Network interface card structure and clock synchronization method to precisely acquire heterogeneous PTP synchronization information for PTP synchronization network extension

A precision time protocol (PTP) synchronization method using a PTP synchronization network system including a virtual node including a first switch at an ingress point and a second switch at an egress point, wherein the first switch and the second switch are time-synchronized with a second PTP master node;

• a first synchronous switch connected to the first switch, the first synchronous switch being a device synchronized with a first PTP master node;
• and a second synchronous switch connected to the second switch, the second synchronous switch being a device to be synchronized with the first PTP master node at a remote location,
• wherein
• the first switch is lime synchronized with the first PTP master node and the second PIP master node,
• the second switch is time synchronized with the second PIP master node,
• the first switch and the second switch between the first synchronous switch and the second synchronous switch operated as the virtual node,
• the first switch comprises a virtual-node-supported precision PTP network interface card (NIC) comprising a first port, a second port, a first PTP hardware clock (phc), and a second phc, and
• the first phc is synchronized with the second phc such that Ingress_Time of the PTP message of the first PTP master node received through the first port is acquired using the clock synchronized with the second PTP master node,
• the second port performs only PTP message transmission and reception and physical clock functions, except for general user Ethernet frame processing, in order to acquire precise Ingress_Time by minimizing additional hardware,
• the PTP synchronization method comprising operations of:
• allowing the first synchronous switch synchronized with the first PTP master node to transmit a PTP message to the first switch;
• allowing the first switch to acquire ingress time of the PTP message using a clock synchronized with the second PTP master node and deliver the PTP message to the second switch in the virtual node;
• allowing the second switch to acquire egress time of the PTP message using the clock synchronized with the second PTP master node;
• allowing the second switch to calculate residence time using the ingress time and the egress time and then transmit the PTP message to the second synchronous switch;
• and
• allowing the second synchronous switch to acquire a time when the synchronization is made with the first PTP master node using the received PTP message.