Browsing by Author "Kung, HT"

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A new methodology for easily constructing extensible and high-fidelity TCP/IP network simulators
(2002-10-07)
Wang, SY
;
Kung, HT
;
資訊工程學系
;
Department of Computer Science
This paper proposes a new methodology for easily constructing extensible and high-fidelity TCP/IP network simulators. The methodology uses a kernel-reentering technique to reuse the existing real-life network protocol stacks, real application programs that generate traffic, and real utility programs that configure, monitor, or gather network statistics to the maximum extent. Only an event scheduler and some modifications to the kernel are needed to "glue" these existing components to collectively simulate a network. A simulator constructed this way has many advantages that a traditional network simulator cannot provide. First, reuse of real-life implementation in the simulator can generate more accurate results than a traditional simulator that abstracts a lot of away from the real implementation. Second, it can save much time and effort that would be needed if a high-fidelity simulator is developed from scratch. Third, because real application programs cannot distinguish a simulated network constructed by the simulator from a real one, all existing real-life and future application programs can directly run on any node in a simulated network. (C) 2002 Elsevier Science B.V. All rights reserved.
Streaming video over TCP with receiver-based delay control
(2003-02-01)
Hsiao, PH
;
Kung, HT
;
Tan, KS
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Unicasting video streams over TCP connections is a challenging problem, because video sources cannot normally adapt to delay and throughput variations of TCP connections. This paper describes a method of extending TCP so that TCP connections can effectively carry hierarchically-encoded layered video streams, while being friendly to other competing connections. We call the method Receiver-based Delay Control (RDC). Under RDC, a TCP connection can slow down its transmission rate to avoid congestion by delaying ACK packet generation at the TCP receiver based on congestion notifications from routers. We present the principle behind RDC, argue that it is TCP-friendly, describe an implementation that uses 1-bit congestion notification from routers, and demonstrate by simulations its effectiveness in streaming hierarchically-encoded layered video.
TCP with sender-based delay control
(2003-09-01)
Kung, HT
;
Tan, KS
;
Hsiao, PH
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
This paper describes a congestion control method for TCP that adjusts the transmission rate of a TCP connection by changing not only the congestion window size as in normal TCP, but also by delaying the transmission of packets at the sender. We refer to this method as TCP with sender-based delay control, or simply SDC. SDC can keep the window size of a TCP connection above a certain threshold even when its fair share of bandwidth is arbitrarily small. Since TCP fast retransmit and recovery is likely to work when the window size of the connection is sufficiently large, the new method can result in reduced frequency of TCP timeouts for the connection. In particular, SDC allows many TCP flows to share a link without experiencing many timeouts. In addition, SDC can reduce a well-known TCP bias against connections with large RTTs. This paper presents the principle behind SDC, and simulation results demonstrating its properties and advantages. (C) 2003 Elsevier Science B.V. All rights reserved.
Use of TCP decoupling in improving TCP performance over wireless networks
(2001)
Wang, SY
;
Kung, HT
;
資訊工程學系
;
Department of Computer Science
We propose using the TCP decoupling approach to improve a TCP connection's goodput over wireless networks. The performance improvement can be analytically shown to be proportional to root MTU/HP_Sz, where MTU is the maximum transmission unit of participating wireless links and HP_Sz is the size of a packet containing only a TCP/IP header. For example, on a WaveLAN [32] wireless network, where MTU is 1500 bytes and HP_Sz is 40 bytes, the achieved goodput improvement is about 350%. We present experimental results demonstrating that TCP decoupling outperforms TCP reno and TCP SACK. These results confirm the analysis of root MTU/HP_Sz performance improvement.