  Applications running in geographically distributed setting are becoming
prevalent. Large-scale online services often share or replicate their data into
multiple data centers (DCs) in different geographic regions. Driven by the data
communication need of these applications, inter-datacenter network (IDN) is
getting increasingly important.
  However, we find congestion control for inter-datacenter networks quite
challenging. Firstly, the inter-datacenter communication involves both data
center networks (DCNs) and wide-area networks (WANs) connecting multiple data
centers. Such a network environment presents quite heterogeneous
characteristics (e.g., buffer depths, RTTs). Existing congestion control
mechanisms consider either DCN or WAN congestion, while not simultaneously
capturing the degree of congestion for both.
  Secondly, to reduce evolution cost and improve flexibility, large enterprises
have been building and deploying their wide-area routers based on
shallow-buffered switching chips. However, with legacy congestion control
mechanisms (e.g., TCP Cubic), shallow buffer can easily get overwhelmed by
large BDP (bandwidth-delay product) wide-area traffic, leading to high packet
losses and degraded throughput.
  This thesis describes my research efforts on optimizing congestion control
mechanisms for the inter-datacenter networks. First, we design GEMINI - a
practical congestion control mechanism that simultaneously handles congestions
both in DCN andWAN. Second, we present FlashPass - a proactive congestion
control mechanism that achieves near zero loss without degrading throughput
under the shallow-buffered WAN. Extensive evaluation shows their superior
performance over existing congestion control mechanisms.
