Publications
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2008
Probe-aided MulTCP: An Aggregate Congestion Control Mechanism ,
Xiaoming Fu , Fang-Chun Kuo , ACM SIGCOMM Computer Communication Review, Vol. 38, No. 1, Pages 19-28,
ACM, ISSN 0146-4833, January 2008.
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An aggregate congestion control mechanism, namely Probe-Aided MulTCP (PA-MulTCP), is proposed in this paper. It is based on MulTCP, a proposal for enabling an aggregate to emulate the behavior of multiple concurrent TCP connections. The objective of PA-MulTCP is to ensure the fair sharing of the bottleneck bandwidth between the aggregate and other TCP or TCP-friendly flows while keeping lightweightness and responsiveness. Unlike MulTCP, there are two congestion window loops in PA-MulTCP, namely the probe window loop and the adjusting window loop. The probe window loop constantly probes the congestion situation and the adjusting window loop dynamically adjusts the congestion window size for the arriving and leaving flows within the aggregate. Our simulations demonstrate that PA-MulTCP is more stable and fairer than MulTCP over a wide range of the weight N in steady conditions as well as in varying congestion conditions. PA-MulTCP is responsive to flow-arriving/leaving and thus reduces the latency of short-lived transfers. Furthermore, PA-MulTCP is lightweight, since it enjoys above advantages at the cost of only an extra probe window loop, which has a marginal influence on the implementation complexity. Finally, the design of PA-MulTCP decouples the congestion management from the other functionalities in the aggregate flow management. As a result, PA-MulTCP could be potentially applied to a wider range of scenarios, e.g. wireless TCP proxies, edge-to-edge overlays, QoS provisioning and mass data transport.
PDF [758.8 kB]
2007
Probe-Aided MulTCP: An Aggregate Congestion Control Mechanism ,
Xiaoming Fu , Fang-Chun Kuo , Technical Report No. IFI-TB-2007-01, Institute of Computer Science, University of Goettingen, Goettingen, Germany,
ISSN 1611-1044, April 2007.
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A number of new application scenarios, e.g. mobile/wireless TCP proxies, edge to edge overlays, QoS provisioning and mass data transport, are calling for aggregate flow management. In this paper we show that applying a single flowshare to an aggregate flow will result in unfairness in the bandwidth sharing between the aggregate traffic and the background flows sharing the same bottleneck. To overcome this problem, we propose an aggregate congestion control mechanism, namely probe-aided MulTCP, which dynamically adjusts the congestion window loop to support multiple flowshares for an aggregate. The probe-aided MulTCP differs from existing works, such as MPAT, CP, MulTCP, in the following aspects. Firstly, our simulations show that against the traditional MulTCP the probe-aided MulTCP could maintain relatively stable, smooth and fair performance over a wide range of weight N in steady conditions as well as in varied congestion conditions. Secondly, an adjusting window loop is introduced to constantly probe the congestion situation and dynamically adjust the congestion window size for the newly arriving and leaving flows within the aggregate. This integration of congestion information improves the startup performance for new arriving flows, especially for short-lived ones. Thus, the probe-aided MulTCP is lightweight since only one extra probe window loop is used. Our extensive simulation studies show that with the probe-aided MulTCP, the improved performance and fairness will overweight the complexity caused by two congestion window loops.
PDF [665.8 kB]
2006
Generalized Low-Density Parity-Check Coding Aided Multilevel Codes ,
Fang-Chun Kuo , Ronald YS Tee, and Lajos Hanzo, Proc. of the IEEE VTC2006-Spring, Melbourne, Australia,
May 2006.
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Classic Low-Density Parity-Check (LDPC) codes have recently been used as component codes in Multilevel Coding (MLC) due to their impressive BER performance as well as owing to their flexible coding rates. In this paper, we proposed a Multilevel Coding invoking Generalized Low-Density Parity-Check (GLDPC) component codes, which is capable of outperforming the classic LDPC component codes at a reduced decoding latency, when communicating over AWGN and uncorrelated Rayleigh fading
channels.
PDF [117.5 kB]
Comparison Studies between Pre-Shared and Public Key Exchange Mechanisms for Transport Layer Security ,
Xiaoming Fu , Fang-Chun Kuo , Fabian Meyer , Hannes Tschofenig , Proceedings of the 9th IEEE Global Internet Symposium, in conjunction with IEEE INFOCOM 2006, Barcelona, Spain, pages 77-82,
IEEE, ISBN 3-937201-01-7, April 2006.
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The pre-shared key based mechanisms for Transport Layer Security (TLS) were recently standardized by the IETF to extend the set of ciphersuites by utilizing existing key management infrastructures. The benefit of pre shared based mechanisms is the avoidance or reduction of the cryptographic operations used in public-key based mechanisms. However, so far there are no performance measurements for pre-shared key based ciphersuites available. In this paper, we present a systematic analysis and performance comparison between the pre-shared key exchange mechanisms and the standard public key exchange mechanisms in TLS. Our performance metrics are processing
time and transmitted amount of data for a handshake establishment. Furthermore, the interaction between the overall TLS handshake duration and the network environment is evaluated. The results for different key exchange mechanisms are comparatively studied and the design choices of pre-shared key based key exchange mechanisms have been validated. Experimental results give details about the performance improvement of the preshared key based mechanisms compared to the standard public key based mechanisms.
PDF [331.4 kB]
Symbol-Flipping Based Decoding of Generalized Low-Density Parity-Check Codes Constructed over GF(q) ,
Fang-Chun Kuo , Lajos Hanzo, Proc. of the IEEE Wireless Communications and Networking Conference 2006, Las Vegas, NV USA, IEEE,
April 2006.
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An efficient symbol-flipping based decoding algorithm designed for nonbinary Generalized Low-Density Parity-Check (GLDPC) codes is proposed. By extending the concept of the Weighted Bit Flip Voting (WBFV) algorithm designed for binary Hamming-code based GLDPC codes, the symbol-flipping
decoding algorithm can be beneficially employed for decoding the family of GLDPC codes constructed from nonbinary constituent codes, such as nonbinary Bose Chaudhuri Hocquenghem (BCH) codes or Reed Solomon (RS) codes. The simulation results demonstrate that improvements of 1 dB and 2.7 dB are achieved by the proposed coding scheme in comparison to the more conventional binary GLDPC codes using the WBFV decoding algorithm, when using the Galois Field GF(32) for communicating over AWGN and uncorrelated Rayleigh fading channels, respectively.
PDF [223.3 kB]
Multilevel Generalized Low-Density Parity-Check Codes ,
Fang-Chun Kuo , Ronald YS Tee, and Lajos Hanzo, IEE Electronics Letters, Vol. 42, Issue 3, Pages 167 - 168,
ISSN: 0013-5194, February 2006.
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Multilevel coding invoking generalised low-density parity-check component codes is proposed, which is capable of outperforming the classic low-density parity check component codes at a reduced decoding latency.
PDF [86.0 kB]
Comparison Studies between Pre-Shared Key and Public Key Exchange Mechanisms for Transport Layer Security (TLS) ,
Xiaoming Fu , Fang-Chun Kuo , Fabian Meyer , Hannes Tschofenig , Technical Report No. IFI-TB-2006-01, Institute of Computer Science, University of Göttingen, Göttingen, Germany,
ISSN 1611-1044, January 2006.
Read abstract
The public-key based handshake process of TLS is regarded as part of bottleneck that significantly degrades the performance. The pre-shared key based key exchange mechanisms for TLS were recently standardized by the IETF for avoiding or reducing the cryptographic operations in public-key based mechanisms. However, so far there is no performance measurement for pre-shared key based key exchange suites available. In this paper, we present a systematic analysis of performance comparison between the pre-shared key exchange mechanisms and the standard public key exchange mechanisms in TLS. Our performance metrics are the processing time in both slow and fast processor machines as well as the transmitted data amount for a handshake establishment. Furthermore, the interaction of the overall TLS handshake duration and the network environment is evaluated. The results for different key exchange mechanisms are comparatively studied and the design choices of pre-shared key based key exchange mechanisms have been validated. It has been observed that pre-shared key based mechanisms perform better than the standard public key based mechanisms.
PDF [357.6 kB]
