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CSE111: Great Ideas in Computer Science

CSE111: Great Ideas in Computer Science. Dr. Carl Alphonce 219 Bell Hall Office hours: M-F 11:00-11:50 645-4739 alphonce@buffalo.edu. cell phones off (please). Announcements. Exam 1 handback . HW3 due March 5. Second exam is March 17 (week after spring break). Today’s Agenda.

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CSE111: Great Ideas in Computer Science

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  1. CSE111: Great Ideas in Computer Science Dr. Carl Alphonce 219 Bell Hall Office hours: M-F 11:00-11:50 645-4739 alphonce@buffalo.edu

  2. cell phones off (please)

  3. Announcements • Exam 1 handback. • HW3 due March 5. • Second exam is March 17 (week after spring break).

  4. Today’s Agenda • Networking

  5. Networking • What sorts of networks do we use? • Wired networks (in the labs) • Wireless (WIFI) networks (right now?) • Wireless cell phone networks • Wireless bluetooth (“personal area networks”)

  6. Configurations • Bus network • Devices connected to a common communications channel • Devices are peers • Ex. Typical wired network • Star network • Devices connected to a central machine • Devices communicate only via central machine • Ex. Typical wifi network (access point)

  7. Interconnecting networks • Repeater • Propagate signals between networks • Bridge • Propagate some signals between networks • Switch • Bridge with multiple connections • Router • Interface networks with different characteristics (e.g. ethernet bus to WiFi access point)

  8. Routing messages • Each device has an address on the network (IP address) • Messages are routed based on destination IP address. • IPv4: 32 bit address (4.3 X 109) • styx.cse.buffalo.edu (128.205.36.7) • 10000000.11001101.00100100.00000111 • IPv6: 128 bit address (3.4 X 1038)

  9. Domain Name System (DNS) • Translate from mnemonic form styx.cse.buffalo.edu • to IP address 128.205.36.7 (dotted decimal notation) • Determine DNS server • Windows • run ‘ifconfig /all’ at cmd prompt • Mac • Network preferences window • Look at /etc/resolv.conf file

  10. Reverse lookup:whois • Try: whois 128.205.36.7 whois 142.103.7.7

  11. 127.0.0.1 • localhost, or “home” • E.g. own machine provides service

  12. HumorImage from: www.thinkgeek.com

  13. HumorImage from: www.thinkgeek.com

  14. DNS hierarchy • Root servers • Caching domain servers • Applications can cache as well

  15. DNS attacks • Denial-of-service • http://royal.pingdom.com/2009/01/26/dns-attack-slowed-down-hundreds-of-thousands-of-websites/ • DNS poisoning • You look my www.mybank.xyz • You go to web site of www.crooks.xyz • They put up page that looks like your bank’s page – and steal your banking log-on information.

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