access to computers and the internet has become a basic need for education in our society. kent...
Post on 14-Dec-2015
219 Views
Preview:
TRANSCRIPT
CHAPTER 1 INTRODUCTION
Access to computers and the Internet has become a basic need for education in our society. Kent Conrad (US Senator)
5
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。
6
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。
7
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。
8
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。
9
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。
11
Chapter 1: Introduction
Computer Networks vs. Distributed Systems
Users make the decision. O.S. makes the decision.
12
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.
13
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.
14
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)
15
Chapter 1: Introduction
1.1 Uses of Computer Networks
Client-server model
1.1.1 Business Applications
A network with two clients and one server.
16
Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.1 Business Applications
The client-server model involves requests and replies.
17
Chapter 1: Introduction
1.1 Uses of Computer Networks
Client-server model server type
Concurrent server vs. Iterative server
Stateful server vs. Stateless server
1.1.1 Business Applications
Examples:
18
Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.2 Home Applications
• Access to remote informationWorld Wide Web• Person-to-person communicationElectronic mail, IM, Videoconference• Interactive entertainmentVideo-on-Demand, Games• Electronic commerce• Social networks
19
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.
21
Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.2 Home Applications
Some forms of e-commerce.
22
CHAPTER 1: INTRODUCTION
IPTV Ubiquitous Computing Sensor networks Power-line networks RFID (Radio Frequency Identification)
23
Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.3 Mobile Users
Combinations of wireless networks and mobile computing.
24
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
25
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
26
CHAPTER 1: INTRODUCTION
Social Issues Network Neutrality DMCA (Digital Millennium Copyright Act),
DRM (Digital Rights Management) Profiling and cookies Botnet (DDoS) Phishing CAPTCHA
27
Chapter 1: Introduction
1.1 Uses of Computer Networks
1.1.4 Social Issues
PrivacyCopyrightPornographyAnonymitySecurityWorms and Virusfreedom of speech vs. censorshipresponsibility of the service providers…
30
CHAPTER 1: INTRODUCTION
Packet Unicast, Multicast, Broadcast PAN, LAN, MAN, WAN Interplanetary Internet
31
Chapter 1: Introduction1.2 Network Hardware
Classifying by scales
Classification of interconnected processors by scale.
33
Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
IEEE 的定義:A LAN (Local Area Network) is a data communication systemallowing a number of independent devices to communicate directly with each other, within a moderately sized geographicarea over a physical communication channel of moderate datarates.
34
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...)
35
Chapter 1: Introduction
1.2 Network Hardware
Local Area Networks
Ethernet
Token Ring
Two broadcast networks(a) Bus(b) RingWireless and wired LANs. (a)
802.11. (b) Switched Ethernet
36
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)
37
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
39
Chapter 1: Introduction
1.2 Network Hardware
Metropolitan Area Networks
A metropolitan area network based on cable TV.
40
CHAPTER 1: INTRODUCTION
Wireless MAN 3G->4G WiMax (Worldwide Interoperability for
Microwave Access) LTE (Long Term Evolution)
41
CHAPTER 1: INTRODUCTION
WAN
WAN that connects three branch offices in Australia
WAN using a virtual private network
WAN using an ISP network
42
Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
Relation between hosts on LANs and the subnet.
43
Chapter 1: Introduction
1.2 Network Hardware
Wide Area Networks
A stream of packets from sender to receiver.
44
Chapter 1: Introduction
store-and-forward network
A
B
CA sends a message to C through B.
B must store this message until B is sure that C has received it.
Store first, then forward. But when to start forwarding?
1.2 Network Hardware
Wide Area Networks
45
Chapter 1: Introduction
A
B
CA sends a message to C through B.
When to starting forwarding?
1. After the message is completely received2. Start forwarding after a fixed amount of information(bits) received3. Start forwarding immediately after receiving data (cut-through)
store-and-forward network
1.2 Network Hardware
Wide Area Networks
46
Chapter 1: Introduction
A
B
CA sends a message to C through B.
If a message takes 1 minute to travel a link:
(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)
0 m10.25 m2 m10.5 m3 m2 m10.75 m4 m3 m21.0 m4 m31.25 m4
A B Cstore-and-forward network
1.2 Network Hardware
Wide Area Networks
47
Chapter 1: Introduction
The concept of pipeliningIf the message is decomposed into N packets, each packet takes1/N minutes to travel a link. It takes 2 1
N
N
N
minutes.
但分的愈細愈好嗎 ?
bits
header user information trailer
h t
overhead for N packets=N(h+t)overhead for 1 message=h+t
1.2 Network Hardware
Wide Area Networks
48
Chapter 1: Introduction
SwitchingA
B
C
D
E
F
G
H
(1) circuit switching (in telephone)(2) packet switching(3) message switching
Current Internet practice: store-and-forward packet switching
Wide Area Networks:Dod: ARPANET in 1960s (become Internet)IBM: SNA in 1974DEC: DECNET in 1975CCITT X.25 in 1970s
1.2 Network Hardware
Wide Area Networks
49
Switching
Chapter 1: Introduction
Bottleneck in current store-and-forward packet switching network:ROUTING
router
packets delayed (or even discarded) in routers
1.2 Network Hardware
Wide Area Networks
50
1.2 Network Hardware
Wireless Networks
Chapter 1: Introduction
The fast-growing segment of the industry:• notebook computers• personal digital assistants• cellular phones
Before long, we would have:• palmtop computers• wristwatch computers• …
51
1.2 Network Hardware
Wireless Networks
Chapter 1: Introduction
Categories of wireless networks:1. (used for) System interconnection2. Wireless LANs3. Wireless WANs
52
1.2 Network Hardware
Wireless Networks
Chapter 1: Introduction
(a) Bluetooth configuration(b) Wireless LAN
53
1.2 Network Hardware
Wireless Networks
Chapter 1: Introduction
(b) is more efficient and economical.
NEMO: NEtwork MObility
54
1.2 Network Hardware
Home Networks
Chapter 1: Introduction
1. Computers (desktop PC, PDA, shared peripherals2. Entertainment (TV, DVD, VCR, camera, stereo, MP3)3. Telecomm (telephone, cell phone, intercom, fax)4. Appliances (microwave, fridge, clock, furnace, airco, lights)5. Telemetry (utility meter, smoke/burglar alarm, thermostat, babycam).
55
1.2 Network Hardware
Internetworks
Chapter 1: Introduction
NII: National Information Infrastructure -> GII (Global II)
Information Superhighway
Networking is a world wide phenomenon.
Internet
Next Generation Internet
Internet II
57
Chapter 1: Introduction1.3 Network Software
1. Protocol Hierarchies2. Design Issues for the Layers3. Connection-Oriented and Connectionless Services4. Service Primitives5. The Relationship of Services to Protocols
59
Chapter 1: Introduction1.3 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.
61
Chapter 1: Introduction1.3 Network Software
Example information flow supporting virtual communication in layer 5
63
Chapter 1: Introduction1.3 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)
64
Chapter 1: Introduction1.3 Network Software
1.3.3 Connection-Oriented and Connectionless Services
Six different types of service
65
Chapter 1: Introduction1.3 Network Software
1.3.3 Connection-Oriented and Connectionless Services
Initial Destination Packet Error Flow Optionsetup address sequence control control negotiationIssue
Connection Oriented
Connection-less
required
notpossible
only neededduring setup
needed forevery packet
guaranteed
notguaranteed
by networklayer
by transportlayer
by transportlayer
by networklayer
Yes
No
66
Chapter 1: Introduction1.3 Network Software
1.3.4 Service Primitives
Five service primitives for implementing a simple connection-oriented service
67
Chapter 1: Introduction1.3 Network Software
1.3.4 Service Primitives
A simple client-server interaction using acknowledged datagrams.
68
Chapter 1: Introduction1.3 Network Software
1.3.5 The Relationship of Services to Protocols
The relationship between a service and a protocol
69
Chapter 1: Introduction1.3 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.
70
Chapter 1: Introduction1.4 Reference Models
1.4.1 The OSI Reference Model
In the late 1970s, to promote the compatibility of networkdesigns, the International Organization for Standardization(ISO) proposed an architecture model called the opensystems interconnection references model (OSI model).
layer N
layer N-1
layer N
layer N-1PDUs (protocol data unit)
actual data flow on the lowest level
services
71
Chapter 1: Introduction1.4 Reference Models
1.4.1 The OSI Reference Model
What a mess! Much better!
Note: May not be themost efficient!
73
Chapter 1: Introduction1.4 Reference Models
1.4.1 The OSI Reference Model
applicationapplication
presentation
session
transport
network
data link
physical
7
6
5
4
3
2
1 transmission of bits
transmission of packets on one given link
end-to-end transmission of packets
end-to-end delivery of messages
setup and management of end-to-end conversation
formatting, encryption, and compression
network services (email, file transfer)
74
Chapter 1: Introduction1.4 Reference Models
1.4.1 The OSI Reference Model
applicationapplication
presentation
session
transport
network
data link
physical
7
6
5
4
3
2
1
Encapsulation data
dataAH
dataAHPH
dataAHPHSH
dataAHPHSHTH
dataAHPHSHTHNH
dataAHPHSHTHNH
bit streams
DT
H: headerT: trailEach may be empty.
DH
75
Chapter 1: Introduction1.4 Reference Models
1.4.2 The TCP/IP Reference Model
(Transmission Control Protocol/Internet Protocol
76
Chapter 1: Introduction1.4 Reference Models
1.4.2 The TCP/IP Reference Model
The TCP/IP reference model with some protocols we will study
78
Chapter 1: Introduction1.4 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
79
Chapter 1: Introduction1.4 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 4connection-oriented versus connectionless
80
Chapter 1: Introduction1.4 Reference Models
A Critique of the OSI Model and Protocols
1. Bad timing2. Bad technology3. Bad implementation4. Bad politics
81
Chapter 1: Introduction1.4 Reference Models
A Critique of the OSI Model and Protocols
Bad timing
The apocalypse of the two elephants
82
Chapter 1: Introduction1.4 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.
83
CHAPTER 1: INTRODUCTION
Example networks Internet ARPANET NSFNET Third-generation mobile phone networks Wireless LANs: 802.11 RFID and sensor networks
84
Chapter 1: Introduction1.5 Example Networks
1.5.1 The Internet
(a) Structure of the telephone system.(b) Baran’s proposed distributed switching system
85
Chapter 1: Introduction1.5 Example Networks
The ARPANET
The original ARPANET design
IMP: Interface Message Processor
86
Chapter 1: Introduction1.5 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
89
Chapter 1: Introduction1.5 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
91
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
92
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
93
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
94
Chapter 1: Introduction1.5 Example Networks
Wireless LANs: 802.11
(a) Wireless networking with a base station.(b) Ad hoc networking
96
Chapter 1: Introduction1.5 Example Networks
Wireless LANs
The range of a single radio may not cover the entire system
Hidden terminal problem
98
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
99
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
100
Chapter 1: Introduction1.6 Network Standardization
De facto (from the fact)De jure (by law)
Benefits of standards
standard
101
Chapter 1: Introduction1.6 Network Standardization
1.6.1 Who’s Who in the Telecommunications World
102
Chapter 1: Introduction1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
103
ITU• Main sectors
• Radio communications• Telecommunications Standardization• Development
• Classes of Members• National governments• Sector members• Associate members• Regulatory agencies
Chapter 1: Introduction1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
104
Chapter 1: Introduction1.6 Network Standardization
1.6.2 Who’s Who in the International Standards World
105
Chapter 1: Introduction1.6 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.
106
Chapter 1: Introduction1.6 Network Standardization
1.6.3 Who’s Who in the Internet Standards World
top related