Computer Networks. College of Computing. Copyleft 2003~2018. Prof. Lin Weiguo

Transcription

1 Computer Networks

2 Computer Networks Prof. Lin Weiguo Coege of Computing Copyeft 2003~2018

3 Roadmap Introduction Physica Layer Data Link Layer Medium Access Subayer Network Layer Transport Layer Appication Layer 3

4 Chapter 1 Introduction

5 Attention The materias beow are avaiabe for use by others. Instructors are wecome to use them in their own courses, downoad them to their own cass' web site, or modify them to suit. However, you must acknowedge the source of the origina and not attempt to pace your own copyright on this materia. Thanks to: 5

6 Topics 1.1 Uses of computer networks 1.2 Network Hardware 1.3 Network Software 1.4 Reference Modes 1.5 Exampe Networks 1.6 Network Standardization Some of the overa issues we be deaing with in this course. 6

7 A Computer Network Communication Link A coection of computers interconnected by communication inks inwei@cuc.edu.cn 7

8 1.1 Uses of Computer Networks Business Appications Home Appications Mobie Users Socia Issues 8

9 Business Appications Companies have a great number of computers Monitor productions, keep track of inventories, do the payro Those computers may have worked in isoation from the others, but at some point, management may have decided to connect them to be abe to distribute information throughout the company. inwei@cuc.edu.cn 9

10 1 st goa: Resource Sharing The goa is to make a programs, equipment, and especiay data avaiabe to anyone on the network without regard to the physica ocation of the resource and the user. Equipment: Printers, Scanner, CD-Burners Information: Customer records, Product information,inventories, financia statements, tax information inwei@cuc.edu.cn 10

11 Cient machine and Server machine Data A network with two cients and one server. inwei@cuc.edu.cn 11

12 Cient/Server mode The C/S mode is widey used and forms the basis of much network usage. The most popuar reaization is that of a Web appication. The cient/server mode invoves requests and repies. inwei@cuc.edu.cn 12

13 2 nd goa: A Computer network to do with peope A second goa of setting up a computer network has to do with peope rather than information or even computers. A computer network can provide a powerfu communication medium among empoyees. Emai VoIP Videoconferencing Cooperate with other to work: desktop sharing inwei@cuc.edu.cn 13

14 3 rd goa: e-commerce A third goa for many companies is doing business eectronicay with other companies, especiay suppiers and customers. e-commerce B2B: Business to business. B2C: Business to consumer. C2C: Consumer to consumer. inwei@cuc.edu.cn 14

15 Home Appications Access to remote information Web Person-to-person communication Emai,IM, VoIP e-commerce Interactive entertainment IPTV, Gaming 15

16 P2P - Peer to Peer In peer-to-peer system there is no fixed division into cients and servers. inwei@cuc.edu.cn 16

17 Other appications Ubiquitous computing IOT ( Internet of Things) Sensor Networks RFID (Radio Frequency IDentification) inwei@cuc.edu.cn 17

18 Mobie Users Combinations of wireess networks and mobie computing. 18

19 Wearabe Computers 19

20 SoLoMo 20

21 Socia Issues Socia networking issues Empoyee rights vs empoyer rights Government vs citizen Hacker and crimina Copyright protection Again, The Internet addiction? 21

22 1.2 Network Hardware Taxonomy of Networks Persona Networks Loca Area Networks Wide Area Networks Wireess Networks 22

23 Cassifying networks By transmission technoogy By scae 23

24 Transmission technoogy Types of transmission technoogy Broadcast inks Point-to-point inks 24

25 Point-to-point inks Point-to-point inks connect individua pairs of machines. Packets : short messages To go from the source to the destination, a packet on a network made up of point-to-point inks may have to first visit one or more intermediate machines. Often mutipe routes, of different engths, are possibe Unicasting: exacty one sender and one receiver inwei@cuc.edu.cn 25

26 Broadcast Networks Broadcast networks have a singe communication channe that is shared by a the machines on the network. Packets sent by any machine are received by a the others. An address fied within the packet specifies the intended recipient. Upon receiving a packet, a machine checks the address fied. If the packet is intended for the receiving machine, that machine processes the packet; if the packet is intended for some other machine, it is just ignored. inwei@cuc.edu.cn 26

27 Broad/Muti-casting Broadcasting address a packet to a destinations by using a specia code in the address fied. Muticasting Some broadcast systems aso support transmission to a subset of the machines inwei@cuc.edu.cn 27

28 Network Topoogies Think of a topoogy as a network's virtua shape or structure. Router inwei@cuc.edu.cn 28

29 Exampe of a Rea network inwei@cuc.edu.cn 29

30 Cassification by scae. 30

31 PAN (Persona area networks) Buetooth ( IEEE ) inwei@cuc.edu.cn 31

32 Loca Area Networks A LAN is a privatey owned network that operates with in and nearby a singe buiding ike a home, office or factory. LANs are widey used to connect persona computers and consumer eectronics to et them share resources and exchange information. inwei@cuc.edu.cn 32

33 Wireess and wired LANs Wireess and wired LANs. (a) (b) Switched Ethernet. 33

34 WLAN (Wireess LAN) Wireess LAN (Wi-Fi IEEE ) inwei@cuc.edu.cn 34

35 Wired LAN Wired LANs charactoristics Use copper wires, optica fibers Are restricted in size Run at speeds of 10Mbps to 1Gbps Low deay Make very few errors 35

36 Ethernet: IEEE802.3 Ethernet is the most common type of wired LAN Switched Ethernet Each computer speaks the Ethernet protoco and connects to a box caed a switch with a point-to-point ink. A switch has mutipe ports, each of which can connect to one computer. The job of the switch is to reay packets between computers that are attached to it, using the address in each packet to determine which computer to send it to. inwei@cuc.edu.cn 36

37 Expand and divide a LAN Expand a LAN to make it arger Switches can be pugged into each other using their ports Divide one arger physica LAN into smaer ogica LANs. VLAN(virtua LAN) Each switch port is tagged with a coor, the switch then forwards packets so that computers attached to the same coor ports are separated from the others. inwei@cuc.edu.cn 37

38 Cassic Ethernet The origina Ethernet design broadcasts a the packets over a singe inear cabe. At most one machine coud successfuy transmit at a time, and distributed arbitration mechanism was used to resove conficts. Computers coud transmit whenever the cabe was ide If two or more packets coided, each computer just waited a random time and tried ater. inwei@cuc.edu.cn 38

39 Cassic LAN Topoogies Two broadcast networks (a) Bus (IEEE 802.3, Ethernet) (b) Ring (IEEE 802.5, Token Ring) 39

40 Channe Aocation methods for Broadcast networks Static aocation Divide time into discrete intervas and use a round-robin agorithm, aowing each machine to broadcast ony when its time sot comes up. It wastes channe capacity when a machine has nothing to say during its aocated sot, so most systems attempt to aocate the channe dynamicay. Dynamic aocation Centraized: there is a singe entity which determines who goes next. Decentraized : there is no centra entity, each machine must decide for itsef whether to transmit. inwei@cuc.edu.cn 40

41 Metropoitan Area Networks MAN covers a city A metropoitan area network based on cabe TV. inwei@cuc.edu.cn 41

42 Wireess MAN WiMax IEEE

43 Wide Area Networks A WAN spans a arge geographica area, often a country or continent. WAN that connects three branch offices in Austraia inwei@cuc.edu.cn 43

44 Communication subnet Transmission ines copper wire, optica fiber, or even radio inks. Most companies do not have transmission ines ying about, so instead they ease the ines. Switching eements Switches are the speciaized computers caed routers that connect two or more transmission ines Subnet: A coection of routers and communication ines that moved packets from the source host to the destination. inwei@cuc.edu.cn 44

45 Differences between WAN &LAN In WAN, the hosts and subnet are owned and operated by different peope The routers wi usuay connect different kinds of networking technoogy. What is connected to the subnet: Individua computers Coud be entire LANs This is how arger networks are buit from smaer ones 45

46 WAN via the Internet VPN: fexibe but ack contro WAN using a virtua private network. inwei@cuc.edu.cn 46

47 WAN via ISP network The subnet is run by Internet Service Provider WAN using an ISP network. 47

48 WAN Terms Packet / Ce the message is cut into packets before sending Packet-switched / store-and-forward the packet is received at each intermediate router in its entirety, stored there unti the required output ine is free, and then forwarded. Routing agorithm There may be many paths in the network that connect two computers. How the network makes the decision as to which path to use is caed the routing agorithm. inwei@cuc.edu.cn 48

49 Internet Internetworks: Coection of interconnected networks. internet (ower case i) is generic term. Internet (upper case I) is wordwide connection to a kinds of machines. inwei@cuc.edu.cn 49

50 1.3 Network Software Protoco Hierarchies Design Issues for the Layers Connection-Oriented and Connectioness Services Service Primitives The Reationship of Services to Protocos 50

51 Phiosophy of Protoco Hierarchies Layering: To reduce their design compexity, most networks are organized as a stack of ayers or eves, each one buit upon the one beow it. Services: The purpose of each ayer is to offer certain service to the higher ayer, shieding those ayers from the detais of how the offered services are actuay impemented. inwei@cuc.edu.cn 51

52 Layer n Protoco Layer n on one machine carries on a conversation with ayer n on another machine. The rues and conventions used in this conversation are coectivey known as the ayer n protoco. A protoco is an agreement between communicating parties on how communication is to proceed. inwei@cuc.edu.cn 52

53 What Is A Protoco Human protocos: what s the time? How are you doing? I have a question - Specific messages sent - Specific actions taken when messages received, or other events Network protocos: Machines rather than humans A communication activity in Internet governed by protocos Protocos define format, order of messages sent and received among network entities, and actions taken on message transmission and receipt. inwei@cuc.edu.cn 53

54 Protoco Exampe Human Network Heo Heo TCP connection request TCP connection repy Got the time? HTTP request It s 10:30 HTTP response inwei@cuc.edu.cn 54

55 Protoco Hierarchies Virtua communication Peers Physica communication Layers, protocos, and interfaces. 55

56 Hierarchy Exampe Name Address Name Address Post Office Post Office 56

57 Terminoogy Peers The entities comprising the corresponding ayers on different machines are caed peers. The peers may be processes, hardware devices, or even human beings. In other words, it is the peers that communicate by using the protoco. Interface: Between each pair of adjacent ayers is an interface. The interface defines which primitive operations and services the ower ayer makes avaiabe to the upper one. 57

58 KISS principe "Keep It Simpe, Stupid", Important to keep it simpe and cean to reduce compexity. How many ayers? Cean interfaces Important that each ayer perform a specific coection of we-understood functions. inwei@cuc.edu.cn 58

59 Network architecture Network architecture: A set of ayers and protocos. The spec must contain enough information to aow an impementer to write the program or buid the hardware for each ayer so that it wi correcty obey the appropriate protoco. Functiona interfaces and impementation detais are not part of the spec, since that's not visibe outside the machine. It is not even necessary that the interfaces on a machines in a network be the same, provided that each machine can correcty use a the protocos. inwei@cuc.edu.cn 59

60 Protoco stack Protoco stack: A ist of protocos used by a system, one protoco per ayer, is caed a protoco stack. Network architectures, protoco stacks, and the protocos themseves are the principa subjects of this course inwei@cuc.edu.cn 60

61 Anaogy of Protoco Hierarchies Urdu Engish Chinese French The phiosopher-transator-secretary architecture. 61

62 Virtua Communication: Sino-US Tak Xi Jinping meets with Barack Obama. 62

63 Information fow Horizonta Exampe information fow supporting virtua communication in ayer 5. Layer4 thinks "SendtoPeer" rather than CaNextLayerDown". 63

64 Terminoogy Header: Upper ayer puts a header in front of the message to identify the message and passes the resut to ower ayer The header incudes contro information such as sequence numbers to keep the right order. Size of messages There is aways a imit to the size of messages imposed by certain ayer protoco. So incoming messages must be broken into smaer units (packets) in this ayer. inwei@cuc.edu.cn 64

65 An Internet Enveope 65

66 TCP/IP Hierarchies CRC HTTP FTP Data HTTP FTP TCP UDP Appication TCP UDP IP ICMP IGMP ARP Transport Internet IP ICMP IGMP ARP ATM Ethernet Preambe ATM Ethernet 66

67 Software or hardware? Athough this section is caed ' network software, it is worth pointing out that the ower ayers of a protoco hierarchy are frequenty impemented in hardware or firmware. Nevertheess, compex protoco agorithms are invoved, even if they are embedded (in whoe or in part) in hardware. inwei@cuc.edu.cn 67

68 Design Issues for the Layers Reiabiity Network Evoution Resource Location Against Threats 68

69 Reiabiity Reiabiity: Making a network that operates correcty even though it is made up of a coection of components that are themseves unreiabe. Mechanisms: Error detection Find errors in received information. Error correction Fix errors in received information. Routing Find a working path through a network. inwei@cuc.edu.cn 69

70 Network Evoution issue Protoco Layering Support change Addressing or Naming Every ayer needs a mechanism for identifying senders and receivers. Internetworking Different network technoogies often have different imitations. Scaabe Design work we when the network gets arge inwei@cuc.edu.cn 70

71 Resource Location Networks provide a service to hosts from their underying resource, such as the capacity of transmission ines. Statistica mutipexing Share network bandwidth dynamicay Fow contro Keep a fast sender from swamping a sow receiver with data. Congestion Network overoading Quaity of Service Differentia service for rea-time deivery and other. inwei@cuc.edu.cn 71

72 Against Threats Confidentiaity Against eavesdropping Authentication Prevent impersonation Integrity Prevent surreptitious changes to messages 72

73 Connection-Oriented vs. Connectioness Services Layers can offer two different types of service to the ayers above them: Connection-oriented Connectioness 73

74 Connection-oriented service Like the teephone system. The system estabishes a connection, uses it, and coses it. Acts ike a tube(circuit). Data comes out the other end in the same order as it goes in. Connection Setup (negotiation) Data Transfer Connection Termination inwei@cuc.edu.cn 74

75 Connectioness service Like the posta system. Each message carries the fu destination address and each one is routed through the intermediate nodes inside the system independent of a the subsequent messages. It is possibe that the first one sent can be deayed so that the subsequent messages arrive first. Message has a name: a packet in network ayer Store-and-forward switching vs. cut-through switching. inwei@cuc.edu.cn 75

76 Quaity of service Each service can be characterized by a QoS: Reiabiity: Wi the message arrive? A reiabe service is impemented by acknowedgement (a receipt from the receiver). Deay (Latency) Deays and overhead are introduced in the ack process inwei@cuc.edu.cn 76

77 Reiabe connection-oriented service A reiabe connection-oriented service guarantees success. They never ose data. Message sequence - message boundaries and order are maintained. Byte streams - messages are broken up or combined; fow is bytes. Can pair mechanism with upper-ayer requirements. A typica situation in which a reiabe connectionoriented service is appropriate is fie transfer. inwei@cuc.edu.cn 77

78 Unreiabe Connectioness Service Connectioness Service /Datagram Service: For some appications, the transit deay introduced by acks are unacceptabe. Like Voice Over IP. Not a appications require connections. Like junk mai. It's not worth the cost to determine if it actuay arrived. Needs a high probabiity of arriva, but 100% not required. Connectioness, no acknowedgment. Acknowedged datagram service: As above, but improved reiabiity via acknowedgment. Request-repy service: Acknowedgment is in the form of a repy. inwei@cuc.edu.cn 78

79 Connection-Oriented and Connectioness Services Six different types of service. 79

80 Service Primitives A service is formay specified by a set of primitives (operations) avaiabe to a user process to access the service. These primitives te the service to perform some action or report on an action taken by a peer entity. If the protoco stack is ocated in the operating system, as it often is, the primitives are normay system cas inwei@cuc.edu.cn 80

81 Service Primitives Five service primitives for impementing a simpe connection-oriented service. inwei@cuc.edu.cn 81

82 Service Primitives Packets sent in a simpe cient-server interaction on a connection-oriented network.( but ife is not so simpe) inwei@cuc.edu.cn 82

83 Services to Protocos Reationship A service is a set of primitives (operations) that a ayer provides to the ayer above it. The service defines what operations the ayer is prepared to perform on behaf of its users, but it says nothing at a about how these operations are impemented. A protoco, in contrast, is a set of rues governing the format and meaning of the packets, or messages that are exchanged by the peer entities within a ayer. Entities use protocos to impement their service definitions. inwei@cuc.edu.cn 83

84 Layer K: a service and a protoco. In other words, services reate to the interfaces between ayers. In contrast, protocos reate to the packets sent between peer entities on different machines. inwei@cuc.edu.cn 84

85 1.4 Reference Modes The OSI Reference Mode The TCP/IP Reference Mode The Mode used in this course A Comparison of the OSI and TCP/IP A Critique of the OSI Mode and Protocos A Critique of the TCP/IP Reference Mode inwei@cuc.edu.cn 85

86 OSI vs. TCP/IP reference mode The protocos associated with the OSI(Open System Interconnect) mode are rarey used any more, the mode itsef is actuay quite genera and sti vaid, and the features discussed at each ayer are sti very important. The TCP/IP mode has the opposite properties: the mode itsef is not of much use but the protocos are widey used. 86

87 The OSI Reference Mode Deveoped by ISO: Internationa Standards Organization (1983,revised in 1995) Principes used to deveop OSI Layering: 1. Need a ayer for each different eve of abstraction. 2. Each ayer performs a we defined function. 3. Each ayer shoud be standardizabe. 4. Layer boundaries shoud minimize data fow across those boundaries. 5. The right number of ayers - don't put too many functions together, but not too many ayers either. inwei@cuc.edu.cn 87

88 The OSI Reference Mode The OSI reference mode. 1983,

89 Physica Layer Purpose Transmits raw bits across a medium. Concerns are Votage: how many vots for 1 / 0 Timing: how many ns a bit asts Dupexing: transmission in both directions? Connectors: how many pins? What is each pin? etc. inwei@cuc.edu.cn 89

90 Data Link Layer Purpose: Transform a raw transmission ine into a ine that appears free of undetected transmission errors to the networks ayer Concerns: Framing - Breaks apart input data into frames and transmit the frames sequentiay. Error handing if the service is reiabe, the receiver confirms correct receipt of each frame by sending back an acknowedgement frame. Fow contro - keeps a fast transmitter from drowning a sow receiver in data. Medium Access Contro how to contro access to the shared channe for broadcast networks. inwei@cuc.edu.cn 90

91 Network Layer Purpose Route packets from source to destination Concerns Routing - What path is foowed by packets from source to destination. Can be based on a static tabe, can be determined when the connection is created, or can be highy dynamic, being determined anew for each packet, to refect the current network oad. Congestion - Contros the number packets in the subnet. Qos Quaity of service provided(deay, transit time, jitter ) Heterogeneity - Interfacing so one type of network can tak to another. Addressing, packet size, protocos inwei@cuc.edu.cn 91

92 Transport Layer Purpose Accept data from above it, spit it up into smaer units if need be, pass them to network ayer, and ensure that the pieces a arrive correcty at the other end. Concerns Service Decisions - What type of service to provide; error-free point to point, datagram, etc. End-to-end: it carries data a the way from the source to the destination. Reiabiity - Ensures that packets arrive at their destination. Reassembes out of order messages. Hides network - Aows detais of the network to be hidden from higher eve ayers. Mapping - Determines which messages beong to which connections. Fow contro - keeps a fast transmitter from fooding a sow receiver. inwei@cuc.edu.cn 92

93 Session Layer Purpose Aow users on different machines to estabish sessions between them Concerns Diaog contro - keep track of whose turn it is to transmit Token Management prevent two parties from attempting the same critica operation at the same time Synchronization checkpointing ong transmissions to aow them to pick up from where they eft off in the event of a crash and subsequent recovery. inwei@cuc.edu.cn 93

94 Presentation Layer Purpose Make it possibe for computers with different data representations to communicate Concerns Syntax and semantics of information transmitted. Understands the nature of the data being transmitted. Converts ASCII/EBCDIC, big endian/itte endian 94

95 Appication Layer contains a variety of protocos that are commony needed by users. HTTP FTP SMTP inwei@cuc.edu.cn 95

96 The TCP/IP Reference Modes Link ayer Internet ayer Transport ayer Appication ayer 96

97 U.S. DoD ARPANET Was a research network sponsored by the DoD Network be abe to survive oss of subnet hardware, with existing conversations not being broken off. A fexibe architecture was needed since appications with divergent requirements were envisioned, ranging from transferring fies to reatime speech transmission inwei@cuc.edu.cn 97

98 The TCP/IP Reference Modes The TCP/IP reference mode (Cerf & Kahn1974, Cark 1988) 98

99 The Key a packet-switching network based on a connectioness ayer that runs across different networks. inwei@cuc.edu.cn 99

100 Link Layer Describes what ink such as seria ines and cassic Ethernet must do to meet the needs of the connectioness internet ayer. It is not reay a ayer at a, in the norma sense of the term, but rather an interface between hosts and transmission inks. inwei@cuc.edu.cn 100

101 The Internet Layer Permit hosts to inject packets into any network and have them trave independenty to the destination ( potentiay on a different network, ike internationa mai) Routing and Congestion contro IP (Internet Protoco) ICMP(Internet Contro Message Protoco) inwei@cuc.edu.cn 101

102 Transport Layer End2End: Aows peer entities to communicate. TCP - Transmission Contro Protoco provides a reiabe connection oriented protoco that deivers a byte stream from one node to another. Guarantees deivery and provides fow contro. UDP - User Datagram Protoco provides an unreiabe connection-ess protoco for appications that provide their own. inwei@cuc.edu.cn 102

103 Appication Layer Termina - Tenet Fie transfer FTP The Web - HTTP inwei@cuc.edu.cn 103

104 The TCP/IP Reference Modes The TCP/IP reference mode with some protocos we wi study 104

105 The mode used in this course The reference mode used in this course. 105

106 Comparing OSI and TCP/IP Modes Concepts centra to the OSI mode Services Interfaces Protocos OSI has good definition of service, interface, and protoco as discussed before. Fits we with object oriented programming concepts. Protocos are better hidden. 106

107 Comparing OSI and TCP/IP Modes The TCP/IP mode did not originay distinguish between service, interface, and protoco. With TCP/IP, the protocos came first; mode was just a description of the protocos. But then the mode isn't good for any other protocos. inwei@cuc.edu.cn 107

108 Different phiosophy Which is first? Reference Mode vs Corresponding protocos 108

109 Specific differences Number of ayers: 7 vs. 4 Connectioness vs. connection-oriented OSI supports both in the network ayer, but ony Connection-oriented communication in the transport ayer TCP/IP supports ony connectioness mode in the network ayer but supports both in the transport ayer, giving the users a choice. inwei@cuc.edu.cn 109

110 A Critique of the OSI Mode and Protocos Why OSI did not take over the word Bad timing Bad technoogy Fawed, too compex More poitica than technica of 7 ayers decision Bad impementations Huge, unwiedy, Poor quaity Bad poitics Academia vs Bureaucrats inwei@cuc.edu.cn 110

111 Bad Timing The apocaypse of the two eephants. 111

112 A Critique of the TCP/IP Reference Mode Service, interface, and protoco not distinguished Not a genera mode Link ayer not reay a ayer No mention of physica and data ink ayers Minor protocos deepy entrenched, hard to repace inwei@cuc.edu.cn 112

113 1.5 Exampe Networks The Internet 3G Mobie Phone Networks Wireess LANs: RFID and Sensor networks 113

114 The history The story begins in the ate 1950s. At the height of the Cod War, the DoD wanted a command-and-contro network that coud survive a nucear war. This eads to the ARPANET: 1968 Originay intended as reiabe network, with mutipe routing. Used TCP/IP precursor, which got buit into eary UNIX. (ARPA, the Advanced Research Projects Agency ) inwei@cuc.edu.cn 114

115 The ARPANET (a) Structure of the teephone system. (b) Baran s proposed distributed switching system. inwei@cuc.edu.cn 115

116 The ARPANET (2) The origina ARPANET design. IMPs (Interface Message Processors) 116

117 The ARPANET (3) NAP (Network Access Point). Growth of the ARPANET (a) December (b) Juy (c) March (d) Apri (e) September

118 NSFNET The NSFNET backbone in

119 NSFNET Late 1970s - Many other foks wanted to get on the net, but Arpanet was essentiay imited to miitary contractors. NSF set up another network to hande this need. Started at 448 Kbps and by 80's upgraded to 1.5 Mbps Formed ANS (Advanced Networks and Services) - MERIT, MCI, IBM took over from the government running at 45 Mbps ANSNET sod to AOL, who now runs it. inwei@cuc.edu.cn 119

120 Internet Usage Growing exponentiay. A nodes run TCP/IP. Means that a nodes have an IP address by which they can be contacted. Traditiona appications ( ) E-mai News Remote ogin Fie transfer inwei@cuc.edu.cn 120

121 Internet Usage 1990s : the WWW (Word Wide Web) invented by CERN physicist Tim Berners-Lee Together with the Mosaic browser Written by Marc Andreessen at the Nationa Center for Supercomputer Appications in Urbana, Iinois ISPs (Internet Service Providers) Offer individua users at home the abiity to ca up one of their machines and connect to the Internet inwei@cuc.edu.cn 121

122 Architecture of the Internet Overview of the Internet architecture 122

123 3G Mobie Phone Networks Ceuar design of mobie phone networks 123

124 3G Mobie Phone Networks Architecture of the UMTS 3G mobie phone network. 124

125 3G Mobie Phone Networks Mobie phone handover (a) before, (b) after. 125

126 Wireess LANs - WiFi (802.11) (a) Wireess networking with a base station. (b) Ad hoc networking. inwei@cuc.edu.cn 126

127 Wireess LANs: Mutipath fading 127

128 Wireess LANs: The range of a singe radio may not cover the entire system. inwei@cuc.edu.cn 128

129 Wireess LANs standards The deveopment of the standard : 1Mbps, 2Mbps (2.4 GHz) a-1999: 54Mbps (5 GHz band) b-1999:11Mbps(2.4 GHz) g-2003: 54Mbps (2.4 GHz) n-2009:upto 600Mbps (operates on both the 2.4 GHz and the esser used 5 GHz bands) ac-2012:upto 1Gbps(5GHz) inwei@cuc.edu.cn 129

130 RFID and Sensor Networks RFID used to network everyday objects. 130

131 RFID and Sensor Networks Mutihop topoogy of a sensor network inwei@cuc.edu.cn 131

132 1.6 Network Standardization Who s Who in the Teecommunications Word Who s Who in the Internationa Standards Word Who s Who in the Internet Standards Word De facto and De jure inwei@cuc.edu.cn 132

133 ITU (Internationa Teecommunication Union) Main sectors ITU-R: Radio communications ITU-T: Teecommunications Standardization ITU-D: Deveopment Casses of Members Nationa governments Sector members Associate members Reguatory agencies 133

134 Network Standardization ISO (Internationa Standards Organization) ANSI (American Nationa Standards Institute) NIST (Nationa Institute of Standards and Technoogy) IEEE (Institute of Eectrica and Eectronics Engineering) 134

135 IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with gave up and disbanded itsef. 135

136 IEEE 802 Standards 136

137 Internet standards Internet Architecture Board. IETF: Internet Engineering Task Force RFC: Request for comments IRTF (Internet Research Task Force) Internet Society 137

138 END OF CH-1 138