1. Solving End-to-End Problems Internet2 Staff Meeting Ann Arbor 29 November, 2001

2. The Problem Applications Developer System Administrator LAN Administrator Campus Networking Gigapop BackboneCampus Networking LAN Administrator System Administrator Applications Developer How do you solve a problem along a path? Hey, this is not working right! The computer Is working OK Talk to the other guysEverything is AOK No other complaints The network is lightly loaded All the lights are green We don’t see anything wrong Looks fine Others are getting in ok Not our problem

3. Problem 1 You finally get your own brand new personal polycom unit to do videoconferencing with your colleagues so you will stop hogging the conference room. You plug it into an ethernet port in your office that has been working just fine for email and web surfing. You power it up, and try to contact your colleague in San Diego. It connects,but you get lots of "lightening symbols" on the display, the video is very jerky, and the audio drops out.

4. Problem 2 You start an application that transfers massive amounts of data overnight. You go home and in the middle of the night the other site calls and tells you the the transfer rate has fallen dramatically, the network must be broken and you need to get it fixed. Of course it all worked fine in the tests on smaller data sets.

5. Problem 3 You just got your new computer, a GoFast 9000 with GigE interfaces and want to see what this puppy will do. You know that you have a fast path all the way to U of X and want to test the file transfer speed. You crank up an FTP and watch the stats expecting, through slow-start, that it will speed up until some packet loss where it will back down. The performance pegs at 10k packets per second but there is still no packets loss.

6. Problem 4 You are trying to transfer 10GB of medical research image data between your site in California and your colleague's site in New York.The data servers your site are well tuned for TCP: they have large buffers,and allow large window sizes, and have all the latest spiffy TCP options to recover from packet loss. They both have GigE connections locally, although you know the wide-area bottleneck is an OC- 3 POS connection.You try to run a transfer, and find you get 7 megabits a second! Why aren't you getting a significant fraction of the bandwidth? It's going to require a lot of coffee to wait for this connection to complete...

7. How can we improve problem solving? Knowing what is possible Diagnostic tools Finding people Modes of communication Scaling of it all