MPLS-Based Hierarchical SDN for Hyper-Scale DC/Cloud
This document describes Hierarchical SDN (HSDN), an architectural solution to scale the Data Center (DC) and Data Center Interconnect (DCI) networks to support tens of millions of physical underlay endpoints, while efficiently handling both Equal Cost Multi Path (ECMP) load-balanced traffic and any-to-any end-to-end Traffic Engineered (TE) traffic. HSDN achieves massive scale using surprisingly small forwarding tables in the network nodes. HSDN introduces a new paradigm for both forwarding and control planes, in that all paths in the network are pre-established in the forwarding tables and the labels can identify entire paths rather than simply destinations. The HSDN forwarding architecture is based on four main concepts: 1. Dividing the DC and DCI in a hierarchically-partitioned structure; 2. Assigning groups of Underlay Border Nodes in charge of forwarding within each partition; 3. Constructing HSDN MPLS label stacks to identify endpoints and paths according to the HSDN structure; and 4. Forwarding using the HSDN MPLS labels.