The flexible Ethernet (FlexE) combines some technical features of the Ethernet and a transport network (for example, an optical transport network (OTN), and a synchronous digital hierarchy (SDH)), and is an important milestone in the evolution of an Ethernet technology. With emergence of a flexible Ethernet technology, Ethernet physical interfaces show virtualization characteristics. A plurality of Ethernet physical interfaces may be bonded together, to support several virtual logical ports. For example, a 400-gigabit (400G) flexible Ethernet physical interface group obtained by bonding four 100-gigabit Ethernet (100GE) physical interfaces may support several logical ports.
The Ethernet physical interface is an asynchronous communications interface, and is allowed to have a clock frequency difference of ±100 ppm (one ten-thousandth). For example, in 10GE, for two physical interfaces whose nominal bandwidths are 10 G, one bandwidth may be one ten-thousandth larger than the nominal value, and the other bandwidth is one ten-thousandth smaller than the nominal value, that is, 10G*(1+0.0001) and 10G*(1−0.0001). A clock frequency at the logical port inherits a clock frequency characteristic on the physical interface, and therefore the logical port also has a difference of 100 ppm. For example, actual bandwidths of two logical ports that are formed by different physical interfaces or physical interface groups and whose nominal bandwidths are 25 G may be approximately 25G*(20460/20461)*(1+0.0001) and 25G*(20460/20461)*(1−0.0001) when overheads of timeslot division and timeslot management in the flexible Ethernet are considered. When the flexible Ethernet is used to bear a service, idle-code-block (Idle) insertion or deletion needs to be performed hop by hop, to adapt a service rate to a bandwidth rate difference between the service and the physical interfaces or the logical ports. FIG. 1 is a schematic diagram of service transport in the flexible Ethernet in the prior art. As shown in FIG. 1, when a service between customer devices Ca and Cb is borne by using flexible Ethernet devices Pa, Pb, and Pc, the Pa, the Pb, and the Pc needs to perform idle-unit insertion or deletion.
However, idle-code-block insertion or deletion causes loss of a clock frequency and time phase information of the service, that is, the clock frequency and the time phase information of the service cannot be transparently transported, and consequently the clock frequency and the time phase cannot be synchronized between a source network device and a sink network device of the service.