说明：  PTN是基于分组交换、面向连接的多业务统一传送技术，不仅能较好地承载以太网业务，而且兼顾了传统的TDM和ATM业务，满足高可靠、可灵活扩展、严格QoS和完善的OAM等基本属性。
(PTN is a multi service unified transmission technology based on packet switching and connection oriented. It can not only better carry Ethernet services, but also take into account the traditional TDM and ATM services, and meet the basic attributes of high reliability, flexible expansion, strict QoS and perfect OAM.)