  Today's datacenters face important challenges for providing low-latency
high-quality interactive services to meet user's expectation. For improving the
application throughput, recent research works have embedded application
deadline information into design of network flow schedule to meet the latency
requirement. Here, arises a critical question: does application-level
throughput mean providing better quality service? We note that there are
usually a set of semantic related responses (or flows) for answering a query;
and, some responses are highly correlative with the query while others do not.
Thus, this observation motivates us to associate the importance of the contents
with the application flows (or responses) in order to enhance the service
quality. We first model the application importance maximization problem in a
generic network and in a server-centric network. Since both of them are too
complicated to be deployed in the real world, we propose the importance-aware
delivery protocol, which is a distributed event-driven rate-based delivery
control protocol, for server-centric datacenter networks. The proposed protocol
is able to make use of the multiple disjoin paths of server-centric network,
and jointly consider flow importance, flow size, and deadline to maximize the
goodput of most-related semantic data of a query. Through real-data-based or
synthetic simulations, the results show that our proposed protocol
significantly outperforms D3 and MPTCP in terms of the precision at K and the
sum of application-level importance.
