Home > Storage > PowerScale (Isilon) > Product Documentation > Networking > PowerScale: Ethernet Back-end Network Overview > Overview
Before the introduction of the latest generation of PowerScale scale-out NAS storage platforms, inter-node communication in a Dell Isilon cluster was performed using a proprietary, unicast (node-to-node) protocol known as Remote Block Manager (RBM). This inter-node communication uses a fast low-latency InfiniBand (IB) network. This back-end network, which is configured with redundant switches for high availability, acts as the backplane for the Isilon cluster. This backplane enables each Isilon node to act as a contributor in the cluster and provides node-to-node communication with a private, high-speed, low-latency network. This back-end network uses Internet Protocol (IP) over IB (IPoIB) to manage the cluster. Sockets Direct Protocol (SDP) is used for all data traffic between nodes in the cluster.