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Hybrid circuit/packet networks where circuit and packet networks coexist are becoming attractive to support future Internet applications. They support both packet/ IP services and circuit/wavelength services. Packet services include traditional data services such as VPN, VoIP, and email, while dynamic circuit services include end-to-end bandwidth-intensive applications such as terascale science experiments. In present hybrid networks, such as ESnet, the bandwidth boundary between the circuit and packet sections of the network is fixed. However, a flexible boundary between the circuit and packet sections will enable cost-efficient bandwidth management in the network. Our study investigates two methods to dynamically migrate capacity between the circuit and packet sections, called vertical stacking and horizontal partitioning, and serves as a tutorial. In vertical stacking, the backup capacity of wavelength circuits can be dynamically exchanged between packet and wavelength services while ensuring survivability. The backup capacity can be used to protect wavelength services in the event of a failure and route packet traffic otherwise. In horizontal partitioning, the excess capacity on links in the packet section can be loaned to circuit services. We have conducted experiments using a snapshot of real traffic on ESnet with horizontal partitioning. Control mechanisms for our approaches that can be operational in ESnet are presented.