Reliable Group Data Delivery (RGDD) is a pervasive traffic pattern in data centers. In an RGDD group, a sender needs to reliably deliver a copy of data to all the receivers. Existing solutions either do not scale due to the large number of RGDD groups (e.g., IP multicast) or cannot efficiently use network bandwidth (e.g., end-host overlays). The authors design Datacast for RGDD. Datacast turns group state management to in-network packet caching by leveraging the Content Centric Networking (CCN) concept. It uses centrally calculated multiple edge-disjoint trees for efficient and fast data delivery.