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Showing posts with label COMPUTING KNOWLEDGE. Show all posts

WEB DESIGN

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1. Introduction to Web Design
* Web design is the process of planning and creating a website. Text, images, digital media and interactive elements are used by web designers to produce the page seen on the web browser. Web designers utilize mark up language, most notably HTML for structure and CSS for presentation as well as JavaScript to add interactivity to develop pages that can be read by web browsers.
 
* The process of web design can include conceptualization, planning, producing, post-production, research, advertising. The site itself can be divided up into pages. The site is navigated by using hyperlinks, which are commonly blue and underlined but can be made to look like anything the designer wishes. Images can also be hyperlinks.
2. Website A website is like a book that contains information on a single or more topics while a web page is a page of the website similar to the page of a book that focuses on a particular topic. Designing a web page or a website or a web application using web designing tools and technologies is known as Web Designing technique. Designing a website is an art that also includes science to attract the surfers on the internet.

A website contains two parts front end and back end. The term front end reflects on the computer screen in the form of visible content such as page layout, page colour, user interface, graphics, text, audio, and video, before the end user. On the other hand, back-end refers to intertwining of source code, invisible scripted functions, and the server-side components that process the output from the front-end.


3. Uses of web sites
* Hobbies or other special interests.
* Entertainment (including music and games) .
* News.
* Learning about health issues that they're too embarrassed to talk about .
* E-commerce.
* School resources.
* Health.
* News and entertainment.
* Non-profits.
* Online quizzes .
* Forms for providing feedback or asking questions .
* Online voting.

* Games .
* Features for sharing pictures or stories.
*Forums for offering and receiving advice.
* Features for creating a website or otherwise adding content .
* Travel
4. HTML 5
* HTML 5 is a new specification of HTML designed to follow HTML 4.01 and was created by designers .
* HTML 5 adds features to help web application developers and to improve the interoperability among web browsers and user agents.
* HTML 5 is the latest specification of HTML. HTML 5 adds a lot of new features to the HTML specification.


Features of HTML 5 Tags to help with the structure of your pages like section, article, and aside.
* New form tags to get more specific data in your forms
* Multimedia tags to assist you in adding video and audio to your web pages.
5. HTML5Page Put the doc type as the first line in your HTML document. Then add the <html> tag and start the <head> of your document. Inside the head, you should indicate the title of your document and the character set:

<html>
　 <head>
　　 <title>My First HTML 5 Document</title>
　　 <meta charset="UTF-8">
　 </head>

Write your HTML 5 document. Put your content in the <body> tag and close both the body tag and the html tag at the very bottom of the document.

(a) Here is a sample HTML 5 document
<!doctypehtml>
<html>
　<head>
　<title>My First HTML 5 Document</title>
　<meta charset="UTF-8">
　</head>
　<body>
　<p>Put your HTML 5 tags here</p>
　</body>
</html>
　
　
　
　
(b) New Structure:
* <section> - to define sections of pages
* <header> - defines the header of a page
* <footer> - defines the footer of a page
* <nav> - defines the navigation on a page
* <article> - defines the article or primary content on a page
* <aside> - defines extra content like a sidebar on a page
* <figure> - defines images that annotate an article
(c) New Form Types: HTML 5 supports all the standard form input types, but it adds a few more:
* datetime
* datetime-local
* date
* month
* week
* time
* number
* range
* email
* url

NETWORKING

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1. Concept of Networking Networking is a concept of connecting multiple computers so that resources, such as printers, hard disks, and files can be shared. A typical network is depicted in the figure below.

2. Local area network
A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. Each computer or device on the network is a node. Current wired LANs are most likely to be based on Ethernet technology.
Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 40 and 100 Gbit/s. LANs can be connected to Wide area network by using routers.

Characteristics Of LAN:
(a) Operates within the limited geographical area.
(b) Allow access through high bandwidth up to 1000 mbps.
(c) Controls the network under local administration
(d) Provides the full time connectivity to local system.
(e) Connects physical adjacent devices.
3. Metropolitan area network (MAN) 
   
 MAN is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks (or WAN) and the Internet. The IEEE 802-2002 standard describes a MAN.
MAN geographic scope falls between a WAN and LAN. MANs provide Internet connectivity for LANs in a metropolitan region, and connect them to wider area networks like the Internet.
 
4. Wide area network (WAN)
WAN is a telecommunication network that covers a broad area (i.e., any network that links across metropolitan, regional, or national boundaries). WANs as computer networking technologies used to transmit data over long distances, and between different LANs, MANs and other localised computer networking architectures.
While local area networks are perfect for sharing resources within a building or campus, they cannot be used to connect distant sites.
Wide area networks (WANs) fill this need. Stated simply, wide area networks are the set of connecting links between local area networks.
These links are made over telephone lines leased from the various telephone companies. In rare instances, WANs can be created with satellite links, packet radio, or microwave transceivers.

NETWORK TOPOLOGY

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.1 Topology
* Network topology is the layout pattern of interconnections of the various elements of a computer or biological network. Network topologies may be physical or logical.
 
* Physical topology refers to the physical design of a network including the devices,
location and cable installation.
 
* Logical topology refers to how data is actually transferred in a network as opposed to its physical design. In general physical topology relates to a core network whereas logical topology relates to basic network.
The study of network topology recognizes is five basic topologies
*Bus
*Star
*Ring or circular
*Mesh
*Tree
2. Bus topology

*In local area networks where bus topology is used, each node is connected to a single cable. Each computer or server is connected to the single bus cable. A signal from the source travels in both directions to all machines connected on the bus cable until it finds the intended recipient.
 
*If the machine address does not match the intended address for the data, the machine ignores the data.
 
*Alternatively, if the data matches the machine address, the data is accepted. If the network cable is terminated on both ends and when without termination data transfer stop and when cable breaks, the entire network will be down.


Bus Topology are two types:
  (a) Linear bus

(b) Distributed bus


(a) Linear bus The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network simultaneously.



　
(b) Distributed bus The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has more than two endpoints that are created by adding branches to the main section of the transmission medium.
  Advantages of Bus topologies
* A bus uses relatively little cable compared to other topologies and arguably
has the simplest wiring arrangement.
* Since nodes are just attached to the main line, it’s easy to add or remove
nodes from a bus. This makes it easy to extend a bus topology.
 Disadvantages of Bus topology
* Diagnosis/troubleshooting (fault-isolation) can be difficult.
* The limited length of the cable in a network restricts the number of devices that can be connected.
2. Star Topology

* In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device.
* All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement.
* An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure.
There are two types of star topology -

(a) Extended star
(b) Distributed Star
(a) Extended star In this topology the repeaters being used to extend the maximum transmission distance of the point-to-point links between the central node and the peripheral nodes beyond that which is supported by the transmitter power of the central node or beyond that which is supported by the standard upon which the physical layer of the physical star network is based.
(b) Distributed Star A type of network topology that is composed of individual networks that are based upon the physical star topology connected in a linear fashion　– i.e., 'daisy-chained'　– with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').

　
　
 Advantages of star topology are as follows
* Troubleshooting and fault isolation is easy.
* Also, it is easy to add or remove nodes and to modify the cable layout.
* Failure in any star network cable will only affect the connected computer and not the entire network.
 Disadvantage of this topology are
* If the hub fails, the entire network fails.
* It requires more cable than bus topology.
3. Ring Topology
 
    A network topology that is set up in a circular fashion in which data travels around the ring in one direction and each device on the right acts as a repeater to keep the signal strong as it travels. Each device incorporates a receiver for the incoming signal and a transmitter to send the data on to the next device in the ring. The network is dependent on the ability of the signal to travel around the ring.




　
　



　
4.   Mesh Topology
 
     In a mesh topology there are at least two nodes with two or more paths between them to provide redundant paths to be used in case the link providing one of the paths fails. Full mesh topology is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with (n) nodes. Networks designed with this topology are usually very expensive to set up, but provide a high degree of reliability due to the multiple paths for data that are provided by the large number of redundant links between nodes. This topology is mostly seen in military applications

Fully connected




　

　

　

　

　
Partially connected The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link　– this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

5.    Tree Topology

A tree topology is a hybrid physical topology that combines features of star and bus topologies. In this topology multiple star topologies are connected to a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points).






The disadvantages of this topology are as follows
* If the root goes down, the entire network goes down.
* If any hub goes down, all branches off of that hub go down.
Access becomes a problem if the entire conglomerate becomes too big.

OSI REFFERENCE MODEL AND TCP/IP PROTOCOL SUITE

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OSI Model The international Standards Organization (ISO) developed the OSI model in 1983. This model connects systems that are open to communicate with each other regardless of the protocols that each system uses. This model allows computers from different manufacturers to communicate with each other without requiring any logical changes to the hardware and software. The OSI model is represented in seven layers that define the entire process of communication between two computers on a network. The common functions of each layer are -


Data unit
Layer
Function

Host
layers
Data
7. Application
Network process to application

6. Presentation
Data representation, encryption and decryption, convert machine dependent data to machine independent data

5. Session
Interhost communication, managing sessions between applications

Segments
4. Transport
End-to-end connections, reliability and flow control

Media
layers
Packet/Datagram
3. Network
Path determination and logical addressing

Frame
2. Data link
Physical addressing

Bit
1. Physical
Media, signal and binary transmission

1. Physical layer The physical layer defines electrical and physical specifications for devices. In particular, it defines the relationship between a device and a transmission medium, such as a copper or optical cable. This includes the layout of pins, voltages, cable specifications, hubs, repeaters, network adapters, host bus adapters (HBA used in storage area networks) and more.


　

2. Data link layer The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer. Originally, this layer was intended for point-to-point and point-to-multipoint media, characteristic of wide area media in the telephone system. The IEEE 802.2 LLC layer is not used for most protocols on the Ethernet, and on other local area networks, its flow control and acknowledgment mechanisms are rarely used.

3. Network layer The network layer provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network, while maintaining the quality of service requested by the transport layer .The network layer performs network routing functions, and might also perform fragmentation and reassembly, and report delivery errors. Routers operate at this layer.

4. Transport layer The transport layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The transport layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state- and connection-oriented.

5. Session layer The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes check pointing, termination, and restart procedures.

6. Presentation layer The presentation layer establishes context between application-layer entities, in which the higher-layer entities may use different syntax and semantics if the presentation service provides a mapping between them. If a mapping is available, presentation service data units are encapsulated into session protocol data units, and passed down the stack.


This layer provides independence from data representation by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats and encrypts data to be sent across a network. It is sometimes called the syntax layer.

7. Application layer The Application Layer refers to the higher-level protocols used by most applications for network communication. In application layer protocols include the File Transfer Protocol (FTP) and the Simple Mail Transfer Protocol (SMTP). Data coded according to application layer protocols are then encapsulated into one or (occasionally) more transport layer protocols (such as the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP)), which in turn use lower layer protocols to effect actual data transfer.



Some protocols are used in this layer are as under
* Hypertext Transfer Protocol (HTTP),
* File Transfer Protocol (FTP),
* Simple Mail Transfer Protocol (SMTP)
* Simple Network Management Protocol (SNMP).

　



TCP/IP Protocol Suite

　

　



The TCP/IP layer model is based on a four-layered network. Protocols came first and model was a description of the existing protocols. Supports only connection- less communication in the network layer, but both connectionless & connection-oriented communication in transport layer.

　


　

　

　

　

8. Network Access Layer (Link Layer) Network Access Layer is the networking scope of the local network connection to which a host is attached. This is the lowest component layer of the Internet protocols.

The Link Layer is used to move packets between the Internet Layer interfaces of two different hosts on the same link. The processes of transmitting and receiving packets on a given link can be controlled both in the software device driver for the network card, as well as on firmware or specialized chipsets.

9. Internet Layer The Internet Layer solves the problem of sending packets across one or more networks. Internetworking requires sending data from the source network to the destination network. This process is called routing.


In the Internet Protocol Suite, the Internet Protocol performs two basic functions:
* Host Addressing and identification: This is accomplished with a hierarchical addressing system.
* Packet routing: This is the basic task of getting packets of data (datagrams) from source to destination by sending them to the next network node (router) closer to the final destination.
10. Transport Layer The Transport Layer's responsibilities include end-to-end message transfer capabilities independent of the underlying network, along with error control, segmentation, flow control, congestion control, and application addressing. End to end message transmission or connecting applications at the transport layer can be categorized as either connection-oriented, implemented in Transmission Control Protocol (TCP), or connectionless, implemented in User Datagram Protocol (UDP).

11. Application Layer The Application Layer refers to the higher-level protocols used by most applications for network communication. In application layer protocols include the File Transfer Protocol (FTP) and the Simple Mail Transfer Protocol (SMTP). Data coded according to application layer protocols are then encapsulated into one or (occasionally) more transport layer protocols (such as the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP)), which in turn use lower layer protocols to effect actual data transfer.

NETWORK COMPONENTS

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1. NIC (Network Interface Card)

      A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring. Network interface cards provide a dedicated, full-time connection to a network.



 
 




　
Function of NIC The NIC card has one or more user-accessible ports to which the network cabling medium is connected. Adapter card drivers inhabit the Data Link layer of the OSl model or, more specifically, the Media Access Control (MAC) sub layer of the Data Link layer. A network adapter card driver is sometimes called a MAC driver.

The network adapter card and its accompanying software and firmware perform several roles.

Microsoft identifies the following roles for the network adapter card:
(a) Preparing data for the transmission medium
(b) Sending data
(c) Controlling the flow of data

Preparing Data for the Transmission Medium The data travels on the network in serial form. Inside the PC, however, data moves along the data bus in parallel form (8, 16, or 32 bits at a time). The network adapter card, therefore, must convert the parallel data from the bus into the serial form required for network transmission.

  Switch -

    In a telecommunications network, a switch is a device that channels incoming data from any of multiple input ports to the specific output port that will take the data toward its intended destination. In local area network (LAN), a switch determines from the physical device (Media Access Control or MAC) address in each incoming message frame which output port to forward it to and out of.

　

In a wide area packet-switched network such as the Internet, a switch determines from the IP address in each packet which output port to use for the next part of its trip to the intended destination.

In the Open Systems Interconnection (OSI) communications model, a switch performs the Layer 2 or Data-link layer function. That is, it simply looks at each packet or data unit and determines from a physical address (the "MAC address") which device a data unit is intended for and switches it out toward that device.

There are two types of switches-
(a) Layer2 switch
(b) Layer3 switch
1- Layer 2 switch Layer 2 refers to the Data Link layer of the commonly-referenced multilayered communication model, Open Systems Interconnection (OSI). The Data Link layer is concerned with moving data across the physical links in the network. In a network, the switch is a device that redirects data messages at the layer 2 level, using the destination Media Access Control (MAC) address to determine where to direct the message.

The Data-Link layer contains two sub layers that are described in the IEEE-802 LAN standards:
* Media Access Control (MAC) sub layer
* Logical Link Control (LLC) sub layer
The Data Link layer ensures that an initial connection has been set up, divides output data into data frames, and handles the acknowledgements from a receiver that the data arrived successfully. It also ensures that incoming data has been received successfully by analysing bit patterns at special places in the frames.

2-  Layer3switch A network device that forwards traffic based on layer 3 information at very high speeds. Traditionally, routers, which inspect layer 3, were considerably slower than layer 2 switches. In order to increase routing speeds, many "cut-through" techniques were used, which perform an "inspect the first packet at layer 3 and send the rest at layer 2" type of processing.



The switching technique are as under
* Cut -Through Switch Cut-through switches read the MAC address as soon as a packet is detected by the switch. After storing the 6 bytes that make up the address information, they immediately begin sending the packet to the destination node, even as the rest of the packet is coming into the switch.
* Store and Forward A switch using store-and-forward will save the entire packet to the buffer and check it for CRC errors or other problems before sending. If the packet has an error, it is discarded. Otherwise, the switch looks up the MAC address and sends the packet on to the destination node. Many switches combine the two methods, using cut-through until a certain error level is reached and then changing over to store-and-forward. Very few switches are strictly cut-through, since this provides no error correction.
* Fragment-Free A less common method is fragment-free. It works like cut-through except that it stores the first 64 bytes of the packet before sending it on. The reason for this is that most errors, and all collisions, occur during the initial 64 bytes of a packet.

　
　
　
　
　
3-     Difference between layer 2 &Layer 3 Switch




Layer 2 switch
Layer 3 switch
a) Layer 2 is for peer to peer communication.
a) Layer 3 is for process to process communication.

b) Routing in inter network with Layer 2 switches is not possible.
b) Routing in inter network with Layer 3 switches.
c) Layer 2 switch can only do switching.
c) Layer 3 can do switching as well as routing.
d) Layer 2 uses the Mac address for switching.　
d) layer 3 uses the IP address for routing.
e) Layer 2 in the header portion contains source and destination physical addresses.
e) layer 3 in the header portion contains　 logical IP of the source and in the destination portion it contains logical IP of gateway of that(of source) network.

f) L2 Switch, restrict only collision.
f) L3 Switch, enable to restrict broadcast.
g) Peer is identified by MAC address.

g) Process is identified by Socket.
h) Layer 2 switch has multi collision and single broadcast domain. h) Layer 3 switch has multi collision and multi broadcast domain.




  Repeater

     A network device used to regenerate or replicate a signal. Repeaters are used in transmission systems to regenerate analog or digital signals distorted by transmission loss. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.

In a data network, a repeater can relay messages between subnets that use different protocols or cable types. Hubs can operate as repeaters by relaying messages to all connected computers. A repeater cannot do the intelligent routing performed by bridges and routers.



  Bridge

     A bridge device filters data traffic at a network boundary. Bridges reduce the amount of traffic on a LAN by dividing it into two segments.

Bridges operate at the data link layer (Layer 2) of the OSI model. Bridges inspect incoming traffic and decide whether to forward or discard it. An Ethernet bridge, for example, inspects each incoming Ethernet frame - including the source and destination MAC addresses, and sometimes the frame size - in making individual forwarding decisions.

Bridges serve a similar function as switches that also operate at Layer 2. Traditional bridges, though, support one network boundary, whereas switches usually offer four or more hardware ports. Switches are sometimes called "multi-port bridges" for this reason.

  Router

     A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs network. Routers are located at gateways, the places where two or more networks connect.

　

Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP (Internet Control Message Protocol) to communicate with each other and configure the best route between any two hosts. Router links dissimilar networks which are not transparent to end stations. Router acts on a network layer frame.



  Hubs

     A hub is a repeater with multiple ports. Hubs operate at physical layer of the OSI reference model. Hubs are used to connect computers to a server in Networks that use the star topology. Hubs can also be used to connect multiple segments of the same network, and transfer data from one segment to another. In a network, a hub acts as a central point for devices such as computers, printers, and routers. If a node sends data to any one of the other node, hub receives the data and transmits the signal to all the ports. This increases the Network traffic.



Hubs can be classified as follows
*Active Hub An active hub is usually powered and it amplifies the signal to its original strength. Active hubs are the most common type of hubs used in Networks. They are useful when the segments of the networks are not close to one another and the signal may require amplification.
*Passive Hub A passive hub is typically unpowered and makes only physical electrical connections. It does not regenerate or amplify the signal.
*Intelligent Hub An intelligent hub is an active hub with additional features such as Network monitoring capabilities.

MEDIA

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1. Transmission Media The means through which data is transmitted from one place to another is called transmission or communication media. There are two categories of transmission media used in computer communications.
1- Bounded/guided media
2- Unbounded/unguided media

(a). Bounded Media Bounded media are the physical links through which signals are confined to narrow path. These are also called guide media. Bounded media are made up of a external conductor (Usually Copper) bounded by jacket material. Bounded media are great for LABS because they offer high speed, good security and low cast. However, some time they cannot be used due distance communication. Three common types of bounded media are used of the data transmission. These are
1- Twisted Pairs Cable
2- Coaxial Cable
3- Fiber Optics Cable
2. Twisted Pair Cable

The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mbps. Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerability to EMI and cross talk. The number of pairs in the cable depends on the type. There are two types of twisted pairs cable.
1- Unshielded twisted pair (UTP)
2- Shielded twisted pair (STP)
(a) Unshielded twisted pair (UTP)
(aa) UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and is easily available due to its many use.
(ab) UTP cables are generally used to construct an Ethernet network in a star arrangement. UTP connectors are called RJ-45 connector. UTP cable comes in various grades called Categories for example CAT 1, 2, 3, 4, 5& CAT 6 etc.







　


　

　

　

Categories of Unshielded Twisted Pair
Category
Speed
Use
1 1 Mbps Voice Only (Telephone Wire)
2 4 Mbps Local Talk & Telephone (Rarely used)
3 16 Mbps 10BaseT Ethernet
4 20 Mbps Token Ring (Rarely used)
5 100 Mbps (2 pair) 100BaseT Ethernet
1000 Mbps (4 pair) Gigabit Ethernet
5e 1,000 Mbps Gigabit Ethernet
6 10,000 Mbps Gigabit Ethernet







Characteristics of UTP
1- High speed capacity.
2- High attenuation.
3- Affected to EMI.
4- 100 meter distance limit.
Disadvantages of UTP

Short distance due to attenuation

(b). Shielded twisted pair (STP) It is similar to UTP but has a mesh shielding that’s protects it from EMI which allows for higher transmission rate. In STP, an extra layer of metal foil present between the twisted pairs of copper wires and the outer sheath. The purpose of this layer is to provide additional protection from EMI and RFI. However, this shielding reflects back the normal radiation emitted by the wires. This radiation may interfere with signal transmitted by the cable. To prevent this reflection a coating of dielectric insulator which absorbs the radiation is provided on the internal surface of the metal foil.

　
　
　







　

　

　

　

　

　

　

　

 Characteristics of STP
1- Higher capacity than UTP
2- Higher attenuation, but same as UTP
3- Medium immunity from EMI
4- 100 meter limit
3. UTP Connectors RJ45 (Registered Jack 45) is a standard type of connector for network cables. RJ45 connectors have eight pins to which the wire strands of a cable are connected.


　
　
　
(a) Colour coding of UTP cable

RJ 45 Pin NO
Pin 1
Pin 2
Pin 3
Pin 4
Pin 5
Pin 6
Pin 7
Pin 8
Colour coding
White/orange
Orange
White/green
Blue
White/blue
Green
White/brown
Brown




There are two types of UTP cable wires connections-
1- Straight through cables
2- Crossover Cables.


Straight-through cable means that wire 1 coming in connects to wire 1, going out wire 2 connects to wire 2 and so on.



　
Straight Cable Connection
RJ-45 Pin
Colour coding of UTP wires
Function
RJ-45 Pin
Colour coding of UTP wires
Function
1
White Orange
Tx+
1
White Orange
Rx+
2
Orange
Tx-
2
Orange
Rx-
3
White Green
Rx+
3
White Green
Tx+
4
blue
Not used
4
blue
Not used
5
White Blue
Not used
5
White Blue
Not used
6
Green
Rx-
6
Green
Tx-
7
White Brown
Not used
7
White Brown
Not used
8
Brown
Not used
8
Brown
Not used


A crossover cable directly connects two network devices of the same type to each other over Ethernet.


Cross Cable connection
Switch A side
Switch B side
RJ-45 Pin
Colour coding of UTP wires
Function
RJ-45 Pin
Colour coding of UTP wires
Function
1
White Orange
Tx+
1
White Green
Tx+
2
Orange
Tx-
2
Green
Tx-
3
White Green
Rx+
3
White Orange
Rx+
4
blue
Not used
4
blue
Not used
5
White Blue
Not used
5
White Blue
Not used
6
Green
Rx-
6
Orange
Rx-
7
White Brown
Not used
7
White Brown
Not used
8
Brown
Not used
8
Brown
Not used





4. Coaxial Cable
Coaxial cable is very common & widely used communication media. e.g. TV wire is usually coaxial.
Coaxial cable gets its name because it contains two conductors that are parallel to each other. The centres conductor in the cable is usually copper. The copper can be either a solid wire or stranded martial.
Outside this central Conductor is a non-conductive material. The other Conductor is a fine mesh made from Copper. It is used to help shield the cable form EMI.
There are two types of coaxial cable-
1- Thin coaxial cable
2- Thick coaxial cable
　


Characteristics Of Coaxial Cable


 1- Up to 10Mbps capacity.
2- Medium immunity from EMI.
3- Medium attenuation.

 　
　
Connector of coaxial cable

　


　
5. Fiber Optics Fiber optic cable uses electrical signals to transmit data. In fiber optic cable light moves in one direction, for two way communication to take place a second connection must be made between the two devices. It is actually two stands of cable. Each stand is responsible for one direction of communication. A laser at one device sends pulse of light through this cable to other device. These pulses translated into "1’s" and "0’s" at the other end.

In the center of fiber cable is a glass stand or core. The light from the laser moves through this glass to the other device around the internal core is a reflective material known as CLADDING. No light escapes the glass core because of this reflective cladding. Fiber optic cable has bandwidth more than 2 Gbps (Gigabytes per Second)





Characteristics Of Fiber Optic Cable


 1- Capable of extremely high speed
2- Extremely low attenuation
3- No EMI interference

 　
　
　
　
　
　


Connectors

6. Fiber Optic Cable Connectors
(a) SC Connector A fiber-optic cable connector that uses a push-pull latching mechanism similar to common audio and video cables. For bi-directional transmission, two fiber cables and two SC connectors (Dual SC) are generally used.



(b) ST Connector A fiber-optic cable connector that uses a half-twist bayonet type of lock to keep the connection secure. For bi-directional transmission, two fiber cables and two ST connectors are generally used.



(c) MTRJ The MTRJ connector is a small form-factor fiber optic connector which resembles the RJ-45 connector used in Ethernet networks.



(d) FC The FC connector is a fiber-optic connector with a threaded body, which was designed for use in high-vibration environments. It is commonly used with single-mode optical fiber. FC connectors are used in data com, telecommunications, measurement equipment, and single-mode lasers. They are becoming less common, displaced by SC and LC connectors.






　



　

　

　

　

　

7. Media Type Comparison

Media Type Maximum Segment Length Speed Cost Advantages Disadvantages
UTP 100 m 10 Mbps to 1000 Mbps Least expensive Easy to install; widely available and widely used Susceptible to interference; can cover only a limited distance
STP 100 m 10 Mbps to 100 Mbps More expensive than UTP Reduced crosstalk; more resistant to EMI than Thinnet or UTP Difficult to work with; can cover only a limited distance
Coaxial 500 m (Thicknet)
185 m (Thinnet)		 10 Mbps to 100 Mbps Relatively inexpensive, but more costly than UTP Less susceptible to EMI interference than other types of copper media
Difficult to work with (Thicknet); limited bandwidth; limited application (Thinnet); damage to cable can bring down entire network
Fiber-Optic 10 km and farther (single-mode)
2 km and farther (multimode)		 100 Mbps to 100 Gbps (single mode)
100 Mbps to 9.92 Gbps (multimode)		 Expensive Cannot be tapped, so security is better; can be used over great distances; is not susceptible to EMI; has a higher data rate than coaxial and twisted-pair cable Difficult to terminate

8. Wireless media Wireless communication uses radio frequencies (RF) or infrared (IR) waves to transmit data between devices on a LAN. For wireless LANs, a key component is the wireless hub, or access point, used for signal distribution

To receive the signals from the access point, a PC or laptop must install a wireless adapter card (wireless NIC).

No physical medium is necessary for wireless signals, making them a very versatile way to build a network. Wireless signals use portions of the RF spectrum to transmit voice, video, and data.

Wireless frequencies range from 3 kilohertz (kHz) to 300 gigahertz (GHz). The data-transmission rates range from 9 kilobits per second (kbps) to as high as 54 Mbps.

Low-frequency electromagnetic waves have a long wavelength while high-frequency electromagnetic waves have a short wavelength.





　

　

　

　

Applications of wireless comn
1- Accessing the Internet using a cellular phone
2- Establishing a home or business Internet connection over satellite
3- Beaming data between two hand-held computing devices
4- Using a wireless projectors, keyboard and mouse for the PC
5- Another application of wireless data communication is the wireless LAN (WLAN), IEEE 802.11 standards. WLANs typically use radio waves ( 902 megahertz ), microwaves ( 2.4 GHz), and IR waves ( 820 nanometers) for communication.

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