LESSON-2::UNDERSTANDING THE COMMUNICATION MODEL

OSI Reference Model   

                                                            The Open System Interconnection reference model provides a means of describing how data is transmitted over a network.

                                                      Why a Layered Network Model  

Reduce Complexity:                                      7, Application

The OSI model breaks network communication in to smaller components to make learning easier.

Standardizes Interfaces:                             6, Presentation

The OSI model provides for efficient update and improvement to individual components without affecting other components or having to rewrite the entire protocol.

Facilitates modular engineering:               5, Session

The OSI model prevents changes in one layer from affecting the other layer, thus allowing for quicker development.

Ensures Interoperable technology:               4, Transport 

The OSI model allow different types of network hardware and software to communicate with one another.

Accelerates Evolution:                                      3,Network

The OSI model of standardizes network components to allow multi vendor development and support.

Simplifies teaching and learning:                2, Data Link

The OSI model breaks network communication in to smaller, simpler parts.

                   OSI Model Layers and Their Functions

layer1: the physical layer

                                           The physical layer defines the electrical, mechanical, procedural and functional specification for activating, deactivating and maintaining the physical link for transmission between end devices. Physical layer specification are defining characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distance, physical connectors and other similar attributes. 

layer2: the data link layer

The data link layer defines how data is formatted for transmission and how access to the physical media is controlled. This layer also typically includes error detection and correction to ensure reliable delivery of the data.  

layer3: the network layer

The network layer provides connectivity and path selection between two host system that may be located on geographically separated network. The growth of the internet has increased the number of users that access information from sites around the world. The network layer is the layer that manages the connectivity of these users by providing logical addressing. 

layer4: the transport layer

The transport layer defines services to segment, transfer and reassemble the data for individual communication between the end devices. For example, business users in large corporations often transfer large files from field locations to a corporate sites. Reliable delivery of the files is important, so the transport layer will break down file in to smaller segment that are less likely to incur transmission problems.
                                      The transport layer shields the upper layer from transport implementations details. Specifically, issues such as reliability of transport between two hosts are assigned to the transport layer. In providing a communication a communication service the transport layer establishes, maintain and properly terminates virtual circuit. Transport error detection and recovery, as well as information flow control, ensure reliable service. 

layer5: the session layer  

The session layer establishes, manages and terminates session between two communicating hosts. The session layer also synchronizes dialog between the presentation layers of the two hosts and manages their data exchange. For example, web server have many users, so there are many communication process open at a given time. It is important then to keep track of which user communicates on which path. In addition to session regulation, the session layer offers provision for efficient data transfer, class of service(CoS) and exception reporting of session layer and application layer problems.

layer6: the presentation layer 

The presentation layer ensures that the information that is sent at the application layer of one system is readable by the application layer of another system. For example, a PC program communicate with another computer. One PC is using extended binary coded decimal interchange code (EBCDIC) and the other one is using ASCII to represent the some characters. If necessary the presentation layer translates between multiple data formats by using a common format.

layer7: The application layer      

The application layer is the OSI layer that is closest to the user. This layer provides network service to the application of the user, such as email, file transfer and terminal emulation. The application layer differs from the other layer in that it does not provide service to any other OSI Layer. It provides services only to application outside the OSI model. The application layer establishes the availability of intended communication partner, and synchronizes and establishes aggrement on procedures for error recovery and control of data integrity.

               ENCAPSULATION & DE-ENCAPSULATION

Information that is transmitted over a network must undergo a process of  conversion at the sending end the receiving end of the communication. That conversion process is known as encapsulation and de-encapsulation of data. This topic describes the encapsulation and de-encapsulation process.

ENCAPSULATION:

                                     The information that is sent on a network is referred to as data or data packets. As application data is passed down the protocol stack on its way to be transmitted across the network media, various protocols add information to it at each level. This process is commonly known as the encapsulation process. Each layer adds a header (and a trailer, if applicable) to the data before passing it to a lower layer.The headers and trailers contain control information for the network devices and receiver to ensure proper delivery of the data and to ensure that the receiver can correctly interpret the data.

These steps shows you in which manner data travels through the layers.  

Step1: 

The user data is sent from an application to the application layer.

Step2:

The application layer adds the application layer header (Layer 7 header) to the user data. The layer 7 header and the original user data become the data that is passed down to the presentation layer.

Step3:

The presentation layer adds the presentation  layer header (Layer 6 header) to the data. The layer 6 header and the previous data become the data is passed down to the session layer.

Step4:

The session layer adds the session layer header (Layer 5 header) to the data. The Layer 5 header and the previous data become the data that is passed down to the transport layer.

Step5:

The transport layer adds the transport layer header (Layer 4 header) to the data. The layer 4 header and the previous data become the data that is passed down to the network layer.

Step6:

The network layer adds the network layer header (Layer 3 header) and the previous data become the data that is passed down to the data link layer.

Step7:

The data link layer adds the data link layer header & trailor(Layer 2 header and trailer) to the data. A layer 2 trailer is usually the frame check sequence(FCS), which is used by the receiver to detect whether the data is in error. The layer 2 header and the previous data become the data that is passed down to the physical layer.

   

LESSON-1::EXPLORING THE FUNCTION OF NETWORKING

What is a Network:-

                                   A Network is a connected collection of devices and end systems, such as computers and servers, which can communicate with each other. Networks carry data in many types of environment, including homes, small businesses and large enterprises.

                                             PHYSICAL COMPONENTS OF A NETWORK

Pc: The computers serve as a end point in  a network. They send and receive data. 

Interconnection: The interconnection consists that components which provide  a platform to a point to other point. Eg:- NIC Card, cable, connector.

Switch: Switches are the devices that provide network attachment to the end system.

Routers: Routers interconnect network and choose best path between networks.

Wireless LAN: W-LAN devices connect network devices computers and other end point  to the network without routers .

                                                       NETWORK USER APPLICATION

Email: Email is very valuable application for most network user. User can communicate information, message and files with an electronically method to same network and other also. 
Web Browser: A web browser allows access to the internet through a common interface. A web browser provides a common interface for communicating with suppliers and customers. Some famous web browser like Microsoft internet explorer, Mozilla fire fox, apple safari and google chrome.

Database: In this application servers stored data in  a centralized form on a network such  as file server, exchange server, and AD.All connected users access this information easily.   

                                            CHARACTERISTICS OF A NETWORK

Speed: Speed is the most important part in a  network.Its depend on ISP that how fast data transmitted over the network.
Security: Security is describe as a firewall of a network. Its use for save the transmit information from un-authorised used that flow on  a Network.
Topology: In networks, there are physical and logical topology. Physical is used for wiring the devices and logical is used for how data send one to another by physical.   

                                 LOGICAL VS. PHYSICAL TOPOLOGIES

Logical Topology: The logical topology of a network refers to the logical paths that the signal use to travels from one point in the network to another point. This paths defines the way in which data accesses the network media and transmits packets across it.
Physical topology: The physical topology of a network to the physical structure layout of the devices and cabling. There are three primary category of physical topologies:-
(i). Bus: Computers and other network devices were cabled together in  a line using coaxial cable. In modern bus topologies using twisted pair wiring.
(ii). Ring: Computers and other network devices connect like as to create a ring.
(iii). Star: All computers and devices are connected by a central cabling.
 

 

World top 10 super human

WHAT IS NETWORKING

For best describing the answer of this question fist we have to learn what is network, its characteristic and how its is work.

WHAT IS NETWORK:- 

A Computer Network is a group of network that are connect together to communicate ans share resources such as files,printers and email, a network protocol control the network communication.

                             "A Network consists of two or more computers that are linked in order to share resources(such as printer and CD's), exchange and transfer files or allow electronic communication. The Computers on a network may be linked through cables, telephone lines, radio waves, satellite, or infrared light beams."

                                                                                                In actually network is like a way that we use for networking. if we want to doing networking we must have connected all computers in a manner to connect a specific network, is called networking.

NETWORK MODELS:-

(i)Centralized Network:

A type of Network where all users connect to a central server, which is the acting agent for all communication and the user account information. Most public instant messaging platforms use a centralized network also called a centralized server structure. Centralized network are also called. "hierarchical networks" and "host based networks".

(ii) Client-Server Network:

A Client-Server network is a network in which computer functionality is divided  in to two roles: Server computer, which provide services and control network operations and client computer.

(iii) Peer to Peer Network:

A peer to peer network, sometimes called a work-group, is a network in which resources sharing, processing and communications are completely decentralized. All clients and computers are equal in terms and permission.

NETWORK INTERFACE CARD  

A Network Interface Card or N.I.C. is an electronic device that provide a platform to a computer to connect to connect on the network. It is considered as a hardware part of Computer. 

Characteristic of N.I.C.

All network adapter have a globally unique physical address burned on to the card, its mean at the time of making card manufacture registered  it. The physical address uniquely identifies every individual card that connects to the network cable or media, that's why the physical address is also called the "MEDIA ACCESS CONTROL" , MAC address.

What is MAC

The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.
MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:

                                          MM:MM:MM:SS:SS:SS

                                          MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body. The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example, 00:A0:C9:14:C8:29

   The prefix 00-00-0E indicates the manufacturer is Fujitsu Limited, Japan

Why MAC is must:

Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI Model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.

Difference between MAC and IP:

Whereas MAC addressing works at the data link layer, IP addressing functions at the network layer (layer 3). It's a slight oversimplification, but one can think of IP addressing as supporting the software implementation and MAC addresses as supporting the hardware implementation of the network stack. The MAC address generally remains fixed and follows the network device, but the IP address changes as the network device moves from one network to another.

IP networks maintain a mapping between the IP address of a device and its MAC address. This mapping is known as the ARP cache or ARP table. ARP supports the logic for obtaining this mapping and keeping the cache up to date.

       Hardware Vendors and Registered MAC Address IDs 

Company                                                                                                                   Hex Address

Xerox Corporation, USA	00-00-00 – 00-00-09
Omron Tateisi Electronics Co., Japan	00-00-0A
Matrix Corporation, USA	00-00-0B
Cisco Systems, Inc., USA	00-00-0C
Fibronics LTD., Israel	00-00-0D
Fujitsu Limited, Japan	00-00-0E
Next, Inc., USA	00-00-0F
Sytek Inc., USA	00-00-10
Normerel Systemes, France	00-00-11
Information Technology Limited, United Kingdom	00-00-12
Camex, USA	00-00-13
Netronix, USA	00-00-14
Datapoint Corporation, USA	00-00-15
Du Pont Pixel Systems, United Kingdom	00-00-16
Tekelec, USA	00-00-17
Webster Computer Corporation, USA	00-00-18
Applied Dynamics International, USA	00-00-19
Advanced Micro Devices, USA	00-00-1A
Novell Inc., USA	00-00-1B
Bell Technologies, USA	00-00-1C

1.1-WHAT PIECES ARE FOUND IN A COMPUTER?

(i) Adapter - Most of the time it refers to a card that plugs into the motherboard adding special capabilities not originally found on the computer.Other times it refers to tools to convert one connector type to another. 

(ii) Cables - A thick wire that connects the computer to the external device or power. 

(iii)Cache - An interface between the CPU and the memory (RAM and ROM). It helps the CPU keep running even though the RAM may be too slow.It does this by keeping a copy of what the processor has read/written. 

(iv)Card Slot - 

1. HARDWARE: “WHAT DO I NEED TO KNOW TO BUY A COMPUTER?”

What is a computer? I guess the easiest way I can explain it is as a little machine that follows very specific instructions over and over. A computer cannot learn and,unless told to do so, won’t respond to anything. Think of it as a very dumb dog that you have to teach to catch a ball every day and every time you want to play.

Computers do very complex math. Mind you, it is always related to the basics: add,subtract, multiply and divide. But as anyone who has had algebra and calculus will tell you: if you do enough of these basics, you can get approximations of more sophisticated math that are pretty close to reality. Computers do this math very quickly. Often these calculations are done in millions per second. Imagine multiplying 10 million pairs of multi-digit numbers per second. I have a hard enough time myself doing a 3-digit multiplication in less than a minute.

  

Computers can store a vast amount of information and retrieve it at extraordinary speeds.When everything works correctly, this data is as fresh and unblemished by time as when it was first stored. It can record information about everything (given it has sufficient

storage capacity). While this may not seem to be a great achievement, think about this:when you last went to the store, how much did you pay for each item you bought? Computers can store this kind of information a lot better than we can recall it. Also, one

of those DVD-ROMs that we see so frequently can store the entire Encyclopedia Britannica along with photos.(Please note that if you buy their DVD-ROM set, it has more than just text and photos. So, the set has several DVD-ROMs.)

What have computers done for us? Consider the following: 
1. Made the world incredibly smaller by facilitating communications.
2. Advanced science and medical discovery more in 10 years than in centuries of history.
3. Designed cars, roads, cities, clothing, etc.
4. Tested transportation long before the prototypes ever left their studios.
5. Exploded our imaginations with color and virtual reality.
6. Controlled our market-place and caused the “Black Monday” crash.
7. Opened freedom of speech to areas all over the world via the Internet.

The list goes on and on. The computer has done a lot to shape the modern world—some good and some bad. In all, it has been a great blessing when properly used. What can computers do for you? Well, hopefully, this text will show you.

 

 

 

WIRELESS SECURITY

Setting up  a wireless router is fairly easy if you follow the instruction that come with the device. Still, if you're not confident about setting up a router, take the help of a techie friend, or your internet service provider.

PASSWORD PROTECTION

You wouldn't want anybody to mooch off your internet connection.Restrict access to your network by using WPA2 encryption and changing the default router password.

PREVENT MISUSE

You can also protect your network from misuse with the help of parental controls and bandwidth monitoring tools.

GUEST LOGIN

Create an alternative login for guests. It's safer and smarter.

FIREWALL

Some routers include a firewall, providing blanket protection to all the devices on the network from possible hack attacks.

WIIRELESS USB DONGLES

With a wireless USB dongle, you can add Wi-Fi or Bluetooth connectivity to your PC without upgrading it. First, you need to fix on the one you need....

WHICH DONGLE IS RIGHT FOR YOU  

Bluetooth dongle:

Allow you to use Bluetooth  to connect to other devices.

Wi-Fi dongle:

Adds wireless abilities to a PC without built-in Wi-Fi.

3G dongle:

In case your network is internet-dependent, consider a 3G dongle as a backup. Just make sure your router supports these 3G USB sticks. Besides, portable wireless adaptors that take 3G dongles will also allow you to share your connection on the move.

WHAT IS WIRELESS ROUTER

WIRELESS ROUTER

This piece of hardware is essential to going wireless. It allow devices with built-in Wi-Fi -laptop, smartphones, tablets and e-book readers to connect to the internet without the need of cables.

Now depending on type of your connection, you will need.....

An ADSL Route: 

If you use your telephone line for internet access, you will need to invest in such a router. You can also get this router from your service provide(MTNL or  BSNL), for a small fee.

Non-ADSL:

For other connections, like if your service provide is your local cable operator: then you will need a non-ADSL router. These routers take input from the RJ45 connector that you would generally attach to the network port on your desktop PC or laptop in a LAN card.

BENEFITS

Internet sharing:

A wireless router allows multiple users- with Wi-Fi enabled devices- to share a single internet connection.

Sharing  data over WiFi:

If the router has a USB port, you will be able to share the contents of a flash drive or portable hard drive with other.Wi-F- enabled devices in the network.Some routers even printers to be shared via its USB port [You will need to refer to the router's setup guide to do this]  but it will make your printer accessible to more devices on your network.

Control Internet Access:

You will also be able to configure the kind of content that can be accessed from the web. More importantly, the router can also be used as your first line of defence against internet hackers.
Note: How, about wireless security you can find it on wireless security link. 

HOW TO BUY

Look for the '802.11n'  standard:

The 'n' standard indicates the router's maximum speed over an un-wired  connection (the older ones being 'a' , 'b' and 'g'). There is a newer 'ac' standard, but 'n' will serve all your present-day purposes.

Consider dual band:

Wi-Fi routers, microwave ovens, cordless phones and Bluetooth device operate in the same2.4Ghz frequency band. Understandably, this cause congestion, reducing the router's signal strength. In such cases, you would be better off with a dual-band router. Such a router allow for connection over the additional 5Ghz band simultaneously.

USB ports(s):

Like we mentioned earlier, router with USB ports will let you plug flash drives, hard disks and even printers to share these resources over the network.

Multiple antennas:

External antennas increase the overall range of your router; ideal for when you might want to access the router from behind a wall or  glass doors.

WHAT’S THE DIFFERENCE BETWEEN VIRTUALIZATION AND CLOUD COMPUTING?

While virtualization and cloud computing might share a common bond, there is a difference between them and it’s important to understand what that difference is.

One common misconception I routinely notice when talking with people about technology is the idea that virtualization and cloud computing are the same thing. It’s not impossible to see where this conclusion stems from, given the influx of overwhelming information concerning both concepts. While these technologies might share a common bond of maximizing computing resources, there is a difference between them and it’s important to understand what that difference is.

Virtualization in a nutshell

To put it simply, virtualization is the process of simulating “virtual” versions of infrastructure resources, such as computing environments, operating systems, storage devices or network components, as opposed to creating actual or physical versions of those same resources. For example, you have a physical server (the “host”) that controls all of its physical resources (the operating system, memory, storage, etc.) – those resources can be allocated to virtual machines (“VM”s) that run in containers provided by that host. Virtualization enables multiple instances of infrastructure resources to run on the same hardware, with access to those resources being controlled by a hypervisor (I’ll get to that in a second.) Take a look at the picture below.

 

 A hypervisor, also referred to as a virtual machine manager (“VMM”), is the software layer that controls access to the host’s physical hardware, and creates and runs the VMs. There are two types of hypervisors: bare metal/native or hosted. In a bare metal instance, the hypervisor runs directly on the host’s hardware and allows running multiple operating systems on the same physical hardware. Hosted hypervisors run on top of the host’s operating system, and additional operating system environments are run within the host’s OS. In a nutshell, bare metal hypervisors run directly on hardware while hosted hypervisors run on top of an operating system such as Windows or Linux.

 

That’s great…but where does the cloud come in?

Cloud computing is the delivery of shared computing resources, software or data as a service via the Internet, as opposed to virtualization, which is part of a physical infrastructure. For users of either technology, it may appear that the two are one in the same, as the applications or data they’re accessing are pulled from a virtual machine somewhere unconnected to a physical host. That’s partly where some of the confusion happens.

Cloud computing is built on top of a virtualized infrastructure, consisting of compute, storage and network components. There are a variety of different service models that represent cloud computing, such as SaaS, IaaS, and PaaS (I’ll cover these in a later post), and there are many key characteristics that define the “cloud”, such as agility, scalability, automation, and on-demand service delivery.

 So there you have it

By itself, virtualization can reduce complexity for end users while allowing an organization’s IT resources to be utilized more effectively. But cloud computing takes the use of those resources to the next level by delivering access to those components on-demand as a service, further reducing complexity, cost and burden. Essentially, virtualization is a logical action for businesses to take when considering the adoption of a cloud computing strategy.

LARGER ADDRESS SPACE FOR GLOBAL REACHABILITY AND SCALABILITY

The availability of an almost unlimited number of IP addresses is the most compelling benefit of implementing IPv6 networks. Compared to IPv4, IPv6 increases the number of address bits by a factor of 4, from 32 bits to 128 bits. The 128 bits provide approximately 3.4x1038 addressable nodes, enough to allocate about 1030 addresses per person on this planet. Figure 1 shows the general format of an IPv6 address.

Figure 1: IPv6 Address Format

 The ability to provide a unique address for each network device enables end-to-end reachability, which is especially important for residential IP telephony. IPv6 also provides full support for application protocols without requiring special processing at the edges of the networks, eliminating the problems associated with NAT.