Chapter 1
Introduction
Contents
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•
•
•
•
•
•
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Definition
Utility of computer networking
Technology milestones
Packetization
Layering
TCP/ IP model
OSI model
Principles of Internet protocols
2
Definition
• Business Data Communications
• Used synonymously with “computer
networking”
3
Typical data network
ISP network
Optical fiber
Campus network
Home
network
Web server
Unique features of computer
networks
• Common set of technologies support all
networked computer applications
• Basic principles unchanged for over 4 decades
• An essential component of modern economy
Utility of computer networking
• One of the world’s largest industries
• Networking infrastructure is a driver of the
economy
• Digital economy likely to exceed $4Trillion by
2016
CISCO Global IP traffic forecast
2014
2019
CAGR 2014-2019
By type (peta bytes/ month)
Fixed Internet
39,909
111,899
23%
Mobile data
2,514
24,221
57%
By segment
Consumer
47,740
138,415
24%
Business
12,108
29,563
20%
By geography
Asia-Pacific
20,729
54,434
21%
North America
19,628
49,720
20%
Western Europe
9,601
24,680
21%
7
What’s in it for me?
• Bureau of Labor Statistics estimates (2012)
– Network and computer system administrators
• 2012 employment :
• Median pay
:
366,400
$72,560
• Growth rate: 12% (until 2022)
8
Technology milestones
•
Telegraph
– Information carried as electrical signals over wires
•
Multiplexing
•
Circuit switching
– March 10, 1891, Strowger switch patented
•
•
Tampa connection - Buried in St. Pete - http://en.wikipedia.org/wiki/Almon_Strowger
Packet switching
– Signals sent and switching performed only when information ready to be transferred
Source: Wikipedia
9
Telegraph
Sender
Receiver
Electromagnet
Switch
Marker
Battery
Multiplexing and switching
• Multiplexing
• Circuit switching
–
A
B
A
B
Switch
D
C
D
C
Packet switching
• Packet switching (1969 - )
12
Data communications timeline
940
#2
SRI
#4
Utah
PDP
10
360
1840
Samuel Morse
patents Telegraph
in the U.S.
#3
UCSB
#1
UCLA
1874
Thomas Edison
Invents quadruplex switch
3/7/1876
Alexander Graham Bell
Makes first telephone call
3/10/1891
Strowger switch
patented
Sigma 7
10/29/1969
First Internet transmission
Between UCLA and SRI
06/06/2012
IPv6 day
7/20/1969
Neil Armstrong and “Buzz”
Aldrin land on the moon
Today
13
Circuit switching vs packet
switching
• A circuit is an electronic closed-loop path
among two or more points
• Packet switches are called routers
• Circuit switched networks typically bill by the
minute
• Packet switched networks typically bill by the
MB
Packetization overview
• Packetization is
• Each segment or packet has two parts
15
Packets analogy
Packet
To: John Doe
From: Jill Wright
~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~
Letter
Header
To: John Doe
From: Jill Wright
Sub: Soccer schedule
Dear Sir
Body
~~~~~~~~~
~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~
~~~~~~~
Sincerely
Jill
Packetization in retail
Factors favoring packet switching over
circuit switching
• Increase in interactive data traffic (as opposed
to voice traffic) has increased “burstiness” of
data (high ratio of peak usage to mean usage)
• Packet switching enables efficient utilization of
communication links by averaging needs
among large numbers of users
18
Traffic aggregation
Advantages of packetization
• Communication link costs are now very high
relative to switching costs
• Eliminates single points of failure in data
communication systems
• Ease of transport
20
Layering
• Arranging functionality in a hierarchical
manner, such that
• This is how we create and process packets
• Example (corporate)
21
Layering examples
• Example (software)
Analysts,
regulators,
shareholders
CEO
Browser
VP
Windows
Manager
Print driver
Worker
Machines,
tools, work
22
Advantages of layering
• Specializes technology development
• Separation of functionality
• Simplification in adding new technology
23
Layering in data communication
End user uses web
browser
Web browser uses network software
Layered network software
Signals sent over physical medium towards web server
Typical packet structure
• Five important datacomm tasks
– User needs (e.g. get web page, web page body)
– Segmentation and reassembly
– Identifying and locating destination
– Error control
– Signaling - Converting data into a form suitable for
transmission over wires
25
Typical packet structure
• These and other related datacomm tasks are
accomplished by adding additional required
information to information packets
• Routers perform packet switching
26
Important header information
Networking task
Specify user needs
Segmentation and reassembly of packets
Identifying and locating destination
Error control
Signaling
Header information
User commands
Sequence numbers
Address
Error check
None
Typical packet structure
• A typical packet contains
User commands
Sequence
number
Destination
address
Error check
– Information sent from the layers above
– and
User data
28
5-layered TCP/ IP stack
• Modern computer networks implement
layering in 5 layers
• Called the TCP/ IP stack
• Integrates two popular sets of technologies
29
Layer names and tasks
Layer
Layer name Networking task
number
5
Application Specify user needs
4
Transport
Segmentation and reassembly of packets
3
Network
Identifying and locating destination
2
Data-link
Error control
1
Physical
Signaling
Header information
User commands
Sequence numbers
Address
Error check
None
TCP/ IP stack layer technologies
Protocol layer and function
Popular technologies
Application layer
(what user wants)
E-mail (SMTP, IMAP, POP), web
(HTTP)
Transport layer
(ensure reliable data stream)
TCP, UDP
Network layer
(routing)
IP
Data link layer
(error-free transmission over hop)
Ethernet, Wi-fi, ATM
Physical layer
(data sent as signals over media)
AM, FM, CDMA, Manchester
encoding, SONET
31
OSI model
• OSI – Open Systems Interconnection
• Early networks involved multiple networking
technologies
• Even the current dominant TCP/ IP 5-layer
stack integrates two major technologies –
TCP/ IP and Ethernet
32
OSI model
• The OSI model is a logical structure for
communications networks, standardized by
the International Organization for
Standardization (ISO)
• Current status: Useful as an introduction to
data networks
33
OSI model
OSI model layer
Layer function
Application layer
Request-reply mechanism for
remote operations across a
network
Presentation layer
Syntax conversion from hostspecific syntax to syntax for
network transfer
Session layer
Create and terminate connection;
establish synchronization points
for recovery in case of failure
Transport layer
Segmentation, reassembly of
packets in one connection,
multiplexing connections on one
machine
Network layer
Routing and network addressing
Data link layer
Error-free data transmission over a
single link
Physical layer
Convert data to signals for
transmission over physical media
34
OSI model strengths and weaknesses
• Strengths
• Weaknesses
35
OSI and TCP/ IP
OSI model layers
TCP/ IP stack layers
Application layer
Application layer
Presentation layer
Session layer
Transport layer
Transport layer
Network layer
Network layer
Data link layer
Data link layer
Physical layer
Physical layer
36
Principles of Internet protocols
• The Internet would be a network of multiple
independent networks
• Multiple applications could use the Internet,
including those not yet conceived
37
Principles of Internet protocols
• Standardized message block to serve any
application
-- Baran 1964
–
38
TCP/ IP technologies by layer
Application
layer
HTTP
Application
layer
Application
layer
SMTP
Application
layer
FTP
Application
layer
SSH
IM
Transport
layer
Transport
layer
TCP
UDP
Application
layer
Application
layer
SIP
(VoIP)
NFS/ SMB
(File & printer
sharing)
Network
layer
IP
Data link
layer
MPLS
Data link
layer
Frame
Relay
Physical
layer
SONET
(Optical fiber)
Data link
layer
Ethernet
Physical
layer
Manchester
encoding
(Ethernet)
Data link
layer
Data link
layer
Wireless
LAN
ATM
Physical
layer
Physical
layer
QAM(Phone
modem)
CDMA
(Cell phone)
39
A typical computer network
Verizon FiOS network
Cogent network
Legend
Peer
in
g po
int
Wireless link
Campus backbone
Department LAN
Wireless
router
(DNS
and
DHCP
server)
Optical fiber
SONET
Home PC
link
Web server
Router
40
Standards reference
• Internet technology standards are publicly available
as Requests For Comment (RFCs)
– http://www.ietf.org/rfc.html
• Highly recommended standards
–
–
–
–
–
–
Email: http://www.ietf.org/rfc/rfc0821.txt
HTTP: http://www.ietf.org/rfc/rfc2616.txt
TCP: http://www.ietf.org/rfc/rfc0793.txt
IP: http://www.ietf.org/rfc/rfc0791.txt
TCP/ IP tutorial: http://www.ietf.org/rfc/rfc1180.txt
Domain names: http://www.ietf.org/rfc/rfc1034.txt
41
Rest of the course
• Chapters 2 – 6: Layers of TCP/ IP stack
• Chapters 7 – 11: Technologies supporting networking
• Chapters 12 – 13: Technologies related to computing
• Chapter 14: Managerial issues in IT infrastructures
• See anatomy of a web request
Anatomy of a web request
DHCP server
DNS server
Prior configuration
ISP networks (chapter 10)
Real time use
Packets routed hop by 7
hop
(chapter 4)
(chapter 7)
DNS gives IP address of etsu
User network
4
(chapter 7)
PC gets IP address from DHCP
1
Administrators 2
configure routers
(chapter 8)
Router
Router
User requests web page3
www.etsu.edu
(chapter 6)
Packets sent as signals
(chapter 2)
8
Web page sent in response to request
(chapter 6)
6
Router
Response broken into 9
datagrams
(chapter 5)
Web
server
www.etsu.edu
(chapters 12-13)
Defend against intruders
(chapter 11)
5
Request sent as packets
(chapter 3)
1
0
Case study – Domino’s Pizza
• Pizza tracker
• Bringing the computer network into the food
industry
• Anecdotal evidence is positive
• Almost 40% of orders come online
Hands-on exercise
• Traceroute
IT infrastructure design exercise
EMEA
Service Center
Corporate
Headquarters
100 employees
Service and Repair
Backup Data Center
300 employees
Corporate Office
Call
Center
Data Center
200 employees
AP
Service
Center
200 employees
Marketing
Repair
N
W
E
S
Summary
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•
•
•
•
•
•
•
•
Why computer networks
Important milestones in datacomm
Why packetization
Typical packet structure
Why layering
Layers of TCP/ IP
Functions of each layer in TCP/ IP model
OSI model
Internet protocol principles
47