Fast circuit switching and connection-oriented packet switching are two sides of the same coin. Fast circuit switching can closely emulate the characteristics of connection-oriented packet switching, and vice versa. Most communication functions can be efficiently supported by either technique.
Although from a theoretical point of view, fast circuit switching and connection-oriented packet switching are equivalent, there are practical differences. The best approach for convergence involves a tradeoff between efficiency and performance on the one hand and compatibility with legacy networks on the other hand.
Both connection-oriented packet switching and fast circuit switching can be readily implemented in the same network using similar protocols and common equipment. Generalized Multi-Protocol Label Switching (GMPLS) can accommodate connection-oriented packet switching via external labels (MPLS headers attached to packets) and fast circuit switching via implicit labels (time slots containing the data). The key to implementing a converged transport network is a label switch that can handle connection-oriented packet switching and fast circuit switching simultaneously. For the packet switching mode of operation, the routing of data by the label switch is determined on the fly based on information in the packet headers. For the fast circuit switching mode of operation, the switching pattern of the label switch is determined prior to the arrival of the data, based on information in the GMPLS signaling channel. Otherwise, operation of the label switch is similar for the packet switching and circuit switching modes. To accommodate legacy users and enable interoperability with legacy networks, the proposed label switch could also operate as a conventional router to transport unlabeled packets based on IP addresses.
Using current technologies, network elements that are capable of both the connection-oriented packet switching and fast circuit switching modes of operation can be implemented in a straightforward manner. As these elements are initially deployed, transport should be based on IP/MPLS, which is compatible with existing networks. However, fast circuit switching has significant advantages over connection-oriented packet switching. Eventually, fast circuit switching could replace the IP/MPLS approach for most applications. This reduces overhead and enhances security.
Here link to a paper to a paper that discusses in detail the equivalence of fast circuit switching and connection-oriented packet switching.