer or router uses an attached modem to audio frequency signals,  respectively. 

Internet Service Provider (ISP) / Internet And Networking

Internet Service Provider (ISP) 
                An internet Service Provider (ISP) is a company that provides a telecommunications connection to the internet that allows a user to "be online". The connection may be provided in many different forms.  It could use existing telephone lines,  existing cable TV lines,  new fiber optic cable may be strung or the user has to use a modem and dial a phone number.  Examples of ISPs are : Wali known As: internet Service Provider,  ISP,  internet Access Provider or IAP

Examples of ISP 
Broadband :
               The term broadband refers to the wide bandwidth characteristics of  a transmission medium and it's ability to transport multiple signals and traffic simultaneously.  The medium can be coax,  optical fiber,  twisted pair or wireless.  In contrast,  base and,  describes a communication system in which information is transported across a single channel

Advantage of Broadband: 

• Unlimited Internet access for fixed amount. 
• Enjoy speeds of upto 100 Mbps *.
• With Always-On internet access you can run anything from mall servers to FTP sites. 
• Mobile High Speed internet Device Band width-on-Demanf (BoD) allows you to temporarily upgrade your bandwidth to a higher speed giving you the flexibility of pay "as you use". You can scale up the speed of your connection as per your requirement. 
• Do more,  with Fiber-to-home (FTTHX the Next Generation Network technology where a single fiber can give you Voice,  Video Data,  Cable  TV,CCTV, DTH,  internet etc carried across to you over optical fibers instead of copper cables. 

Default gateway / Internet and Networking

Default gateway 
               In computer networking, a gatwaybis a made (a router)  on a TCP/IP network that server as an access point to another.  A default gateway is the node on the computer network that the network software user when an IP Addre'ss does not match any other routes in the routing table. 
In home computing configurations, an ISP often provides a physical device which both connects cable modems.
In other words,  a default gateway provides an entry point and an exit point in a network 

Firewall(computing) /Internet and Networking

Firewall (computing)
                A firewall can either be software - based or hardware -based and is used to help keep a network secure ItI primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not,  based on a predetermined rule set.  A network's builds a bridge between the internal network or computer ft protects,  upon security that the other network secure and trusted,  usually an external (inter)  network, such as the internet,  that is not assumed to be secure and trusted.
Many personal computer operating systems include software-based firewall to protect against threats the public internet, Many routers that pass data between networks contain firewall components and,  converse many firewalls can perform basic routing functions. 

Search Engine/ Internet and Networking

Search Engine :
Search engines are programs that search documents for specified keywords and returns a list of the documents where the keywords were found.  A search engine is really a general class of programs; however,  the term is often used to specifically describe systems like Google,  Bing and Yahoo!  Search that enable users to search for documents on the World Wide Web.

• Google (http://www.google.com)
• Bing (http://www.bing.com)
• Wikipedia (http://www.wikipedia.org)
• yahoo (http:/www.yahoo.com)
• search.com (http://search.com)
• Easy Searcher (http://www.easyseareher.com)
• Ask (http://www-ask. com) 
• Webopedia (http://www.webopedia.com)

MAN (metropolitan Area Network / Internet and Networking

MAN (Metropolitan Area Network) 
                 A MAN is optimized for a large geographical area than a LAN,  ranging from several blocks of building to entire cities,  MANs can also depend on communications channels of moderate-to-high data rates.  A MAN might be owned and operated by a single organization,  but it usually will be used by many individuals and organizations, MANs might also be owned and operated as public utilities.  They will often provide for internet working of local networks.
                A Metropolitan Area Network (MAN) is a large computer network that spams a metropolitan area or campus.  It's geographic scope falls between a WAN and MANs provide internet connectivity for LANs in a metropolitan region,  and connect them to wider area networks like the internet.

Wide Area Network / Internet and Networking

Wide Area Network :
               WAN - Wid3 Network - usually a large network of interconnected computers and devices.  WANs typically span a large enterprise that has systems that communication with each other throughout several offices located in numerous cities and/or countries.

Local Area Network (LAN) / Internet and Networking

Local Area Network (LAN) :-
               A  Local Area network (LAN)  is a network that is confined to a relatively small area.  It is generally limited to a geographic area such as a writing lab,  school or building.  Rarely are LAN computers more than mile apart.
           In a typical LAN configuration,  one computer is designated as file server.  It stores all of the software that can be shared by the computers connected to the file server are called workstations.  The workstations can be less powerful than the fife server,  and they may have additional software on their hard drives.  On most LANs cables are used to connect the network interface cards in each computer . Following Figure indicates the LAN Networks

Directory servers / Internet and Networking

Directory servers :-hold a list of the user accounts that are allowed to log on to the network.  This list of users accounts is stored in a database (known as the directory database)  and can store information about these user accounts such as address,  city,  phone number,  and fax number.  A directory service is designed to be a central database that can be used to store everything about such objects as users and printers.
          In a server-based network environment,  the centralized administration comes from the fact that the directory server stores all user accounts on its directory database.  When a user sits at a client machine to log on to the network, the login request is sent to directory server.  If the username and password exist in the directory database,  the client is allowed to access network resources. It is important to Korea that a server can have numerous roles at the same time.  A server can be a file and print server,  as well as an application server,  or it can be a file,  print,  and directory server all at the same time.  Because a single server can perform multiple roles,  a company will not need to purchase an additional server every time a very time a new product (or feature)  is implemented on the network,  and this fact reduces the cost of a server-basee network. 

Web server / Internet and Networking

Web servers :- are server that run the Hypertext Transfer Protocol (HTTP)  and designed to publish information on the Internet or the corporate intranet.  Web server are popular in today's businesses because they host web applications (web sites)  for the organization.  These web applications could be designed for internal use,  or they could be used to publish information to the rest of the world on the internet.
Example of web server software are Microsoft's Internet Information Service that runs on Windows of Apache web server software that runs on UNIX/Linux , Novella NetWare,  and windows.

Application servers / Internet and Networking

Application servers :- are servers that run some from of special program on the server.
A good example of an application server is a server that runs the company's E-mail server.  The e-mail server software is special software that can be run on a server operating system.  Another example of software that would run on an application server is a database server product such as Microsoft SQL server.  A database server is a server that holds the company's core business data and typically gives this data to custom applications that run on the workstations.  These are some applications that you might find on an application server.

• Microsoft SQL Server 
• Oracle 
• Microsoft Exchange Server 
• IBM lotus Domino 

What is c? / Computer programming

What is c? 

• C is the high level and structural programming language that all programming Dennis Ritchie in 1972 developed a UNIX at bell labs 
• Interaction and C consict of turn data very classy sent to Algebraic contraction sultans English key word such as if,  else,  dus while,  etc. 
• C contain sultans additional fichars that a lot is to use as level activities as a Ritchie it is machine language and high level language it a small inctraction see don't include extencial lyricist function with a mark basic inctraction C as no beam a vaidly use profectional language for very reason. 

1. Easy language 
2. Structured language 
3. It can also handle low level Activity 

File and print servers / Internet and Networking

File and print servers :- control and share printers and files among clients on the network.  File and print servers were the original reason to have a network; a large number of users needed access to the same files,  so the files were placed on a server,  and all clients were connected to the server when they needed to work with the files.  File server often have the following characteristics;

•  Large amounts of memory 
•  Fast hard disks 
•  Multiple CPUs 
•  Fast I/O buses 
•  High-capacity tape drive 
•  Fast network adapters
•  Redundant power supplies
•  Hot-swappable hard disks and power supplies 

File and print servers also check the access control list (ACL)  of each resource before allowing a user to access a file or use a printer.  If the user or a group to which the user belongs is not listed in the ACL,  the user is not allowed to use the resource,  and an "access denied" message appears on the user's screen. 

Wand, Lans, and Mans/ Internet and Networking

Wand,  Lans,  and Mans:-
              Some other terms that you will hear often are LAN,  WAN,  and MAN.  A local area network (LAN)  typically I'd confined to a single building,  such as on office building, your name network,  or a college campus. A wide area network (WAN)  spans multiple geographic location and is typically made up of multiple LANs. For example,  I have a company with an office in Halifax, Nova Scotia(that's a city in Canada next door to the penguins)  that has 100 computers all connected together.  This would be considered a LAN.  Now if we expand the company and create an office in Toronto,  the network in Toronto also would be considered a LAN.  If we want allow the two offices to share together,  creating a WAN.
         The term metropolitan area network (MAN)  is not used often anymore; it refers to a network that exists within a single city or metropolitan area.  If we had two different buildings within a city that were connected together,  it would be considered a MAN. 

Client - Server Relationship / Internet and Networking

Client - Server Relationship 

The two computers, the client and the server,  communication using Hypertext Transfer Protocol,  or HTTP,  a language both computers understand.  Protocols are rules which determine how computers act when talking to one another.  No matter what hardware you use (Apple,  Dell,  Toshiba,  HP,  etc.) the computers can communicate because they are speaking the same language. 

Types of networks :- 

                 Organizations of different sizes,  structures , and budgets need different types of networks.  A local newspaper company has needs for it's network that would be different from the needs of a multinational company.  Networks can be divided into one of two categories: peer-to-peer or server based networks.

Peer-to-Peer network :-

                A peer-to-peer network has no dedicated servers; instead information or devices.  When there is no dedicated server,  all workstations are considered equal; any one of them can participate as the client or the server.  Peer-to-peer networks are designed to satisfy the networking needs of home networks or of small companies needs of home networks or of small companies that do not want to spend a lot of money on a dedicated server but still want to have the capability to share information or devices.  For example,  a small accounting firm with there employees that needs to access customer data from any of the three systems or print to one printer from any of the three systems may not want to spend a lot of money on a dedicated server. A small peer-to-peer network will allow these three computer to share the printer and the customer information with one another (see Figure 1 -1).  The extra cost of a server was not incurred because the existing clients systems were networked together to create the peer-to-peer network.
The Microsoft term for a peer-to-peer network is a workgroup.  Be aware that peer-to-peer networks typically consist of fewer than 10 systems.
Most of the modern operating systems such as Windows XP and Windows Vista already have built- in peer-to-peer networked capabilities, which is why building a peer-to-peer network would be a "cheap" network solution.  The disadvantage of a peer-to-peer network is the lack of centralized administration with peer-to-peer networks , you need to build user accounts and configure security on each system.
Server-based Networks:-
                A big disadvantage of peer-to-peer networking is that you can't do your day-to-day administration in a single place.  With peer-to-peer networking,  user accounts typically are created on all the systems, and data files are stored throughout all the systems . This leads to a more complicated environment and makes you job harder as a network administrator . Usually after four or five systems have been networked , the user accounts and data files becomes apparent - this is a server - based networks
The advantage of a server - based network is that the data files that will be used by all of the user's are stored on the one server.  This will help you by giving you a central point to set up permissions on the data files,  and it will give you a central point from which to back up all of the day in case data loss should occur.  With a server - based networks,  the network server stores a list of users who many use network resources and usually holds the resources as well.
The server in a server - based network may provide a number of different services.
The services it will often to the network usually are decided by the server's role.
There are a number of different roles that a server could play on a network:

•  File and print servers 
•  Application servers
• Web server 
• Directory servers 

Ethernet network access strategy / Internet and Networking

Ethernet network access strategy 
               Ethernet provides access to the networking using carrier sense Multiple Access with Collision Detection (CSMA/CD).This strategy of network access basically means that the devices on the network listen to the network and wait until the line is clear; they "sense " when the line is clear and they can transmit data.  The computer then sends it's packets out onto the line. If there is more than one computer transmitting,  collisions result.  Sensing the collisions, the computer stop transmitting and wait until the line is free.  One of the computers will then transmit,  gaining control of the line and completing the transmission of the data.
            To receive data,  computers just sit and wait,  listening to the line.  When they sense that a particular transmission is meant for then,  they receive it on their network card.
The main advantage of Ethernet is that it is one of the cheapest network architectures to the hardware required for other architectures such as token ring.  A major disadvantage of Ethernet relates to collisions on the network.  The more collisions,  the slower the network will run,  and excessive collisions can ever bring down the network. 

Networking / Internet and Networking

Networking
               Networks consist of the computers, wiring,  and other devices, such as hubs,  switched and routers,  that make up the network infrastructure.  Some devices,  such as network interface cards,  serve as the computer connection to the network.  Devices such as switches and routers provide traffic-control strategies for the network All sorts of different technologies can actually be employed to make data from one place to another,  including wires, radio waves, and even microwave technology. 

Servers, Workstations, and Hosts/ Internet and networking

Servers,  Workstations, and Hosts:-
               A typical network outwork involves having users sit at workstations, running such applications as word processors or spreadsheet programs  . The workstation also is known as a client,  which is just a basic computer running a client operating system such as Windows XP or Linux.  These users typically store their files on a central server so that can share the files with other users on the network.  The server is a special computer that contains more disk space and memory than are found on client workstations.  The server has special software installed that allows it to function as a server.  This special software can provide file and print services (to allow sharing of files and printers), provide web pages to clients,  or provide e-mail functionality to the company .
The term host refers to any computer or device that is connected to a network and sends or receives information on that network.  A host can be a server,  a workstation,  a printer with its own network card,  or a device such as a router. We can summarize by saying that any system or device that is connected to the network is known as a host 

Database Server /INTERNET AND NETWORKING

Database Server 
              A database server is a computer program that provides database services to other computer programs or computer,  as defined by that may also refer to a computer dedicated to running such a program.  Database management systems frequently provide database server functionality,  and some DBMSs [e. g.,  MySQL] rely exclusively on the client-server for database access.

What is Network / Internet and Networking

What is Network 
               A network consists of two or more computer that are linked in order to share resources (such as printers and CDs), exchange files,  or allow electronic communications. The computers on a network may be linked through cables, telephone lines,  radio waves,  satellites , or infrared light beams.
Two very common types of networks include :

• Local Area Network (LAN) 
• Wide Area Network (WAN) 

You may also see references to a Metropolitan Area Networks (MAN), a Wireless LAN [WLANJ, or a wireless WAN (WWAN). 

Client Server / Internet and Networking

Client Server 
               The term client-server refers to a popular model for computer networking that utilizes client and server devices each designed for specific purposes . The client-server model can be used on the Internet as well as local area networks (lans). .
The model assigns one of two roles to the computers in a network; a client is a computer or computer program that initiates contact with a server in order to make of a resource.  Data,  cpus,  printers,  and data storage devices are some examples of resources.

Web Browsers / Internet and Networking

Web Browsers

              Web browser,  is a software application used to enable computers users to locate and access web pages. Browsers translates the basic HTML (hypertext Mark Up Language) code that allows us to see images, text videos and listen to audios on websites,  along with hyperlink that let us travel to different web pages.  The browser gets in contact with the web server and requests for information.  The web server receives the information and displays it on the computer. 

Here are some familiar common web browsers :

•  Mozilla FireFox 
• Netscape Navigator 
• Microsoft Internet Explorer 
• Opera 
• Google Chrome 

What is an IP Addre'ss / Internet and Networking

What is an IP Addre'ss 
               Every device connected to the public Internet is assigned a unique number known as an Internet Protocol HP) address.  IP addresses consist of four numbers separated by Paris (also called a'dotted-quad") and look something like 127.0.0.1
               There number are usually assigned to internet service providers within region-based blocks,  an IP Addre'ss can often be  used to identify the region or country from which a computer is connecting to the Internet.  An IP address can sometimes be used to show the user's general location.
The following command find the IP Address of your Computer

Introduction to the World Wide Web / INTRNET AND NETWORKING

> The Would Wide Web (also referred to as WWW or W3) is the fastest growing ares of the internet,  While gopher was an important step in allowing users to "browse" through the Internet's vast resources,  the World Wide Web has raised excitement about Internet to new heights.
> What makes the World Wide Web has raised appealing and innovative is it's use of hypertext as a way of linking documents to each other.  A highlighted word or phrase in one document acts as a pointer to another documents that amplifier or relates to the first documents.  When looking at a WWW documents,  the reader doesn't have to follow every pointer,  or link (also called a hypertext link) , only those that look interesting or useful.  In this way,  the user tailors the experience to suit his or her needs or interests.  The other very appealing aspect of the World Wide Web is the use of graphics and sound capabilities.
> Documents on the WWW include text,  but they may also include still images,  video,  and audio for a very exciting presentation. People who create WWW documents often include a photograph of themselves along with detailed professional information and personal interests.  (This is often called a person's home page.) 

Introduction to Gopher / INTERNET AND NETWORKING

> Gopher is a client/server system that allows you to access many Internet resources simply by making selection from a sequence of menus.  Each time you make 3 selections, Gopher carries out your request to the computer that contains the information and "serves" it up.  For example,  if you select a menu item that represents a text file,  Gopher will get that file-wherever it happens to be and display it for you.
>As you use Gopher,  some menu items lead to other menus.  If you choose one of these,  Gopher will retrieve the new menu and display it for you.  Thus you can move from menu to menu,  using only a few key strokes or a mouse to navigate.  The power of Gopher is that the resources listed in a menu may be anywhere on the Internet, 
> As Gopher connects to computers to comply with your menu selection,  you don't need to be preoccupied with the behind-the-scenes work of connecting to and disconnecting from these various computers.  Gopher does this for you without your even needing to be aware of it.  This automatic connecting makes Gopher popular and useful.