about networking

1. An Introduction
to Networking
By
Surya kumar.G.K

2. 2
Builds
• Slides with the “mouse click” icon in the upper
right hand corner are “build” slides
• Not everything on the slide will appear at once
• Each time the mouse click icon is clicked, more
information on the slide will appear.

3. Part I: Basic Networks
Concepts
Concepts we will see
throughout the book

4. 4
Figure 1-1: Basic Networking Concepts
• What Is a Network?
– A network is a transmission system that connects two
or more applications running on different computers.
NetworkNetwork

5. 5
Figure 1-1: Basic Networking Concepts
• Client/Server Applications
– Most Internet applications are client/server applications
– Clients receive service from servers
– The client is often a browser
Client Computer
Server Computer
Server
Program
Client
Program
Services

6. Part II: The Nine Elements
of a Network
Although the idea of “network”
is simple, you must understand the
nine elements found in most networks

7. 7
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
1
Switch
2
Switch
3
Message (Frame)Message (Frame)
Access
Line
Trunk
Line
Server ApplicationClient Application
1.
Networks connect
applications on different computers.
1.
Networks connect
applications on different computers.
Networks connect computers:
2. Clients (fixed and mobile) and
3. Servers
Networks connect computers:
2. Clients (fixed and mobile) and
3. Servers

8. 8
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
1
Switch
3
Message (Frame)
Trunk
Line
Server ApplicationClient Application
4.
Computers (and routers)
usually communicate
by sending messages
called frames
4.
Computers (and routers)
usually communicate
by sending messages
called frames

9. 9
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
4
Message (Frame)Message (Frame)
Trunk
Line
Server ApplicationClient Application
Switch 2Switch 2
Switch 1Switch 1
Switch 3Switch 3
Client
Sends
Frame
to Sw1
Client
Sends
Frame
to Sw1
Sw1 Sends
Frame
to Sw2
Sw1 Sends
Frame
to Sw2
Sw2 Sends
Frame
To Sw3
Sw2 Sends
Frame
To Sw3
Sw3 Sends
Frame to
Server
Sw3 Sends
Frame to
Server
5.
Switches Forward
Frames Sequentially
5.
Switches Forward
Frames Sequentially

10. 10
Figure 1-5: Ethernet Switch Operation
A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65
Switch
D4-47-55-C4-B6-F9
C3-2D-55-3B-A9-4F
Port 15
Frame to C3…Frame to C3…
A1- sends a frame to C3-A1- sends a frame to C3-
Frame to C3…Frame to C3…
Switch sends frame to C3-Switch sends frame to C3-
Switching Table
Port Host
10 A1-44-D5-1F-AA-4C
13 B2-CD-13-5B-E4-65
15 C3-2D-55-3B-A9-4F
16 D4-47-55-C4-B6-F9
Switching Table
Port Host
10 A1-44-D5-1F-AA-4C
13 B2-CD-13-5B-E4-65
15 C3-2D-55-3B-A9-4F
16 D4-47-55-C4-B6-F9
15 C3-2D-55-3B-A9-4F15 C3-2D-55-3B-A9-4F
C3- is out Port 15C3- is out Port 15
1
2
3

11. 11
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
1
Switch
2
Switch
3
Switch
4
Message (Frame)Message (Frame)
Access
Line
Trunk
Line
Server ApplicationClient Application
6.
Wireless Access
Points Connect
Wireless Stations
to Switches
6.
Wireless Access
Points Connect
Wireless Stations
to Switches

12. 12
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
1
Switch
2
Switch
3
Switch
4
Message (Frame)Message (Frame)
Access
Line
Trunk
Line
Server ApplicationClient Application
7.
Routers connect networks
to the outside world;
Treated just like computers
in single networks
7.
Routers connect networks
to the outside world;
Treated just like computers
in single networks
Yes, single networks can
contain routers

13. 13
Figure 1-3: Elements of a Network
Wireless
Access Point
Mobile
Client
Router
Outside
World
Server
Computer
Client
Computer
Switch
1
Switch
2
Switch
3
Switch
4
Message (Frame)Message (Frame)
Access
Line
Trunk
Line
Server ApplicationClient Application
8. Access Lines
Connect Computers
to Switches
8. Access Lines
Connect Computers
to Switches
9. Trunk Lines Connect
Switches to Switches and
Switches to Routers
9. Trunk Lines Connect
Switches to Switches and
Switches to Routers

14. 14
Figure 1-4: Packet Switching and Multiplexing
Client
Computer A
Mobile Client
Computer B
Router D
Server
Computer C
AC
AC
AC
AC
ACAC
BD
BD
BD
BD
Access
Line
Trunk Line
Multiplexed Packets
Share Trunk Lines
So Packet Switching
Reduces the Cost of Trunk Lines
Breaking Communications into
Small Messages is Called
Packet Switching, even if the
Messages are Frames

15. 15
Network Elements: Recap
• Name the 9 Elements of Single networks.
– Without looking back through
your handout
Never talk about an
innovation “reducing cost,”
“increasing speed,” etc.
without specifying
which element is
cheaper or faster.
For example, multiplexing
only reduces the cost of
trunk lines; other
costs are not decreased
Never talk about an
innovation “reducing cost,”
“increasing speed,” etc.
without specifying
which element is
cheaper or faster.
For example, multiplexing
only reduces the cost of
trunk lines; other
costs are not decreased

16. Part III: Transmission
Speed

17. 17
Figure 1-6: Transmission Speed
• Measuring Transmission Speed
– Measured in bits per second (bps)
– In metric notation:
• Increasing factors of 1,000 …
– Not factors of 1,024
• Kilobits per second (kbps)-note the lowercase k
• Megabits per second (Mbps)
• Gigabits per second (Gbps)
• Terabits per second (Tbps)

18. 18
Figure 1-6: Transmission Speed
• Measuring Transmission Speed
– What is 23,000 bps in metric notation?
– What is 3,000,000,000 in metric notation?
– What is 15,100,000 bps in metric notation?
• Occasionally measured in bytes per second
• If so, written as Bps
• Usually seen in file download speeds

19. 19
Figure 1-6: Transmission Speed
• Writing Transmission Speeds in Proper Form
– The rule for writing speeds (and metric numbers in
general) in proper form is that there should be 1 to 3
places before the decimal point
– 23.72 Mbps is correct (2 places before the decimal
point).
– 2,300 Mbps has four places before the decimal point, so
it should be rewritten as 2.3 Gbps (1 place).
– 0.5 Mbps has zero places to the left of the decimal point.
It should be written as 500 kbps (3 places).

20. 20
Figure 1-6: Transmission Speed
• Writing Transmission Speeds in Proper Form
– How to convert 1,200 Mbps to proper form
• Divide the number 1,200 by 1000
– Move decimal point three places to the left: 1.200
• Multiply the metric suffix Mbps by 1,000
– Gbps
• Result:
– 1.2 Gbps

21. 21
Figure 1-6: Transmission Speed
• Writing Transmission Speeds in Proper Form
– How to convert 0.036 Mbps to proper form
• Multiply the number 0.036 by 1000
– Move decimal point three places to the right: 36
• Divide the metric suffix Mbps by 1,000
– kbps
• Result:
– 36 kbps

22. 22
Figure 1-6: Transmission Speed
• Writing Transmission Speeds in Proper Form
– How should you write the following in proper form?
• 549.73 kbps
• 0.47 Gbps
• 11,200 Mbps
• .0021 Gbps

23. 23
Figure 1-6: Transmission Speed
• Rated Speed
– The speed in bits per second that you should get
(advertised or specified in the standard).
• Throughput
– The speed you actually get
– Almost always lower than the rated speed
• On Shared Transmission Lines
– Aggregate throughput—total throughput for all users
– Individual throughput—what individual users get

24. Part IV: LANs and WANs

25. 25
Figure 1-8: LANs Versus WANs
CharacteristicsCharacteristics
ScopeScope
LANsLANs WANsWANs
For transmission within
a site. Campus,
building, and SOHO
(Small Office or Home
Office) LANs
For transmission within
a site. Campus,
building, and SOHO
(Small Office or Home
Office) LANs
For transmission
between sites
For transmission
between sites
Building
LAN
Building
LAN
Home
LAN
Home
LAN
Campus
LAN
Campus
LANWide Area
Network

26. 26
WANsCharacteristics LANs
Cost per bit Transmitted Low High
Figure 1-8: LANs Versus WANs
Typical Speed
Unshared 100 Mbps
to a gigabit per
second to each
desktop. Even faster
trunk line speeds.
Shared 128 kbps to
several megabits per
second trunk line
speeds
It’s simple economics. If the cost per unit is higher, the number
of units demanded will be lower.
Corporations cannot afford high-speed for most of their WAN
transmission

27. 27
Figure 1-8: LANs Versus WANs
Characteristics
ManagementManagement
LANs WANsWANs
On own premises, so
firm builds and
manages its own LAN
or outsources the
Work
On own premises, so
firm builds and
manages its own LAN
or outsources the
Work
Must use a carrier with
rights of way for
transmission in public
Area. Carrier handles
most work but
Charges a high price.
Must use a carrier with
rights of way for
transmission in public
Area. Carrier handles
most work but
Charges a high price.
ChoicesChoices UnlimitedUnlimited Only those offered by
carrier
Only those offered by
carrier

28. 28
Figure 1-9: Local Area Network (LAN) in a
Large Building
Router Core Switch
Workgroup Switch 2
Workgroup Switch 1
Wall Jack
To
WAN
Wall Jack
Server
Client
Frames from the client to the server go through Workgroup Switch 2,
through the Core Switch, through Workgroup Switch 1, and then to the
server

29. Part V: Internets

30. 30
Figure 1-11: Internets
• Single LANs Versus Internets
– In single networks (LANs and WANs), all devices
connect to one another by switches—our focus so far.
– In contrast, an internet is a group of networks connected
by routers so that any application on any host on any
single network can communicate with any application on
any other host on any other network in the internet.
LANLAN WANWAN LANLAN
Application Application
Router Router

31. 31
Figure 1-11: Internets
• Internet Components
– All computers in an internet are called hosts
– Clients as well as servers
Cat
(Ignores
Internet)
InternetInternet
Client PC
(Host)
Cellphone
(Host)
VoIP Phone
(Host)
PDA
(Host)
Server
(Host)
Host

32. 32
Figure 1-11: Internets
• Hosts Have Two Addresses
• IP Address
– This is the host’s official address on its internet
– 32 bits long
– Expressed for people in dotted decimal notation (e.g.,
128.171.17.13)
• Single-Network Addresses
– This is the host’s address on its single network
– Ethernet addresses, for instance, are 48 bits long
– Expressed in hexadecimal notation (e.g., AF-23-9B-
E8-67-47)

33. 33
Figure 1-11: Internets
• Networks are connected by devices called routers
– Switches provide connections within networks, while
routers provide connections between networks in an
internet.
• Frames and Packets
– In single networks, message are called frames
– In internets, messages are called packets

34. 34
Figure 1-11: Internets
• Packets are carried within frames
– One packet is transmitted from the source host to the
destination host across the internet
• Its IP destination address is that of the destination
host
Frame
PacketPacket
LANLAN WANWAN LANLAN
Router Router

35. 35
Figure 1-11: Internets
• Packets are carried within frames
– In each network, the packet is carried in (encapsulated
in) a frame
– If there are N networks between the source and
destination hosts, there will be one packet and N
networks between the source and destination hosts,
there will be one packet and N frames for a transmission
Frame
PacketPacket
LANLAN WANWAN LANLAN
Router Router

36. 36
Figure 1-12: Internet with Three Networks
Host B
Host A
Network X
Network Y
Network Z
R1
R2
Route A-B
PacketPacket
A packet goes all the
way across the internet;
It’s path is its route
A packet goes all the
way across the internet;
It’s path is its route

37. 37
Figure 1-12: Internet with Three Networks
Mobile Client
Host
Server
Host
Switch
Switch
X2
Switch
X1
Switch
Router R1
D6-EE-92-5F-C1-56
Network X
Route A-BRoute A-B
A route is a packet’s
path through the internet
A route is a packet’s
path through the internet
Details in
Network X
Details in
Network X
Data link
A-R1
Data link
A-R1
A data Link is a
frame’s path through
its single network
A data Link is a
frame’s path through
its single network
In Network X, the Packet is Placed in Frame X
Packet
Frame X
Host A
10.0.0.23
AB-23-D1-A8-34-DD

38. 38
Figure 1-12: Internet with Three Networks
Router R1
Router R2
AF-3B-E7-39-12-B5
Packet
Frame Y
To
Network X
To
Network Z
Network Y
Data Link
R1-R2
Route
A-B
Details in
Network Y
Details in
Network Y

39. 39
Figure 1-12: Internet with Three Networks
Host B
www.pukanui.com
1.3.45.111
55-6B-CC-D4-A7-56
Mobile Client Host
Switch
Z1
Switch
Switch
Z2
Switch
Packet
Frame Z
Network Z
Router R2
Router
Data Link
R2-B
Details in
Network Z
Details in
Network Z
Mobile Client
Computer

40. 40
Figure 1-12: Internet with Three Networks
• In this internet with three networks, in a
transmission,
– There is one packet
– There are three frames (one in each network)
• If a packet in an internet must pass through 10
networks,
– How many packets will be sent?
– How many frames must carry the packet?

41. 41
1000000010101011000100010000110110000000101010110001000100001101
Figure 1-13: Converting IP Addresses into
Dotted Decimal Notation
Divided into 4 bytes. These
are segments.
10000000 10101011 00010001 0000110100001101
Dotted decimal notation
(4 segments separated by
dots)
Dotted decimal notation
(4 segments separated by
dots)
IP Address (32 bits long)
Convert each byte to
decimal (result will be
between 0 and 255)*
128 171 17 1313
*The conversion process is described in the Hands On section
at the end of the chapter.
128.171.17.13128.171.17.13

42. 42
Figure 1-25: Windows Calculator
3.
Click on Bin to
Indicate that the
Source number
Is binary.
3.
Click on Bin to
Indicate that the
Source number
Is binary.
2.
Choose
View, Scientific
2.
Choose
View, Scientific
1.
Windows Calculators is under
Programs  Accessories
1.
Windows Calculators is under
Programs  Accessories
4.
Enter the bits of an 8-bit segment
(The calculator has an 8-bit limit)
4.
Enter the bits of an 8-bit segment
(The calculator has an 8-bit limit)

43. 43
Figure 1-25: Windows Calculator
5.
Click on Dec
To do the conversion
5.
Click on Dec
To do the conversion
6.
See the result
6.
See the result

44. 44
Converting Decimal to Binary
• Click on Dec to indicate that the input is decimal
• Type a decimal number between 0 and 255
• Click on Bin to do the conversion
• The result must be eight bits long to be a segment
of an IP address
– So if the calculator shows 1100,
– the correct answer is 00001100

45. 45
Figure 1-17: The Internet
2.
User PC’s
Internet Service
Provider
2.
Webserver’s
Internet Service
Provider
ISP ISP
1.
User PC
Host
Computer
1.
Webserver
Host
Computer
4.
NAPs = Network Access Points
Connect ISPs
Router
NAPNAP
NAPNAP
NAPNAP
ISP
ISP
3.
Internet Backbone
(Multiple ISP Carriers)Access
Line
Access
Line

46. 46
Figure 1-18: Subnets in an Internet
LAN 1
LAN 2
LAN Subnet
10.1.x.x
WAN
Subnet
123.x.x.x
LAN Subnet
60.4.3.x
LAN Subnet
10.2.x.x
LAN Subnet
10.3.x.x
LAN Subnet
60.4.15.x
LAN Subnet
60.4.7.x
Note: Subnets are single networks (collections of switches, transmission lines)
Often drawn as simple lines to focus on routers for internetworking
Router
R1
Router R3
Router
R4
Router R2
LAN Subnet
60.4.131.x

47. 47
Figure 1-19: Terminology Differences for Single-
Network and Internet Professionals
By Single-Network
Professionals
By Internet
Professionals
By Internet
Professionals
Single Networks Are
Called
Networks SubnetsSubnets
Internets Are CalledInternets Are Called InternetsInternets NetworksNetworks
In this book, we will usually call internets “internets”
and subnets “single networks”

48. 48
Figure 1-14: The Internet, internets,
Intranets, and Extranets
• Lower-case internet
– Any internet
• Upper-case Internet
– The global Internet
• Intranet
– An internet restricted to users within a single company
• Extranet
– A group of resources that can be accessed by authorized
people in a group of companies

49. 49
Figure 1-20: IP Address Management
• Every Host Must Have a Unique IP address
– Server hosts are given static IP addresses (unchanging)
– Clients get dynamic (temporary) IP addresses that may
be different each time they use an internet
• Dynamic Host Configuration Protocol (DHCP)
(Figure 1-21)
– Clients get these dynamic IP addresses from Dynamic
Host Configuration Protocol (DHCP) servers (Figure 1-
21)

50. 50
Figure 1-21: Dynamic Host Configuration
Protocol (DHCP)
Client PC
A3-4E-CD-59-28-7F
DHCP
Server
1. DHCP Request Message:
“My 48-bit Ethernet address is A3-4E-CD-59-28-7F”.
Please give me a 32-bit IP address.”
2. Pool of
IP Addresses
3. DHCP Response Message:
“Computer at A3-4E-CD-59-28-7F,
your 32-bit IP address is 11010000101111101010101100000010”.
(Usually other configuration parameters as well.)

51. 51
Figure 1-20: IP Address Management
• Domain Name System (DNS) (Figure 1-22)
– IP addresses are official addresses on the Internet and
other internets
– Hosts can also have host names (e.g., cnn.com)
• Not official—like nicknames
– If you only know the host name of a host that you want to
reach, your computer must learn its IP address
• DNS servers tell our computer the IP address of a
target host whose name you know. (Figure 1-22)

52. 52
Figure 1-22: The Domain Name System
(DNS)
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
DNS Table1.
Client Host
wishes to reach
Voyager.cba.hawaii.edu;
Needs to know
its IP Address
2. Sends DNS Request Message
“The host name is Voyager.cba.hawaii.edu”
Voyager.cba.hawaii.edu
128.171.17.13
Local
DNS
Host

53. 53
Figure 1-22: The Domain Name System
(DNS)
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
DNS Table
4. DNS Response Message
“The IP address is 128.171.17.13”
Voyager.cba.hawaii.edu
128.171.17.13
5.
Client sends packets to
128.171.17.13
3.
DNS Host
looks up the
target host’s
IP address
DNS
Host

54. 54
Figure 1-22: The Domain Name System
(DNS)
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
Host Name IP Address
… …
… …
Voyager.cba.hawaii.edu128.171.17.13
… …
DNS Table
Client Host
1. DNS Request Message
Anther DNS Host
Local
DNS
Host
3. DNS Response Message
The local DNS host
sends back the response;
the user is unaware that
other DNS hosts were involved
The local DNS host
sends back the response;
the user is unaware that
other DNS hosts were involved
If local DNS host does not
have the target host’s IP address,
it contacts other DNS hosts
to get the IP address
If local DNS host does not
have the target host’s IP address,
it contacts other DNS hosts
to get the IP address
2.
Request &
Response

55. Part VI: Security

56. 56
Figure 1-23: Firewall and Hardened Hosts
Legitimate
Host
Legitimate
Packet
Border
Firewall
Hardened
Server
Allowed Legitimate
Packet
Hardened
Client PC
Internal
Corporate
Network
Border firewall
should pass
legitimate packets
Border firewall
should pass
legitimate packets
The
Internet
Attacker
Log File

57. 57
Figure 1-23: Firewall and Hardened Hosts
Legitimate
Host
Attack
Packet
Denied
Attack
Packet
Hardened
Server
Hardened
Client PC
Internal
Corporate
Network
Border firewall
should deny (drop)
and log
attack packets
Border firewall
should deny (drop)
and log
attack packets
The
Internet
Border
Firewall
Attacker
Log File

58. 58
Figure 1-23: Firewall and Hardened Hosts
Legitimate
Host
Attacker
Attack
Packet
Denied
Attack
Packet
Internal
Corporate
Network
The
Internet
Border
Firewall
Hardened
Server
Hardened
Server
Hardened
Client PC
Hardened
Client PC
Attack
Packet
Attack
Packet
Log File
Hosts should
be hardened
against attack packets
that get through
Hosts should
be hardened
against attack packets
that get through

59. 59
Figure 1-24: Cryptographic Protections
• Cryptography
– The use of mathematical operations to thwart attacks on
message dialogues between pairs of communicating
parties (people, programs, or devices)
• Initial Authentication
– Determine the other party’s identity to thwart impostors

60. 60
Figure 1-24: Cryptographic Protections
• Message-by-Message Protections
– Encryption to provide confidentiality so that an
eavesdropper cannot reach intercepted messages
– Electronic signatures provide message-by-message
authentication to prevent the insertion of messages by
an impostor after initial authentication
– Electronic signatures usually also provide message
integrity; this tells the receiver whether anyone has
changed the message en route

61. Topics Covered

62. 62
Network Elements: Recap
• Applications (the only element that users care about)
• Computers
– Clients
– Servers
• Switches and Routers
• Transmission Lines
– Trunk lines
– Access Lines
• Messages (Frames)
• Wireless Access Points
Never talk about an
innovation “reducing cost,”
“increasing speed,” etc.
without specifying
which element is
cheaper or faster.
For example, multiplexing
only reduces the cost of
trunk lines; other
costs are not decreased
Never talk about an
innovation “reducing cost,”
“increasing speed,” etc.
without specifying
which element is
cheaper or faster.
For example, multiplexing
only reduces the cost of
trunk lines; other
costs are not decreased

63. 63
Recap: LANs and WANs
• LANs transmit data within
corporate sites
• WANs transmit data
between corporate sites
• Each LAN or WAN is a
single network
• LAN costs are low and
speeds are high
• WAN costs are high
and speeds are lower
WANWAN

64. 64
LANLAN WANWAN LANLAN
Recap: Internets
• Most firms have multiple LANs and WANs.
• They must create internets
– An internet is a collection of networks connected
by routers so that any application on any host on
any single network can communicate with any
application on any other host on any other network
in the internet.
Application Application
Router Router

65. 65
LANLAN WANWAN LANLAN
Recap: Internets
• Elements of an Internet
– Computers connected to the internet are called
hosts
• Both servers and client PCs are hosts
– Routers connect the networks of the internet
together
• In contrast, switches forward frames within
individual networks
Router
Client PC Host Server Host
Router

66. 66
Recap: Internets
• Hosts Have Two Addresses
• IP Address
– This is the host’s official address on its internet
– 32 bits long
– Expressed for people in dotted decimal notation (e.g.,
128, 171, 17.13)
• Single Network Addresses
– This is the host’s address on its single network
– Ethernet addresses, for instance, are 48 bits long
– Expressed in hexadecimal notation, e.g., AF-23-9B-
E8-67-47

67. 67
Recap: Internets
• Switches versus Routers
– Switches move frames through a single network (LAN
or WAN)
– Routers move packets through internets
• Messages
– Messages in single networks are called frames
– Messages in internets are called packets
– Packets are encapsulated within (carried inside)
frames

68. 68
Recap: Security
• Security
– Firewalls
– Hardened Hosts
– Cryptographic security
for sensitive dialogues
• Initial authentication
• Encryption for
confidentiality
• Electronic signatures for
authentication and
message integrity