Transcript Information Networks

CHAPTER 1 INTRODUCTION
Access to computers and the Internet has become a
basic need for education in our society. Kent Conrad
(US Senator)
CHAPTER 1: INTRODUCTION
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Chapter 1: Introduction
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CHAPTER 1: INTRODUCTION
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CHAPTER 1: INTRODUCTION
這個世界原本屬於一群高喊知識就是力量、重
視理性分析的特定族群──會寫程式的電腦工
程師，專搞訴狀的律師，和玩弄數字的ＭＢＡ。
 如今，世界將屬於具有高感性能力的另一族群
──有創造力、具同理心、能觀察趨勢，以及
為事物賦予意義的人。
 我們正從一個講求邏輯、循序性與計算機效能
的資訊時代，轉化為一個重視創新、同理心，
與整合力的感性時代。

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CHAPTER 1: INTRODUCTION

六種攸關最近的未來有無前途的關鍵性能力
 一、不只有功能，還重設計。
 光是提供堪用的產品、服務、體驗或生活型態，已經不
夠了。如今無論為賺錢或為成就感，都必須創作出好看、
獨特，或令人感動的東西。
 二、不只有論點，還說故事。
 現代人面對過量資訊，一昧據理力爭是不夠的。總有人
會找到相反例證來反駁你的說法。想要說服別人、灌輸
資訊，甚至說服自己，都必須具備編織故事的能力。
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CHAPTER 1: INTRODUCTION

六種攸關最近的未來有無前途的關鍵性能力
 三、
不只談專業，還須整合。
 工業時代和資訊時代需要專業和專才，但隨著白領工作
或被外包出去，或被軟體取代，與專業相反的才能也開
始受到重視：也就是化零為整的整合能力。今日社會最
需要的不是分析而是綜合──綜觀大趨勢、跨越藩籬、
結合獨立元素成為新好產品的能力。
 四、不只講邏輯，還給關懷。
 邏輯思考是人類專屬能力之一。不過在一個資訊爆炸、
分析工具日新月異的世界裡，光靠邏輯是不行的。想在
未來繼續生存，必須了解他人的喜好需求、建立關係，
並展現同理心。
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CHAPTER 1: INTRODUCTION

六種攸關最近的未來有無前途的關鍵性能力
 五、不只能正經，還會玩樂。
 太多證據顯示多笑、保持愉悅心情、玩遊戲和幽默感，
對健康與工作都有極大好處。當然該嚴肅的時候要嚴肅，
不過太過正經對事業不見得有益，對健康更有害。在感
性時代，無論工作還是居家，都需要玩樂。
 六、
不只顧賺錢，還重意義。
 我們生活在一個物質極為充裕的世界。無數人因此掙脫
了營生桎梏，得以追求更深層的渴望：生命目的、出世
意義，以及性靈滿足。
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CHAPTER 1: INTRODUCTION

這六種關鍵能力來自兩種感知：高感性（High
Concept）與高體會（High Touch）
 高感性，指的是觀察趨勢和機會，以創造優美或
感動人心的作品，編織引人入勝的故事，以及結
合看似不相干的概念，轉化為新事物的能力。
 高體會，則是體察他人情感，熟悉人與人微妙互
動，懂得為自己與他人尋找喜樂，以及在繁瑣俗
務間發掘意義與目的的能力。
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CHAPTER 1: INTRODUCTION
Why is all this happening?
 Because of the Internet!

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Chapter 1: Introduction
Computer Networks
Users make the decision.
vs.
Distributed Systems
O.S. makes the decision.
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Chapter 1: Introduction
Middleware: The software layer that lies between the operating
system and applications on a distributed computing system in a
network.
Middleware services provide a more functional set of
application programming interfaces to allow an application to:
1. Locate transparently across the network, thus providing
interaction with another service or application
2. Be independent from network services
3. Be reliable and available always
when compared to the operating system and network services.
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CHAPTER 1: INTRODUCTION
A well-known example of a distributed system is
the World Wide Web.
 It runs of top of the Internet and presents a
model in which everything looks like a
document (Web page).
 In a computer network, this coherence, model,
and software are absent.

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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.1 Business Applications
Goals:
•Resource Sharing
•High Reliability
•Saving Money
•Communication Medium (people to people, machine to machine)
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.1 Business Applications
Client-server model
A network with two clients and one server.
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.1 Business Applications
The client-server model involves requests and
replies.
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.1 Business Applications
Client-server model server type
Concurrent server vs. Iterative server
Stateful server vs. Stateless server
Examples:
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.2 Home Applications
•Access to remote information
World Wide Web
•Person-to-person communication
Electronic mail, IM, Videoconference
•Interactive entertainment
Video-on-Demand, Games
•Electronic commerce
•Social networks
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.2 Home Applications
In peer-to-peer system there are no fixed clients and servers.
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CHAPTER 1: INTRODUCTION
BitTorrent
 Instant Messaging
 Twitter
 Facebook, Google+
 Wikipedia

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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.2 Home Applications
Some forms of e-commerce.
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CHAPTER 1: INTRODUCTION
IPTV
 Ubiquitous Computing
 Sensor networks
 Power-line networks
 RFID (Radio Frequency Identification)

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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.3 Mobile Users
Combinations of wireless networks and mobile
computing.
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CHAPTER 1: INTRODUCTION
Wi-Fi (Wireless Fidelity) (from Hi-Fi) (IEEE
802.11 standard)
 Hopspots
 Mobile phones
 SMS, MMS (Short Message Service,
Multimedia MS)

 Texting,

Intexicated, Sexting,
Smart phones
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CHAPTER 1: INTRODUCTION

GPS (Global Positioning System)
 Location-based
services (can you give some
examples?)

M-commerce (mobile-commerce)
 RFID
(Radio Frequency Identification) again
 NFC (Near Field Communication)

Wearable Computers
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CHAPTER 1: INTRODUCTION

Social Issues
 Network
Neutrality
 DMCA (Digital Millennium Copyright Act), DRM
(Digital Rights Management)
 Profiling and cookies
 Botnet (DDoS)
 Phishing
 CAPTCHA
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Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.4 Social Issues
Privacy
Copyright
Pornography
Anonymity
Security
Worms and Virus
freedom of speech vs. censorship
responsibility of the service providers
…
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Chapter 1: Introduction
1.2 Network Hardware
Broadcast Networks
shared link (may be wireless)
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Chapter 1: Introduction
1.2 Network Hardware
Point-to-point Networks
point to point link
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CHAPTER 1: INTRODUCTION
Packet
 Unicast, Multicast, Broadcast
 PAN, LAN, MAN, WAN
 Interplanetary Internet

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Chapter 1: Introduction
1.2 Network Hardware
Classifying by scales
Classification of interconnected processors by scale.
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CHAPTER 1: INTRODUCTION

Personal Area Networks
 Bluetooth
 RFID
Bluetooth PAN configuration
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Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
IEEE的定義：
A LAN (Local Area Network) is a data communication system
allowing a number of independent devices to communicate
directly with each other, within a moderately sized geographic
area over a physical communication channel of moderate data
rates.
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Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
LAN:
•short geographical distance (a few kilometers)
•high speed (Larger than 10 Mbps)
•multiple access (Many can use it at the same time)
•sharing (hardware, software, idea, feeling, emotion...)
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Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
Ethernet
Token
Ring
Two broadcast networks
(a) Bus
Wireless
and wired LANs. (a)
(b) Ring
802.11. (b) Switched Ethernet
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Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
Standardization Body
IEEE (Institute of Electric and Electronic Engineers) 802 group
For example:
802.3: CSMA/CD (Carrier Sense Multiple Access with
Collision Detection) (Ethernet is one of them.)
802.11: Wireless LANs (Wi-Fi: Wireless Fidelity)
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CHAPTER 1: INTRODUCTION

Home network
 The
networked devices have to be very easy to install
 The network and devices have to be foolproof in
operation
 Low price is essential for success
 It must be possible to start out with one or two devices
and expand the reach of network gradually (no format
wars)
 Security and reliability will be very important
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CHAPTER 1: INTRODUCTION

Virtual LAN
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Chapter 1: Introduction
1.2 Network Hardware
Metropolitan Area Networks
A metropolitan area network based on cable TV.
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CHAPTER 1: INTRODUCTION

Wireless MAN
 3G->4G
 WiMax
(Worldwide Interoperability for Microwave
Access)
 LTE (Long Term Evolution)
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CHAPTER 1: INTRODUCTION
WAN using a virtual private network

WAN
using an three
ISP network
WANWAN
that connects
branch offices in Australia
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
Relation between hosts on LANs and
the subnet.
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
A stream of packets from sender
to receiver.
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
store-and-forward network
B
A
A sends a message to C through B.
C
B must store this message until B is sure that C has received it.
Store first, then forward. But when to start forwarding?
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
store-and-forward network
B
A
A sends a message to C through B.
C
When to starting forwarding?
1. After the message is completely received
2. Start forwarding after a fixed amount of information(bits) received
3. Start forwarding immediately after receiving data (cut-through)
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
store-and-forward network
B
A
A sends a message to C through B.
C
If a message takes 1 minute to travel a link:
A B C
0
m1
0.25 m2 m1
0.5 m3 m2 m1
0.75 m4 m3 m2
1.0
m4 m3
1.25
m4
(1) A to B, then B to A: 2 minutes
(2) message is decomposed into 4 parts: 1.25 minutes
(each part is called a packet)
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
The concept of pipelining
If the message is decomposed into N packets, each packet takes
1/N minutes to travel a link. It takes 2  N  1 minutes.
N
N
但分的愈細愈好嗎?
bits
h
header
t
user information
trailer
overhead for N packets=N(h+t)
overhead for 1 message=h+t
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
B
Switching
D
G
A
E
H
C
F
(1) circuit switching (in telephone)
(2) packet switching
(3) message switching
Wide Area Networks:
Dod: ARPANET in 1960s
(become Internet)
IBM: SNA in 1974
DEC: DECNET in 1975
CCITT X.25 in 1970s
Current Internet practice: store-and-forward packet switching
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Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
Switching
Bottleneck in current store-and-forward packet switching network:
ROUTING
router
packets delayed (or even discarded) in routers
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Chapter 1: Introduction
1.2 Network Hardware
Wireless Networks
The fast-growing segment of the industry:
•notebook computers
•personal digital assistants
•cellular phones
Before long, we would have:
•palmtop computers
•wristwatch computers
•…
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Chapter 1: Introduction
1.2 Network Hardware
Wireless Networks
Categories of wireless networks:
1. (used for) System interconnection
2. Wireless LANs
3. Wireless WANs
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Chapter 1: Introduction
1.2 Network Hardware
Wireless Networks
(a) Bluetooth configuration
(b) Wireless LAN
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Chapter 1: Introduction
1.2 Network Hardware
Wireless Networks
(b) is more efficient and economical.
NEMO: NEtwork MObility
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Chapter 1: Introduction
1.2 Network Hardware
Home Networks
1.
2.
3.
4.
5.
Computers (desktop PC, PDA, shared peripherals
Entertainment (TV, DVD, VCR, camera, stereo, MP3)
Telecomm (telephone, cell phone, intercom, fax)
Appliances (microwave, fridge, clock, furnace, airco, lights)
Telemetry (utility meter, smoke/burglar alarm, thermostat, babycam).
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Chapter 1: Introduction
1.2 Network Hardware
Internetworks
Networking is a world wide phenomenon.
NII: National Information Infrastructure -> GII (Global II)
Information Superhighway
Internet
Internet II
Next Generation Internet
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Internet Usage
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Chapter 1: Introduction
1.3 Network Software
1.
2.
3.
4.
5.
Protocol Hierarchies
Design Issues for the Layers
Connection-Oriented and Connectionless Services
Service Primitives
The Relationship of Services to Protocols
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Chapter 1: Introduction
1.3 Network
Software
peers
1.3.1 Protocol
Hierarchies
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Chapter 1: Introduction
1.3 Network Software
1.3.1 Protocol Hierarchies
A set of layers and protocols is called a network architecture.
A list of protocols used by a certain system, one protocol per
layer, is called a protocol stack.
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An analogy
French
The common Dutch
can be replaced
with another.
Email can be used
instead of fax.
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Chapter 1: Introduction
1.3 Network Software
Example information flow
supporting virtual
communication in layer 5
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Chapter 1: Introduction
1.3 Network Software
Relations between layers at an interface
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Chapter 1: Introduction
1.3 Network Software
1.3.2 Design Issues for the Layers
•A mechanism for identifying senders and receivers (naming
and addressing)
•rules of transfer (simplex, half-duplex, full-duplex)
•error control (error correction and error detection)
•ordering and sequencing
•flow control, congestion control, quality of service
•message or packet size (disassembling and reassembling)
•multiplexing and demultiplexing
•Routing, scalability
•Security (confidentiality, authentication, integrity)
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Chapter 1: Introduction
1.3 Network Software
1.3.3 Connection-Oriented and Connectionless Services
Six different types of service
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Chapter 1: Introduction
1.3 Network Software
1.3.3 Connection-Oriented and Connectionless Services
Issue
Initial Destination Packet
Error Flow Option
setup
address sequence control control negotiation
only needed
by
by
guaranteed
during setup
network network
layer
layer
Connection
Oriented
required
Connectionless
needed for
by
by
not
not
possible every packet guaranteed transport transport
layer
layer
Yes
No
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Chapter 1: Introduction
1.3 Network Software
1.3.4 Service Primitives
Five service primitives for implementing a simple
connection-oriented service
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Chapter 1: Introduction
1.3 Network Software
1.3.4 Service Primitives
A simple client-server interaction using
acknowledged datagrams.
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Chapter 1: Introduction
1.3 Network Software
1.3.5 The Relationship of Services to Protocols
The relationship between a service
and a protocol
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Chapter 1: Introduction
1.3 Network Software
1.3.5 The Relationship of Services to Protocols
A service defines what operations the layer is prepared to
perform on behalf of its users, but it says nothing at all about
how these operations are implemented.
A protocol, in contrast, is a set of rules governing the format
and meaning of the frames, packets, or messages that are
exchanged by the peer entities within a layer. Entities use
protocols in order to implement their service definitions.
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Chapter 1: Introduction
1.4 Reference Models
1.4.1 The OSI Reference Model
In the late 1970s, to promote the compatibility of network
designs, the International Organization for Standardization
(ISO) proposed an architecture model called the open
systems interconnection references model (OSI model).
services
layer N
PDUs (protocol data unit)
layer N-1
layer N-1
layer N
actual data flow on the lowest level
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Chapter 1: Introduction
1.4 Reference Models
1.4.1 The OSI Reference Model
What a mess!
Much better!
Note: May not be the
most efficient!
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Chapter 1: Introduction
1.4 Reference Models
1.4.1 The OSI Reference Model
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Chapter 1: Introduction
1.4 Reference Models
1.4.1 The OSI Reference Model
7
application
6
presentation
5
session
4
3
transport
2
1
data link
network
physical
network services (email, file transfer)
formatting, encryption, and compression
setup and management of end-to-end conversation
end-to-end delivery of messages
end-to-end transmission of packets
transmission of packets on one given link
transmission of bits
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Chapter 1: Introduction
1.4 Reference Models
1.4.1 The OSI Reference Model
7
application
6
presentation
5
session
4
3
transport
2
data link
1
network
physical
Encapsulation
H: header
T: trail
Each may be empty.
data
AH data
PH
AH data
SH
PH
AH data
TH SH
PH
AH data
NH TH SH
PH
AH data
DH NH TH SH
PH
AH data DT
bit streams
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Chapter 1: Introduction
1.4 Reference Models
(Transmission Control
Protocol/Internet Protocol
1.4.2 The TCP/IP Reference Model
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Chapter 1: Introduction
1.4 Reference Models
1.4.2 The TCP/IP Reference Model
The TCP/IP reference model with some
protocols we will study
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CHAPTER 1: INTRODUCTION

Model used in this book
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Chapter 1: Introduction
1.4 Reference Models
A Comparison of the OSI and TCP/IP Reference Model
The OSI reference model was devised before the (OSI)
protocols were invented.
•Not biased toward any one particular set of protocols
•The designers did not have much experience with the
subject and did mot have a good idea of which
functionality to put in which layer
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Chapter 1: Introduction
1.4 Reference Models
A Comparison of the OSI and TCP/IP Reference Model
With the TCP/IP, the protocols came first, and the model was
really just a description of the existing protocols. The model did
not fit any other protocol stacks.
7 layers versus 4
connection-oriented versus connectionless
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Chapter 1: Introduction
1.4 Reference Models
A Critique of the OSI Model and Protocols
1. Bad timing
2. Bad technology
3. Bad implementation
4. Bad politics
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Chapter 1: Introduction
1.4 Reference Models
A Critique of the OSI Model and Protocols
Bad timing
The apocalypse of the two
elephants
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Chapter 1: Introduction
1.4 Reference Models
A Critique of the TCP/IP Reference Model
1. The model does not clearly distinguish the concepts of
service, interface, and protocol.
2. The model is not general and is poorly suited to describing
andother protocol stack.
3. The model does not distinguish (or even mention) the
physical and data link layer.
4. Only TCP and IP are carefully thought out and implemented.
Many other protocols are ad hoc.
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CHAPTER 1: INTRODUCTION

Example networks
Internet
 ARPANET
 NSFNET
 Third-generation mobile phone networks
 Wireless LANs: 802.11
 RFID and sensor networks

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Chapter 1: Introduction
1.5 Example Networks
1.5.1 The Internet
(a) Structure of
the telephone
system.
(b) Baran’s
proposed
distributed
switching system
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Chapter 1: Introduction
1.5 Example Networks
The ARPANET
IMP: Interface Message Processor
The original ARPANET design
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Chapter 1: Introduction
1.5 Example Networks
1.5.1 The Internet
Growth of the ARPANET
(a) December 1969. (b) July
1970. (c) March 1971. (d)
April 1972. (e) September
1972
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Chapter 1: Introduction
1.5 Example Networks
The NSFNET backbone in 1988
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Chapter 1: Introduction
1.5 Example Networks
Architecture of the Internet
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Chapter 1: Introduction
1.5 Example Networks
The Internet Society http://www.isoc.org
A brief history of the Internet
http://www.isoc.org/internet/history/brief.html
Hobbes' Internet Timeline
http://www.isoc.org/guest/zakon/Internet/History/HIT.html
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Chapter 1: Introduction
1.5 Example Networks
Ethernet
Architecture of the original
Ethernet
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THIRD-GENERATION MOBILE PHONE NETWORKS (1)
Cellular design of mobile phone networks
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
91
THIRD-GENERATION MOBILE PHONE NETWORKS (2)
Architecture of the UMTS 3G mobile phone
network.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
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THIRD-GENERATION MOBILE PHONE NETWORKS (3)
Mobile phone handover (a) before, (b) after.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
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Chapter 1: Introduction
1.5 Example Networks
Wireless LANs: 802.11
(a) Wireless networking with a base
station.
(b) Ad hoc networking
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CHAPTER 1: INTRODUCTION

Signal Fading
Multipath fading
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Chapter 1: Introduction
1.5 Example Networks
Wireless LANs
The range of a
single radio may
not cover the
entire system
Hidden terminal problem
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Chapter 1: Introduction
1.5 Example Networks
Wireless LANs
A multicell 802.11 network
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RFID AND SENSOR NETWORKS (1)
RFID used to network everyday objects.
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
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RFID AND SENSOR NETWORKS (2)
Multihop topology of a sensor network
Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011
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Chapter 1: Introduction
1.6 Network Standardization
Benefits of standards
De facto (from the fact)
De jure (by law)
standard
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Chapter 1: Introduction
1.6 Network Standardization
1.6.1 Who’s Who in the Telecommunications World
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Chapter 1: Introduction
1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
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Chapter 1: Introduction
1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
ITU
• Main sectors
• Radio communications
• Telecommunications Standardization
• Development
• Classes of Members
• National governments
• Sector members
• Associate members
• Regulatory agencies
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Chapter 1: Introduction
1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
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Chapter 1: Introduction
1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
The 802 working groups. The important ones are marked with *.
The ones marked with  are hibernating. The one marked with †
gave up and disbanded itself.
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Chapter 1: Introduction
1.6 Network Standardization
1.6.3 Who’s Who in the Internet Standards World
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Chapter 1: Introduction
1.7 Metric Units
The principal metric prefixes
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Chapter 1: Introduction
Exercises:
1. Compare the cost of Internet access at home between Taiwan
and USA.
Chapter Problems:
4, 8, 25, 35
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