Reading for next class No new reading, but there will be a quiz Ch 4.1 – 4.23: Internet applications

Review: Traceroute 3 probes Local host: Alice Remote host: Jack Probe successive hops to find network path – sends 3 packets that will reach each router on path towards destination – Each router returns packets to sender – sender times interval between transmission and reply.

Review: Traceroute Local host: Alice Remote host: Jack Technically, a hop is defined as the action that occurs when a packet “jumps” from one router to the next. 1 hop 2 hop 3 hop N-1 hop N hop

Traceroute Example 1 C:\> tracert allspice.lcs.mit.edu 1 20ms 25ms 15ms philadelphia4.t3.ans.net ( ) ms 120ms 140ms New-York2.t3.ans.net ( ) 3 300ms 280ms 260ms Cambridge1.bbnplanet.net ( ) 4 339ms 279ms 279ms Allspice.lcs.mit.edu ( ) 3 delay measurements

Traceroute Question 6 C:\> tracert allspice.lcs.mit.edu 1 20ms 25ms 15ms philadelphia4.t3.ans.net ( ) ms 120ms 140ms New-York2.t3.ans.net ( ) 3 300ms 280ms 260ms Cambridge1.bbnplanet.net ( ) 4 339ms 279ms 279ms Allspice.lcs.mit.edu ( ) How many computers are there in this route? How many hops?

Traceroute Question 7 C:\> tracert allspice.lcs.mit.edu 1 20ms 25ms 15ms philadelphia4.t3.ans.net ( ) ms 120ms 140ms New-York2.t3.ans.net ( ) 3 300ms 280ms 260ms Cambridge1.bbnplanet.net ( ) 4 339ms 279ms 279ms Allspice.lcs.mit.edu ( ) How many packets are sent by local host? How many packets are forwarded by New York (New- York2.t3.ans.net )?

Traceroute Question 8 C:\> tracert allspice.lcs.mit.edu 1 20ms 25ms 15ms philadelphia4.t3.ans.net ( ) ms 120ms 140ms New-York2.t3.ans.net ( ) 3 300ms 280ms 260ms Cambridge1.bbnplanet.net ( ) 4 339ms 279ms 279ms Allspice.lcs.mit.edu ( ) What’s the average round trip time form local host to Cambridge1.bbnplanet.net?

Traceroute Example 2 C:\> tracert ms 1 ms 1 ms ms 11 ms 9 ms c hsd1.pa.comcast.net [ ] 3 11 ms 10 ms 10 ms te sur02.statecollege.pa.pitt.comcast.net [ ] 4 17 ms 15 ms 15 ms be-3-ar03.lowerpaxton.pa.pitt.comcast.net [ ] 5 21 ms 21 ms 27 ms he ar01.pittsburgh.pa.pitt.comcast.net[ ] 6 45 ms 31 ms 32 ms be-7016-cr01.newyork.ny.ibone.comcast.net [ ] 7 29 ms 28 ms 29 ms ae12.edge1.NewYork2.level3.net [ ] ms 302 ms 306 ms ae-4-4.car1.Manchesteruk1.Level3.net [ ] ms 210 ms 207 ms ae-4-4.car1.Manchesteruk1.Level3.net [ ] ms 103 ms 106 ms ms 107 ms 107 ms ae29.erdiss-sbr1.ja.net [ ] ms 106 ms 106 ms ae31.londpg-sbr1.ja.net [ ] ms 109 ms 109 ms ae21.read-rbr3.ja.net [ ] ms 117 ms 105 ms ae1.read-rbr2.ja.net [ ] ms 107 ms 107 ms ae2.oxfo-rbr2.ja.net [ ] ms 107 ms 107 ms Oxford-University-2.ja.net [ ] ms 110 ms 108 ms csurb.backbone.ox.ac.uk [ ] ms 110 ms 110 ms boucs.backbone.ox.ac.uk [ ] ms 107 ms 107 ms boucs-lompi1.sdc.ox.ac.uk [ ] ms 109 ms 108 ms aurochs-web-154.nsms.ox.ac.uk [ ] Trace complete. Level3: Trans-atlantic link comcast Janet: UK’s research network oxford

Traceroute Exercise 1 Step 1: Start  Run  cmd Step 2: Trace route to – Somewhere in the U.S. – Somewhere outside U.S. Discuss the results with classmates next to you – How may hops are there in the path? – What’s the average delay from you computer to the remote host? – How many major networks does the path traverse? What are they? – For destination outside US, from which router do the packets leave US?

Traceroute Exercise 2 For this exercise, you need to use the traceroute server at traceroute.pl. When you view this web page, execute a traceroute (trace) to: traceroute.pl 1.your machine 2.Somewhere in US 3.Somewhere outside US

Traceroute Exercise 3 At the command prompt, type: – tracert Describe what is strange about the observed output, and why traceroute gives you such an output