III Bcom Web Technology notes

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Q) Explain briefly about Network.
Generally, networks are distinguished based on their geographical span. A network can be as small as distance between your mobile phone and its Bluetooth headphone and as large as the internet itself, covering the whole geographical world,
A computer network consists of two or more computers that are interconnected with each other and share resources such as printers, servers, and hardware and exchange the data in the form of files, facilitating electronic communication. Computers on a network can be connected through twisted pair cables, telephone lines, radio waves, satellites or optical fiber cables. The first computer network designed was the ‘Advanced Research Projects Agency Network (ARPANET)’ by the United States Department of Defense. Since then, myriads of new computer networking technologies have been designed. 



Computer networks can be classified into different types based on their scale of operation. They include:
    • LAN: A local-area network (LAN) is a computer network that spans a relatively small area. Most often, a LAN is confined to a single room, building or group of buildings, however, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. Local Area Networks cover a small physical area, like a home, office, or a small group of buildings, such as a school or airport.
    • WAN: A computer network that spans a relatively large geographical area, generally having a radius of more than 1 km. . Typically, a WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites.
    • 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).
    • SAN: SAN (storage area network) is a high-speed network of storage devices that also connects those storage devices with servers. It provides block-level storage that can be accessed by the applications running on any networked servers. Storage Area Networks help attach remote computer storage devices, such as disk arrays, tape libraries, and optical jukeboxes, to servers in such a manner that that they appear to be locally attached to the operating system.
    • CAN: A Controller Area Network (CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer.
    • PAN: A personal area network (PAN) is a computer network used for data transmission amongst devices such as computers, telephones, tablets, personal digital assistants, fax machines and printers, that are located close to a single user.
    • GAN: A global area network (GAN) is a network used for supporting mobile across an arbitrary number of wireless LANs, satellite coverage areas, etc. 
       
Q) What is Network Topology? Explain its types.
Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.

BUS Topology

Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology

Features of Bus Topology


  1. It transmits data only in one direction.
  2. Every device is connected to a single cable

Advantages of Bus Topology

  1. It is cost effective.
  2. Cable required is least compared to other network topology.
  3. Used in small networks.
  4. It is easy to understand.
  5. Easy to expand joining two cables together.

Disadvantages of Bus Topology

  1. Cables fails then whole network fails.
  2. If network traffic is heavy or nodes are more the performance of the network decreases.
  3. Cable has a limited length.
  4. It is slower than the ring topology.

RING Topology

It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device

Features of Ring Topology


  1. A number of repeaters are used for Ring topology with large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network.
  2. The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology.
  3. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
  4. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.

Advantages of Ring Topology

  1. Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
  2. Cheap to install and expand

Disadvantages of Ring Topology

  1. Troubleshooting is difficult in ring topology.
  2. Adding or deleting the computers disturbs the network activity.
  3. Failure of one computer disturbs the whole network.

STAR Topology

In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.  


Features of Star Topology


  1. Every node has its own dedicated connection to the hub.
  2. Hub acts as a repeater for data flow.
  3. Can be used with twisted pair, Optical Fibre or coaxial cable.

Advantages of Star Topology

  1. Fast performance with few nodes and low network traffic.
  2. Hub can be upgraded easily.
  3. Easy to troubleshoot.
  4. Easy to setup and modify.
  5. Only that node is affected which has failed, rest of the nodes can work smoothly.

Disadvantages of Star Topology

  1. Cost of installation is high.
  2. Expensive to use.
  3. If the hub fails then the whole network is stopped because all the nodes depend on the hub.
  4. Performance is based on the hub that is it depends on its capacity

MESH Topology

It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.
There are two techniques to transmit data over the Mesh topology, they are :
  1. Routing
  2. Flooding

MESH Topology: Routing

In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance. Or, routing logic which has information about the broken links, and it avoids those node etc. We can even have routing logic, to re-configure the failed nodes.

MESH Topology: Flooding

In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required. The network is robust, and the its very unlikely to lose the data. But it leads to unwanted load over the network. 

Types of Mesh Topology


  1. Partial Mesh Topology : In this topology some of the systems are connected in the same fashion as mesh topology but some devices are only connected to two or three devices.
  2. Full Mesh Topology : Each and every nodes or devices are connected to each other.

Features of Mesh Topology

  1. Fully connected.
  2. Robust.
  3. Not flexible.

Advantages of Mesh Topology

  1. Each connection can carry its own data load.
  2. It is robust.
  3. Fault is diagnosed easily.
  4. Provides security and privacy.

Disadvantages of Mesh Topology

  1. Installation and configuration is difficult.
  2. Cabling cost is more.
  3. Bulk wiring is required.

TREE Topology

It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.
 


Features of Tree Topology

  1. Ideal if workstations are located in groups.
  2. Used in Wide Area Network.

Advantages of Tree Topology

  1. Extension of bus and star topologies.
  2. Expansion of nodes is possible and easy.
  3. Easily managed and maintained.
  4. Error detection is easily done.

Disadvantages of Tree Topology

  1. Heavily cabled.
  2. Costly.
  3. If more nodes are added maintenance is difficult.
  4. Central hub fails, network fails.

HYBRID Topology

It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology)

Features of Hybrid Topology

  1. It is a combination of two or topologies
  2. Inherits the advantages and disadvantages of the topologies included

Advantages of Hybrid Topology

  1. Reliable as Error detecting and trouble shooting is easy.
  2. Effective.
  3. Scalable as size can be increased easily.
  4. Flexible.

Disadvantages of Hybrid Topology

  1. Complex in design.
               2. Costly




Q) Write a note on HTML?
  1. HTML stands for Hyper Text Markup Language.
  2. An HTML file is a text file containing markup tags. The markup tags tell the Web browser how to display the page.
  3. An HTML file must have an ‘htm’ or ‘html’ file extension.
  4. An HTML file can be created using a simple text editor.
  5. The rule-making body of the Web is World Wide Web Consortium (W3C). W3C puts together specifications for Web standards. The most essential Web standards are HTML, CSS and XML.
  6. The latest HTML standard is XHTML 1.0.

Advantages of HTML:
1. First advantage it is widely used.
2. Every browser supports HTML language.
3. Easy to learn and use.
4. It is by default in every windows so you don't need to purchase extra software.


Disadvantages of HTML:
1. It can create only static and plain pages so if we need dynamic pages then HTML is not useful.
2. Need to write lot of code for making simple webpage.
3. Security features are not good in HTML.
4. If we need to write long code for making a webpage then it produces some complexity.


Q) Explain the structure of HTML document.
Structure of an HTML document: All HTML documents follow the some basic structure. They have the root tag as <html>, which contains <head> tag and <body> tag. The head tag is used for control information by the browser and the body tag contains the actual user information that is to be displayed on the screen. The basic document is shown below.
<html>
<head>
<title> Title  Here </title>
</head>
<body>
-----Body Text-----
</body>
</html>


Example: Creating a simple web page
  1. Start Notepad.
  2. Type in the following text
<html>
<head>
<title>Title of page</title>
</head>
<body>
This is a very basic webpage. <b>This text will be displayed in bold</b>
</body>
</html>
3.      Save the file as "firstpage.html". 
4.      Double click the saved file the browser will display the page.
Q) Write a note on HTML Tags?

HTML Tags

  1. HTML tags are used to mark-up HTML elements
  2. HTML tags are surrounded by the two characters < and >
  3. The surrounding characters are called angle brackets
  4. HTML tags normally come in pairs like <b> and </b>
  5. The first tag in a pair is the start tag, the second tag is the end tag
  6. The text between the start and end tags is the element content
  7. HTML tags are not case sensitive, <b> means the same as <B>
Tags can have attributes. Attributes can provide additional information about the HTML elements on your page.
Ex:  <body bgcolor="red">.
Attributes always come in name/value pairs like this: name="value".
Attributes are always added to the start tag of an HTML element.

Q) Explain briefly about Document Body.

The body tag defines the document’s body. It contains all the contents of an HTML document, such as text, images, lists, table, etc.
Attribute of Body Tag
1. Background attribute
This attribute allow you to include a background image.
<BODY background =”Pic.jpg”>
This above statement will set pic.jpg image as background of the body of  web page.
2. Background color, Text Color, Link Color
By default browsers display text in black. If you want to change the color or text (by TEXT attribute), color of links (by
LINK attribute), color of active links (by ALINK attribute) and background color (by BGCOLOR attribute ).

Example:
<BODY bgcolor = “teal” text = “magenta” link = “yellow” alink = “red”>
-          The background color is teal. (bgcolor = “teal”)
-          Text color is magenta.
-          Links that have not been visited recently are made yellow(link = “yellow”)
-          Links that are currently being clicked on (alink = “lime”)

3. Setting Left and Top Margins
-          The margin refer to the blank area left from the edge of page.
-          If you want to leave some blank area in the left side, you can use LEFTMARGIN attribute as follows:
<BODY leftmargin = value>
-          The value is the number of pixels (72 pixels make an inch) to be left blank.
e.g. <BODY leftmargin = “60”>
-          If you want to set the top margin i.e. distance from the top edge, you can use TOPMARGIN attribute.
e.g. <BODY topmargin = “70”>
 





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