This document provides an introduction to networking concepts including: - Binary and hexadecimal number systems and how they relate to IP addressing. - Network layers including the OSI and TCP/IP models. - Common network devices, media, and protocols used to connect local and wide area networks. - Key functions of each layer in the OSI model including physical, data link, network, transport, and application layers. - How data is encapsulated as it moves up the OSI model layers and de-encapsulated as it moves down.

1. 1
Module 1
Introduction to
Internetworking
By Dr. Percy DIAS
© 2009, Cisco Systems, Inc. All rights reserved.

2. 2
Computing Measurement Terms
• Bits are binary digits. They are either 0s or
1s. In a computer, they are represented by
On/Off switches or the presence or
absence of electrical charges, light pulses,
or radio waves.

3. 3
Computing Measurement Terms

4. 4
Base 10 (Decimal) Number
System

5. 5
Base 10 (Decimal) Calculations
• Should be familiar because you’ve used it since childhood
• Example: the number 235 = (2 x 100) + (3 x 10) + (5 x 1)
• Because you’ve used it so long, you probably don’t think
about it

6. 6
Base 2 (Binary) Numbers

7. 7
Base 2 (Binary) Numbers
• Binary uses just two digits, 0 and 1
• Similar to Base 10; differences are in the details
• Example: the binary number 11101011 is equivalent to the
decimal number 235 – Add the decimal value of each bit to
get the decimal number
• (1 * 128) + (1 * 64) + (1 * 32) + (0 * 16) + (1 * 8) + (0 * 4) + (1
* 2) + (1 * 1) = 235 decimal
1

8. 8
Four-Octet Dotted-decimal
Representation of 32-Bit Binary
Numbers
• Split the binary number into four groups of eight
binary digits. Then convert each group of eight
bits, also known as an octet into its decimal
equivalent.

9. 9
Converting IP Addresses
Between Decimal and Binary
• IP addresses are 32-bit binary numbers
• Humans find it easier to read decimal
numbers, so IP addresses are often
expressed in dotted-decimal format
• Each decimal number represents 8 binary
digits, also know as an “octet”
• Each octet can be converted to a decimal
number between 0 and 255, inclusive

10. 10
Converting Decimal to Binary
Start by dividing the decimal by the largest
number in the Value row that will go.

11. 11
Converting 8-bit Binary Numbers to
Decimal Numbers

12. 12
Converting 8-Bit Binary to Decimal
• Binary numbers are converted to decimal
numbers by multiplying the binary digits by
the base number of the system, which is
base 2, and raised to the exponent of its
position.

13. 13
Hexadecimal
• The base 16, or hexadecimal (hex), number
system is used frequently when working with
computers, because it can be used to
represent binary numbers in a more readable
form.

14. 14
Hexadecimal
• Popularly called “hex”
• Each hex digit represents 4 bits
• Uses 16 symbols:
0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
• A = 10, B = 11, C = 12, D = 13, E = 14,
F = 15

15. 15
Conversion

16. 16
Boolean or Binary Logic
• Boolean logic is based on digital circuitry
that accepts one or two incoming voltages.
• Boolean logic is a binary logic that allows
two numbers to be compared and generate
a choice based on the two numbers.

17. 17
Boolean or Binary Logic

18. 18
Network Protocols
• Communication must follow a set of rules
• Networking rules are defined by a set of
standards and protocols
• A single standard or protocol defines what a
small part of the network does
• The Transmission Control Protocol/Internet
Protocol (TCP/IP) suite defines a large set of
standards and protocols used to network
computers

19. 19
Media
• Media refers to the various physical
environments through which transmission
signals pass.
• Common network media include twisted-
pair, coaxial, fiber-optic cable, and the
atmosphere through which wireless
transmission occurs.

20. Network Media
Media Example Encoding
Copper Twisted-pair cable usually
used as LAN media
Electrical pulses
Fiber-optic Glass or plastic fibers in a
vinyl coating usually used
for long runs in a LAN as
a trunk
Light pulses
Wireless Connects local users
through the air
Electromagnetic
waves
20

21. Network Media
21

22. 22
Local-area Networks (LANs)
LAN Technology: Ethernet, Token Ring,
FDDI (Fiber Distributed Data Interface)

23. 23
Wide-area Networks (WANs)

24. Internetworks Made Up of LANs
and WANs
24

25. 25
Importance of Bandwidth
• Bandwidth is defined as the amount of
information that can flow through a
network connection in a given period of
time

26. 26
Bandwidth Pipe Analogy

27. 27
Bandwidth Highway Analogy

28. 28
The Need for Networking
Protocols and Standards
• 1960s to 1980s – Each vendor set its own
proprietary protocols and standards
• Equipment from different vendors would
not interoperate
• Eventually, open standards were agreed
upon
• Open standards allow more competition,
which increases speed of development

29. 29
Using Layers to Describe Data
Communication
• Data communication is a very complex process.
• Difficult to understand this process as a whole.
• Solution is to break down the total network
communication system into a series of layers.
• Each layer is responsible for a specific part of
network communication.
• These layers interact with the layer above and
below.
• Two common network models that use layers
are Open System Interconnection (OSI)
reference model and the TCP/IP reference
model.

30. 30
OSI Reference Model

31. 31
Functions of Layer 7
• Application Layer: Network Process to
Applications
– Provides network services to the user’s
application
– User interface
– Examples – Telnet, HTTP, Web browsers

32. 32
Functions of Layer 6
• Presentation Layer: Data Representation
–Ensures that the information that the application
layer of one system sends out is readable by the
application layer of another system
–How data is presented
–Special processing, such as data format,
compression and encryption

33. 33
Functions of Layer 5
• Session Layer: Interhost
Communication
–Establishes, manages, and
terminates session between two
communication host.

34. 34
Functions of Layer 4
• Transport Layer: End-to-End Connection
– How reliable transport between two hosts is
accomplished is the concern of the transport
layer.
– Reliable or unreliable delivery
– Examples: TCP, UDP

35. 35
Functions of Layer 4
• TCP breaks large data into
segments
• TCP marks each data packet with
a sequence number
• A missing packet can be resent

36. 36
Functions of Layer 3
• Network Layer: Address and Best Path
– Provides connectivity and path selection
between two host systems that may be located
on geographically separated networks
– Provides logical addressing which routers use
for path determination
– Examples: IP

37. 37
Functions of Layer 2
• Data Link Layer: Access to media
– Concerned with physical (as opposed
to logical) addressing
– Access to media using MAC address
– Error detection

38. 38
Functions of Layer 1
• Physical Layer: Binary
transmission
–Moves bits between devices

39. 39
The Seven Layers of the OSI
Reference Model
• The application (upper) layers
– Layer 7: Application
– Layer 6: Presentation
– Layer 5: Session
• The data-flow (lower) layers
– Layer 4: Transport
– Layer 3: Network
– Layer 2: Data link
– Layer 1: Physical

40. 40
OSI Model and TCP/IP Model

41. 41
TCP/IP Protocol Graph

42. 42
Use of the OSI Model in the
CCNA Curriculum

43. 43
Encapsulation
The lower layers use encapsulation to put the
protocol data unit (PDU) from the upper layer into its
data field and to add headers and trailers that the
layer can use to perform its function.

44. 44
Names for Data at Each Layer

45. 45
De-Encapsulation
• When the data link layer receives
the frame, it does the following:
–It reads the physical address and
other control information provided by
the directly connected peer data link
layer.
–It strips the control information

46. 46
Cisco Academy 3 References
• CCNA1 Online Materials
– Slide 2 – 17 : 1.2.2 -1.2.9
– Slide 18 – 23 : 2.1.5 – 2.1.7
– Slide 25 - 29 : 2.2.1 – 2.2.3
– Slide 30 – 45 : 2.3.2 – 2.3.7

47. 47
Cisco Academy 4 Exploration
Reference
• Networking Fundamentals
– Slide 2 – 17 : 6.1.1 – 6.1.4
– Slide 18 – 23 : 2.1.6 – 2.2.3
– Slide 25 – 29 : 2.3.2 – 2.4.2
– Slide 30 – 45 : 2.4.1 – 2.4.8