OSI (Open Systems Interconnection) Model

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Open Systems Interconnection



OSI model is the layer approach to design, develop and implement network. OSI provides following advantages: -
  • Designing of network will be standard base.
  •  Development of new technology will be faster.
  •  Devices from multiple vendors can communicate with each other.
  •  Implementation and troubleshooting of network will be easy.

1.  Application Layer: -
 Application layer accepts data and forward into the protocol stack. It creates user  interface between application software and protocol stack.

2.  Presentation Layer: -
This layer decides presentation format of the data. It also able to performs other function like compression/decompression and encryption/decryption.

3.  Session Layer: -
This layer initiate, maintain and terminate sessions between different applications. Due to this layer multiple application software can be executed at the same time.

4.  Transport Layer: -
Transport layer is responsible for connection oriented and connection less communication. Transport layer also performs other functions like
Error checking

  • Flow Control
  • Buffering
  • Windowing
  • Multiplexing
  • Sequencing
  • Positive Acknowledgement
  • Response


5.  Network Layer
This layer performs function like logical addressing and path determination. Each networking device has a physical address that is MAC address. But logical addressing is easier to communicate on large size network.

Logical addressing defines network address and host address. This type of addressing is used to simplify implementation of large network. Some examples of logical addressing are: - IP addresses, IPX addresses etc.

6.  Data Link Layer
The functions of Data Link layer are divided into two sub layers
  • Logical Link Control
  • Media Access Control
Logical Link Control defines the encapsulation that will be used by the NIC to delivered data to destination. Some examples of Logical Link Control are ARPA (Ethernet), 802.11 wi-fi.

Media Access Control defines methods to access the shared media and establish the identity with the help of MAC address. Some examples of Media Access Control are CSMA/CD, Token Passing.

7.  Physical Layer
Physical Layer is responsible to communicate bits over the media this layer deals with the standard defined for media and signals. This layer may also perform modulation and demodulation as required.
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Protocols

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              Protocols

When two humans converse, they may have to use the same language but they generally understand each other without having to adhere to rigid rules of grammar or formal language frameworks. Computers, on the other hand, have to have everything explicitly defined and structured. If computers wish to communicate with one another, they have to know in advance exactly how information is to be exchanged and precisely what the format will be. Therefore, standard methods of transmitting and processing various kinds of information are used and these methods are called "protocols". Protocols are established by international agreement and ensure that computers everywhere can talk to one another. There are a variety of protocols for different kinds of information and functions. This article will discuss some of the common protocols that the average PC user is likely to encounter.

Types of protocols

                           HTTP  (hyper text transfer protocol)

                          DNS (Domain Name server)

                         ARP(Address Resolution Protocol)

                         RARP(Reverse Address Resolution Protocol )

                        ICMP(Internal Controal Message Protocol)

                       TELNET(Telecommunication network)

                        DHCP(Dynamic Host Configuration Protocol)

                        FTP(File transfer Protocol)

                       TFTP(Trivial File Transfer Protocol)

                       POP-3(Post office Protocol)

                       IMAP(Internal  Message Address Protocol)

                       SNMP(Simple network management Protocol)

                       SMTP(Simple Mail Transfer Protocol)

                      SSH(Server Shell)



Hypertext Transfer Protocol
Web pages are constructed according to a standard method called Hypertext Markup Language (HTML). An HTML page is transmitted over the Web in a standard way and format known as Hypertext Transfer Protocol (HTTP). This protocol uses TCP/IP to manage the Web transmission.
A related protocol is "Hypertext Transfer Protocol over Secure Socket Layer" (HTTPS), first introduced by Netscape. It provides for the transmission in encrypted form to provide security for sensitive data. A Web page using this protocol will have https: at the front of its URL.

File Transfer Protocol
File Transfer Protocol (FTP) lives up to its name and provides a method for copying files over a network from one computer to another. More generally, it provides for some simple file management on the contents of a remote computer. It is an old protocol and is used less than it was before the World Wide Web came along. Today, Its primary use is uploading files to a Web site. It can also be used for downloading from the Web but, more often than not, downloading is done via HTTP. Sites that have a lot of downloading (software sites, for example) will often have an FTP server to handle the traffic. If FTP is involved, the URL will have ftp: at the front.

Mail Protocols POP3 and SMTP
Email requires its own set of protocols and there are a variety, both for sending and for receiving mail. The most common protocol for sending mail is Simple Mail Transfer Protocol (SMTP). When configuring email clients, an Internet address for an SMTP server must be entered. The most common protocol used by PCs for receiving mail is Post Office Protocol(POP). It is now in version 3 so it is called POP3. Email clients require an address for a POP3 server before they can read mail. The SMTP and POP3 servers may or may not be the same address. Both SMTP and POP3 use TCP for managing the transmission and delivery of mail across the Internet.
A more powerful protocol for reading mail is Interactive Mail Access Protocol (IMAP). This protocol allows for the reading of individual mailboxes at a single account and is more common in business environments. IMAP also uses TCP to manage the actual transmission of mail.

ICMP
A different type of protocol is Internet Control Message Protocol (ICMP) . It defines a small number of messages used for diagnostic and management purposes. It is also used by Ping and Traceroute.

DNS
 Domain Name System - translates network address (such as IP addresses) into terms     understood by humans (such as Domain Names) and vice-versa

DHCP
Dynamic Host Configuration Protocol - can automatically assign Internet addresses to computers and users

FTP
 File Transfer Protocol - a protocol that is used to transfer and manipulate files on the Internet

HTTP
 HyperText Transfer Protocol - An Internet-based protocol for sending and receiving webpages

IMAP
Internet Message Access Protocol - A protocol for e-mail messages on the Internet

IRC
 Internet Relay Chat - a protocol used for Internet chat and other communications

POP3
Post Office protocol Version 3 - a protocol used by e-mail clients to retrieve messages from remote servers

SMTP

Simple Mail Transfer Protocol - A protocol for e-mail messages on the Internet.



XXX
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Topology

4:00 PM | Posted by | | | Edit Post

     

            Network Topology:-

The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. 

    Main Types of Physical Typologies


                
I. Linear Bus
II. Star
III. Tree (Expanded Star)
IV. Ring


Linear Bus:- A linear bus topology consists of a main run of cable with a terminator at each end . All nodes (file server, workstations, and peripherals) are connected to the linear cable.



 linear bus topology

 

            Advantages of a Linear Bus Topology

  • Easy to connect a computer or peripheral to a linear bus.
  • Requires less cable length than a star topology.

            Disadvantages of a Linear Bus Topology

  • Entire network shuts down if there is a break in the main cable.
  • Terminators are required at both ends of the backbone cable.
  • Difficult to identify the problem if the entire network shuts down.
  • Not meant to be used as a stand-alone solution in a large building.

       Star

A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator .
Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.


 star topology

           

       Advantages of a Star Topology

  • Easy to install and wire.
  • No disruptions to the network when connecting or removing devices.
  • Easy to detect faults and to remove parts.

       Disadvantages of a Star Topology

  • Requires more cable length than a linear topology.
  • If the hub, switch, or concentrator fails, nodes attached are disabled.
  • More expensive than linear bus topologies because of the cost of the hubs, etc.

         

       Tree or Expanded Star

A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.


Tree topology

       

          Advantages of a Tree Topology

  • Point-to-point wiring for individual segments.
  • Supported by several hardware and software venders.

          Disadvantages of a Tree Topology

  • Overall length of each segment is limited by the type of cabling used.
  • If the backbone line breaks, the entire segment goes down.
  • More difficult to configure and wire than other topologies.

All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances.






ring topology


XXX

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What is Network?

2:30 PM | Posted by | | | Edit Post

What Is Computer Network?

A network consists of two or more computers 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 mediums such as,cables, telephone lines, radio waves, satellites, or infrared light beams.


           Types of network

  1.                LAN(Local Area Network)
  2.            WAN(Wide Area Network)
  3.                MAN(Metropolitan Area Network)
  4.               CAN(Campus Area Network)
  5.               HAN(Home Area Network)

    

Read more »
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Privet Browsing/incognito Tab

1:03 PM | Posted by | | | Edit Post

Privet Browsing/incognito Tab


You know that if u want to browse something on web without being noticed by anyone, you can do it by using an option in various browsers,I will tell u how to use it :-

For Google Chrome :-

1.click on menu button of chrome.
2.A new window will be appear,click on "New incognito window" & enjoy privet browsing.



                                             Now you are in ur privet window

FOR Firefox :-
1.click on menu button


2.Then click on  "New privet window"

DONE!!!!!!!!


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Hide Drives Without Using Any Software

5:04 PM | Posted by | | | Edit Post

Hide Drives Without Using Any Software

Hi friends now u can hide your drivers without using any software.In our computer labs we see only "C" drive and think that there are no drivers are available except "C" drive,but all drivers are hidden by lab in charge...
Let see how to hide drivers without using any software :-
  • Press window + R  key. 
  • Open gpedit.msc


A new window will be appear as Local Group Policy Editor.
  •   Click & expand User Configuration >Administrative Templates > Windows Component


  • After Double click on Windows component on the right side bar Windows Explorer (for window 7 & xp) File Explorer (for window 8,8.1 & 10) 
  • Now click on Hide These Specified drives in My computer.
  • Click on Enable then choose below the drives you want to hide on Pick one of the following combination.
  • Then click Apply & Ok.

  • For Unhide Drive follow the same steps, In step 7 just click on  Not Configure then apply & OK
Thank you.

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