ANAND.ppt

1.1
Chapter 1
Introduction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

1.2
1-1 NETWORK
Two or More Computers Connected together
Purposes :
• Communication
• Resource sharing
 Components of a data communications system
 Data Flow
Topics discussed in this section:

1.3
Figure 1.1 Components of a data communication system

1.4
Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

1.5
Network Criteria
 Performance
 Depends on Network Elements
 Measured in terms of Delay and Throughput
 Reliability
 Failure rate of network components
 Measured in terms of availability/robustness
 Security
 Data protection against corruption/loss of data due to:
 Errors
 Malicious users

1.6
Physical Structures
 Type of Connection
 Point to Point - single transmitter and receiver
 Multipoint - multiple recipients of single transmission
 Physical Topology
 Connection of devices
 Type of transmission - unicast, mulitcast, broadcast

1.7
Figure 1.3 Types of connections: point-to-point and multipoint

1.8
Figure 1.4 Categories of topology

1.9
Figure 1.5 A fully connected mesh topology (five devices)

1.10
Figure 1.6 A star topology connecting four stations

1.11
Figure 1.7 A bus topology connecting three stations

1.12
Figure 1.8 A ring topology connecting six stations

1.13
Figure 1.9 A hybrid topology: a star backbone with three bus networks

1.14
Categories of Networks
 Local Area Networks (LANs)
 Short distances
 Designed to provide local interconnectivity
 Wide Area Networks (WANs)
 Long distances
 Provide connectivity over large areas
 Metropolitan Area Networks (MANs)
 Provide connectivity over areas such as a city, a campus

2.15
2-1 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.
Sender, Receiver, and Carrier
Hierarchy

2.16
Figure 2.1 Tasks involved in sending a letter

2.17
2-2 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.
Layered Architecture
Peer-to-Peer Processes
Encapsulation

2.18
ISO is the organization.
OSI is the model.
Note

2.19
Figure 2.2 Seven layers of the OSI model

2.20
Figure 2.3 The interaction between layers in the OSI model

2.21
Figure 2.4 An exchange using the OSI model

2.22
2-3 LAYERS IN THE OSI MODEL
In this section 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

2.23
Figure 2.5 Physical layer

2.24
The physical layer is responsible for movements of
individual bits from one hop (node) to the next.
Note

2.25
Figure 2.6 Data link layer

2.26
The data link layer is responsible for moving
frames from one hop (node) to the next.
Note

2.27
Figure 2.7 Hop-to-hop delivery

2.29
The network layer is responsible for the
delivery of individual packets from
the source host to the destination host.
Note

2.30
Figure 2.9 Source-to-destination delivery

2.31
Figure 2.10 Transport layer

2.32
The transport layer is responsible for the delivery
of a message from one process to another.
Note

2.33
Figure 2.11 Reliable process-to-process delivery of a message

2.34
Figure 2.12 Session layer

2.35
The session layer is responsible for dialog
control and synchronization.
Note

2.36
Figure 2.13 Presentation layer

2.37
The presentation layer is responsible for translation,
compression, and encryption.
Note

2.38
Figure 2.14 Application layer

2.39
The application layer is responsible for
providing services to the user.
Note

2.40
Figure 2.15 Summary of layers

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