  To meet the timing requirements of interactive applications, the no-frills
congestion-agnostic transport protocols like UDP are increasingly deployed
side-by-side in the same network with congestion-responsive TCP. In cloud
platforms, even though the computation and storage is totally virtualized, they
lack a true virtualization mechanism for the network (i.e., the underlying data
centers networks). The impact of such lack of isolation services, may result
into frequent outages (for some applications) when such diverse traffics
contend for the small buffers in the commodity switches used in data centers.
In this paper, we explore the design space of a simple, practical and
transport-agnostic scheme to enable a scalable and flexible end-to-end
congestion control in data centers. Then, we present the the shortcomings of
coupling the monitoring and control of congestion in the conventional system
and discuss how a Software-Defined Network (SDN) would provide an appealing
alternative to circumvent the problems of the conventional system. The two
systems implements a software-based congestion control mechanisms that perform
monitoring, control decisions and traffic control enforcement functions. Both
systems are designed with a major assumption that the applications (or
transport protocols) are non-cooperative with the system, ultimately making it
deployable in existing data centers without any service disruption or hardware
upgrade. Both systems are implemented and evaluated via simulation in NS2 as
well as real-life small-scale test-bed deployment and experiments.
