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Ooi Wei Tsang

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Hello world!

Wednesday, August 4th, 2010

Welcome to your new Blog.nus site. This is your first post. Edit or delete it, then start blogging! Please remember to the Terms of Service: 1. Please use the blog for academic, educational, research and administrative purposes only. 2. Please adhere to Singapore laws and the NUS Acceptable Use Policy for IT Resources: http://www.nus.edu.sg/comcen/security/aup/ 3. […]

Assignment 3: Grades and Comments

Friday, December 4th, 2009

Here are your grades for Assignment 3. You may pick up the assignment from me from my office. More than half of the class got a grade in the A range (A– to A+). These are students that provide detailed analysis of the traces (e.g., values of b, maximum window sizes, careful sampling of RTT, […]

Clarifications for Lecture 9 and Lecture 10

Tuesday, November 24th, 2009

Some questions from a discussion in my office this morning. 1. Can you give an example of redundant retransmissions caused by coarse feedback? During class I explained what coarse feedback means but never gave a real example on how this could lead to redundant retransmissions. Vern Paxson gave a real example in his thesis (Page […]

Final Exam Reminder

Wednesday, November 18th, 2009

The final exam will be on 25 November 2009 (Wed), 1 – 3pm, in SR3 and SR10. Please come 5-10 minutes before the exam starts. This is an open book examination with six questions. Please bring an NUS-approved calculator (details on the Registrar’s website). The exam covers all topics that were taught during lectures (except […]

Assignment 2: Grades

Wednesday, November 18th, 2009

Here are your grades for Assignment 2, which I have returned last week. Please double check to make sure that we have entered your grades correctly.

Lecture 11: DNS

Thursday, November 5th, 2009

In this lecture, we are going to first look at how DNS works in details through a measurement study, and then see how we can exploit DNS to help us measure latency between any pair of end hosts on the Internet. Readings J. Jung, E. Sit, H. Balakrishnan, R. Morris “DNS Performance and the Effectiveness […]

Discussion 10: Internet Routing

Friday, October 30th, 2009

1 In the measurement studies by Stefan Savage et. al., a graph is constructed to represent a set of hosts and links between them. They then run shortest path algorithm on the graph to determine the best alternate path between any two hosts. Should the graph be a undirected or directed graph? Explain. 2 Vern […]

Lecture 10: Internet Routing

Wednesday, October 28th, 2009

In this lecture, we are going to look at two measurement-based papers on Internet routing. We will see if Internet routes are stable, symmetric, and optimal. Readings V. Paxson “End-to-end Routing Behaviour in the Internet,” SIGCOMM 1996 [ Google Scholar] This paper won the SIGCOMM test-of-time award. See here for a retrospective review of the […]

Assignment 3: Clarifications

Monday, October 26th, 2009

1. Can we do this over LAN? Yes, this can be one of the scenario if you really want to. But I doubt you will get anything interesting from the traces. It would be more fun to collect traces of TCP flows over WAN. 2. It takes 2 hours to transfer a 200MB file. Is […]

Discussion 9: Internet Packet Dynamics

Friday, October 23rd, 2009

1 Vern Paxson uses PBM (“packet bunch modes”) to estimate the bottleneck bandwidth. PBM uses a range of packet-bunch sizes to form receiver-side estimates, and is designed to overcome several limitations of packet pair techniques, including bottleneck bandwidth changes. Is using more than two packets strictly necessary to detect a change in bottleneck bandwidth? Justify […]