SSthreshless Start: A Sender-Side TCP Intelligence for Long Fat Network

Measurement shows that 85% of TCP flows in the internet are short-lived flows that stay most of their operation in the TCP startup phase. However, many previous studies indicate that the traditional TCP Slow Start algorithm does not perform well, especially in long fat networks. Two obvious problems are known to impact the Slow Start performance, which are the blind initial setting of the Slow Start threshold and the aggressive increase of the probing rate during the startup phase regardless of the buffer sizes along the path. Current efforts focusing on tuning the Slow Start threshold and/or probing rate during the startup phase have not been considered very effective, which has prompted an investigation with a different approach. In this paper, we present a novel TCP startup method, called threshold-less slow start or SSthreshless Start, which does not need the Slow Start threshold to operate. Instead, SSthreshless Start uses the backlog status at bottleneck buffer to adaptively adjust probing rate which allows better seizing of the available bandwidth. Comparing to the traditional and other major modified startup methods, our simulation results show that SSthreshless Start achieves significant performance improvement during the startup phase. Moreover, SSthreshless Start scales well with a wide range of buffer size, propagation delay and network bandwidth. Besides, it shows excellent friendliness when operating simultaneously with the currently popular TCP NewReno connections.Comment: 25 pages, 10 figures, 7 table

The effect of alcohol on the performance of lipase-immobilized enzymatic membrane reactor for esterification of (R,S)-ketoprofen

The effect of alcohols on the performance of lipase-immobilized enzymatic membrane reactor (EMR) for enantioselective esterification of (R,S)-ketoprofen has been studied. In this work, mixed solvent medium was used and the (R)-ketoprofen was reacted with the different alcohols in the presence of immobilized lipase B from Candida antartica, leaving the target product (S)-ketoprofen in its unreacted form. The alcohols involved in the reactions were ethanol, butanol, heptanol and 2-ethoxyethanol. The chain length of alcohol was found to significantly affect the performance of the esterification in EMR. Through the alcohols screening, the esterification reaction using ethanol in EMR showed higher initial rate, conversion, enzyme enantioselectivity, enantiomeric excess of substrate (ees) and enantiomeric excess of product (eep). However the results with butanol showed less inhibition effect on a wider range of temperatur