Introduction - NET331

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Introduction - NET331 Powered By Docstoc
					Kingdom of Saudi Arabia
Prince Norah bint Abdul Rahman University
College of Computer Since and Information System

         T.Najah Al_Subaie
Chapter 2
   OSI Model
   TCP/IP Model
Layered Tasks
   We use the concept of layers in our daily life. As an
    example, let us consider two friends who
    communicate through postal mail.
   The process of sending a letter to a friend would be
    complex if there were no services available from
    the post office.
Tasks Involved in Sending a Letter
The OSI Model
   Established in 1947,
   the International Standards Organization (ISO) is a
    multinational body dedicated to worldwide
    agreement on international standards.
    An ISO standard that covers all aspects of network
    communications is the Open Systems Interconnection
    (OSI) model.
   It was first introduced in the late 1970s.
 ISO is the organization.
 OSI is the model.
Seven layers of the OSI model
The OSI Model
   ISO model is not a protocol. It is a model for
    understanding and designing a network
   It shows how to facilitate communication between
    different system without requiring changes to the
    logic of the underlying hardware and software.
The OSI Model
   It is a layered framework for the design of network
    systems that allows communication between all
    types of computer systems.
   Consists of seven separated but related layers.
   Each layer defines a part of the process of moving
    information across a network
Layered Architecture
   Each layer groups the networking functions that had
    related uses.
   Each layer uses the services provided by the layer
    just below it.
   Between machines, the corresponding layers are
    communicated using a set of protocols.
     Peer   to Peer processes.
The interaction between layers in the
OSI model
The philosopher-translator-secretary
Interfaces Between Layers
   Each interface defines the information and services
    a layer must provide for the layer above it.
   Interfaces allows the specific implementation of the
    layer’s functionality to be changed or replaced
    without requiring changes to the surrounding layers.
An exchange using the OSI model
Organization of the Layer
   At the sender:
       each layer adds a header or possibly a trailer.
   At the receiver:
     each   layer removes its corresponding header or trailer
        and performs the appropriate actions.
   When the message reaches layer 7 (application
    layer) , the message is in a form appropriate to the
   The data portion of a packet at level N-1 carries
    the whole packet ( data and header/ trailer) from
    level N.
Layers in the OSI Model.
   We briefly describe the functions of each layer in
    the OSI model.
     Physical Layer
     Data Link Layer

     Network Layer

     Transport Layer

     Session Layer

     Presentation Layer

     Application Layer
Physical Layer
   The physical layer is responsible for movements
    of individual bits from one hop (node) to the
Physical Layer
   It is also concerned with:
     Physical characteristics of interfaces and medium.
     Representation of bits.

     Data rate.

     Synchronization of bits.

     Line configuration.

     Physical topology.

     Transmission mode.
Data Link Layer
   The data link layer (DLL) is responsible for
    moving frames from one hop (node) to the
Data Link Layer
Data Link Layer
   It is also concerned with:
       Framing.
           Data units in DLL.
       Physical addressing
           Adding header to define header/receiver of the frame.
       Flow control
           To avoid overwhelming the receiver.
       Error control
           A set of mechanisms to keep a reliable transmission.
       Access control
           To control the traffic in the link.
Hop-to-hop delivery by the DLL
Network Layer
   The network layer is responsible for the
    delivery of individual packets from the source
    host to the destination host.
Network Layer
Source-to-Destination Delivery
Transport Layer
   The transport layer is responsible for the delivery
    of a message from one process to another.
Transport Layer
Transport Layer
   It is also concerned with:
     Service point addressing.
     Segmentation and reassembly.

     Connection control.

     Flow control.

     Error control.
Process to Process Delivery by the
Transport Layer
Session Layer
   The session layer is responsible for dialog
    control and synchronization.
   Its functionalities:
     Dialog control.
     Synchronization.
Session Layer
Presentation Layer
   The presentation layer is responsible for
    translation, compression, and encryption.
Presentation Layer
Application Layer
   The application layer is responsible for
    providing services to the user.
Application Layer
Summary of Layers
TCP/IP Reference Model
   the TCP/IP protocol suite is made of five layers:
     physical,

     data link,
     network,

     transport,

     application.
TCP/IP and OSI model

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