Network federation is a promising approach for organizations to improve their infrastructure by pooling their resources and creating a larger, more scalable network. Despite the many benefits of network federation, there are also significant challenges that must be addressed, such as security, interoperability, and policy management. Various efforts have been underway for many years to develop common standards and protocols, to overcome these challenges. This paper provides a comprehensive overview of the challenges and opportunities of network federation, and presents the standardization efforts in the field.