network models t.najah al_subaie kingdom of saudi arabia prince norah bint abdul rahman university...
Post on 23-Dec-2015
213 Views
Preview:
TRANSCRIPT
NETWORK MODELS
T.Najah Al_Subaie
Kingdom of Saudi Arabia
Prince Norah bint Abdul Rahman University
College of Computer Since and Information System
NET331
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.
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.
The OSI Model
ISO model is not a protocol. It is a model for understanding and designing a network architecture.
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.
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.
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 applications.
Encapsulation
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 next.
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 next.
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.
Network Layer
The network layer is responsible for the delivery of individual packets from the source host to the destination host.
Transport Layer
The transport layer is responsible for the delivery of a message from one process to another.
Transport Layer
It is also concerned with: Service point addressing. Segmentation and reassembly. Connection control. Flow control. Error control.
Session Layer
The session layer is responsible for dialog control and synchronization.
Its functionalities: Dialog control. Synchronization.
Presentation Layer
The presentation layer is responsible for translation, compression, and encryption.
TCP/IP Reference Model
the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, application.
top related