1-1CS 519Computer Networkshttp://www.cs.cornell.edu/courses/cs519/MW 2:55 – 4:10P Upson B17 (?)SP 2003-2Overview❒ Many of the same concepts you’ve seen in EE 445❍ Reliable communication, Routing Algorithms, etc.❒In 519, the emphasis is on the realization of these concepts in the Internet -3Top DownApplicationTransportNetworkPhysicalusersnetworkHTTP, SMTP, FTP, TELNET, DNS, …TCP, UDP.IP, OSPF, BGPPoint-to-point links,LANs, radios, ...-4Along the way❒ What does traffic on real networks look like?❍ Analyze packet traces and map back on to fundamental concepts behind the protocol design❒What does the Internet really look like?❍ Traceroute, DNS info❒How do you write network applications?❍ Socket programming❒How do you write the TCP/IP layer of a kernel?❍ Building reliable communication over unreliable-5Ethereal-6Traceroute/tracert2-7Graphical Traceroute (plus DNS information ☺)-8Internet Map❒ Traceroute gives one slice through the Internet topology❒ What does the Internet really look like?❍ That is a actually a hard question to answer❍ Internet Atlas Project• http://www.caida.org/projects/internetatlas/• Techniques, software, and protocols for mapping the Internet, focusing on Internet topology, performance, workload, and routing data-9CAIDA’s skitter plotHighly connectedFew connectionsLocation (longitude)Skitter data16 monitors probing approximately 400,000 destinations626,773 IP addresses1,007.723 IP links48,302 (52%) of globally routable network prefixesEuropeNorth America AsiaTop 15 ASes are in North America (14 in US, 1 in Canada)Many links US to Asia and Europe; few direct Asia/Europe
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