Chapter 4: Networking and the Internet. Copyright 2015 Pearson Education, Inc.

Transcription

1 Chapter 4: Networking and the Internet

2 Chapter 4: Networking and the Internet 4.1 Network Fundamentals 4.2 The Internet 4.3 The World Wide Web 4.4 Internet Protocols 4.5 Security 4-2

3 Network Classifications Scope Personal area network (PAN) Local area network (LAN) Metropolitan area (MAN) Wide area network (WAN) Ownership Closed versus open Topology (configuration) Bus (Ethernet) Star (Wireless networks with central Access Point) 4-3

4 Figure 4.1 Network topologies 4-4

5 Figure 4.1 Network topologies (continued) 4-5

6 Protocols CSMA/CD Carrier Sense, Multiple Access w/ Collision Detection Used in Ethernet Silent bus provides right to introduce new message 은폐단말기 (hidden terminal) 문제가있는경우사용불가 ( 방해물이나거리때문에직접상대의신호를들을수없는경우 ) 4-6

7 Protocols CSMA/CA Carrier Sense, Multiple Access w/ Collision Avoidance Used in WiFi 통신채널이쉬고있을때, 조금더기다려보고여전히쉬고있으면송신시작 여전히사용중이면무작위의시간을기다린후다시시도 우선권인정 Hidden terminal problem: AP 에게승인요청으로해결 4-7

8 Figure 4.2 Communication over a bus network 4-8

9 Figure 4.3 The hidden terminal problem 4-9

10 Connecting Networks Repeater: Extends a network Bridge: Connects two compatible networks Switch: Connects several compatible networks Router: Connects two incompatible networks resulting in a network of networks called an internet 4-10

11 Figure 4.4 Building a large bus network from smaller ones 4-11

12 Figure 4.5 Routers connecting two WiFi networks and an Ethernet network to form an internet 4-12

13 Inter-process Communication Client-server One server, many clients Server must execute continuously Client initiates communication Peer-to-peer (P2P) Two processes communicating as equals Peer processes can be short-lived 4-13

14 Figure 4.6 The client/server model compared to the peer-to-peer model 4-14

15 Distributed Systems Systems with parts that run on different computers Cluster computing Grid computing Cloud computing Amazon s Elastic Compute Cloud Google Drive 4-15

16 The Internet The Internet: An internet that spans the world Original goal was to develop a means of connecting networks that would not be disrupted by local disasters Today a commercial undertaking that links a worldwide combination of PANs, LANs, MANs, and WANs involving millions of computers 4-16

17 Internet Architecture Internet Service Provider (ISP) Tier-1 Tier-2 Access or tier-3 ISP: Provides connectivity to the Internet Hot spot (wireless) Telephone lines Cable/Satellite systems DSL Fiber optics 4-17

18 Figure 4.7 Internet Composition 4-18

19 Internet Addressing IP address: pattern of 32 or 128 bits often represented in dotted decimal notation Mnemonic address: Domain names Top-Level Domains Domain name system (DNS) Name servers DNS lookup 4-19

20 인터넷주소체계 : IP 주소 IP 주소 : 32 비트 /128 비트컴퓨터식별자비트패턴 네트워크식별자 : ICANN 에의해할당 호스트주소 : 도메인관리자에의해할당 점찍는 10 진표기법 : IP 주소표시방법 ( 바이트단위 ) 예 : Pearson Addison-Wesley. 0-20All rights reserved

21 인터넷주소체계 : 호스트이름 기호식주소는두부분으로이루어진다 : 도메인이름 등록대행사가지정 예 : aw.com 최상위도메인 (Top Level Domain): 도메인소유자에대한분류 용도구분 : 예 :.com = commercial 국가구분 : 예 :.au = Australia 부도메인 (Subdomain) 과개별호스트이름 도메인소유자가지정 예 : r2d2.compsci.nowhereu.edu 2007 Pearson Addison-Wesley. 0-21All rights reserved

22 인터넷주소체계 : 호스트이름 기호식주소와 IP 주소사이의변환은네임서버에의해처리된다 DNS (Domain Name System) 인터넷차원의디렉토리시스템 DNS Lookup (DNS 조회 ) 주소변환을위해 DNS 사용절차 Pearson Addison-Wesley. 0-22All rights reserved

23 Internet Corporation for Assigned Names & Numbers (ICANN) Allocates IP addresses to ISPs who then assign those addresses within their regions. Oversees the registration of domains and domain names. 4-23

24 Early Internet Applications Network News Transfer Protocol (NNTP) File Transfer Protocol (FTP) Telnet and SSH Hypertext Transfer Protocol (HTTP) Electronic Mail ( ) Domain mail server collects incoming mail and transmits outing mail Mail server delivers collected incoming mail to clients via POP3 or IMAP 4-24

25 SMTP Simple Mail Transfer Protocol 220 mail.tardis.edu SMTP Sendmail Gallifrey-1.0; Fri, 23 Aug :34:10 HELO mail.skaro.gov 250 mail.tardis.edu Hello mail.skaro.gov, pleased to meet you MAIL From: Sender ok RCPT To: Recipient ok DATA 354 Enter mail, end with "." on a line by itself Subject: Extermination. EXTERMINATE! Regards, Dalek r7njyael Message accepted for delivery QUIT mail.tardis.edu closing connection 4-25

26 More Recent Applications Voice Over IP (VoIP) Internet Multimedia Streaming N-unicast ( 네트워크에부담 ) Multicast( 라우터에분배문제를넘김 ) 그룹주소와방송국식별주소로구성 클라이언트들은그룹가입요청 라우터들은그룹요청을전파하고클라이언트관리 On-demand streaming Content delivery networks (CDNs) 4-26

27 World Wide Web Hypertext combines internet technology with concept of linked-documents Embeds hyperlinks to other documents Browsers present materials to the user Webservers provide access to documents Documents are identified by URLs and transferred using HTTP 4-27

28 Figure 4.8 A typical URL 4-28

29 Hypertext Markup Language (HTML) Encoded as text file Contains tags to communicate with browser Appearance <h1> to start a level one heading <p> to start a new paragraph Links to other documents and content <a href =... > Insert images <img src =... > 4-29

30 Figure 4.9 A simple webpage 4-30

31 Figure 4.9 A simple webpage (continued) 4-31

32 Figure 4.10 An enhanced simple webpage 4-32

33 Figure 4.10 An enhanced simple Web page (continued) 4-33

34 Extensible Markup Language (XML) XML: A language for constructing markup languages similar to HTML A descendant of SGML Opens door to a World Wide Semantic Web 4-34

35 Using XML <staff clef = treble > <key>c minor</key> <time> 2/4 </time> <measure> < rest> egth </rest> <notes> egth G, egth G, egth G </notes></measure> <measure> <notes> hlf E </notes></measure> </staff> 4-35

36 Figure 4.11 The first two bars of Beethoven s Fifth Symphony 4-36

37 Client Side Versus Server Side Client-side activities Javascript Macromedia Flash Server-side activities Common Gateway Interface (CGI) Servlets JavaServer Pages (JSP) / Active Server Pages (ASP) PHP 4-37

38 Figure 4.12 Package-shipping example 4-38

39 Internet Software Layers Application: Constructs message with address Transport: Chops message into packets Network: Handles routing through the Internet Link: Handles actual transmission of packets 4-39

40 Figure 4.13 The Internet software layers 4-40

41 OSI (Open Systems Interconnec tion) 7 Layer 2007 Pearson Addison-Wesley. 0-41All rights reserved

42 OSI model & Internet model Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Application Layer Transport Layer Internet Layer Network Access Layer Physical Layer 2007 Pearson Addison-Wesley. 0-42All rights reserved

43 Figure 4.14 Following a message through the Internet 4-43

44 TCP/IP Protocol Suite Transport Layer Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Network Layer Internet Protocol (IP) IPv4 IPv6 4-44

45 Figure 4.15 and UDP Choosing between TCP 4-45

46 Security Attacks Malware (viruses, worms, Trojan horses, spyware, phishing software) Denial of service (DoS) Spam Protection Firewalls Spam filters Proxy Servers Antivirus software 4-46

47 Encryption HTTPS and SSL Public-key Encryption Public key: Used to encrypt messages Private key: Used to decrypt messages Certificates and Digital Signatures 인증서 : 개인정보 + 공개키 디지털서명 : 전자서명 + 개인키암호화 Certificate authorities 4-47

48 Figure 4.16 Public-key encryption 4-48

49 IoT 4-49

50 End of Chapter