Using MIS 2e Chapter 6 Appendix How the Internet Works

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Oct 23, 2013 (3 years and 10 months ago)

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© Pearson Prentice Hall 2009

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Using MIS 2e


Chapter 6 Appendix




How the Internet Works

David Kroenke


10/02


4:00PM

© Pearson Prentice Hall 2009

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Study Questions


Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com become 165.193.123.253?

© Pearson Prentice Hall 2009

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Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com become 165.193.123.253?

© Pearson Prentice Hall 2009

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Q1


How does email travel?


There are
many different network components

involved in
sending an email message across the Internet.



Different types of
computers
, like a PC or a MAC, are used.



Different types of
operating systems
, such as Windows, MAC
OS, or Linux, are used.



Different types of
email application programs
, such as Outlook
or Mozilla Thunderbird, are used.



A combination of
wired and wireless connections

are used.


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Q1


How does email travel?

We resolve these differences by using the following process for all
internet transmissions.



Messages are broken down first into
segments using

TCP
, and
then into
packets using IP
, which
routers

send over an internet,
and finally into
frames using the data link protocol
, which the
NIC
sends using the appropriate protocol for the transmission
media in use.



Once a message arrives at its intended destination, the data link and
TCP/IP protocols combine the
frames into packets
, the
packets
into segments
, and the
segments into a message

for the
receiving application program
.



The key concept is to
divide & conquer by using four layers of
software and one layer of firmware based on the protocol
layers
.


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Q1


How does email travel?

Application Layer

Document
-

5 Document


TCP Layer

Segments
-

4 Segments


IP Layer


Packets
-

3 Packets Packets


Data Link Layer

Frames
-

2 Frames Frames


Firmware

NIC

-

1
Router

NIC

Sending Computer

Receiving Computer

Switch

Switch

Logical Address

Physical Address

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Segment, Packet, Frame Architecture


All segments, packets, and frames have the
same basic
architecture

(see below).


A
segment
is broken into
packets
and a packet is broken into
frames
.


The
small frames

can work their way through an internet, taking
various different paths based on congestion, with much greater
throughput then the large segments.


Plus,
retransmitting a few frames

takes much less time, in the
case of errors, then retransmitting segments.


Header

Trailer

Message Bits

Addressing

Reliability

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Q1


How does email travel?

Fig 6A
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1 Sample Networks


This figure shows how an email message uses various hardware
components to cross an internet.
Transmissions go from computer to
switch to switch … to router to router … to switch to switch … to
computer.

The protocol used to direct the transmission across a link (
IP
or
PPP
) depends on the
device receiving the transmission
.

IP
is necessary
for routing across multiple devices and
PPP

is adequate for simple, point
-
to
-
point transmissions between adjacent devices.

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Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com become 165.193.123.253?

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Q2


What is a communications protocol?


A
protocol

is a standardized means for coordinating an activity
between two or more entities.



The two communicating computers must
agree

on the protocol to be
used.



The
protocol

specifies the
format

for the segments, packets, and
frames, and the
interactions

between computers, at the
transport
and internet layers
, to assure reliable transmissions.

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Q2


What is a communications protocol?


Layers of communication protocols

coordinate the activity
between two or more communicating computers and allow
messages to pass back and forth.



Each layer

accomplishes a different function then passes the
message to the next layer in the protocol


up
if the message is
incoming and
down

if the message is outgoing.



All messages are processed as a
stream of bits
, not bytes, by all
layers except for the
application layer
, the top layer.


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Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five
TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com become 165.193.123.253?

© Pearson Prentice Hall 2009

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Q3


What are the functions of the five TCP/IP

OSI layers?


The Internet uses
layered protocols
, also called
protocol
architectures,
which specify the

format
of a data transmission and
the

processing rules
implemented by the

TCP/IP software
at each
layer.



The
International Organization for Standardization (ISO)

developed a
seven
-
layered Reference Model

for
Open Systems
Interconnection (OSI) architecture.



The
Internet Engineering Task Force (IETF)

developed a
four
-
layered Transmission Control Program/Internet Protocol
(TCP/IP) architecture.



Portions of these two architectures are combined to provide the
Internet with the
TCP/IP

OSI architecture
.

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Q3


What are the functions of the five TCP/IP

OSI layers?

Fig 6A
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3 TCP/IP
-
OSI Architecture


This chart gives
you the
specific
and broad
functions

of each
layer in the
TCP/IP
-
OSI
architecture.



All computers
using the Internet
use all
five layers

of the TCP
-
OSI
architecture.

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Q3


What are the functions of the five TCP/IP

OSI layers?


Throughout this appendix, and while you’re using the Internet, you’ll
hear these terms used frequently.


Remember, the
architecture

and the
protocols

are just
concepts
.
They do not actually exist in a physical form. The
software and
hardware

implement these concepts.



Architecture

is the arrangement of protocol layers (
application,
transport, internet, data link, physical
) with each given specific tasks.



Protocols

are sets of rules that accomplish tasks in each layer. These
rules specify the
format

of segments, packets, and frames, and the
interactions

between the
sending

and
receiving
computers at the
transport (TCP) and internet

(IP)

layers to assure
reliability
.



Programs

are specific software products that implement the
rules

and
interactions

for
reliability

specified by the protocols at each layer.

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Q3


What are the functions of the five TCP/IP

OSI layers?


Layer 5

is the application layer and uses protocols to govern how
applications

work with each other. The following applications are
examples of programs which implement the TCP/IP protocols:



The
Simple Mail Transfer Protocol (SMTP)

is contained in
email application programs like Outlook and Mozilla Thunderbird.



The
Hypertext Transfer Protocol (HTTP)

is contained in Web
browser programs like Internet Explorer and Mozilla Firefox.



The
File Transfer Protocol (FTP)

is used to copy or move files
from one computer to another, generally within a Web browser
program.



The
Web

is a
subset
of the Internet. The Web consists of sites
and users that process the
HTTP

protocol using browsers mostly.

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Q3


What are the functions of the five TCP/IP

OSI layers?


Layer 4
, the transport layer, contains the
Transmission Control
Program (TCP) protocols

that convert the
application data

of
layer 5 into
segments

of bit streams with
identifying headers and
trailers

for
addressing

and
message transmission reliability
in
the

sending computer
. The reverse of this operation is performed
by the
receiving computer
.



Layer 3
, the Internet layer, contains the
Internet protocols (IP)

that
route messages across an internet using a
router computer
. The
segments
from layer 4 are broken into
packets

with
identifying
headers and trailers

for
addressing

and
message transmission
reliability

and are transmitted through
multiple routers

using
tables of router addresses

at each router until they reach their
intended destination. The
reverse of this operation

is performed by
the
receiving computer
.


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Q3


What are the functions of the five TCP/IP

OSI layers?


Layer 1, the physical layer
, and
layer 2, the data link layer
,
provide basic computer connectivity using
switches and NICs.
The
packets
from
layer 3

are broken into
frames
in
layer 2
, and then
into
electronic signals

in
layer 1

for the transmission media in use.
The
reverse of this operation

is performed by the
receiving
computer.


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Q3


What are the functions of the five TCP/IP

OSI layers?


This figure depicts the
TCP/IP

OSI layers

that an email message
travels through.


Fig 6A
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4 TCP/IP on Your Computer

switches

NICs

routers

computers

application

transmission

media

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Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com become 165.193.123.253?

© Pearson Prentice Hall 2009

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Q4


How does the Internet work?


Each computer has
two addresses
, a
physical

and a
logical

address, that
networks and the Internet use to route messages to the correct location.



The
physical address

or
MAC, media access control address,

is
assigned to each
NIC, network interface card
, by the manufacturer. No
two are alike. This address is used by the protocols in
layer 2

of the
TCP/IP

OSI architecture.



The
logical address
, or
IP address
, is used on internets, the Internet, and
private networks by the protocols in
layer 3

of the TCP/IP

OSI
architecture. This address is written as numbers, like 192.168.2.28.
Hardware devices are not hard
-
coded with logical addresses but are
assigned as needed
.



Physical addresses

are only known, shared, and used within a
particular
network, not an internet.
Each MAC belongs to one and only one
hardware device.



Logical addresses

are not permanently assigned to any hardware device,
are used within
internets
, and can be reassigned when necessary.



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Q4


How does the Internet work?


There are two kinds of logical addresses:


Public IP addresses

are used on the Internet and are unique across all
computers on the Internet. They are assigned by
ICANN

(Internet
Corporation for Assigned Names and Numbers)


Private IP addresses

are used within private networks and internets
and are controlled by the company that operates the network.



Dynamic Host Configuration Protocol
software is used

on
DHCP
servers
. These programs loan
temporary IP addresses

to users when
they connect to a private network. Once the online session is completed,
the temporary IP address is returned to the DHCP server for re
-
use. Your
ISP
uses DHCP to assign you a temporary IP address when you connect to
the Internet.


Each DHCP server is assigned a
range of IP addresses

to loan on its
network.


Within a private network, administrators normally assign
fixed, private IP
addresses

permanently to servers so all computers on the network can
know immediately the addresses of all the servers for that network. The
end
-
user does not have to find the server address.

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Q4


How does the Internet work?

Fig 6a
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5 Hotel LAN in Hawaii


This figure shows how a typical LAN transmits messages within the
network using a
DHCP server
.


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Q4


How does the Internet work?


Switches
(special computers that receive and transmit messages
on a LAN) use
MAC addresses

on a specific network that tell them
where to send traffic. They work in
layer 2

of the TCP/IP

OSI
architecture.



Similarly,
routers

use tables of
router IP addresses

on an internet
that tell them where to send traffic. They work in
layer 3

of the
TCP/IP

OSI architecture.



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Q4


How does the Internet work?

Fig 6A
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6 Accessing the (Private) Hotel Web Server


Part 1


You can use the
figure on this slide
and the next one to
trace messages as
they pass through the
TCP/IP

OSI
protocols, switches,
and routers, using
private IP addresses.


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Q4


How does the Internet work?

Fig 6A
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6 Accessing the (Private) Hotel Web Server


Part 2

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Q4


How does the Internet work?

Fig 6A
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7 Hawaii Hotel to Ohio Company via Internet


This figure shows how TCP/IP

OSI protocols over the Internet use
Network Address Translation

to change a
public IP address

into
a
private IP address

and vice versa.

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Q1


How does email travel?



Q2


What is a communications protocol?



Q3


What are the functions of the five TCP/IP

OSI layers?



Q4


How does the Internet work?



Q5


How does www.prenhall.com
become 165.193.123.253?

© Pearson Prentice Hall 2009

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Q5


How does www.prenhall.com become 165.193.123.253?


It’s much easier for people to recognize alphabetical names rather
than a group of numbers. However, computers can only use
numbers. The
domain name system (DNS)

converts user
-
friendly,
domain names

that people can use to
IP addresses

that
computers can use. The process is called
resolving the domain
name
. Just like you do when you find the telephone number for a
person’s name in a telephone directory.



Every domain name must be
unique

throughout the world and
recorded in a
global directory
, just like telephone numbers.



ICANN

administers how companies register domain names and it
manages the
domain name resolution system.



The term
top
-
level domain (TLD)

refers to the last letters in a
domain name. In the domain name www.prenhall.com


the last
three letters,
com
, is the
TLD
.

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Q5


How does www.prenhall.com become 165.193.123.253?


Each Web address is called a
Uniform Resource Locator

(URL).

www.prenhall.com

is the URL for Prentice Hall.



Converting a domain name into a public IP address is called
Domain Name
Resolution
: www.prenhall.com = 165.193.123.253



ICANN manages
13 root servers

distributed around the world which
maintain lists of IP addresses of servers that resolve each type of TLD.
These root servers are augmented by thousands of
domain name
resolvers

around the world to provide quick domain name resolution.



Domain name resolvers

(DNRs)

are the bottom layer of servers which the
ISPs hit with a domain name to resolve. If the DNR server has a match for
the domain name in its
IP address table cache
, then the DNR server can
resolve the domain name into an IP address. If not, then the DNR server
hits the
regional root server

for the
top
-
level domain name

for the
domain name resolution. The DNR servers store the results of domain
name resolutions by the TLD root servers in a
cache
, and they periodically,
systematically
audit

their cache contents against appropriate TLD root
servers.



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VOIP and IPTV


The
TCP/IP
-
OSI
architecture can transmit anything represented by bits
which is formatted according to the TCP/IP protocols.



Voice over IP (VoIP)

uses the TCP/IP
-
OSI architecture to carry telephone
voice conversations.



With VoIP, voice conversations are
digitized by sampling
, and are stored
as
bits
, packaged according to the
TCP/IP protocol
, and routed over the
Internet. You need to have
appropriate application software

and your
telephones

connected to your computers to do this.



A problem occurs when a user connected to the Internet wants to contact
someone who has only telephone access, or the reverse situation.



This problem has been resolved by companies (
Skype
for example, who
offer their subscribers unrestricted telephone access using VoIP.



IPTV (Internet Protocol Television)

uses TCP/IP
-
OSI to transmit television
and other video signals. A broadband connection is required. A
set
-
top box

receives the signal and distributes it to multiple users within a site. This set
-
top box can provide VoIP and text chat.