ISO/IEC 27033-1:2009 provides an overview of network security and related definitions. It defines and describes the concepts associated with, and provides management guidance on, network security. (Network security applies to the security of devices, security of management activities related to the devices, applications/services and end-users, in addition to security of the information being transferred across the communication links.)
It is relevant to anyone involved in owning, operating or using a network. This includes senior managers and other non-technical managers or users, in addition to managers and administrators who have specific responsibilities for information security and/or network security, network operation, or who are responsible for an organization's overall security program and security policy development. It is also relevant to anyone involved in the planning, design and implementation of the architectural aspects of network security.
ISO/IEC 27033-1:2009 also

• provides guidance on how to identify and analyse network security risks and the definition of network security requirements based on that analysis,
  
• provides an overview of the controls that support network technical security architectures and related technical controls, as well as those non-technical controls and technical controls that are applicable not just to networks,
  
• introduces how to achieve good quality network technical security architectures, and the risk, design and control aspects associated with typical network scenarios and network "technology" areas (which are dealt with in detail in subsequent parts of ISO/IEC 27033), and
  
• briefly addresses the issues associated with implementing and operating network security controls, and the on-going monitoring and reviewing of their implementation.
  

Overall, it provides an overview of the ISO/IEC 27033 series and a "road map" to all other parts.