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Chapter 2: Motivation & Tools

Chapter 2: Motivation & Tools. Motivation of Networking & Internetworking Services Tools for exploration. Motivation. Cost effective Early computers were expensive, scare and centralized Couldn't afford to put computers everywhere

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Chapter 2: Motivation & Tools

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  1. Chapter 2: Motivation & Tools • Motivation of Networking & Internetworking • Services • Tools for exploration

  2. Motivation • Cost effective • Early computers were expensive, scare and centralized • Couldn't afford to put computers everywhere • interconnect computers so that computing powers can be shared by many sites • Resource sharing • access peripheral devices through the network • Eg. Many users sharing the same printer • sharing the same files on a disk • Higher reliability

  3. Communication Services • Access to remote information • World-Wide-Web • File Transfer (FTP) • Exchange of information • Email • USENET News

  4. ARPA • Advanced Research Projects Agency initiated project to connect researchers with computers • Adopted new technology: • Packet switching (accept & deliver individual parcels of data called packets) • Internetworking • Resulted in system for remote access to expensive resources

  5. Packet switching • Data transmitted in small, independent pieces • Source divides outgoing messages into packets • Destination recovers original data • Each packet travels independently • Includes enough information for delivery • May follow different paths • Can be retransmitted if lost

  6. Internetworking • Many (mutually incompatible) network technologies • No one technology appropriate for every situation • Internetworking glues together networks of dissimilar technologies with routers

  7. History and growth • ARPAnet began in late 1960s (not using TCP/IP) • TCP/IP developed in late 1970s • ARPAnet switched to TCP/IP in early 80s • Start of Internet • Few hundred computers • Few tens of networks

  8. Growth since 1981

  9. Growth (logarithmic axis)

  10. Probing the Internet • Two tools: • ping - sends message that is echoed by remote computer • traceroute - reports path to remote computer

  11. ping • Sends packet to remote computer • Remote computer replies with echo packet • Local computer reports receipt of reply % ping merlin.cs.purdue.edu merlin.cs.purdue.edu is alive

  12. Ping Example 1a: Output from Prof. Sim’s SUN Workstation on Dec 26, 2003 at 17:30hrs • Can arrange to send multiple packets • Reports round trip time From Prof. Sim’s Work Station > /usr/sbin/ping -s www.sears.com 56 5 PING www.sears.com: 56 data bytes 64 bytes from 129.33.131.131: icmp_seq=0. time=272. ms 64 bytes from 129.33.131.131: icmp_seq=1. time=267. ms 64 bytes from 129.33.131.131: icmp_seq=2. time=271. ms 64 bytes from 129.33.131.131: icmp_seq=3. time=264. ms 64 bytes from 129.33.131.131: icmp_seq=4. time=269. ms ----www.sears.com PING Statistics---- 5 packets transmitted, 5 packets received, 0% packet loss round-trip (ms) min/avg/max = 264/268/272

  13. Ping Example 1b: Output from Prof. Sim’s SUN Workstation on Dec 27, 2003 at 15:35hrs > /usr/sbin/ping -s www.sears.com 56 5 PING www.sears.com: 56 data bytes 64 bytes from 129.33.131.131: icmp_seq=0. time=268. ms 64 bytes from 129.33.131.131: icmp_seq=1. time=266. ms 64 bytes from 129.33.131.131: icmp_seq=2. time=270. ms 64 bytes from 129.33.131.131: icmp_seq=3. time=263. ms 64 bytes from 129.33.131.131: icmp_seq=4. time=268. ms ----www.sears.com PING Statistics---- 5 packets transmitted, 5 packets received, 0% packet loss round-trip (ms) min/avg/max = 263/267/270 • Compare the round-trip time with Example 1a, the results may be different when ping is executed at different time

  14. Ping Example 1c: From Fig 2.3 in the textbook

  15. Ping Example 1d: Output from Prof. Sim’s PC > ping -n 5 -l 56 www.sears.com Pinging sears.com [129.33.131.221] with 56 bytes of data: Reply from 129.33.131.221: bytes=56 time=265ms TTL=236 Reply from 129.33.131.221: bytes=56 time=265ms TTL=236 Reply from 129.33.131.221: bytes=56 time=265ms TTL=236 Reply from 129.33.131.221: bytes=56 time=265ms TTL=236 Reply from 129.33.131.221: bytes=56 time=266ms TTL=236 Ping statistics for 129.33.131.221: Packets: Sent = 5, Received = 5, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 265ms, Maximum = 266ms, Average = 265ms

  16. Ping Example 1e: Default Output from Prof. Sim’s PC >ping www.sears.com Pinging sears.com [129.33.131.221] with 32 bytes of data: Reply from 129.33.131.221: bytes=32 time=266ms TTL=236 Reply from 129.33.131.221: bytes=32 time=266ms TTL=236 Reply from 129.33.131.221: bytes=32 time=266ms TTL=236 Reply from 129.33.131.221: bytes=32 time=265ms TTL=236 Ping statistics for 129.33.131.221: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 265ms, Maximum = 266ms, Average = 265ms

  17. Ping Example 2: Fig 2.4 (text)

  18. Ping Example 3: Fig 2.5 (Text)

  19. Ping Example 4 C:\>ping cornell.edu Pinging cornell.edu [132.236.56.6] with 32 bytes of data Request timed out. Request timed out. Reply from 132.236.56.6: bytes=32 time=297ms TTL=232 Reply from 132.236.56.6: bytes=32 time=297ms TTL=232 Ping statistics for 132.236.56.6: Packets: Sent = 4, Received = 2, Lost = 2 (50% loss) Approximate round trip times in milli-seconds: Minimum = 297ms, Maximum = 297ms, Average = 148ms

  20. No response • Some companies configure their sites to reject ping packets • Delays are unreasonably long because of dense congestion in data traffic in the network • Remote computer was turned off, or disconnected or its interface fails • Software in remote computer are not programmed to respond to ping

  21. traceroute • Format: traceroute host name or IP address • Eg traceroute merlin.cs.purdue.edu • or traceroute 128.10.2.3 • Sends series of packets along path to destination • Each successive packet identifies the next intermediate computer along path • Reports list of packets (usually 3) sent to each intermediate computer along the path • Example (next slide): traceroute reported 9 lines (8 intermediate computers + destination) • the destination is 9 hops away from the source; each hop correspond to an intermediate computer along the path

  22. Traceroute Example 1 Results from: traceroute merlin.cs.purdue.edu: (executed from http://www.net.cmu.edu/cgi-bin/netops.cgi) 1 STERNUM-FA4-1-0.GW.CMU.NET (128.2.4.1) 2.011 ms 1.422 ms 1.384 ms 2 RTRBONE-FA4-0-0.GW.CMU.NET (128.2.0.2) 1.782 ms 1.939 ms 1.801 ms 3 killifish.psc.net (198.32.224.11) 2.192 ms 2.04 ms 2.054 ms 4 abilene-psc.abilene.ucaid.edu (192.88.115.121) 5.285 ms 5.339 ms 5.325 ms 5 ipls-clev.abilene.ucaid.edu (198.32.8.25) 11.676 ms 11.542 ms 12.06 ms 6 cisco-tel-ab.tcom.purdue.edu (192.5.40.9) 17.382 ms 17.4 ms 17.427 ms 7 cisco2-242.tcom.purdue.edu (128.210.242.7) 18.841 ms 75.275 ms 18.291 ms 8 cisco-cs-252.tcom.purdue.edu (128.210.252.21) 18.2 ms 18.658 ms 18.454 ms 9 merlin.cs.purdue.edu (128.10.2.3) 28.505 ms 19.663 ms 19.981 ms

  23. Traceroute Example 2 Results from: traceroute DANDELION-PATCH.MIT.EDU: (executed from http://www.net.cmu.edu/cgi-bin/netops.cgi) 1 STERNUM-FA4-1-0.GW.CMU.NET (128.2.4.1) 2.155 ms 1.546 ms 1.572 ms 2 RTRBONE-FA6-0-0.GW.CMU.NET (128.2.255.2) 1.82 ms 1.696 ms 1.591 ms 3 killifish.psc.net (198.32.224.11) 2.605 ms 5.047 ms 2.89 ms 4 abilene-psc.abilene.ucaid.edu (192.88.115.121) 5.337 ms 5.499 ms 5.485 ms 5 nycm-clev.abilene.ucaid.edu (198.32.8.30) 17.585 ms 17.324 ms 17.444 ms 6 192.5.89.45 (192.5.89.45) 23.803 ms 23.75 ms 24.181 ms 7 192.5.89.10 (192.5.89.10) 24.606 ms 24.202 ms 23.678 ms 8 NW12-RTR-FDDI.MIT.EDU (18.168.0.16) 25.074 ms 24.714 ms 25.162 ms 9 DANDELION-PATCH.MIT.EDU (18.181.0.31) 24.795 ms * 24.405 ms

  24. Traceroute Example 2 • 3 time parameters on each line are the results of sending 3 probe packets to each intermediate computer • * is printed when there is no response after 3 seconds

  25. TracerouteExample 3 Results from: traceroute merlin.cs.purdue.edu 1 CCSServC (134.82.7.254) 2 ms 1 ms 1 ms 2 134.82.254.253 (134.82.254.253) 2 ms 2 ms 3 ms 3 12.127.210.89 (12.127.210.89) 22 ms 20 ms 20 ms 4 gr1-a3100s5.wswdc.ip.att.net (192.205.34.9) 20 ms 20 ms 20 ms 5 Hssi2-1-0.GW1.DCA1.ALTER.NET (157.130.32.21) 20 ms 20 ms 20 ms 6 104.ATM2-0.XR2.DCA1.ALTER.NET (146.188.161.30) 21 ms 39 ms 20 ms 7 194.ATM2-0.TR2.DCA1.ALTER.NET (146.188.161.146) 20 ms 20 ms 20 ms 8 101.ATM6-0.TR2.CHI4.ALTER.NET (146.188.136.109) 40 ms 41 ms 56 ms 9 198.ATM7-0.XR2.CHI4.ALTER.NET (146.188.208.229) 41 ms 41 ms 41 ms 10 194.ATM8-0-0.GW1.IND1.ALTER.NET (146.188.208.165) 63 ms 66 ms 51 ms 11 purdue-gw.customer.alter.net (157.130.101.106) 56 ms 54 ms 54 ms 12 cisco-cs-atm.gw.purdue.edu (128.210.252.21) 66 ms 65 ms 63 ms 13 merlin.cs.purdue.edu (128.10.2.3) 68 ms 84 ms 63 ms

  26. TracerouteExample 4 Results from: traceroute 134.82.7.254 (executed from http://www.net.cmu.edu/cgi-bin/netops.cgi): 1 STERNUM-FA4-1-0.GW.CMU.NET (128.2.4.1) 2.733 ms 1.786 ms 1.734 ms 2 RTRBONE-FA6-0-0.GW.CMU.NET (128.2.255.2) 2.127 ms 2.31 ms 1.868 ms 3 killifish.psc.net (198.32.224.11) 2.397 ms 2.788 ms 2.658 ms 4 500.Serial3-3.GW6.PIT1.ALTER.NET (157.130.248.129) 3.01 ms 2.685 ms 2.911ms 5 554.at-2-1-0.XR2.TCO1.ALTER.NET (152.63.40.106) 9.887 ms 9.786 ms 9.59 ms 6 192.ATM6-0.GW4.PHL1.ALTER.NET (152.63.37.13) 17.412 ms 16.719 ms 16.802 ms 7 fastnetoc-gw.customer.alter.net (157.130.251.174) 14.316 ms 13.965 ms 13.76 ms 8 pos3-0-0-core01.abepa.fast.net (206.245.159.113) 23.859 ms 23.187 ms 23.508 ms 9 gw-fastnet-phl-T3.fast.net (206.245.159.34) 20.537 ms 20.442 ms 18.646 ms 10 fngw2-T3-prolog.nerep.net (206.245.157.226) 45.392 ms 235.327 ms 25.693 ms 11 gateway-atm5-0-0-309-wb2iro.wb.ptd.net (207.44.123.109) 23.346 ms 23.517 ms 24.295 ms 12 204.186.240.74 (204.186.240.74) 27.078 ms 27.155 ms 27.044 ms 13 CCSServC.bucknell.edu (134.82.7.254) 104.139 ms 37.463 ms 95.598 ms

  27. TracerouteExample 5a: Fig 2.6 in textbook

  28. TracerouteExample 5b: traceroute BERKELEY.EDU:(executed from http://www.net.cmu.edu/cgi-bin/netops.cgi) 1 CAMPUS-VL4.GW.CMU.NET (128.2.4.1) 1.108 ms 1.007 ms 3.967 ms 2 CORE255-VL255.GW.CMU.NET (128.2.255.12) 10.521 ms 11.810 ms 1.692 ms 3 HYPER-VL502.GW.CMU.NET (128.2.33.233) 1.331 ms 0.965 ms 0.761 ms 4 bar-cmu-ge-4-0-0-1.psc.net (192.88.115.185) 0.832 ms 0.673 ms 0.633 ms 5 beast-bar-g4-0-1.psc.net (192.88.115.18) 0.697 ms 0.704 ms 0.547 ms 6 abilene-psc.abilene.ucaid.edu (192.88.115.124) 10.307 ms 10.230 ms 10.215 ms 7 atla-washng.abilene.ucaid.edu (198.32.8.65) 26.093 ms 25.986 ms 25.952 ms 8 hstnng-atlang.abilene.ucaid.edu (198.32.8.33) 45.732 ms 45.746 ms 45.579 ms 9 losang-hstnng.abilene.ucaid.edu (198.32.8.21) 77.433 ms 77.253 ms 77.223 ms 10 hpr-lax-gsr1--abilene-LA-10ge.cenic.net (137.164.25.2) 77.567 ms 78.120 ms 77.411 ms 11 dc-lax-dc1--lax-hpr1-ge.cenic.net (137.164.22.12) 77.591 ms 77.448 ms 90.853 ms 12 dc-sac-dc1--lax-dc1-pos.cenic.net (137.164.22.127) 86.702 ms 86.569 ms 86.576 ms 13 dc-oak-dc2--csac-dc1-ge.cenic.net (137.164.22.110) 89.181 ms 88.879 ms 88.881 ms 14 ucb--oak-dc2-ge.cenic.net (137.164.23.30) 89.215 ms 96.290 ms 88.978 ms 15 vlan210.inr-203-eva.Berkeley.EDU (128.32.255.10) 89.493 ms 89.363 ms 89.350 ms 16 arachne.Berkeley.EDU (169.229.131.109) 89.608 ms 89.156 ms 89.235 ms

  29. Compare Examples 5a and 5b • Compare Example 5b with Fig. 2.6 (Example 5a) in the text (executed from author’s workstation) • The results are difference since the path from the author’s workstation to BERKELEY.EDU and the path from http://www.net.cmu.edu/cgi-bin/netops.cgi to BERKELEY.EDU are different

  30. Web access to tools • http://www.net.cmu.edu/cgi-bin/netops.cgi

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