Seven Layers of Iso Osi Model

The Iso Osi model are explained below. The seven layers of the Osi model are:

Application Presentation Session Transport Network Antiqua">Data Link Physical
1 Application layer:

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This layer provides a means for the user to entrance information on the network through an application. Many user applications that need to recapitulate over the network interact with the Application layer protocol directly. The user applications are not part of Osi Application layer, use the networking services offered by the networking protocol suite. Application layer functions typically comprise identifying communication partners, and determining availability of required resources. Some examples of application layer implementations comprise Telnet, File transfer Protocol (Ftp), and straightforward Mail transfer Protocol (Smtp).

2 Presentation layer:

Presentation layer converts local host computer data representations into a thorough network format for transmission on the network. On the receiving side, it changes the network format into the thorough 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.
Examples of Presentation layer coding and conversion schemes comprise base data representation formats, conversion of character representation formats, base data compression schemes, and base data encryption schemes.

Presentation layer implementations are not typically related with a single protocol stack. Some familiar standards for video comprise QuickTime and request for retrial photograph Experts Group (Mpeg). QuickTime is an Apple Computer specification for video and audio, and Mpeg is a thorough for video compression and coding.

3. Session layer:

The session layer establishes, manages, and terminates communication sessions. communication sessions consist of service requests and service responses that occur in the middle of applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations comprise AppleTalk's Zone information Protocol (Zip), and Decent Phase Session control Protocol (Scp).

4.Transport layer:

Transport layer is responsible for providing reliable service in the middle of the hosts. Upper layer datagrams are broken down into manageable datagrams and then thorough header information (such as sequence number, port number, etc.) is added to the datagram before passing it on to the Network layer. Two frequently used converyance protocols are the Tcp (Transmission control Protocol) and the Udp (User Datagram Protocol).

Important features of converyance layer:

Transport layer ensures reliable service. Breaks the message (from sessions layer) into smaller datagrams, and appends thorough unit header information. Responsible for communicating with the Session layer
Important features of Tcp/Udp:

Tcp/Ip widely used protocol for Transport/Network layers Tcp: (Transport control Protocol) Tcp ensures that a packet has reached its intended destination by using an acknowledgement. If not, it retransmits the lost messages. Hence, Tcp is called a relationship oriented protocol. Udp (Universal Data gram Protocol): Udp plainly transmits packets over the internet. It does not wait for an acknowledgement. It is the accountability of upper layer protocols to ensure that the information had reached the intended partner(s). Hence, Udp is often called connectionless protocol. Application programs that do not need connection-oriented protocol generally use Udp.
5. Network layer:

Network layer is responsible for the routing of packets through the entire network. The layer uses logical addressing for this purpose. Note that the physical address (like Mac address) keeps changing from hop to hop when a packet travels from source to destination. As a result, an address that doesn't change is required to ensure continuity in the middle of hops. This is nothing but logical address. For Ip networks, Ip address is the logical address; and for Novell network, Ipx address is the logical address, and so on. This layer also provides for congestion control, and accounting information for the network. Ip (Internet Protocol) is an example of a network layer protocol.

6. Data link layer:

Data link layer provides delivery of information frames in the middle of communicating partners. This layer is responsible for flow regulation, error detection and correction, and framing of bits for transmission. The network data frame is made up of checksum, source address, destination address, and the data itself. The largest frame size that can be sent is known as the maximum transmission Unit (Mtu).

Important features of Data link layer:

Logical Link control (Llc): Defines how data is transferred over the cable and provides data link service to the higher layers. Medium entrance control (Mac): Controls media entrance by regulating the communicating nodes using pre-defined set of rules. (i.e. Token passing, Ethernet [Csma/Cd] all have Mac sub-layer protocol).


Different Data link layer protocols define different network and protocol characteristics, together with physical addressing, network topology, error notification, sequencing of frames, and flow control. physical addressing (as opposed to logical addressing) defines how devices are addressed at the data link layer. The protocols used in Data link layer are Slip, Ppp, and Cslp.

7. physical layer:

This is the bottom-most layer of the Osi model. The physical layer handles the bit-level communications over the physical medium. The physical medium could be made up of wired electrical signals, or light, or radio (wireless) signals. physical layer specifications define characteristics such as media, data rates, maximum transmission distances, and physical connectors.

Some of the leading standards that deal with physical layer specifications are:

Rs-232(for serial communication lines), X.21, Eia 232, and G730.

Physical layer and Data link layer implementations can be categorized as whether Lan or Wan specifications.

Seven Layers of Iso Osi Model

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