  Large cloud companies manage dozens of datacenters across the globe connected
using dedicated inter-datacenter networks. An important application of these
networks is data replication which is done for purposes such as increased
resiliency via making backup copies, getting data closer to users for reduced
delay and WAN bandwidth usage, and global load balancing. These replications
usually lead to network transfers with deadlines that determine the time prior
to which all datacenters should have a copy of the data. Inter-datacenter
networks have limited capacity and need be utilized efficiently to maximize
performance. In this report, we focus on applications that transfer multiple
copies of objects from one datacenter to several datacenters given deadline
constraints. Existing solutions are either deadline agnostic, or only consider
point-to-point transfers. We propose DDCCast, a simple yet effective deadline
aware point to multipoint technique based on DCCast and using ALAP traffic
allocation. DDCCast performs careful admission control using temporal planning,
uses rate-allocation and rate-limiting to avoid congestion and sends traffic
over forwarding trees that are carefully selected to reduce bandwidth usage and
maximize deadline meet rate. We perform experiments confirming DDCCast's
potential to reduce total bandwidth usage by up to $45\%$ while admitting up to
$25\%$ more traffic into the network compared to existing solutions that
guarantee deadlines.
