The widespread use of high speed Ethernet links, e.g., 10GigE links, in data centers and numerous video applications have driven the need for higher speed Ethernet interfaces in the data centers and other core networks. Ever growing user traffic and expansion of enterprise local area network traffic has be a major driver for transporting Ethernet across metropolitan and core optical networks. Using optical transport network (OTN), per ITU-T G.709 standard, which is incorporated herein by reference in its entirety, provides a cost-efficient transport layer that supports various applications and technology including a dense wavelength division multiplexing (DWDM). As such, OTN can serve as a converged transport layer for new packet based services as well as existing time division multiplexing services.
Further, the optical transport network architecture allows transport Ethernet transparently over an optical transport network. This means that synchronization signals such as SyncE may be transported over an optical transport network tunnel, via Ethernet physical layer, however, if a Time of Day (ToD) needs to be transported, it is not possible to do so because the current implementation of the OTN network has large variable delays for packet transport. Further, in the existing implementation of the OTN network, an average delay of a data path is not deterministic and changes for several hundreds of nanoseconds every time a link is re-connected and/or a system is re-powered.
For implementation of ToD protocols such as a network timing protocol (NTP) and IEEE1588 using the existing technology, it is assumed that the delay is constant and equal in both directions. If NTP or IEEE1588 protocols are used via Ethernet packets that are transported through an OTN network, variable delays of the OTN network will degrade the performance of the ToD distribution in such a way that it is required to distribute the ToD via another path. Another option is to use the IEEE1588 transparent clock (TC) function may be implemented using the existing technology, but the implementation of the IEEE1588 TC protocol breaks the SyncE feature. Since it requires to convert the Ethernet line-code to packets, search for IEEE1588 packets, calculate expected delay through a system, add the measured system delay in the IEEE1588 packet, and convert the packets back to the Ethernet line-code, thus breaking the layer 1 synchronization.
As such, there is still a need for further improved and more efficient methods and systems for transporting Ethernet packets over an optical transport network.