The document discusses requirements for applying Software Defined Networking (SDN) in carrier grade networks using Openflow. It addresses three key requirements: 1) Scalability in terms of supporting a huge number of network elements and flows across multiple network domains. Openflow controllers must be able to scale sustainably to handle this. 2) Availability in that carriers require reliable failover and their networks cannot stop operating. Openflow controllers need to guarantee uninterrupted network function. 3) The IRIS SDN controller from ETRI aims to solve scalability and availability issues through a clustered, hierarchical design that can support large networks split across multiple operational units.