This document provides an overview of computer networks and the physical layer. It defines internet versus Internet, outlines the history of the Internet, and describes protocol layering and the TCP/IP protocol suite. It also discusses the OSI model. Key points include: Internet refers to the global system of interconnected networks, while an internet can be any interconnected network; the Internet has revolutionized communication and information access; protocol layering divides communication tasks between layers with standardized protocols; and the TCP/IP protocol suite and OSI model each use layered architectures and protocols to enable communication between devices on a network.

1. CS – 8591
COMPUTER NETWORKS
Unit - I
INTRODUCTION AND
PHYSICAL LAYER
Ms. Angayarkanni S A
Assistant Professor, IT, RMKEC

2. Outline of Day 2
 Internet Vs internet
 History of Internet
 Protocol Layering
 TCP/IP Protocol suite
 OSI Model
1.2

3. Internet Vs internet
Internet
 set of all networks which
are interconnected and
interoperate using the
IETF standard protocols.
internet
 Any network of devices
which can communicate
with each other.
Internet is a superset of internets. The
Internet is the network of networks.

4. 1.4
The Internet
• The Internet has revolutionized many aspects of our
daily lives.
• It has affected the way we do business as well as the
way we spend our leisure time.
• The Internet is a communication system that has
brought a wealth of information to our fingertips
and organized it for our use.

5. Q-A
 Network of devices which can
communicate with each other
 internet
 Father of internet
 Vint Cerf
 Father of WWW
 Tim Berners Lee
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6. Protocol Layering
 Protocol 
 defines the rules that both the sender and receiver
and all intermediate devices need to follow to be
able to communicate effectively.
 Communication
 Simple  need only one simple protocol.
 complex,  need to divide the task between
different layers, in which case we need a protocol
at each layer, or protocol layering
1.6

7. Protocol Layering
 Let us develop two simple scenarios to better
understand the need for protocol layering.
 In the first scenario, communication is so simple
that it can occur in only one layer.
 In the second, the communication between Maria
and Ann takes place in three layers
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8. Protocol Layering
 First Scenario
 Maria and Ann are neighbors with a lot of
common ideas.
 Communication (one layer)
 face to face, in the same language,
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9. Protocol Layering
 First Scenario - Protocols
1. Greet each other when they meet
2. Confine the vocabulary to the level of friendship
3. Refrain from speaking if one is speaking
4. Opportunity to talk both on an issue (dialog / monolog)
5. Exchange nice words when departing
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10. Protocol Layering
 Second Scenario
 Maria and Ann are physically far away.
 Communication (three layer)
 Letters/Mail
 Should be in a secure way
 Listen/Talk

11. Second Scenario
Postal carrier facility
Protocol Layering
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12. Principles of Protocol Layering
1. if we want bidirectional communication  need to
make each layer so that it is able to perform two
opposite tasks, one in each direction.
2. we need to follow in protocol layering is that the two
objects under each layer at both sites should be
identical.

13. Logical Connections
 Layer-to-layer communication.
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14. Protocol suite
 Suite set of
interconnected rooms under
one room number
 a set of rooms designated for
one person's or family's use or
for a particular purpose
 Protocol suite Collection
of protocols that are
designed to work together.
 Set of protocols organized in
different layers
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15. TCP/IP Protocol Suite
 TCP/IP : Transmission Control Protocol/Internet
Protocol
 TCP/IP is a protocol suite (a set of protocols
organized in different layers) used in the Internet
today.
 It is a hierarchical protocol made up of interactive
modules, each of which provides a specific
functionality.
 The original TCP/IP protocol suite was defined as
four software layers built upon the hardware. Today,
however, TCP/IP is thought of as a five-layer model.
 Department of Defense Four-Layer Model
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16. Layers in TCP/IP Protocol Suite
Original layers Present day layers
1.16

17. Layered Architecture
Communication through an internet
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18. Layered in the TCP/IP Protocol Suite
Logical connections between layers in TCP/IP
Logical connections
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19. Layered in the TCP/IP Protocol Suite
Identical objects in the in TCP/IP protocol suite
Identical objects (messages)
Identical objects (segment or user datagram)
Identical objects (datagram)
Identical objects (frame)
Identical objects (bits)
Identical objects (datagram)
Identical objects (frame)
Identical objects (bits)
1.19

20. Encapsulation and Decapsulation
1.20

21. McGraw-Hill ©TheMcGraw-HillCompanies,Inc., 2000
TCP/IP Protocol Suite
Layers

22. Physical Layer
 1. Physical Characteristics of Interface and medium :
Type of Transmission medium
 2. Representation of Bits : Encoding Techniques ;
Conversion of Bits to Electrical/Optical signals
 3. Data rate: bits/sec
 4. Synchronization: Clock Synchronization at Sender &
receiver
 5. Physical Topology: Star, Bus, Mesh, Ring etc
 6. Line Configuration : Point to Point, Multipoint
Configurations
 7. Transmission Mode : Simplex , Half-Duplex, Full-
Duplex
Physical layer is responsible for movements of bits from one hop(node)
to the next

23. Data Link Layer
 1. Framing
 2. Physical Addressing
 3.Flow control
 4. Error Control: Detection & Correction
 5. Access Control
Data link layer is responsible for moving frames from one hop(node) to the
next
e.g., ARP, IEEE
802.3 and IEEE
802.11
Source: Data Communications and Networking 5E,
Forouzan
Image Source:
http://www.highteck.net/EN/DataLink/
Data_Link_Layer.html

24. Network Layer
 1. Logical Addressing: IPv4, IPv6
 2. Routing: Routing algorithms & table
(traffic routing & control)
Network layer is responsible for delivery of individual packets
from source host to destination host
e.g., IP,
ICMP, IGMP,
DHCP
Image Source:
Weblink
https://fossbytes.com/
network-layer-osi-
model/

25. Transport Layer
 1. Service point addressing: Port Address
 2. Segmentation : Divided into transmittable
segments with sequence numbers
 3. Connection Control
 4. Flow Control
 5. Session Multiplexing
 6. Error Detection & Correction (resends)
 7. Message reordering (reassembly)
Transport layer is responsible for the delivery of the message
from one process to another
e.g., TCP,
UDP

26. Application Layer
 1. Network virtual terminal (e.g. usgs)
 2.File transfer, access and management
 3.Mail services
 4.Directory services
Application layer is responsible for
providing services to the user.

27. 2.2.5 Addressing
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28. Multiplexing and Demultiplexing
Multiplexing and Demultiplexing
1.28

29. 2.29
THE OSI MODEL
o Established in 1947, the International
Standards Organization (ISO) is a
multinational body dedicated to worldwide
agreement on international standards.
o An ISO standard that covers all aspects of
network communications is the Open Systems
Interconnection (OSI) model.
o It was first introduced in the late 1970s.
ISO is the organization.
OSI is the model.

30. The OSI Model
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31. TCP/IP and OSI Model
TCP/IP and OSI model
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32. Lack of OSI Model’s Success
 The OSI model appeared after the TCP/IP
protocol suite.
 Changing it cost a lot.
 Some layers in the OSI model were never fully
defined
 OSI did not show a high enough level of
performance
1.32

33.  A device operating at network layer is
called ____
a) Router
b) Equalizer
c) Bridge
d) Repeater
1.33
Q-A

34.  A device operating at network layer is
called ____
a) Router
b) Equalizer
c) Bridge
d) Repeater
1.34
Q-A

35.  An IP Packet is called ____
a) User datagram
b) segment
c) datagram
d) frames
1.35
Q-A

36.  An IP Packet is called ____
a) User datagram
b) segment
c) datagram
d) frames
1.36
Q-A

37.  An TCP Packet is called ____
a) User datagram
b) segment
c) datagram
d) bits
1.37
Q-A

38.  An TCP Packet is called ____
a) User datagram
b) segment
c) datagram
d) bits
1.38
Q-A

39.  The physical layer is concerned with
___________
a) bit-by-bit delivery
p) process to process delivery
c) application to application delivery
d) port to port delivery
1.39
Q-A

40.  The physical layer is concerned with
___________
a) bit-by-bit delivery
p) process to process delivery
c) application to application delivery
d) port to port delivery
1.40
Q-A

41. THANK YOU
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