Chapter : The OSI Model and the TCP/IP Protocol Suite, Engineering - Computer Science Engineering (CSE) PDF Download

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The OSI Model and the TCP/IP Protocol Suite

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

OBJECTIVES

To discuss the idea of multiple layering in data communication and networking and the interrelationship between layers.

To discuss the OSI model and its layer architecture and to show the interface between the layers.
To briefly discuss the functions of each layer in the OSI model.
To introduce the TCP/IP protocol suite and compare its layers with the ones in the OSI model.
To show the functionality of each layer in the TCP/IP protocol with some examples.
To discuss the addressing mechanism used in some layers of the TCP/IP protocol suite for the delivery of a message from the source to the destination.

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

Example

Assume Maria and Ann are neighbors with a lot of common ideas. However, Maria speaks only Spanish, and Ann speaks only English. Since both have learned the sign language in their childhood, they enjoy meeting in a cafe a couple of days per week and exchange their ideas using signs. Occasionally, they also use a bilingual dictionary. Communication is face to face and Happens in one layer

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

Example

Now assume that Ann has to move to another town because of her job. Before she moves, the two meet for the last time in the same cafe. Although both are sad, Maria surprises Ann when she opens a packet that contains two small machines. The first machine can scan and transform a letter in English to a secret code or vice versa. The other machine can scan and translate a letter in Spanish to the same secret code or vice versa. Ann takes the first machine; Maria keeps the second one. The two friends can still communicate using the secret code, as shown in Fig.

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

THE OSI MODEL

Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. Almost three-fourths of countries in the world are represented in the ISO. 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 and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

Topics Discussed in the Section

Layered Architecture
Layer-to-layer Communication
Encapsulation
Layers in the OSI Model

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

NOTE

ISO is the organization;

OSI is the model.

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

The OSI model

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

PHYSICAL LAYER

Responsible for movement of data from one node to another node.

• Concerned with
•Physical Characteristics of the medium
•Representation of bits- Electrical, Electromagnetic, Optical
•Data rate
•Line Configuration
•Synchronization
•Physical Topology
•Transmission Mode- Simplex, Duplex, Half Duplex

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

Physical Layer

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

DATA LINK LAYER

Responsible for moving frames from one node to the other- Next hop delivery

Framing- divides the data from N/W layer into frames
Physical Addressing- Sender and Rx if the Rx is within the N/W, otherwise next hop addressing.
Data Flow Control on the sender
Error detection/control with the use of trailer
Access control- in case of Multi Link system

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

NETWORK LAYER

Source to Destination Delivery of Packets
Not required in peer-to-peer delivery
Adds Logical addresses of sender and Rx.
Routing for internetwork communication

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

Network Layer

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

TRANSPORT LAYER

• Process to Process Delivery of message b/w Tx & Rx
• Create connection b/w two end ports for sake of security.
• Service Point or Port Addressing – Yahoo Messenger
• Segmentation and Reassembly- Divide the message received from Session layer in to Segments and number them to make a sequence for reassembly at the receiving side
• Flow Control
• End to End rather than across a link.
• Controls duplication of message
• Connection Control
  • Connection Oriented Transport Layer, like Telephone
  • Connectionless Transport Layer, like E-Mail
• Error Control
• End to End rather than across a link.
• Sending transport layer makes ensure that the entire message arrives at the receiving transport layer without error.

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

SESSION LAYER

Network dialog controller. Establishes, maintains and Synchronizes interaction b/w comm. systems
Dialog Controlling – Half Duplex or Full Duplex
Synchronization – Allows a process to add checkpoints to a stream of data

The OSI Model and the TCP/IP Protocol Suite------------- Next Slide------------------- Behrouz A. Forouzan

PRESENTATION LAYER

• Concerned with Syntax and Semantics of the information exchanged b/w the two communication systems
• Translation – Encoding and Decoding
  • Sender to Common format on Sending side
  • Common to Receiving format on Rx side
• Encryption – for security and privacy purpose
• Compression – reducing the number of bits to sent over network.