TCP Variants for Data Center Networks: A Comparative Study

Transmission Control Protocol (TCP) has been the workhorse of the Internet ever since its inception. The success of the Internet, infact, can be partly attributed to the congestion control mechanisms implemented in TCP. Though the scale of the Internet and its usage increased exponentially in recent past, TCP has evolved to keep up with the changing network conditions and has proven to be scalable and robust. However, the performance of TCP in Data Center Networks has been a major concern recently because it leads to impairments such as TCP Incast, TCP Outcast, Queue build-up and Buffer pressure. With cloud computing becoming an important part of the foreseeable future, it has become extremely important to enhance the performance of TCP in Data Center Networks and overcome these impairments. In this paper, we describe the above mentioned impairments in brief and then compare the TCP variants proposed so far to ovecome these impairments in Data Center Networks. The advantages and shortcomings of every TCP variant are highlighted with respect to its efficacy and the deployment complexity. A few open issues related to TCP's performance in Data Center Networks are also discussed.