China Telecom China Telecom R. Lohiya Telecom Italia Huawei Technologies Huawei Technologies ZDNS Tsinghua University IP addresses work as a basic element for providing broadband network services. However, the increase in number, diversity and complexity of modern network devices and services creates unprecedented challenges for the currently prevailing approach of manual IP address management. Manually maintaining IP addresses could always be sub- optimal for IP resource utilization. Besides, it requires heavy human effort from network operators. To achieve high utilization and flexible scheduling of IP network addresses, it is necessary to automate the address scheduling process. This document describes an architecture for the IP address space management. It includes architectural concepts and components used in the CASM (Coordinated Address Space Management), with a focus on those interfaces to be standardized in the IETF.