Category - Layers

Presentation Layer

Manages the presentation of the information in an ordered and meaningful manner. This layer’s primary function is the syntax and semantics of the data transmission. It converts local host computer data representations into a standard network format for transmission on the network. On the receiving side, it changes the network format into the appropriate host computer’s format so that data can be utilized independent of the host computer. ASCII and EBCDIC conversions, cryptography, and the like are handled here.

The presentation layer provides a variety of coding and conversion functions that are applied to application layer data. These functions ensure that information sent from the application layer of one system would be readable by the application layer of another system. Some examples of presentation layer coding and conversion schemes include common data representation formats, conversion of character representation formats, common data compression schemes, and common data encryption schemes.

Common data representation formats, or the use of standard image, sound, and video formats, enable the interchange of application data between different types of computer systems. Using different text and data representations, such as EBCDIC and ASCII, uses conversion schemes to exchange information with systems. Standard data compression schemes enable data that is compressed.

Presentation layer implementations are not typically associated with a particular protocol stack. Some well-known standards for video include QuickTime and Motion Picture Experts Group (MPEG). QuickTime is an Apple Computer specification for video and audio, and MPEG is a standard for video compression and coding.

Among the well-known graphic image formats are Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF). GIF is a standard for compressing and coding graphic images. JPEG is another compression and coding standard for graphic images, and TIFF is a standard coding format for graphic images.

  • Presents data to the application¬†layer.
  • Acts as a data format translator.
  • Handles the structuring of data and negotiating data transfer syntax to Layer 7.
  • Processes involved include data encryption, decryption, compression, and
  • decompression.

Points:

  • Provide format and Present data in¬†appropriate¬†format.
  • extension : gif,jpg,doc,xcls
  • gif will not open in notepad
  • notepad will not open in gif

Application Layer

Application Layer enable the user, whether human or software, to access the network. It provides user interfaces and support for services such as electronic mail,file access and transfer, access to system resource, surfing the world wide web, and network management.

Application layer is Responsible for Providing Services to the user.

  • Application Layer is a term used in categorizing protocols and methods in architectural models of computer networking. Both the OSI model and the Internet Protocol Suite (TCP/IP) define application layers.
  • In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications via an Internet Protocol (IP) network using the Transport Layer protocols to establish underlying host-to-host connections.
  • Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
  • The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.

Examples

Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

                                                                                                OSI  Model

Points:

  • Application Layer do¬†Interaction (Providing Services to the user)
  • 80% Application on internet do interact
  • i.e ¬†google.com —–> will auto —–> ¬†www.google.com ——> Here www intract ¬†on port 80
  • i.e ¬†for buy house property dealer do interact

Application Layer Protocols

Application Layer Protocols

Application Protocols Supported by the Application Layer

  • Telnet

A TCP/IP protocol that provides terminal emulation to a remote host by creating a virtual terminal. TeraTerm is one program that can be installed on a user computer to create Telnet sessions. This protocol requires authentication via a username and password.

application layer

  • Hypertext Transfer Protocol (HTTP):

Enables web browsing with the transmission of Hypertext Markup Language (HTML) documents on the Internet.

  • Secure Hypertext Transfer Protocol (HTTPS):

Enables secure web browsing. A secure connection is indicated when the URL begins with https:// or when a lock symbol is in the lower-right corner of the web page that is being viewed.

  • File Transfer Protocol (FTP) :

Allows a user to transfer files. Provides access to files and directories.

  • Trivial File Transfer Protocol (TFTP):

A bare-bones version of FTP that does not provide access to directories. With TFTP you can simply send and receive files. Unlike FTP, TFTP is not secure and sends smaller blocks of data.

  • Domain Name System (DNS):

Resolves hostnames such as cisco.com into IP addresses.

 

  • Simple Mail Transfer Protocol (SMTP):

Sends email across the network.

  • Post Office Protocol 3 (POP3):

Receives email by accessing a network server.

 

  • Network File System (NFS):

Allows users with different operating systems (that is, NT¬†and Unix workstations) to share files through a network.Remote files appear as though they reside on a local¬†machine even though the local machine might be ‚Äúdiskless.‚ÄĚ

  • Network News Transfer Protocol (NNTP)

Offers access to Usenet newsgroup postings.Simple Network Management Protocol (SNMP) Monitors the network and manages configurations.Collects statistics to analyze network performance and
ensure network security.

  • Network Time Protocol (NTP)

Synchronizes clocks on the Internet to provide accurate local time on the user system.
Dynamic Host Configuration Protocol (DHCP) Works dynamically to provide an IP address, subnet mask, domain name, and a default gateway for routers. Works with DNS and WINS (used for NetBIOS addressing).

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