The document discusses network models and the OSI model. It describes the seven layers of the OSI model which provides a logical breakdown of network interaction to facilitate communication standards. Each layer deals with a particular aspect of network communication, from the physical layer which deals with physical interfaces and transmission to the application layer which provides services to the user. The document also discusses the TCP/IP protocol suite and how it maps to the OSI model, containing five layers, as well as addressing in networks including physical, logical, port, and specific addresses.

1. Networking Fundamentals
Network Models
2.1

2. 2.2
LAYERED TASKSLAYERED TASKS
We use the concept ofWe use the concept of layerslayers in our daily life. As anin our daily life. As an
example, let us consider two friends who communicateexample, let us consider two friends who communicate
through postal mail. The process of sending a letter to athrough postal mail. The process of sending a letter to a
friend would be complex if there were no servicesfriend would be complex if there were no services
available from the post office.available from the post office.

3. 2.3
Tasks involved in sending a letter

4. 2.4
THE OSI MODELTHE OSI MODEL
Established in 1947, the International StandardsEstablished in 1947, the International Standards
Organization (Organization (ISOISO) is a multinational body dedicated to) is a multinational body dedicated to
worldwide agreement on international standards. An ISOworldwide agreement on international standards. An ISO
standard that covers all aspects of networkstandard that covers all aspects of network
communications is the Open Systems Interconnectioncommunications is the Open Systems Interconnection
((OSIOSI) model. It was first introduced in the late 1970s and) model. It was first introduced in the late 1970s and
published in 1984.published in 1984.

5. 2.5
ISO is the organization.
OSI is the model.
Note

6. 2.6
Seven layers of the OSI model
A seven-layer logical break
down of network interaction
to facilitate communication
standards
Each layer deals with a
particular aspect of network
communication
"All people seem to need data processing."

7. 2.7
The interaction between layers in the OSI model
Hierarchy_

8. 2.8
An exchange using the OSI model
Encapsulation_

9. 2.9
LAYERS IN THE OSI MODELLAYERS IN THE OSI MODEL
Lets briefly describe the functions of each layer in theLets briefly describe the functions of each layer in the
OSI model.OSI model.

10. 2.10
Physical layer
The physical layer is responsible for movement of
individual bits from one hop (node) to the next. It deals with the
mech & electrical specs of the interface & transmission medium,
as well as the procedures & functions they have to perform for
transmission to occur.

11. 2.11

12. 2.12
Data link layer
The data link layer is responsible for moving
frames from one hop (node) to the next. It makes the physical
layer, a raw transmission facility into a reliable link.

13. 2.13

14. 2.14
Hop-to-hop delivery

15. 2.15
Network layer
The network layer is responsible for the delivery of individual
packets from the source host to the destination host, possibly
across multiple networks (links).

16. 2.16

17. 2.17
Source-to-destination delivery

18. 2.18
Transport layer
The transport layer is responsible for the delivery
of a message from one process to another. It ensures that the
whole message arrives intact & in order.

19. 2.19

20. 2.20
Reliable process-to-process delivery of a message

21. 2.21
Session layer
The session layer is responsible for dialog
control and synchronization.

22. 2.22

23. 2.23
Presentation layer
The presentation layer is responsible for translation, compression,
and encryption. It is concerned with the syntax and semantics of
the information exchanged between the two systems.

24. 2.24

25. 2.25
Application layer
The application layer is responsible for providing services to the
user. It enables the user to access the network.

26. 2.26

27. 2.27
Summary of layers

28. 2.28
TCP/IP PROTOCOL SUITETCP/IP PROTOCOL SUITE
• It was first introduced in 1974 and v4 was publishedIt was first introduced in 1974 and v4 was published
in 1979.in 1979.
• The layers in theThe layers in the TCP/IP protocol suiteTCP/IP protocol suite do notdo not
exactly match those in the OSI model. The originalexactly match those in the OSI model. The original
TCP/IP protocol suite was defined as having fourTCP/IP protocol suite was defined as having four
layers:layers: host-to-networkhost-to-network,, internetinternet,, transporttransport, and, and
applicationapplication..
• However, when TCP/IP is compared to OSI, weHowever, when TCP/IP is compared to OSI, we
can say that the TCP/IP protocol suite is made of fivecan say that the TCP/IP protocol suite is made of five
layers:layers: physicalphysical,, data linkdata link,, networknetwork,, transporttransport, and, and
applicationapplication..
• We can call this the Hybrid model.We can call this the Hybrid model.

29. 2.29
TCP/IP and OSI model

30. 2.30

31. 2.31

32. 2.32

33. 2.33
ADDRESSINGADDRESSING
Four levels of addresses are used in an internet employingFour levels of addresses are used in an internet employing
the TCP/IP protocols:the TCP/IP protocols:
• physicalphysical,,
• logicallogical,,
• portport, and, and
• specificspecific..

34. 2.34
Relationship of layers and addresses in TCP/IP

35. 2.35

36. 2.36
Physical addresses
Example

37. 2.37
As we will see later, most local-area networks use a 48-
bit (6-byte) physical address written as 12 hexadecimal
digits; every byte (2 hexadecimal digits) is separated by a
colon, as shown below:
Example
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.

38. Ethernet (?) network card showing its MAC address

39. 2.39
An IPv4 address is a 32-bit address that uniquely and universally defines the
connection of a device (for example, a computer or a router) to the Internet.
Dotted-decimal notation and binary notation for an IPv4 address:

40. 2.40
Next Figure shows a part of an internet with two routers
connecting three LANs. Each device (computer or
router) has a pair of addresses (logical and physical) for
each connection. In this case, each computer is
connected to only one link and therefore has only one
pair of addresses. Each router, however, is connected to
three networks (only two are shown in the figure). So
each router has three pairs of addresses, one for each
connection.
Example

41. IP addresses
Routing Table used to find the next hop logical address & ARP gives the physical address.

42. 2.42

43. 2.43
Figure shows two computers communicating via the
Internet. The sending computer is running three
processes at this time with port addresses a, b, and c. The
receiving computer is running two processes at this time
with port addresses j and k. Process a in the sending
computer needs to communicate with process j in the
receiving computer. Note that although physical
addresses change from hop to hop, logical and port
addresses remain the same from the source to
destination.
Example

44. 2.44
Port addresses

45. 2.45
Example
As we will see later, a port address is a 16-bit address
represented by one decimal number as shown.
107
A 16-bit port address represented
as one single number.

46. 2.46
What is a socket?
is the combination of an IP address (the location of the computer)
and a port (which is mapped to the application program process)
into a single identity, much like one end of a telephone connection
is the combination of a phone number and a particular extension.

47. 2.47