HALR: A TCP Enhancement Scheme Using Local Caching in High-Availability Cluster

Yi-Hsuan FENG  Nen-Fu HUANG  Yen-Min WU  

IEICE TRANSACTIONS on Communications   Vol.E92-B   No.1   pp.26-33
Publication Date: 2009/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.26
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Networking Technologies for Dependable Networks)
high availability,  TCP enhancement,  modeling,  local loss recovery,  

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In this paper, we study the end-to-end TCP performance over a path deploying a High-Availability cluster, whose characteristics are highlighted by the failover procedure to remove single-point failure. This paper proposes an approach, called High-Availability Local Recovery (HALR), to enhance TCP performance in the face of a cluster failover. To minimize the latency of retransmission, HALR saves TCP packets selectively and resends them locally after the failover is finished. For better understanding, we further develop simple analytic models to predict the TCP performance in the aspect of flow latency under a range of failover times and the effects of HALR. Using simulation results, we validate our models and show that HALR improves the TCP performance significantly over a failover event as compared with the original TCP. Typically, HALR reduces the flow latency from 4.1 sec to less than 1.9 sec when the failover time equals to 500 ms. The simulation by real packet trace further demonstrates that the memory requirement of the proposed solution is not a concern for modern network equipments.