In proportion to the rapid development of telecommunication service, Telecom Operators already have made a strategic
transition from "Network, Communication Operators" into "integrated information service provider" to provide
customer with varied information service, such as the BT "21st century plan", "Next" plan proposed by France Telecom,
FNE and BMS plan by Australia Telstra, RANE Programs by NTT. Domestic Carries also made strategic transition
plans. And the priority of network transition is to find the way to build a unified and integrated network supporting
carrier-grade Ethernet service also compatible with the conventional network service.
The division of the service results in the Packet transmission, namely packet technology, makes Packet-based
Transmission Network keeping the virtues of transmission network. The virtues are good scalability, varied operation
and maintenance, high-speed protection switching, connection-oriented feature, and building up connection with NMS.
At the same time, it adds some characteristics to adapt the statistical multiplexing in the packet service, for instance:
connection-oriented label switching, QoS mechanism, dynamic and flexible control plane. The Packet Transmission
Network (PTN) can be divided into four layers: packet transmission channel layer (PTC), packet transmission path layer
(PTP), and optional packet transmission section Layer (PTS) and physical layer.
The key technologies of PTN are as follows: the connection-oriented based label transmission and the statistical
multiplexing on packet switching. The use of layer and sub-domain is to provide good scalability. Supporting for fault
detection and performance testing and other Operation, Management and Maintenance (OAM) function, linear protection
switching, ring protection, dynamics survival technology of pre-placed re-route, QoS, circuit emulation for TDM service,
ATM based on PWE3 technique, and MAC layer or physical layer based packet clock synchronization.
The application PTN could be convergence of packet service in MAN, such ads DSLAM backhauling, wireless
Backhauling and so on. PTN can also take replace the core router in the core network to carry out the high efficient
transmission of packet service.