Ethernet Interface Modules The Cisco ASR 900 Ethernet interface modules are designed to give customers flexibility and value. All Ethernet interface modules share a common core that supports time-stamping on the module for Y.1731 operations, administration, and maintenance (OAM) delay measurement functions, to achieve precise results for one-way and two-way delay measurement. The modules also provide time-stamping functions for the IEEE 1588-2008 protocol. These time stamps help ensure that the Cisco ASR 900 Series Routers achieve outstanding results when deploying IEEE 1588-2008 protocols for frequency and phase synchronization. Not all customers will deploy IEEE 1588-2008 for synchronization, therefore the Ethernet interface modules also support input and output frequency synchronization using synchronous Ethernet (SyncE).