Sangtae Ha

• Sangtae Ha
• Ph.D Candidate
• Department of computer Science
• North Carolina State University, NC 27606.

• Education: 2001 M.S., POSTECH, Korea
• Email: sha2 AT ncsu DOT edu TEL: (919)513-2427 (office)
• Address: 1009 Capability Drive, Research II building, Room 203A,
  
• Centennial Campus, North Carolina State University, Raleigh, NC 27695
• Research areas: congestion control and wireless networking.

Since we released the first working version of CUBIC to Linux community, CUBIC has been improved quite a bit, thanks to the valuable feedbacks from researchers and kernel developers all around the world. The upcoming updates for BIC-TCP and CUBIC are about improving Slow Start which has been known very problematic for high and long-distance paths, especially with a large bottleneck buffer. We recently presented a very effective solution, called Hybrid Slow Start, which is a small plugin to an existing Slow Start and improves throughput substantially. We validated the feasibility of Hybrid Slow Start in our testbed and now we are testing it over real production networks. You can read the details of the algorithm from the paper. I'm still spending most of my time to maintaing and improving CUBIC, which is the default TCP protocol in Linux. You can see the latest CUBIC implementation in the Linux kernel at here. I also maintain TCP testing wiki and update the testing results when a new version of Linux kernel is released. For the controlled TCP testing, we have a dedicated testbed, called BIC LAB. You can see the figure of BIC LAB testbed at here. Recently, we installed a TCP testing server at Centaur LAB to evaluate CUBIC over real production networks such as Internet2 and National Lamda Rail (NLR), which have typically more than 1Gbps bandwidth.

News

• Hybrid Slow Start is under the test over Internet2 (Many thanks to Kazumi Kumazoe at NICT, and Dr. Yunhong Gu at NCDM in UIC for accessing their facilities.)
• CUBIC has recently been updated. See the changelog for this update. Now, CUBIC has a good convergence time and scalability.
• Recent TCP testing results are available on line
• I am working with the WAAS team at Cisco Systems, San Jose, during this summer.

Projects

• TCP Testing
• BIC and CUBIC
• DiffQ

Publications

Journal

• Sangtae Ha, Injong Rhee and Lisong Xu, CUBIC: A New TCP-Friendly High-Speed TCP Variant, accepted to ACM SIGOPS Operating System Review, 2008. PDF
• H. Cai, D. Eun, S. Ha, I. Rhee and L. Xu, Stochastic Ordering for Internet Congestion Control and its Applications, submitted to IEEE Transaction on Networking.
• Sangtae Ha, Long Le, Injong Rhee and Lisong Xu, Impact of Background Traffic on Performance of High-speed TCP Variant Protocols, Computer Networks: The International Journal of Computer and Telecommunications Networking, Volume 15, Issue 4, Aug. 2007, Page(s):852 - 865, 2007. PDF

Conferences

• A. Warrier, S. Ha and I. Rhee, Starvation in Wireless End-to-end Congestion Controlled Networks: A Different Perspective, submitted PDF
• Sangtae Ha and Injong Rhee, Hybrid Slow Start for High-Bandwidth and Long-Distance Networks, PFLDnet, Manchester, UK, 2008 PDF PPT
• Lachlan Andrew, Cesar Marcondes, Sally Floyd, Lawrence Dunn, Romaric Guillier, Wang Gang, Lars Eggert, Sangtae Ha and Injong Rhee, Towards a Common TCP Evaluation Suite, PFLDnet, Manchester, UK, 2008. PDF
• H. Cai, D. Eun, S. Ha, I. Rhee and L. Xu, Stochastic Ordering for Internet Congestion Control and its Applications, Infocom, IEEE, Anchorage, Alaska, USA, 2007 PDF PPT
• H. Cai, D. Eun, S. Ha, I. Rhee and L. Xu, Stochastic Ordering for Internet Congestion Control, PFLDnet, to appear, 2007 PDF PPT
• Sangtae Ha, Yusung Kim, Long Le, Injong Rhee and Lisong Xu, A Step toward Realistic Performance Evaluation of High-Speed TCP Variants, PFLDnet, Nara, Japan, 2006. PDF

Internet Drafts

• I. Rhee, L. Xu and S. Ha, CUBIC for Fast Long-Distance Networks, IETF Internet Draft, 2007. draft-rhee-tcpm-cubic-00.txt

Technical Reports

• A. Warrier, S. Ha, P. Wason and I. Rhee, DiffQ: Differential Backlog Congestion Control for Multi-hop Wireless Networks, NCSU Technical Report. PDF
• Sangtae Ha, Yusung Kim, Long Le, Injong Rhee, and Lisong Xu, A step toward realistic evaluation of high-speed TCP protocols, Web-based Technical Report. HTML

Demo

• A. Warrier, S. Ha, P. Wason, I. Rhee and J. H. Kim, DiffQ: Differential Backlog Congestion Control for Multi-hop Wireless Networks, Demo, SECON 2008. PDF
• Injong Rhee, Ajit Warrier and Sangtae Ha, TCP problem under high bandwidth delay product networks - Demo III (B), The Future of TCP: Train-wreck or Evolution?, Stanford Univ, Stanford, CA, 2008.

Professional Articles

• Sangtae Ha and Hyunjoon Cha, Design and Implementation of Embedded Linux, Programmer's World, Special Issue 3-1, April, 2001.
• Sangtae Ha and Hyunjoon Cha, Embedded Linux for Network Devices, Linux@Works, November, 2001.
• Sangtae Ha and Hyunjoon Cha, Compare Embedded Linux with Other Real-Time Operating Systems, Linux@Works, October, 2001.

Awards and Honors

• Outstanding Teaching Assistant Award, Thirty Eight Annual Teaching Assitant Awards 2006-2007. HTML

Services

-- Main.sha2 - 31 May 2008