Networking and Internet Tian-Li Yu [email_address] Department of Electrical Engineering National Taiwan University
Network classifications <ul><li>Scope </li></ul><ul><ul><li>LAN: local area network </li></ul></ul><ul><ul><li>MAN: metrop...
Network topology Ring Bus Star hub
Protocols <ul><li>Token ring </li></ul><ul><ul><li>Popular in ring topology. </li></ul></ul><ul><ul><li>Token and messages...
Dilbert on token ring Dilbert, Scott Adams
Connecting compatible networks <ul><li>Repeater </li></ul><ul><ul><li>Simply passing through messages. </li></ul></ul><ul>...
Repeater, bridge, and switch Textbook, Figure 4.4
Connecting incompatible networks <ul><li>Router </li></ul><ul><ul><li>Building a network of networks, known as an  interne...
Interprocess communication <ul><li>Server-client </li></ul><ul><ul><li>One server, several clients. </li></ul></ul><ul><ul...
Interprocess communication (contd.) Textbook, Figure 4.6
Distributed systems <ul><li>Infrastructure can be provided by standardized toolkits. </li></ul><ul><ul><li>Enterprise Java...
The  I nternet <ul><li>The most notable example of an internet is the Internet. </li></ul><ul><li>Original goal was to pre...
Internet architecture <ul><li>Domain </li></ul><ul><ul><li>a network or an internet controlled by one single authority. </...
Domains, gateway, and the Internet Textbook, Figure 4.7
Connecting to the Internet <ul><li>ISP (Internet service provider) </li></ul><ul><ul><li>Allow customers to connect their ...
IP addresses <ul><li>IP (Internet protocol) addresses </li></ul><ul><ul><li>32 bit in IPv4 </li></ul></ul><ul><ul><li>128 ...
Host names <ul><li>Mnemonic address made up of two parts </li></ul><ul><li>Domain name </li></ul><ul><ul><li>Assigned by a...
Internet applications <ul><li>VoIP (voice over Internet protocol) </li></ul><ul><li>email (electronic mail) </li></ul><ul>...
World wide web <ul><li>www, w3, web </li></ul><ul><li>hypertext, hyperlink, hypermedia. </li></ul><ul><li>Web page: hypert...
Browsers <ul><li>Presenting the web pages downloaded from the Internet. </li></ul><ul><li>HTTP (hypertext transfer protoco...
Hypertext markup language Textbook, Figure 4.10
eXtensible markup language <ul><li>XML </li></ul><ul><li>Standard style to represent data as text. </li></ul><ul><li>Restr...
Client-side & server-side <ul><li>Client-side </li></ul><ul><ul><li>Java applets </li></ul></ul><ul><ul><li>Java scripts <...
Internet protocol <ul><li>Layers </li></ul><ul><ul><li>Application: constructs message with address </li></ul></ul><ul><ul...
Layers Textbook Figure 4.14
TCP/IP suite <ul><li>TCP and IP are two protocols, TCP/IP refers to a collection of protocols more than just TCP and IP. <...
Security <ul><li>Attacks </li></ul><ul><ul><li>Malware (malicious software) </li></ul></ul><ul><ul><ul><li>Virus, worm, Tr...
Encryption <ul><li>sftp  (ftps as in the textbook) , https, ssh, ssl </li></ul><ul><li>Public/private keys </li></ul><ul><...
Public/private key issues <ul><li>Certificate authority </li></ul><ul><ul><li>Ensure the public key is given by the truste...
Exercises <ul><li>Chapter 4: 1, 7, 8, 12, 20, 26, 27, 35, 37, 39, 40, 43, 46.  </li></ul>
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Networking And Internet

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Networking And Internet

  1. 1. Networking and Internet Tian-Li Yu [email_address] Department of Electrical Engineering National Taiwan University
  2. 2. Network classifications <ul><li>Scope </li></ul><ul><ul><li>LAN: local area network </li></ul></ul><ul><ul><li>MAN: metropolitan area network </li></ul></ul><ul><ul><li>WAN: wide area network </li></ul></ul><ul><li>Ownership </li></ul><ul><ul><li>Closed </li></ul></ul><ul><ul><li>Open </li></ul></ul><ul><li>Topology </li></ul>
  3. 3. Network topology Ring Bus Star hub
  4. 4. Protocols <ul><li>Token ring </li></ul><ul><ul><li>Popular in ring topology. </li></ul></ul><ul><ul><li>Token and messages are passed in one direction. </li></ul></ul><ul><ul><li>Only the machine that gets the token can transmit its own message. </li></ul></ul><ul><li>CSMA/CD </li></ul><ul><ul><li>Carrier sense, multiple access with collision detection. </li></ul></ul><ul><ul><li>Popular in bus topology (Ethernet). </li></ul></ul><ul><ul><li>Broadcasting. </li></ul></ul><ul><ul><li>When collision, both machines wait for a brief random time before trying again. </li></ul></ul>
  5. 5. Dilbert on token ring Dilbert, Scott Adams
  6. 6. Connecting compatible networks <ul><li>Repeater </li></ul><ul><ul><li>Simply passing through messages. </li></ul></ul><ul><ul><li>Connecting two compatible networks. </li></ul></ul><ul><li>Bridge </li></ul><ul><ul><li>Only passing those messages addressed to the other side. </li></ul></ul><ul><ul><li>Connecting two compatible networks more efficiently. </li></ul></ul><ul><li>Switch </li></ul><ul><ul><li>A bridge with multiple connections. </li></ul></ul><ul><ul><li>Connecting several compatible networks more efficiently. </li></ul></ul>
  7. 7. Repeater, bridge, and switch Textbook, Figure 4.4
  8. 8. Connecting incompatible networks <ul><li>Router </li></ul><ul><ul><li>Building a network of networks, known as an internet . </li></ul></ul>Textbook, Figure 4.5
  9. 9. Interprocess communication <ul><li>Server-client </li></ul><ul><ul><li>One server, several clients. </li></ul></ul><ul><ul><li>Clients initiate communications by sending requests. </li></ul></ul><ul><ul><li>Server serves. </li></ul></ul><ul><li>P2P (peer-to-peer) </li></ul><ul><ul><li>Two processes communicating as equals. </li></ul></ul><ul><ul><li>The most popular distribution mode nowadays. </li></ul></ul>
  10. 10. Interprocess communication (contd.) Textbook, Figure 4.6
  11. 11. Distributed systems <ul><li>Infrastructure can be provided by standardized toolkits. </li></ul><ul><ul><li>Enterprise Java Beans by Sun Microsytems </li></ul></ul><ul><ul><li>.NET framework by Microsoft </li></ul></ul>
  12. 12. The I nternet <ul><li>The most notable example of an internet is the Internet. </li></ul><ul><li>Original goal was to prevent disruptions caused by local disaster. </li></ul><ul><li>Now it’s a commercial undertaking. </li></ul>
  13. 13. Internet architecture <ul><li>Domain </li></ul><ul><ul><li>a network or an internet controlled by one single authority. </li></ul></ul><ul><li>ICANN (Internet corporation for assigned names and numbers) </li></ul><ul><ul><li>Oversee the registration of domains. </li></ul></ul><ul><ul><li>Registrar </li></ul></ul><ul><li>Gateway </li></ul><ul><ul><li>A router that connects a domain to the rest of the Internet (the Internet cloud). </li></ul></ul>
  14. 14. Domains, gateway, and the Internet Textbook, Figure 4.7
  15. 15. Connecting to the Internet <ul><li>ISP (Internet service provider) </li></ul><ul><ul><li>Allow customers to connect their domain to the ISP’s equipment or join the domain already established by the ISP. </li></ul></ul><ul><li>Different means </li></ul><ul><ul><li>Telephone (dial-up) </li></ul></ul><ul><ul><li>Cable </li></ul></ul><ul><ul><li>DSL </li></ul></ul><ul><ul><li>Wireless </li></ul></ul>
  16. 16. IP addresses <ul><li>IP (Internet protocol) addresses </li></ul><ul><ul><li>32 bit in IPv4 </li></ul></ul><ul><ul><li>128 in IPv6 </li></ul></ul><ul><li>Network identifier (by ICANN) </li></ul><ul><li>Host address (domain administrator) </li></ul><ul><li>Dotted decimal </li></ul><ul><ul><li>140.112.18.33 </li></ul></ul>
  17. 17. Host names <ul><li>Mnemonic address made up of two parts </li></ul><ul><li>Domain name </li></ul><ul><ul><li>Assigned by a registrar </li></ul></ul><ul><ul><li>edu.tw </li></ul></ul><ul><ul><li>Top-level domain </li></ul></ul><ul><ul><ul><li>By usage: .edu = education </li></ul></ul></ul><ul><ul><ul><li>By country: .tw = Taiwan </li></ul></ul></ul><ul><li>Subdomains and individual host names </li></ul><ul><ul><li>Assigned by domain owner </li></ul></ul><ul><ul><li>www.ee.ntu .edu.tw </li></ul></ul><ul><li>Name server & domain name server (DNS) </li></ul><ul><ul><li>www.ee.ntu.edu.tw  140.112.18.33 </li></ul></ul>
  18. 18. Internet applications <ul><li>VoIP (voice over Internet protocol) </li></ul><ul><li>email (electronic mail) </li></ul><ul><li>FTP (file transfer protocol) </li></ul><ul><li>telnet & ssh (secure shell) </li></ul><ul><li>p2p: bittorrent, edonkey, emule… </li></ul>
  19. 19. World wide web <ul><li>www, w3, web </li></ul><ul><li>hypertext, hyperlink, hypermedia. </li></ul><ul><li>Web page: hypertext document </li></ul><ul><li>Website: a collection of closely related web pages. </li></ul>
  20. 20. Browsers <ul><li>Presenting the web pages downloaded from the Internet. </li></ul><ul><li>HTTP (hypertext transfer protocol) </li></ul><ul><li>URL (uniform resource locator) </li></ul>Textbook, Figure 4.8
  21. 21. Hypertext markup language Textbook, Figure 4.10
  22. 22. eXtensible markup language <ul><li>XML </li></ul><ul><li>Standard style to represent data as text. </li></ul><ul><li>Restricted mapping each opening to each ending. </li></ul><ul><li><x property=“yyy”> …… </x> </li></ul><ul><li>XHTML </li></ul><ul><ul><li>HTML that follows XML format. </li></ul></ul><name code=“ISO-8859-1”> Tian-Li Yu </name> <name code=“Big5”> 于天立 </name> <education> <BS> NTUEE, 1997</BS> <MS> UIUCCS, 2003 </MS> <PhD> UIUCCS, 2006 </PhD> </education>
  23. 23. Client-side & server-side <ul><li>Client-side </li></ul><ul><ul><li>Java applets </li></ul></ul><ul><ul><li>Java scripts </li></ul></ul><ul><ul><li>Flash </li></ul></ul><ul><li>Server-side </li></ul><ul><ul><li>CGI </li></ul></ul><ul><ul><li>Servlets (jsp, asp) </li></ul></ul><ul><ul><li>PHP (Personal Home Page, PHP Hypertext Processor) </li></ul></ul>
  24. 24. Internet protocol <ul><li>Layers </li></ul><ul><ul><li>Application: constructs message with address </li></ul></ul><ul><ul><li>Transport: chops message into packets </li></ul></ul><ul><ul><li>Network: handles routing through the Internet </li></ul></ul><ul><ul><li>Link: handles actual transmission of packets </li></ul></ul><ul><li>Port (not the I/O port) </li></ul>
  25. 25. Layers Textbook Figure 4.14
  26. 26. TCP/IP suite <ul><li>TCP and IP are two protocols, TCP/IP refers to a collection of protocols more than just TCP and IP. </li></ul><ul><li>TCP (transmission control protocol) </li></ul><ul><li>UDP (user datagram protocol) </li></ul><ul><ul><li>No notification before sending message, no retransmission service, no acknowledge of receiving message. </li></ul></ul><ul><li>TCP: more reliable, less efficient </li></ul><ul><li>UDP: more efficient, less reliable </li></ul>
  27. 27. Security <ul><li>Attacks </li></ul><ul><ul><li>Malware (malicious software) </li></ul></ul><ul><ul><ul><li>Virus, worm, Trojan horse, spyware, phishing) </li></ul></ul></ul><ul><ul><li>Denial of service </li></ul></ul><ul><ul><li>Spam </li></ul></ul><ul><li>Protections </li></ul><ul><ul><li>Firewall </li></ul></ul><ul><ul><li>Spam filter </li></ul></ul><ul><ul><li>Proxy </li></ul></ul><ul><ul><li>Antivirus, antispyware </li></ul></ul>
  28. 28. Encryption <ul><li>sftp (ftps as in the textbook) , https, ssh, ssl </li></ul><ul><li>Public/private keys </li></ul><ul><ul><li>Public key  encryption </li></ul></ul><ul><ul><li>Private key  decryption </li></ul></ul>Textbook Figure 4.16
  29. 29. Public/private key issues <ul><li>Certificate authority </li></ul><ul><ul><li>Ensure the public key is given by the trusted one. </li></ul></ul><ul><li>Authentication </li></ul><ul><ul><li>Make sure the author of a message is, in fact, the party it claims to be. </li></ul></ul><ul><ul><li>Use private key to encrypt; public key to decrypt. </li></ul></ul>
  30. 30. Exercises <ul><li>Chapter 4: 1, 7, 8, 12, 20, 26, 27, 35, 37, 39, 40, 43, 46. </li></ul>

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